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23-04-19 Pahala Preliminary Engineering Report - SDWA-UIC-AOC-2017-002
Pahala Large Capacity Cesspool Closure Project Revised Preliminary Engineering Report Prepared for County of Hawaii, Department of Environmental Management April 2023 2261 Aupuni Street, Suite 201 Wailuku, Maui, HI 96793 T: 808.244.7005 April 8, 2023 Ms. Brenda Iokepa-Moses County of Hawaii Wastewater Division 108 Railroad Ave Hilo, HI 96720 152964.704 Subject:Pahala Wastewater Treatment Plant Revised Preliminary Engineering Report Dear Ms. Iokepa-Moses, Brown and Caldwell (BC), in association with Engineering Partners, Inc. (EPI) is pleased to present the attached Revised Preliminary Engineering Report (PER) for the Pahala Large Capacity Cesspool (LCC) Closure Project. Preparation of a Revised PER is required by the Revised Administrative Order on Consent (AOC) that became effective on August 22, 2022. The need for a Revised PER was precipitated by several items: Geophysical and geotechnical investigations identified and confirmed a large subsurface lava tube under the proposed aerated lagoons, prompting the need for a wastewater treatment process with a smaller and shallower footprint. Mechanical treatment technologies in the form of package plants offer the opportunity to achieve these goals. The community has not been receptive to the aerated lagoon technology that was formerly proposed. The Revised AOC no longer requires secondary treatment, opening up the possibility of implementing individual wastewater systems (IWS) to close the LCCs. The Revised AOC requires evaluation of four feasible options: i. A package plant and new collection system. ii. A package plant connected to the existing collection system. iii. A maintenance contract model IWS program. iv. An operating permit model IWS program. This Revised PER consists of three parts: This introductory summary that provides comparisons of all four feasible options. Part A, by BC, which presents updated analysis of feasible options i and ii that are based on using a package plant-based wastewater treatment plant (WWTP) to service the Pahala community and close the LCCs. BC is a nation-wide environmental engineering firm with local Hawaii offices located in Kamuela, Wailuku, and Honolulu. For over 75 years BC has been planning and designing WWTPs throughout the United States. Part B, by EPI, which presents a detailed analysis of feasible options iii and iv that are based on using IWS to service the Pahala community and close the existing LCCs. EPI is a multi-discipline engineering and design firm based in Hilo. EPI has successfully designed IWS systems on Hawaii Island and is well-versed to address implementing IWS in the unique local soil and subsurface geological conditions in Pahala. Ms. Brenda Iokepa-Moses County of Hawaii Wastewater Division April 8, 2023 Page 2 Throughout this Revised PER the following terms are used: “Feasible options” refers to the four specific options (i, ii, iii, iv) listed above and in paragraph V.A.31.a of the Revised AOC. “Alternatives” and “project alternatives” refer to various combinations of systems or technologies that are evaluated within this Revised PER to determine preferences for the feasible options. 1. Comparison of Feasible Options The four feasible options are compared below, 1.1 Protection of Human Health and the Environment Table 1 compares the four feasible options with respect to protection of human health and the environment. The State of Hawaii Department of Health (DOH) regulates both WWTPs and IWS. All four feasible options are protective of human health and the environment when implemented in accordance with the applicable Hawaii Administrative Rules (HAR). Additional discussion is provided in Parts A and B. Table 1. Protection of Human Health and the Environment Feasible Option Regulatory Authority Variances Protective? i. Package plant and new collection system HAR 11-62 Subchapter 2 Variance granted by DOH for WWTP flow capacity Yes ii. Package plant connected to the existing collection system HAR 11-62 Subchapter 2 Variance granted by DOH for WWTP flow capacity Yes iii. A maintenance contract model IWS program HAR 11-62 Subchapter 3 Variances may be required for some lots for setback distances, etc.Yes iv. An operating permit model IWS program HAR 11-62 Subchapter 3 Variances may be required for some lots for setback distances, etc.Yes Ms. Brenda Iokepa-Moses County of Hawaii Wastewater Division April 8, 2023 Page 3 1.2 Capital Cost Comparison of Feasible Options Table 2 summarizes the capital costs for the four feasible options. Note that the IWS capital costs per lot are presented as ranges; greater precision will not be available until designs are complete due to the site-specific nature of IWS implementation on existing developed properties. Table 2. Capital Cost Comparison Feasible Option Capital Cost Cost per Lot i. Package plant and new collection system $37.3 million $214,000 ii. Package plant connected to the existing collection system $23.6 million $136,000 iii. A maintenance contract model IWS program $5.7 - $17.4 million $33,000 - $100,000 iv. An operating permit model IWS program $5.7 - $17.4 million $33,000 - $100,000 As shown in the table the IWS feasible options incur significantly lower capital costs than the package plant alternatives. 1.3 Life-cycle cost comparison A life-cycle cost comparison was prepared for the alternatives. The life-cycle cost is the net present value of cash flows required to implement the project over a 30-year planning period, including capital, operation, maintenance, and replacement costs. The life-cycle cost evaluation includes inflationary effects and the time value of money. Table 3 summarizes the life-cycle cost evaluation results. The IWS approaches assumed the maximum estimated capital costs presented above; the average cost per lot will likely fall between the two extremes shown in Table 2. Table 3. Life-Cycle Cost Evaluation Results Alternative Capital Cost O&M Costs Life-Cycle Cost i. Package plant and new collection system $37.3 million $19.7 million $57.0 million ii. Package plant connected to the existing collection system $23.6 million $21.6 million $45.2 million iii. A maintenance contract model IWS program $17.4 million $9.4 million a $26.8 million iv. An operating permit model IWS program $17.4 million $11.3 million a $28.7 million a Includes replacement costs and IWS O&M costs paid directly by homeowners. Ms. Brenda Iokepa-Moses County of Hawaii Wastewater Division April 8, 2023 Page 4 Figure 1 shows the results graphically. The IWS alternatives have significantly lower life- cycle costs than the package plant alternatives. Figure 1. Life-Cycle Cost Comparison 1.4 Schedule The Revised AOC requires the LCCs be closed no later than July 21, 2026. Parts A and B include preliminary assessments of implementation schedules. Table 4 provides a summary of the preliminary implementation schedule assessments. As discussed in Part A, it will be difficult to implement the WWTP approach to close the LCCs by the deadline, due to entitlement processes, environmental review, land acquisition, and materials supply challenges currently facing the Hawaii construction industry. A design/build approach could potentially reduce the implementation timeframe if equipment procurement and fabrication can occur in parallel with design. However, compliance with the Revised AOC deadline will be a significant challenge with Feasible Options i and ii. Per Part B, the IWS approach may be able to be implemented by the Revised AOC deadline. The IWS approach assumes that the County can address Hawaii Revised Statues (HRS) 343 environmental review requirement via an exemption, and that any alterations to County regulations deemed necessary by the County are achievable within the timeframe. Ms. Brenda Iokepa-Moses County of Hawaii Wastewater Division April 8, 2023 Page 5 Table 4. Summary of Preliminary Implementation Schedule Assessments Feasible Options Description i. Package Plant New Collection System ii. Package Plant Existing Collection System iii. Maintenance Contract Model IWS Program iv. Operating Permit Model IWS Program Entitlements and permitting Q3 2024 Q3 2024 Q1 2024 Q1 2024 Design and construction Q4 2027 Q4 2027 Q2 2026 Q2 2026 Estimated LCC closure Q2 2027 Q2 2027 Q2 2026 Q2 2026 Revised AOC LCC closure milestone July 21, 2026 Risk of missing Revised AOC LCC closure milestone High High Moderate Moderate Note: Q = quarter 2. Revised AOC References The Revised AOC paragraph V.30.A.a lists information that must be included in this Revised PER. Table 5 provides references to the information within. Ms. Brenda Iokepa-Moses County of Hawaii Wastewater Division April 8, 2023 Page 6 Table 5. Revised AOC Paragraph V.30.A.a Checklist Report Reference Section for Feasible Options Revised AOC Paragraph V.30.A.a Description i. Package Plant New Collection System ii. Package Plant Existing Collection System iii. Maintenance Contract Model IWS Program iv. Operating Permit Model IWS Program Description of project details for each feasible option Part A, § 2.2 and 8 Part A, § 2.4 and 8 Part B, § 1, pg. 3 Planning area description Part A, Figure 2-1 Part A, Figure 2-1 Part A, Figure 2-1 Part A, Figure 2-1 Planning period Part A, § 7.2.3 Part A, § 7.2.3 Part A, § 7.2.3 Part A, § 7.2.3 Description of planning phases Part A, § 7.2.3 Part A, § 7.2.3 Part A, § 7.2.3 Part A, § 7.2.3 Owner and operator of facilities Part A, § 1-1 Part A, § 1-1 County /In-house or 3rd party service provider Homeowner / 3rd party service provider Location of facilities (including a map)Part A, Figure 2-1 Part A, Figure 2-1 Part A, Figure 2-1 Part A, Figure 2-1 Design parameters for each feasible option Part A, § 2.2 and 8 Part A, § 2.4 and 8 Part B, Table 1.1 Part B, Table 1.1 Major unit processes:Part A, § 5 Part A, § 5 Part B, § 2 and 3 Part B, § 2 and 3 Flow diagram Part A, Figure 8-2 Part A, Figure 8-2 Part B, Appendix J Part B, Appendix J Pipe lengths, sizes, and locations Part A, Table 2-2 Part A, Table 2-2 Not applicable Not applicable Design criteria Part A, § 8.3 Part A, § 8.3 Part B, § 3, Appendix J Part B, § 3, Appendix J Project costs Part A, § 7 Part A, § 7 Part B, Table 1.2 Part B, Table 1.2 3. Recommended Approach Based solely on the technical analysis presented in Part A and Part B of this report and considering the significantly lower capital and lifecycle costs and favorable implementation schedule associated with of the IWS option, we recommend the County pursue an IWS approach to close the LCCs by the Revised AOC deadline of July 21, 2026. Implementation and logistics of the IWS options (including issues not addressed in this report) are concurrently being investigated by the County. If the IWS approach is selected by the County and approved by the EPA, the next step will be for the County to develop an Implementation Plan that will include definition of the intended IWS management model. Ms. Brenda Iokepa-Moses County of Hawaii Wastewater Division April 8, 2023 Page 7 Brown and Caldwell appreciates that the County has requested our services in assisting with this project. Should you have any questions, please do not hesitate to call Michelle Sorensen at 808.442.3306. Very truly yours, Brown and Caldwell Michelle Sorensen, Project Manager Craig Lekven, Project Director Kamuela, Hawaii Wailuku, Hawaii for PART A: WWTP Approach ii Part A Pahala Wastewater Treatment Plant Revised Preliminary Engineering Report Prepared for County of Hawaii, Department of Environmental Manag ement April 20 2 3 THIS WORK (PART A) WAS PREPARED BY ME OR UNDER MY S UPERVISION April 30, 2024 Signature Expiration Date of the License Pahala WWTP Revised PER Table of Contents iii Table of Contents – Part A List of Figures .............................................................................................................................................. vi List of Tables .............................................................................................................................................. viii List of Abbreviations .................................................................................................................................... ix 1. Introduction .......................................................................................................................................1-1 1.1 Background .............................................................................................................................1-1 1.2 Existing System .......................................................................................................................1-1 1.3 Report Contents ......................................................................................................................1-1 2. Collection System ..............................................................................................................................2-1 2.1 Service Area ............................................................................................................................2-1 2.2 Conventional Gravity Sewers .................................................................................................2-3 2.3 Septic Tank Effluent Pumping (STEP) System ......................................................................2-3 2.4 Reuse Existing Collection System ..........................................................................................2-7 2.5 Cost Evaluations .....................................................................................................................2-7 2.6 Recommendation ...................................................................................................................2-8 3. Flow and Load Projections ................................................................................................................3-1 3.1 Flow Projections Based on City and County of Honolulu Standards ...................................3-1 3.2 Reduced Flows Based on Potable Water Records ...............................................................3-1 3.2.1 Dry Weather I/I Allowance .......................................................................................3-2 3.2.2 Wet Weather I/I Allowance ......................................................................................3-2 3.2.3 Reduced Flow Projections ........................................................................................3-2 3.2.4 Flow Variance ...........................................................................................................3-3 3.3 Influent Characteristics ..........................................................................................................3-3 3.4 Influent Mass Loads ...............................................................................................................3-4 4. Effluent Management Options and Regulatory Requirements ......................................................4-1 4.1 Effluent Management Options ...............................................................................................4-1 4.1.1 Ocean Discharge ......................................................................................................4-1 4.1.2 Subsurface Disposal via Injection Wells .................................................................4-1 4.1.3 Water Recycling ........................................................................................................4-2 4.1.4 Slow Rate Land Treatment ......................................................................................4-2 4.1.5 Subsurface Drip Irrigation Disposal ........................................................................4-4 4.1.6 Leach Field ................................................................................................................4-6 4.1.7 Existing Cesspool Conversion ..................................................................................4-6 4.1.8 Recommendation .....................................................................................................4-6 4.2 Treatment Requirements .......................................................................................................4-8 5. Wastewater Treatment Evaluations .................................................................................................5-1 5.1 Preliminary Treatment ............................................................................................................5-1 Pahala WWTP Revised PER Table of Contents iv 5.1.1 Influent Flow Measurement .....................................................................................5-1 5.1.2 Influent Flow Sampling .............................................................................................5-1 5.1.3 Screening ..................................................................................................................5-1 5.1.4 Grit Removal .............................................................................................................5-2 5.1.5 Odor Control ..............................................................................................................5-7 5.1.6 Recommendation .....................................................................................................5-8 5.2 Secondary Treatment .............................................................................................................5-8 5.2.1 Membrane Bioreactor (MBR) ...................................................................................5-8 5.2.2 Sequencing Batch Reactor (SBR) ......................................................................... 5-10 5.2.3 Nereda (Granular Activated Sludge) Process ...................................................... 5-10 5.2.4 Oxidation Ditch ...................................................................................................... 5-11 5.2.5 Extended Aeration Activated Sludge Package Plant ........................................... 5-12 5.2.6 Activated Sludge with Anoxic Selector ................................................................. 5-13 5.2.7 Recirculating Gravel Filter ..................................................................................... 5-13 5.2.8 Secondary Treatment Technology Screening ...................................................... 5-14 5.3 Maintenance Chlorination ................................................................................................... 5-16 6. Solids Management ..........................................................................................................................6-1 6.1 Aerobic Digestion with Decant Thickening ............................................................................6-1 6.2 Anaerobic Digestion with Biogas Use ....................................................................................6-1 6.3 Screw Press Dewatering .........................................................................................................6-2 6.4 Disposal ...................................................................................................................................6-2 7. Project Alternatives Evaluations .......................................................................................................7-1 7.1 Project Alternative Descriptions .............................................................................................7-1 7.1.1 Project Alternative 1: Activated Sludge with Anoxic Zone Package Plants ...........7-1 7.1.2 Project Alternative 2: MBR Package Plants ............................................................7-2 7.1.3 Project Alternative 3: Imhoff Tank / Recirculating Gravel Filter ............................7-3 7.2 Cost Evaluations .....................................................................................................................7-4 7.2.1 Capital Costs .............................................................................................................7-4 7.2.2 Operation and Maintenance Costs ..........................................................................7-6 7.2.3 Life-Cycle Costs .........................................................................................................7-6 7.3 Non-Economic Evaluation ......................................................................................................7-8 7.3.1 Approach ...................................................................................................................7-8 7.4 Non-Economic Evaluation Criteria .........................................................................................7-9 7.5 Non-Economic Evaluation Results ...................................................................................... 7-11 7.6 Conclusions and Recommendation .................................................................................... 7-11 8. Preliminary Design of Improvements ...............................................................................................8-1 8.1 Site Plan ..................................................................................................................................8-1 8.2 Process Schematic .................................................................................................................8-1 8.3 Preliminary Design Criteria .....................................................................................................8-4 8.4 Preliminary Floor Plan.............................................................................................................8-6 Pahala WWTP Revised PER Table of Contents v 9. Implementation Plan .........................................................................................................................9-1 9.1 Implementation Approach ......................................................................................................9-1 9.1.1 Design Bid Build (DBB) Approach ............................................................................9-1 9.1.2 Design Build (DB) Approach.....................................................................................9-1 9.2 Implementation Schedules ....................................................................................................9-1 9.2.1 Recent Change in State of Hawaii Land Use Commission Policy ..........................9-1 9.2.2 Equipment Procurement Time to Impact Construction Schedule .........................9-2 9.2.3 Implementation Schedules ......................................................................................9-2 9.3 Recommendation ...................................................................................................................9-2 10. References ..................................................................................................................................... 10-1 Appendix A: Cost Estimates ...................................................................................................................... A-1 Appendix B: DOH Variance ...................................................................................................................... B-1 Appendix C: Non-Economic Evaluation ....................................................................................................C-1 Pahala WWTP Revised PER Table of Contents vi List of Figures Figure 1-1. Pahala Existing Sewer Collection System and LCC Service Area ........................................1-3 Figure 2-1. Pahala WWTP service area ....................................................................................................2-2 Figure 2-2. STEP Collection System .........................................................................................................2-4 Figure 2-3. STEP Section View .................................................................................................................2-5 Figure 2-4. Orenco PrelosTM System Tanks in the Field ..........................................................................2-5 Figure 2-5. Orenco STEP System Pump and Screen...............................................................................2-6 Figure 2-6. Orenco PrelosTM System Cutaway .........................................................................................2-6 Figure 2-7. Life-Cycle Cost Comparison of Collection System Alternatives ...........................................2-8 Figure 4-1. Irrigation Demand Assessment .............................................................................................4-2 Figure 4-2. Subsurface Drip Irrigation Concept ......................................................................................4-5 Figure 4-3. Conceptual Subsurface Drip Irrigation System at Pahala ...................................................4-8 Figure 5-1. In-Channel Cylindrical Screen ...............................................................................................5-2 Figure 5-2. Sloped Bottom Vortex Grit Removal Cross Section .............................................................5-3 Figure 5-3. Flat Bottom PISTA® Grit Removal ..........................................................................................5-3 Figure 5-4. Aerated Grit Removal Schematic ..........................................................................................5-4 Figure 5-5. Headcell Process Schematic .................................................................................................5-6 Figure 5-6. Activated Carbon Scrubber (GAC) .........................................................................................5-8 Figure 5-7. Membrane Bioreactor Illustration .........................................................................................5-9 Figure 5-8. Membrane Cassettes at Johns Creek Environmental Campus, Fulton County, GA ...........5-9 Figure 5-9. Nereda Process ................................................................................................................... 5-11 Figure 5-10. Typical Oxidation Ditch Schematic .................................................................................. 5-12 Figure 5-11. Extended Aeration Process Schematic ........................................................................... 5-12 Figure 5-12. Activated Sludge with Anoxic Selector Process Schematic............................................ 5-13 Figure 5-13. Recirculating Gravel Filter for Treatment of Septic Tank Effluent ................................. 5-14 Figure 5-14. Typical Calcium Hypochlorite Feed System .................................................................... 5-16 Figure 6-1. Screw Press Diagram .............................................................................................................6-2 Figure 7-1. Project Alternative 1: Activated Sludge with Anoxic Zone Package Plants ........................7-2 Figure 7-2. Project Alternative 2: MBR Package Plants .........................................................................7-3 Figure 7-3. Project Alternative 3: Imhoff Tank/Recirculating Gravel Filter ...........................................7-4 Figure 7-4. Life-Cycle Cost Evaluation Results ........................................................................................7-8 Figure 7-5. Combined Economic and Non-Economic Results ............................................................. 7-11 Figure 8-1. Overall Site Plan .....................................................................................................................8-2 Pahala WWTP Revised PER Table of Contents vii Figure 8-2. Process Schematic ................................................................................................................8-3 Figure 8-3. Operations Building Preliminary Floor Plan ..........................................................................8-7 Figure 9-1. Implementation Schedules ...................................................................................................9-1 Pahala WWTP Revised PER Table of Contents viii List of Tables Table 2-1. Pahala WWTP Service Area Summary ...................................................................................2-2 Table 2-2. Summary of Pahala Gravity Collection System Projects ......................................................2-3 Table 2-3. Collection System Cost Summary ..........................................................................................2-8 Table 3-1. Pahala WWTP Flows Based on 2017 CCH Standards ..........................................................3-1 Table 3-2. Pahala WWTP Calculated Flow Capacity................................................................................3-2 Table 3-3. Recommended WWTP Capacity .............................................................................................3-3 Table 3-4. Summary of Assumed Influent Characteristics .....................................................................3-4 Table 3-5. Projected Peak Dry Weather Day Influent Mass Loads ........................................................3-4 Table 4-1. Nutrient Water Quality Standards for Class AA Embayments ..............................................4-1 Table 4-2. Pahala WWTP Soil Infiltration Test Results ...........................................................................4-3 Table 4-3. Pahala WTTP Effluent Disposal Water Balance ....................................................................4-4 Table 4-4. Recommended Subsurface Drip Design Criteria ..................................................................4-7 Table 4-5. Applicable HAR 11-62 Land Disposal Requirements ...........................................................4-8 Table 5-1. Induced Vortex – Advantages and Disadvantages ...............................................................5-4 Table 5-2. Aerated Grit Removal – Advantages and Disadvantages .....................................................5-5 Table 5-3. Lamella Plate Settling/HeadCell – Advantages and Disadvantages ...................................5-6 Table 5-4. Grit Capture Size Comparison ................................................................................................5-7 Table 7-1. Capital Cost Estimating Assumptions ....................................................................................7-5 Table 7-2. Capital Cost Estimates Summary ...........................................................................................7-5 Table 7-3. O&M Cost Assumptions ..........................................................................................................7-6 Table 7-4. O&M Cost Estimate Summary ................................................................................................7-6 Table 7-5. Life-Cycle Economic Assumptions ..........................................................................................7-7 Table 7-6. Life-Cycle Cost Analysis Summary ..........................................................................................7-7 Table 7-7. Non-Economic Comparison Criteria .......................................................................................7-9 Table 7-8. Non-Economic Comparison Criteria .................................................................................... 7-10 Table 7-9. Non-Economic Weighted Scores ......................................................................................... 7-11 Pahala WWTP Revised PER Table of Contents ix List of Abbreviations AB aggregate base AC asphalt concrete BMP Best Management Practices BOD5 5-day biochemical oxygen demand CCH City and County of Honolulu CDP Kau Community Development Plan cfs cubic feet per second CFR Code of Federal Regulations DNA deoxyribonucleic acid DEM Department of Environmental Management DOH Department of Health DWS Department of Water Supply ELLF end-of-lamp-life FIRM Flood Insurance Rate Map FOG fats, oils, and grease ft3 cubic feet FTE full-time equivalent GAC granular activated carbon gpm gallons per minute gpd gallons per day gpcd gallons per capita per day gpad gallons per acre per day H2S hydrogen sulfide HAR Hawaii Administrative Rules HDPE high density polyethylene HELCO Hawaii Electric Light Company hp horsepower hp/Mgal horsepower per million gallons hr hour hp-hr horsepower-hour I/I Infiltration and inflow L liter lbs pounds LCC large capacity cesspools LPHO low pressure high output MBR membrane bioreactor Mg milligrams Mgal million gallons Mgd Million gallons per day mL milliliter MLSS mixed liquor suspended solids mm millimeter MSL mean sea level N nitrogen NPV net present value O&M Operation and Maintenance P Phosphorus psi pounds per square inch RNA ribonucleic acid ROW right-of-way scfm standard cubic feet SCS Soil Conservation Service SES sand equivalent size SR slow rate SRT solids residence time TSS total suspended solids UIC Underground Injection Control USEPA United States Environmental Protection Agency UV ultraviolet WQV Water Quality Volume WWTP Wastewater Treatment Plant WWRF Wastewater Reclamation Facility 1-1 Section 1 Introduction 1.1 Background The town of Pahala is located in the Kau district of the Island of Hawaii. According to the 2020 United States Census, the town population is approximately 1,400 persons. The modern Pahala community was first established as the Pahala Plantation by Hawaiian Agriculture Company (HAC) in 1878 to support sugarcane production. A portion of the community is serviced by a sewer system that was privately built, owned, and operated by the C. Brewer Company, which merged with HAC in 1972. The wastewater collected by the sewer system discharges into large capacity “gang” cesspools. The County of Hawaii (County) Department of Environmental Management (DEM) assumed ownership of the sewer system on April 30, 2010. In 1998, the U.S. Environmental Protection Agency (USEPA), promulgated regulations, 40 Code of Federal Regulations (CFR) 144.14, that require the elimination of large capacity “gang” cesspools (LCCs). Options to close the LCCs include construction of a new sewer collection system located within public right-of-way (ROW) and replacement of the existing LCCs with a wastewater treatment plant (WWTP) to address the wastewater treatment and disposal needs of the Pahala community. These centralized WWTP options are the subject of this report. A separate report is being concurrently prepared that evaluates additional options using individual wastewater systems (IWS) in lieu of a new collection system and WWTP to close the LCCs. This report is a revision of the 2019 Preliminary Engineering Report (PER) for the Pahala WWTP and summarizes the proposed facilities needed to treat and dispose of wastewater flow that is currently discharged to the LCCs, plus additional sewer connections. The report presents the existing and estimated future flows and loads to the treatment plant, the proposed treatment processes, recommendation for the WWTP upgrades needed to meet the future treatment needs, and an initial opinion of the cost to construct the improvements project. 1.2 Existing System The existing collection system is a network of gravity sewers that discharge to two existing LCCs. Figure 1-1 shows the collection system network and service areas for the LCCs. A detailed analysis of the existing wastewater collection system was completed by others (M&E Pacific, December 2004). The report concluded that the Pahala community existing sewer system consists of about 3,000 linear feet of 6-inch diameter and 10,000 linear feet of 4-inch diameter pipelines. Residential laterals connect to 4-inch sewers that discharge into 6-inch sewer mains, predominately found in easements on private property, which transmit wastewater to the LCCs. There are approximately 8 manholes in the sewer system. There are no pump stations, and the system is not designed to collect stormwater. 1.3 Report Contents Section 2 presents the service area and alternative collection systems. Section 3 presents flow and load projections for the new WWTP. Section 4 evaluates effluent management options, and the treatment requirements for the preferred option. Section 5 presents evaluations conducted to develop the preliminary design of the proposed WWTP. Solids management is briefly presented in Pahala WWTP Revised PER Section 1 1-2 Section 6, followed by discussion of alternative treatment options that were considered and evaluated in Section 7. Preliminary design of improvements is presented in Section 8. The report concludes with an implementation plan in Section 9. P P P P P P PP P P") ")PUAHALA STPIKAKE STP A K A L A N A S T HINANO ST HUAPALA ST KOKIO STKEAHI STKAMANI ST K O A L I S T P A A U A U P L MAI L E ST WOOD VALLEY RDMEYER RDPAAUAU STHAWAII BELT RDOHIA STILIAU STILIMA ST LOWER MAOULA RDHOLEI ST PUMELI ST SCALE AS SHOWN JOB NO.: 150440 PAHALA WASTEWATER TREATMENT PLANT Pahala Existing Sewer Collection System and LCC Service Area FIGURE 1-1 0 2,0001,000 Feet ± LEGEND Existing Condition to Large Capacity Cesspool (LCC) Proposed Pahala WWTP Site P Pahala Existing SMH and LCC ")Existing Large Capacity Cesspool (LCC) Existing Sewer Mains Existing Large Capacity Cesspool (LCC 1) Existing Large Capacity Cesspool (LCC 2) Ka'u High & Pahala Elementary School Proposed Pahala WWTP Site Ka'u Hospital Existing Connection to Large Capacity Cesspool (LCC) Existing Sewer Manhole 2-1 Section 2 Collection System This section summarizes the alternative collection systems for the service area. 2.1 Service Area Within the town of Pahala, there is an existing wastewater collection system that services approximately 109 properties. The collection system is currently located within easements in private properties and is treated and disposed through two LCCs. Figure 2-1 shows the service area for the new WWTP. The Kau Community Development plan indicates that the sewer system may eventually be expanded to service the entire community; however, the initial collection system and WWTP presented in this report will service the properties currently connected to the LCCs or located adjacent to the new collection system. Table 2-1 provides a summary of the WWTP service area, which includes the properties currently supplying wastewater to the LCCs and the properties that will be “newly accessible” to the wastewater collection system after the replacement collection system is constructed. Pahala WWTP Revised PER Section 2 2-2 Figure 2-1. Pahala WWTP service area Table 2-1. Pahala WWTP Service Area Summary Property Type Number of Parcels Residential 167 Commercial 4 School 1 Industrial 1 Commercial, industrial, and agricultural 1 Total 174 Pahala WWTP Revised PER Section 2 2-3 2.2 Conventional Gravity Sewers A conventional gravity sewer collection system was designed for the Pahala service area shown in Figure 2-1 by Fukunaga & Associates, Inc., to be constructed in two phases. Phase 1 consists of both 8-inch and 12-inch diameter PVC sewer lines connecting the two LCCs along the South end of Pikake Street and continuing down Maile Street to the proposed WWTP. The Phase 1 collection system is designed to tie into Pahala’s existing collection system infrastructure. Phase 2 consists of approximately 9,400 linear feet of 8-inch diameter PVC sewer mainlines with 6-inch diameter PVC county sewer laterals connecting the sewer mainline to property & easement lines. This Phase 2 collection system is designed to connect to the Phase 1 collection system. Table 2-2 provides a summary of the two projects. Table 2-2. Summary of Pahala Gravity Collection System Projects Description Phase 1 Phase 2 Project title Pahala Wastewater Collection System Improvements Phase 1 Pahala Wastewater Collection System Improvements Phase 2 Purpose Connect existing collection system to WWTP easement. Close LCCs New sewers in street to replace existing. Connect houses. Scope summary 1,400 linear feet of 12-inch sewer 700 linear feet of 8-inch sewer 18 manholes Close 2 LCCs 9,391 linear feet of 8-inch sewer 83 manholes 158 County sewer laterals, 6-inch Connect houses. 2.3 Septic Tank Effluent Pumping (STEP) System Typically, a STEP system includes a septic tank with filter screens and electric pumps to convey septic tank effluent to a force main located in the street. These force mains are small (2-inch minimum diameter), low-pressure mains that can be installed with minimum depth of cover and can follow the topography. Figure 2-2 is a schematic diagram of a STEP collection system, Pahala WWTP Revised PER Section 2 2-4 Figure 2-2. STEP Collection System The major suppliers of these systems are Orenco and Zoeller. The STEP pumps are turbine style high- head pumps intended to pump effluent without solids. Solids, disposable wipes, and grease are all retained in the septic tank and are not pumped. By screening and retaining solids in the septic tank portion of the system, a reduced organic load to the WWTP would be realized. STEP systems are often sold as a package system, including a septic tank or pretreatment/solids holding tank, screen, pump, and controls. The pumps in STEP systems must be protected from solids by a screening system. It is recommended that STEP systems be inspected regularly to make sure the screen is functioning and there is not excessive solids or grease build up. Septic tanks associated with STEP systems require pumping to remove the accumulated solids. Examples and illustrations of STEP system installations are provided below in Figures 2-3 to 2-6. Pahala WWTP Revised PER Section 2 2-5 Figure 2-3. STEP Section View Figure 2-4. Orenco PrelosTM System Tanks in the Field Pahala WWTP Revised PER Section 2 2-6 Figure 2-5. Orenco STEP System Pump and Screen Figure 2-6. Orenco PrelosTM System Cutaway Advantages of STEP systems include: · Solids and grease are retained in the tank at the home. Pahala WWTP Revised PER Section 2 2-7 · Minimal infiltration and inflow (I/I) concerns. · The small-diameter sewer mains can be installed at minimum depth of cover and can follow the surface terrain, reducing initial cost. Disadvantages of STEP systems include the following: · Homeowner still has a septic tank to maintain. · Filter screens need to be inspected and cleaned periodically (annually or biannually recommended). · Septic tanks need to be pumped out periodically (typically every 3 to 5 years). The Pahala STEP collection system would align with the County sewer system layout depicted in Figure 2-1 and consist of PVC schedule 40 pipe ranging from 2-inch to 6-inch in diameter. Projected to service 174 parcels, this collection system would consist of approximately 4,200 linear feet of 2- inch diameter, 3,400 linear feet of 3-inch diameter, 3,500 linear feet of 4-inch diameter, and 2,000 linear feet of 6-inch diameter pipe. 2.4 Reuse Existing Collection System In 2004, C. Brewer Company contracted M&E Pacific to perform a sewer system evaluation for the town of Pahala. The results of this investigation determined that the existing sewer lines and manholes do not conform to the County sewer design standards. The existing sewer system was not constructed in the streets, but instead runs through easements located on private properties, with many collection lines running adjacent to or beneath the houses. The results of a smoke test performed during the 2004 sewer system evaluation identified 14 locations of line breaks and/or pipe defects and 7 household units with defective sewer vents. In addition, the existing sewer system is over 80 years old, long surpassing its expected lifespan, and will require extensive repair and rehabilitation if chosen to be reused. The recommended alternative, which received overwhelming support from Pahala voters in 2004, consists of constructing a new sewer system in the streets to meet the County sewer standards and to allow the collection system to be owned and operated by the County (M&E Pacific, December 2004). Nearly 20 years have passed since the 2004 study was completed. In order to reuse the existing collection system into the future an updated condition assessment study is recommended to better identify system deficiencies. Substantial improvements will likely be necessary due to the age of the system. Reusing the existing collection system would require constructing the Phase 1 collection system project described above to tie into the WWTP and close the LCCs. 2.5 Cost Evaluations A summary of the capital costs and life cycle costs for the alternative collection systems are presented in Table 2-3 for comparison. The life cycle costs consist of the 30-year net present value of the capital and O&M costs. Additional detail is included as Appendix A. Pahala WWTP Revised PER Section 2 2-8 Table 2-3. Collection System Cost Summary Collection System Option Capital Cost Annual O&M Cost Life-Cycle Cost a New gravity sewers in streets $21.0 million $40,000/year $22.0 million STEP system $18.6 million $129,000/year $22.2 million Reuse existing collection system $7.3 million $120,000/year $10.2 million a See section 7.2.3 for life-cycle cost assumptions. The life-cycle costs are shown graphically in Figure 2-7. Reusing the existing collection system has the lowest capital and life-cycle costs. Figure 2-7. Life-Cycle Cost Comparison of Collection System Alternatives 2.6 Recommendation Although reusing the existing collection system appears to incur lower life-cycle costs than the other alternatives it is not recommended for implementation. Due to the advanced age of the existing collection system the option would incur substantial financial and other risks to the County: · The piping is at the end of its useful service life, and catastrophic failures are likely to increase in frequency, creating increased risk to public health and the environment. · Most of the system is located in backyard easements, making it difficult to access and maintain. · System expansion to accommodate sewering additional areas of the town (in accordance with the Kau CDP) would not be feasible. · The option does not address the AOC requirement to connect additional properties, that are currently not connected to the collection system, to the WWTP. $21,010,000 $18,608,000 $7,330,000 $942,000 $3,603,000 $2,825,000 $0 $4,000,000 $8,000,000 $12,000,000 $16,000,000 $20,000,000 $24,000,000 New Gravity Collection STEP Collection Reuse Existing CollectionLifecycle Cost (30-year NPV)Capital Cost O&M Cost Pahala WWTP Revised PER Section 2 2-9 A new conventional gravity sewer collection system constructed in the streets is a viable solution to meet the wastewater collection needs of the town of Pahala and is recommended for implementation. Section 3 Flow and Load Projections This section summarizes the wastewater flow and load projections for the new Pahala WWTP. 3.1 Flow Projections Based on City and County of Honolulu Standards HAR section 11-62-24(b) requires Counties to use their adopted wastewater flow standards to develop flow projections for WWTPs. Counties are to use the City and County of Honolulu (CCH) flow standards if they have not adopted their own standards. The County of Hawaii has not adopted its own flow standards, so wastewater flow projections were developed using the current CCH (2017) wastewater standards. Table 3-1 summarizes the flow projections. Table 3-1. Pahala WWTP Flows Based on 2017 CCH Standards Description Value Average dry weather flow 190,000 gpd Peak day dry weather flow 369,000 gpd Peak day wet weather flow a 665,000 gpd Peak hour wet weather flow 625 gpm (900,000 gpd) a Peak day wet weather flow is not part of the CCH standards but is an important WWTP design parameter. Peak day wet weather flow estimate was developed using an appropriate peaking factor. The CCH standards were established for a major metropolitan area that includes vast areas of residential, commercial, and industrial development, with significant proportions of service areas near sea level elevations. Wastewater generation rates are generally lower in rural areas than in urban areas. The County’s experience with the CCH flow standards on other projects (e.g., Honokaa WWTP) has illustrated that the standards are very conservative for small rural communities located at higher elevations on Hawaii Island. Therefore, the current wastewater standards based on urban Honolulu are likely overly conservative for rural communities like Pahala. 3.2 Reduced Flows Based on Potable Water Records The amount of wastewater generated within a residence will not exceed the amount of potable water used by the occupants. Therefore, potable water use records can be used to estimate wastewater generation rates within existing communities where no combined sewers are present. The County of Hawaii Department of Water Supply (DWS) provided potable water use records for the parcels located within the service area from January 2015 through June 2021. Analysis of the potable water use records indicates that a 40,000 gpd monthly wastewater generation rate would reflect the current needs of the service area. Using a 2.5 peaking factor to estimate the maximum wastewater flow into the collection system results in a maximum wastewater flow of 100,000 gpd. Pahala WWTP Revised PER Section 3 3-2 3.2.1 Dry Weather I/I Allowance Groundwater can infiltrate into wastewater collection systems during dry weather, increasing flows to the WWTP. The 2017 CCH standards specify a dry weather infiltration and inflow (I/I) allowance of 35 gallons per capita per day (gpcd). The previous CCH standards (dated 1993) specified a dry weather I/I allowance of 5 gpcd for properties located above the groundwater table. Through the County’s experience at Honokaa evaluating dry weather I/I for a rural collection system located in Hawaii Island’s well-drained geology, at elevations hundreds of feet above sea level and a significant distance from the shoreline, we conclude that continued use of the 1993 standard for dry weather I/I is appropriate for Pahala and using the 2017 standard would be overly-conservative. 3.2.2 Wet Weather I/I Allowance The 2017 CCH standards specify a wet weather I/I allowance of 3,000 gallons per acre per day (gpad). Due to larger parcels within the Pahala service area, wet weather I/I estimates are modified as permitted by the 2017 CCH standards. The modified flows are based on a 50-foot-wide corridor of sewer laterals from existing or assumed building foundations on the property. These assumptions significantly reduce the wet weather I/I estimates for the collection system. Evaluating the effluent flow records at the Honokaa WWTP provides an appropriate analysis of the wet weather peaking factors expected at the Pahala facility. The results of the Honokaa WWTP effluent flow analysis have determined that a peak day wet weather peaking factor of 6.5 is recommended for the Pahala WWTP design. 3.2.3 Reduced Flow Projections Accurately quantifying flow projections for the Pahala community is necessary to design an appropriately sized wastewater treatment and disposal facility. The WWTP design will provide sufficient capacity for the existing parcels within the service area, including newly accessible parcels, reflecting current development. This will allow the County to close the LCCs. Furthermore, the design will provide sufficient area within the WWTP site for future expansion. Table 3-2 provides a summary of the calculated WWTP capacities for the reduced flow projections and for the flow projections for future development based on the 2017 CCH Standards. Table 3-2. Pahala WWTP Calculated Flow Capacity Description Reduced Flow Projections Flow Projections Based on 2017 CCH Standards Base sanitary flow 40,000 gpd 119,000 gpd Peak hour sanitary flow 100,000 gpd (PF=2.5) 298,000 gpd (PF = 2.5) Dry weather I/I 8,000 gpd 71,000 gpd Wet weather I/I 210,000 gpd 533,000 gpd Average dry weather flow 48,000 gpd 190,000 gpd Peak day dry weather flow 108,000 gpd 369,000 gpd Peak day wet weather flow 312,000 gpd (PF=6.5) 665,000 gpd (PF=3.5) Peak hour wet weather flow 221 gpm (318,000 gpd) 625 gpm (900,000 gpd) Pahala WWTP Revised PER Section 3 3-3 HAR 11-62-23.1(i) requires the initiation of a facility planning process when the actual wastewater flows reach 75 percent of the design capacity of the WWTP, and implementation of the facility plan must be initiated when actual wastewater flows reach 90 percent of the design capacity. In anticipation of future development, we recommend the WWTP design be rated to treat an average dry weather flow of 95,000 gpd (approximately twice the projected average dry weather flow) to avoid the potential of having to initiate a facility plan shortly after the project is constructed. Note that the biological processes in the mechanical WWTP will need to be sized to treat the peak day dry weather flow of 108,000 gpd, not the average dry weather flow. The proposed WWTP design capacity is based on actual water use data to establish wastewater generation rates, and rational assumptions to establish I/I allowances, and we believe it is appropriate for the existing conditions, while providing limited capacity for growth. Table 3-3 presents the recommended design capacity for the reduced flow projections. Table 3-3. Recommended WWTP Capacity Description Value Average dry weather flow 95,000 gpd Peak day dry weather flow 108,000 gpd Peak day wet weather flow 312,000 gpd Peak hour wet weather flow 318,000 gpd (221 gpm) 3.2.4 Flow Variance The County applied to DOH for a variance from HAR section 11-62-24(b) based on the above analysis. DOH granted the variance on January 26, 2022 (see Appendix B), and it must be renewed every five years. The variance contains the following conditions: 1. As a minimum, the Pahala Wastewater Treatment Plant (WWTP) shall be designed using an average dry weather flow of 95,000 gallons per day. 2. Plans for the proposed Pahala WWTP shall be designed in accordance with applicable requirements of Chapter 11-62, HAR and be submitted to the Wastewater Branch for review and approval. In addition, the WWTP shall be approved in writing before it may be used. 3. There is no automatic renewal. Should the applicant wish to renew this variance application, the applicant must submit an Application for Variance for renewal, 180 days prior to expiration date. 3.3 Influent Characteristics The properties within the existing service area are primarily residential, but do include commercial, ,multi-family, and industrial zoned parcels. The wastewater characteristics of the WWTP influent are assumed to be similar to typical domestic wastewater. Table 3-4 provides a summary of the assumed influent characteristics. Pahala WWTP Revised PER Section 3 3-4 Table 3-4. Summary of Assumed Influent Characteristics Parameter Value 5-day biochemical oxygen demand (BOD5) 300 mg/L Total suspended solids (TSS) 300 mg/L Total nitrogen 40 mg/L Total phosphorus 7 mg/L Source: Crites and Tchobanoglous, 1998. 3.4 Influent Mass Loads Table 3-5 summarizes the projected loads to the WWTP, based on the proposed peak day dry weather capacity of 108,000 gallons per day and the influent characteristics presented above. Table 3-5. Projected Peak Dry Weather Day Influent Mass Loads Description Value BOD5 270 lbs./day TSS 270 lbs./day Total nitrogen 36 lbs./day Total phosphorus 6 lbs./day Section 4 Effluent Management Options and Regulatory Requirements Effluent management options are evaluated in this section, followed by an assessment of regulatory requirements for the recommended effluent management system. 4.1 Effluent Management Options Effluent management options are evaluated below. 4.1.1 Ocean Discharge Ocean discharge of treated effluent is not considered a viable option for this small community due to the long distance to the shoreline (approximately 3 miles), high cost to construct an outfall, stringent receiving water quality standards, high receiving water monitoring cost, and difficulty and length of time required to secure the required permits. The coastal waters in the Pahala area are classified as “AA” marine waters by DOH. HAR 11-54 does not allow zones of mixing in waters up to a distance of 300 meters (one thousand feet) offshore if there is no defined reef area and if the depth is greater than 18 meters (ten fathoms). The water quality criteria for nutrients for Class AA embayments are listed in Table 4-1. If a mixing zone is not provided, then a WWTP discharging to the coastal waters would be required to treat water to meet the applicable water quality criteria. Treatment to the specified levels is not feasible with current technologies. Therefore, ocean discharge is not feasible. Table 4-1. Nutrient Water Quality Standards for Class AA Embayments Parameter Geometric mean not to exceed Not to exceed the given value more than 10% of the time Not to exceed the given value more than 2% of the time Total nitrogen 200 µg/L 350 µg/L 500 µg/L Ammonia nitrogen 6 µg/L 13 µg/L 20 µg/L Nitrate + nitrate nitrogen 8 µg/L 20 µg/L 35 µg/L Total phosphorus 25 µg/L 50 µg/L 75 µg/L 4.1.2 Subsurface Disposal via Injection Wells Per Hawaii Administrative Rules (HAR), Title 11, Chapter 23, disposal to groundwater via an injection well is not allowed mauka of the State of Hawaii Department of Health (DOH) Underground Injection Control (UIC) line. Since the town of Pahala is located mauka of the UIC line, an injection well is not a viable option. In addition, per Environmental Protection Act 131, DOH is prohibited from issuing permits “for the construction of sewage wastewater injection wells unless alternative wastewater disposal options are not available, feasible or practical”. Therefore, subsurface disposal via injection wells is not feasible. Pahala WWTP Revised PER Section 4 4-2 4.1.3 Water Recycling An irrigation assessment was prepared to assess the viability of water recycling as the primary effluent management system, assuming the recycled water would be used to irrigate macadamia nut trees. Figure 4-1 presents a summary of the assessment, which shows there is typically no irrigation demand for six months of the year due to high rainfall. In addition, the DOH requires that all water recycling programs have a 100 percent backup disposal system in place to handle flow that does not meet recycled water quality standards or when recycled water supply exceeds demand. Therefore, water recycling is not a viable primary or sole effluent management strategy for the community at this time. However, water recycling treatment, storage, and distribution systems could be added in the future. Figure 4-1. Irrigation Demand Assessment 4.1.4 Slow Rate Land Treatment A potential project effluent management concept consists of Type 1 slow rate land treatment, which involves irrigation of vegetation with effluent. Type 1 slow rate land treatment differs from water recycling in that it is a disposal method, and effluent is typically applied in excess of the irrigation needs of the vegetation. The potential effluent management concept calls for removal of the existing macadamia nut trees at the site, grading the site to contain all precipitation, and planting native Hawaiian trees or replacement macadamia nut trees within the effluent disposal area. Effluent would be applied using surface (flood) irrigation techniques. The effluent from the Pahala WWTP would be applied to land within the 14.9-acre WWTP parcel. Approximately 10 acres of the site is available for slow rate land treatment. The soil infiltration rate is a key factor in determining the land area requirements for a slow rate land treatment system. ASTM 0 1 2 3 4 5 6 7 8 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DECInches of WaterMonth Precipitation Evapotranspiration Irrigation Requirement Pahala WWTP Revised PER Section 4 4-3 D3385 double ring infiltrometer testing was conducted in January 2021 to assess the infiltration rate of the site soils. A total of 15 tests were conducted within the slow rate land treatment area; the results are summarized in Table 4-2. Table 4-2. Pahala WWTP Soil Infiltration Test Results Test Location Test Depth (feet) Geologic Unit Infiltration Rate (inches/hour) TP-1 1.2 Fill/tephra 4.2 TP-2 2.5 Weathered tuffaceous deposits 2.8 TP-3 2.0 Weathered tuffaceous deposits 4.5 TP-4 2.2 Fill/tephra 4.3 TP-5 1.3 Weathered tuffaceous deposits 0.6 TP-6 1.5 Fill/tephra 1.2 TP-7 3.8 Weathered tuffaceous deposits 4.1 TP-8 2.8 Weathered tuffaceous deposits 1.9 TP-9 1.0 Fill/tephra 1.0 TP-10 4.0 Weathered tuffaceous deposits 3.8 TP-11 1.0 Fill/tephra 2.6 TP-12 1.0 Fill/tephra 1.9 TP-13 1.2 Fill/tephra 1.3 TP-14 1.0 Fill/tephra 2.9 TP-15 1.0 Fill/tephra 1.4 Average: 2.6 The results of the infiltration rate investigation confirms that the site will provide adequate land area to meet the both the current and future needs of the community using standard slow rate land treatment design criteria. A water balance was prepared for the reduced wastewater flow projections, assuming 10 acres of the site are used for slow rate land treatment. The site water balance includes effluent applied to the site, precipitation on the site, and anticipated evapotranspiration by the trees. Table 4-3 summarizes the results of the water balance. Pahala WWTP Revised PER Section 4 4-4 Table 4-3. Pahala WTTP Effluent Disposal Water Balance Month Days Effluent Application a Average Precipitation b (inches) Evapotranspiration c (inches) Percolate d (inches) (mgal) (inches) Jan 31 2.9 10.8 5.98 3.9 13.0 Feb 28 2.7 9.8 3.77 3.9 9.7 Mar 31 2.9 10.8 5.45 4.2 12.1 Apr 30 2.9 10.5 3.23 4.9 8.9 May 31 2.9 10.8 1.94 5.3 7.5 Jun 30 2.9 10.5 1.56 5.6 6.4 Jul 31 2.9 10.8 3.27 6.1 8.1 Aug 31 2.9 10.8 3.08 5.9 8.0 Sep 30 2.9 10.5 3.60 5.3 8.8 Oct 31 2.9 10.8 3.98 4.8 10.0 Nov 30 2.9 10.5 6.70 4.0 13.2 Dec 31 2.9 10.8 5.82 4.2 12.5 Totals 365 34.7 127.7 48.4 58.0 118.0 a At ADWF capacity = 95,000 gpd. b From Climatography of the United States No. 20, Monthly Station Climate Summaries, 1971-2000, Hawaii. National Oceanic and Atmospheric Administration, April 2005. c Pan evaporation from Pan Evaporation: State of Hawaii, 1894-1983. Report R74. State of Hawaii Department of Land and Natural Resources, August 1985. Crop coefficients for macadamia nuts from Irrigation Water Requirement Estimation Decision Support Systems (IWREDSS) to Estimate Crop Irrigation Requirements for Consumptive Use Permitting in Hawaii. August 2013. State of Hawaii Commission on Water Resources Management, August 2013. d Effluent application plus precipitation minus evapotranspiration. As shown in the table, effluent application and precipitation are expected to exceed the evapotranspiration of the macadamia nut crop during all months of the year. The maximum percolate volume shown in the table assumes all precipitation percolates into the soil. An annual nutrient balance was also prepared for the site, based on the water balance shown in Table 4-3. The orchard of mature macadamia nut trees is expected to use up to 400 lbs. of nitrogen per acre per year (University of Hawaii Agricultural Experiment Station, January 1959). The effluent will supply approximately 289 lbs./acre/year of total nitrogen, assuming an effluent concentration of 10 mg/L. Although the nitrogen uptake of the orchard is expected to be greater than the total mass of nitrogen applied by the effluent, the predominant nitrogen species in the effluent is expected to be nitrate, which is soluble and readily transportable through the soil profile. The trees will only be able to use the nitrate contained within water that is transpired. The percolate volume shown in Table 4-3 is expected to contain approximately 8.5 mg/L of nitrogen as nitrate, because soil denitrification losses of 15 percent can be expected. Therefore, the land treatment system is expected to remove approximately 21 percent of the total nitrogen applied to the site with WWTP effluent. 4.1.5 Subsurface Drip Irrigation Disposal Another effluent management concept is to retain the existing site topography along with the macadamia nut tree orchard and use subsurface drip irrigation technology to apply the effluent. Subsurface drip irrigation would be used to apply effluent to the existing macadamia nut trees within the effluent disposal area. The use of subsurface drip irrigation technology to disperse effluent at the Pahala WWTP Revised PER Section 4 4-5 site will allow the County to retain the existing mature macadamia nut trees, and will significantly reduce the amount of clearing, grubbing, and grading required to construct the facility. In addition, retaining the existing mature orchard is expected to effectively block views of the facility from both the Hawaii Belt Road and Maile Street. Drip irrigation technology has evolved to the point where non-clog emitters are available for subsurface applications of effluent. Non-clog subsurface emitters decrease the potential for the irrigation components to be clogged by roots. Figure 4-2 illustrates the subsurface drip concept. Drip tubing with integral emitters is buried 6 to 9 inches below ground. Effluent emitters are typically designed to operate at a flow rate of 1 gallon per hour (gph) and are typically spaced every 2 feet along a drip line. Pressure compensating drip systems typically operate under pressures ranging from 10 to 45 pounds per square inch (psi). Figure 4-2. Subsurface Drip Irrigation Concept (Courtesy of Geoflow, Inc.) 4.1.5.1 Operation and Maintenance (O&M) Needs Subsurface drip irrigation technology incurs greater operation and maintenance than a surface irrigation system. The County will need to periodically flush the drip lines to remove debris. As described below, a significant number of drip lines will be necessary to accommodate peak flow rates. In addition, periodic chlorination will be required to remove biological growth from the drip lines. These O&M tasks will need to be completed on a regular schedule, because the drip system will be buried and not readily accessible or observable. During periods of dry soil conditions, the County will need to inspect the orchard for patches of wet soil that would indicate a localized failure that requires repair. Flow and pressure monitoring will also be useful tools for validating the status of the subsurface drip system. The land treatment area would be divided into multiple irrigation zones, allowing a zone to be taken out of service for maintenance purposes. A fence will be constructed around the site to deter entry by humans and ungulates. 4.1.5.1.1 Stormwater Runoff Considerations The subsurface drip system would slowly disperse effluent 6 to 9 inches below the ground surface, therefore operating as a subsurface disposal system similar to a leach field. Effluent is not intended to surface with a properly operating subsurface drip system. Precipitation falling on the site will either percolate into the soil or run off as surface drainage. The water balance shown in Table 4-3 assumes all precipitation percolates into the site soil, which is a conservative assumption. The amount of runoff from the site will vary with the storm intensity; precipitation rates in excess of the infiltrative capacity of the site soils will result in runoff. The existing site is graded to drain to a culvert under the Hawaii Belt Road at Maile Street. The implementation of a subsurface disposal system will Pahala WWTP Revised PER Section 4 4-6 allow the existing grading to be retained, because stormwater runoff will not come into contact with, and therefore will not contain, effluent. 4.1.6 Leach Field A leach field could potentially be constructed for subsurface disposal of treated effluent. Preliminary assessment of the concept based on the site soil characteristics indicate approximately 10,000 and 20,000 linear feet of drain field trench would be required to accommodate the anticipated flows for the phase 1 and phase 2 collection system, respectively. It would be difficult to evenly distribute effluent throughout a drain field of this size. In addition, DOH regulations require a redundant drain field for subsurface disposal systems, making this option expensive to implement. This option is considered impractical for the community. 4.1.7 Existing Cesspool Conversion A previous study (SSFM, July 2007) suggested that the existing LCC located on the County-owned parcel TMK 9-6-002:024 could be converted to a seepage pit that would be regulated by DOH as an injection well. HAR 11-23-07 allows injection wells located mauka of the UIC line that were in existence prior to July 6, 1984 to continue to operate. However, the flow to the wells cannot increase, nor can a new well be constructed. Therefore, the earlier plan to convert the existing LCC to a seepage pit is not feasible for the following reasons: · Closing LCC No. 2 that is located on private property would not be allowed, as it would increase the flow to LCC No. 1 (converted to a seepage pit that is regulated as an injection well) that is located on County property. · The capacity, structure, and condition of the existing LCC No. 1 is not known. The LCC could either be a lava tube or a large conventional cesspool. A geotechnical investigation conducted on the site to depths of 30 to 35 feet did not reveal the presence of lava tubes (Masa Fujioka & Associates, January 9, 2007), therefore it is likely a large conventional cesspool. The County attempted to determine the structure and condition of the LCC via closed circuit TV inspection but could not ascertain either due to technological limitations. It is not known if the LCC could accommodate the flow from the existing service area if LCC No. 2 is closed. · HAR 11-62-25 requires new and proposed effluent disposal systems to have a backup disposal system capable of handling the peak flow. A second seepage pit cannot be constructed to comply with the regulatory requirement because the site is located mauka of the UIC line. If the existing seepage pit were to fail, then a replacement cannot be constructed. · The Kau Community Development Plan (CDP) requires the County to provide for eventual construction of sewers throughout the community. Providing sewers for the entire community will increase wastewater flows. Increasing flow to the existing LCC (converted to a seepage pit) would not be allowed. Therefore, the use of the existing LCC as a disposal system could prevent the County from providing the community’s desired future wastewater needs. · The current AOC requires connection of 65 additional properties. This would increase the flow to the existing LCCs (converted to a seepage pit). Increasing flow to the existing LCC (converted to a seepage pit) would not be allowed. For these reasons, converting the existing LCCs to a seepage pit is not considered to be a feasible option. 4.1.8 Recommendation The results of the effluent management investigation have determined that a subsurface drip irrigation system is the recommended method of effluent disposal for the Pahala WTTP. Pahala WWTP Revised PER Section 4 4-7 Recommended design criteria for the subsurface drip irrigation system are presented in Table 4-4. The disposal system will be sized to handle the peak day wet weather flow of 312,000 gpd. An irrigation equalization and control tank are proposed to equalize higher peak flows and to allow discrete dosing of the orchard in irrigation zones; constant application of water would be detrimental to the health of the trees. HAR 11-62 requires a fully redundant subsurface disposal system. The design criteria shown in Table 4-4 are based on providing a subsurface drip system that is two times larger than needed in order to satisfy the HAR 11-62 requirement for redundancy. The drip system will be divided into two separate systems so that the peak day wet weather flow can be disposed on the site using one system while the second system is out of service for maintenance. Table 4-4. Recommended Subsurface Drip Design Criteria Description Value Average dry weather flow 95,000 gpd (66 gpm) Peak day wet weather flow 312,000 gpd (217 gpm) Irrigation equalization and control tank volume 20,000 gallons Land treatment area 10 acres Subsurface drip emitters 1 gallon per hour, pressure compensating Number of emitters needed for peak day wet weather flow 13,000 emitters Number of systems 2 (1 active, one redundant) Number of emitters provided to provide 2x redundancy 26,000 total emitters Emitter spacing 2 feet Drip line length per system 26,000 feet Total drip line length 52,000 feet Drip line depth 6 to 9 inches Number of irrigation zones 6 (3 per system) Length of drip line per zone 8,667 feet Flow per irrigation zone 72 gpm Irrigation system monitoring Flow meter(s) and pressure indicators Figure 4-3 provides a conceptual view of the recommended Pahala subsurface drip system. The subsurface drip lines are to be located between the existing row of trees and spaced to disperse effluent evenly throughout the orchard. During high flow conditions the irrigation control system will open multiple irrigation zones to accommodate the disposal needs. Additional drip lines will need to be added when the WWTP capacity is expanded. The minimum spacing between drip lines is 2 feet, so there will be sufficient space between the initial drip lines to add additional drip lines as part of future expansion project(s). Pahala WWTP Revised PER Section 4 4-8 Figure 4-3. Conceptual Subsurface Drip Irrigation System at Pahala 4.2 Treatment Requirements The DOH regulates subsurface drip irrigation disposal as “land disposal” per Hawaii Administrative Rules (HAR) 11-62. Table 4-5 lists the applicable effluent requirements for land disposal applicable to the project that were in effect at the time this report was prepared. Table 4-5. Applicable HAR 11-62 Land Disposal Requirements Description Value HAR Reference BOD5 30 mg/L monthly average 60 mg/L peak 11-62-26 TSS 30 mg/L monthly average 60 mg/L peak 11-62-26 Disinfection Except for subsurface disposal systems, continuous disinfection of the treated effluent shall be provided 11-62-24 Setbacks Treatment units shall be not less than 25 feet from property lines nor less than 10 feet from any building 11-62-23.1 Public accessibility control 6-foot-high fence surrounding treatment units 11-62-08 Section 5 Wastewater Treatment Evaluations This section presents the evaluations conducted in development of the proposed WWTP. 5.1 Preliminary Treatment The preliminary treatment system will include influent flow measurement, influent sampling equipment, screening, and grit removal. 5.1.1 Influent Flow Measurement Influent flow measurement is recommended to allow assessment of flows and loads to the biological treatment process, and to assess the biological treatment process performance. A Parshall flume will be provided upstream of the screening system to continuously record influent flow rates. Parshall flumes work well for influent measurement because the flume can operate in an open-channel configuration, can accommodate wide ranges of flows, and is self-cleaning. A straight approach length of at least 20 times the flume throat width will be provided upstream of the flume to provide favorable hydraulic conditions. 5.1.2 Influent Flow Sampling An automatic refrigerated composite sampler is recommended to allow influent composite samples to be collected. Influent composite samples, when combined with influent flow measurement, can be used to calculate influent mass loading rates to the WWTP to assess the treatment performance and optimization of aeration rates in the biological treatment process. Periodic influent sampling is also recommended to monitor for changes in the influent characteristics. 5.1.3 Screening Screening is recommended to protect the downstream system operations from large objects, debris, wipes, and rags that can be present in wastewater. The industry trend is towards finer screening systems that remove greater amounts of debris from the waste stream; screens with 6-millimeter (mm) (¼-inch) openings are frequently used for activated sludge treatment systems. Finer screens are used upstream of membrane bioreactors to remove hair that can foul the membranes. The screenings volume at the Pahala WWTP is expected to be small, subsequently screenings disposal is expected to be infrequent; weekly at most. Therefore, the screenings must be washed of organic debris to prevent the accumulation of nuisance odors and flies in the screenings barrel or bag between screening disposal events. 5.1.3.1 In-channel cylindrical screen We recommend an in-channel cylindrical screen for this installation. The in-channel cylindrical screen combines screening, screenings washing, dewatering, compacting, and bagging/disposal within a single unit. The screening portion consists of an inclined screen basket inserted into the wastewater channel. The screening basket can consist of bars, perforated plates or sieves, depending on the application and clear opening required. The controls can be set to allow a mat to build up on the screening surface, allowing finer screening of the wastewater. Controlled by head loss, a rake arm starts rotating within the screen basket, pushing the screenings off the rake and into a perforated screenings hopper located at the screen’s central axis. A shafted auger along the screen axis Pahala WWTP Revised PER Section 5 5-2 conveys the screenings from the hopper through an inclined tube, which dewaters and compacts the screenings. The tube includes a perforated dewatering section. The discharged screenings are about 40-percent dry and can be discharged into a bin or directly into a bagging system. Figure 5-1 illustrates the process. Manufacturers include Lakeside and Huber. The key benefit to this system is the integrated screenings washing system, minimizing additional screenings handling and odor potential. For this installation, the headworks will include one in-channel cylindrical screen, plus a bypass channel with manually cleaned bar rack. Figure 5-1. In-Channel Cylindrical Screen 5.1.4 Grit Removal Grit is comprised of particles that are heavier than the organic biodegradable matter in wastewater. Grit particles can consist of sand, gravel, pebbles, silt, cinders, ground bone, eggshells, coffee grounds, and other materials. Grit in the wastewater collection and treatment system causes abrasive wear to mechanical equipment, piping, and appurtenances. Grit can also form deposits in pipelines, channels, and tanks, which reduces hydraulic capacity and can damage equipment. Removal of grit is very important to help prevent wear to downstream equipment, costly service interruptions and repair. Grit removal systems usually are placed between screening and primary treatment. At this point, the largest materials have been removed by the screens and will not interfere with grit handling equipment. There are several types of grit removal methods, including induced vortex grit removal, aerated grit chambers, and lamella plate settlers. The type of grit removal chosen is mainly dependent on the size of the incoming grit particles and the desired capture rate. Removed grit must be washed, dewatered, and disposed. 5.1.4.1 Induced Vortex Grit Removal Historically, vortex grit removal or the circular grit chamber has been the most widely used method for grit removal in the U.S. Vortex grit removal relies on the principle that grit has a greater specific gravity than organic matter. Pahala WWTP Revised PER Section 5 5-3 There are two configurations of vortex grit removal systems: a sloped bottom unit and a flat bottom unit. The sloped bottom unit relies on particle settling to remove grit. Flow enters the grit chamber tangentially to provide the longest flow path around the inside of the circular grit chamber. This longer flow path is designed to achieve a sufficient retention time to allow grit to settle. The sloped bottom funnels the settled grit into a hopper below the basin. A sloped bottom vortex grit unit cross section is shown in Figure 5-2. Figure 5-2. Sloped Bottom Vortex Grit Removal Cross Section The flat bottom vortex system relies on hydraulic removal instead of specific gravity alone to remove grit from the wastewater stream. Flat bottom vortex systems use two paddles within the interior of the grit chamber that induce a toroidal flow pattern to move grit along the bottom towards the center. Once collected at the center of the grit chamber, a propeller forces excess grit down into the hopper. A flat bottom PISTA® Grit unit is shown in Figure 5-3. Figure 5-3. Flat Bottom PISTA® Grit Removal 5.1.4.2 Vortex Grit Removal Capture Rate In Brown and Caldwell’s experience it is necessary to de-rate vortex type grit removal units by a factor of 50 percent of the advertised capacity to achieve satisfactory performance, due to the short Pahala WWTP Revised PER Section 5 5-4 detention time in the chamber. At large flow rates, the small-chambered vortex type units tend to re- suspend smaller grit particles which become a problem for downstream processes. Table 5-1 lists some advantages and disadvantages of the vortex type grit removal. Table 5-1. Induced Vortex – Advantages and Disadvantages Advantages Disadvantages Low maintenance Re-suspends/low capture rate of fines Low headloss Poor capture efficiency Small footprint 5.1.4.3 Aerated Grit Removal Aerated grit chambers are tanks that function specifically to remove inorganic solids from the wastewater stream. Aerated grit tanks are designed to induce sufficient vertical velocity in order to separate organic and inorganic solids. In theory, inorganic solids have a higher specific gravity than organic solids, and therefore require higher vertical velocities to keep them in suspension. Air diffusers placed near one longitudinal tank wall induce a roll in the contents of the grit tank. This roll creates maximum velocities near the walls and lower velocities at the surface and bottom of the tank. The lower transverse horizontal velocities allow inorganic particles to settle out and be transported to the grit hopper by shear-induced currents. Aerated grit chamber design is based on providing sufficient hydraulic detention time during peak wet weather flow (PWWF) conditions. In Brown and Caldwell’s experience it is necessary to provide at least 10 minutes of detention time to achieve satisfactory grit removal. Aerated grit tanks can provide excellent grit removal with minimal headloss, but the chambers themselves require a larger footprint than induced vortex systems. Proper operation of aerated grit tanks can be difficult under varying hydraulic loads due to the need to make fine adjustments to the air diffusers. Figure 5-4 illustrates the particle settling action of an aerated grit chamber. Figure 5-4. Aerated Grit Removal Schematic Pahala WWTP Revised PER Section 5 5-5 Table 5-2 lists some advantages and disadvantages of aerated grit chambers. Table 5-2. Aerated Grit Removal – Advantages and Disadvantages Advantages Disadvantages Low headloss Large footprint Once airflow is dialed in, the maintenance is low Requires fine tuning diffuser airflow for optimal performance Effective removal of fines High capital cost Provides additional aeration; “freshens” sewage prior to primary clarification. Reduces denitrification in primary clarifiers. High O&M cost due to blowers A variation of aerated grit removal technology that can be used in small WWTPs like Pahala is an aerated grit trap. A small, aerated tank is provided to allow grit to settle. Aeration is provided to maintain organic solids in suspension and to “freshen” the influent. Accumulated grit is periodically removed using a Vactor truck. 5.1.4.4 Lamella Grit Removal This proprietary technology from Eutek, called the HeadCell, consists of sloped trays stacked in deep tanks. Flow enters the tanks tangentially and establishes a vortex flow pattern. Solids settle onto each plate and fall toward an opening at the center of each plate. The grit collects at the cone shaped bottom of the tank where it is pumped to be washed and dewatered. Effluent flows out of the trays, over a weir, and into an effluent trough. Grit capture is all done hydraulically and there are no moving parts. The headloss through each HeadCell is around one foot. HeadCells can be sized to provide up to 50 mgd of capacity within a single unit. With the stacked tray design, the HeadCells can achieve a 95 percent capture rate of grit 75 microns and larger. The multiple trays provide a large surface area for settling multiple size particles. The treatment capacity of the HeadCell is greater than other technologies with the same footprint. Figure 5-5 is an illustration of a section cut through the HeadCell process. Pahala WWTP Revised PER Section 5 5-6 Figure 5-5. Headcell Process Schematic Table 5-3 lists advantages and disadvantages of the Headcell. Table 5-3. Lamella Plate Settling/HeadCell – Advantages and Disadvantages Advantages Disadvantages Effective removal of fines High capital cost Small footprint Short history of installations No moving parts Low operating cost 5.1.4.5 Grit Particle Size Considerations Most grit technologies and literature assume that grit is a clean sand or silica particle with a specific gravity of 2.65. In reality, grit particles are often coated with fats, grease, and organic material that reduce the particle’s specific gravity. Grit particles with lower specific gravity have lower settling velocities, behaving like lighter and smaller grit particles. The sand equivalent size (SES) is the size of a clean sand sphere that exhibits the same settling velocity as the coated grit particles. For example, a grease coated grit particle with a physical size of 200 microns may settle and behave like a clean particle with an SES of 150 microns. 5.1.4.6 Efficiency comparison Each of the alternatives claims a minimum particle size and capture rate. These claims are based on the ideal, clean grit particle. As previously discussed, in reality grit particles are coated with fats and grease and do not exhibit the behavior of ideal grit particles. The capture rates have to be derated to reflect the SES of the particles. Table 5-4 compares the claimed minimum particle size captured of the alternatives discussed. Pahala WWTP Revised PER Section 5 5-7 Table 5-4. Grit Capture Size Comparison Alternative Targeted Particle Size Induced Vortex 105 µm Aerated Grit Removal 105 µm HeadCell 75 µm The Headcell is able to remove the finest particles, with up to 95 percent removal of particles with a physical size down to 75 microns. 5.1.4.7 Grit Removal Recommendation A simple aerated grit trap located downstream of the screening process is recommended for the Pahala WWTP. Accumulated grit would be periodically removed using a Vactor truck, and dried onsite in a small drying bed. The dewatered grit would be disposed at the landfill. An aerated grit trap provides adequate performance with a relatively uncomplicated process. Although a Headcell grit removal system could potentially provide a slightly increased grit capture rate, that benefit is not likely to surpass its significantly higher costs and operational complexity. The capture rate of an aerated grit trap is sufficient to protect the downstream processes recommended in this report. High levels of grit removal are particularly important for anaerobic digestors, which are not anticipated for this facility. 5.1.5 Odor Control A notorious location for foul odor is the headworks of a wastewater treatment plant. This odor is caused by hydrogen sulfide (H2S), which is formed under anaerobic conditions of the wastewater collection system. Due to H2S low solubility in wastewater, when there is an excessive concentration of H2S in the wastewater or if there is turbulence, H2S gas escapes into the atmosphere. This release produces the distinct rotten egg smell. In addition to H2S, there are other foul odorous compounds that can be released from wastewater, such as ammonia, amines, diamines, mercaptans, skatole, and organic sulfides. Treatment of foul odors can be approached in two ways: preventing odors through liquid treatment or controlling odors in the gas phase. While liquid treatment provides control of odors prior to their release, gas phase treatment involves the collection and treatment of gases once they have been released from wastewater. Treatment methods can be aimed at one type of odor or can treat a range of odors. 5.1.5.1 Granular Activated Carbon A granular activated carbon (GAC) scrubber is recommended for the Pahala WWTP headworks. A GAC scrubber passes odorous air through a bed of activated carbon, which adsorbs the odorous constituents within the pore spaces of the carbon. Chemical oxidation or reduction of some compounds can also occur. As pore spaces become occupied, efficiency degrades, and the carbon must be replaced or regenerated. Carbon is most effective on higher molecular weight molecules such as the organic sulfur compounds, which makes it the technology of choice. Package GAC scrubbers are available for small headworks and vessels can be situated vertically, horizontally, or radially to optimize footprints and reduce structure elevation profiles. Figure 5-6 illustrates the process. The County currently operates GAC scrubbers at other facilities and purchases the GAC media in bulk to reduce costs. Pahala WWTP Revised PER Section 5 5-8 Figure 5-6. Activated Carbon Scrubber (GAC) 5.1.6 Recommendation The following are recommended for the Pahala WWTP headworks: · Parshall flume influent flow measurement. · Refrigerated automatic composite sampler. · In-channel cylindrical screen with integrated washer. · Aerated grit trap. · Covered channels with foul air collection and GAC scrubber 5.2 Secondary Treatment Secondary treatment process provides BOD5, TSS, and nutrient removal via biological treatment. This section provides descriptions of various secondary treatment options including advantages, disadvantages and applicability to the Pahala WWTP. The treatment options are then screened to identify technologies for further evaluation. 5.2.1 Membrane Bioreactor (MBR) A membrane bioreactor (MBR) has the smallest footprint of the various biological treatment systems available and provides the highest quality effluent. An MBR basically combines an aeration basin with membrane filtration, eliminating the need for tertiary treatment if a very high-quality effluent is desired for water reuse purposes. Membranes provide an absolute barrier to large particles; total suspended solids (TSS) concentrations of the effluent (also known as “filtrate”) are typically less than 1 mg/L. Effluent from an MBR process can meet stringent water recycling turbidity requirements without an additional filtration process. The main difference between MBRs and other biological treatment technologies is the method of separating the bacteria from the clean water. MBRs have thin membranes with many thousands of Pahala WWTP Revised PER Section 5 5-9 micro-perforations. Depending on the manufacturer, these perforations are 0.04 to 0.2 microns (4 to 20 hundred-thousandths of a millimeter) in diameter, too small for the passage of most microorganisms or other particles present in the wastewater, but large enough to allow the passage of water molecules. Figure 5-7 is an illustration of an MBR. Figure 5-8 shows submerged MBR membranes in clean water. Figure 5-7. Membrane Bioreactor Illustration Figure 5-8. Membrane Cassettes at Johns Creek Environmental Campus, Fulton County, GA Pahala WWTP Revised PER Section 5 5-10 Important considerations of an MBR system include: · Small capacity MBRs can be purchased as a packaged treatment system. · MBRs can be designed and programmed to achieve nutrient reduction. · The membranes cost is significant and membranes must be replaced every 10 to 15 years. · Membrane fouling can occur with wastewater with high fats, oils, and grease (FOG) levels · MBRs require the use of membrane cleaning chemicals, typically sodium hypochlorite and citric acid. · The process requires a computer control system and is difficult to operate efficiently if the computer malfunctions. · The process incurs high electrical power costs, relatively high costs for cleaning chemicals, and high overall O&M costs. Highly skilled labor is required for some of the O&M tasks. The MBR process would produce an effluent that is of high quality and has a small footprint, but has high overall capital, O&M, and lifecycle costs. MBR is retained for further evaluation. 5.2.2 Sequencing Batch Reactor (SBR) Sequencing batch reactors (SBRs) are fill-and-draw systems that combine the processes of activated sludge in a single reactor. The reactor is filled with wastewater, where aeration, settling, and decanting occurs. By combining these processes, the need for secondary settling is not required. Denitrification can be achieved by incorporating an anoxic fill step in the cycle or a separate anoxic zone. A minimum of two SBR reactors are typically used for the process. SBRs are capable of producing high quality effluent and are potentially space saving in that separate secondary sedimentation is not needed. However, SBRs are operated by a proprietary computer control system, cannot be operated in manual mode, and may require influent and/or effluent equalization (and thus increasing the footprint requirements). Considering these challenges, SBRs will not be considered further. 5.2.3 Nereda (Granular Activated Sludge) Process The Nereda technology is a granular activated sludge process that utilizes proprietary granules in an SBR. Features of the process include simultaneous fill and draw, fast settling, and approximately 1/5 the footprint of traditional activated sludge systems. The process was developed in Europe and most current full-scale applications are located in Europe. In the U.S., the process is marketed by Aqua Aerobic Systems, Inc, according to the supplier website, there are currently only two full-scale operating systems treating municipal wastewater in the United States. One is a demonstration facility, and the other is a 3.6 mgd facility in Alabama that began operation in early 2020. Figure 5-9 is a conceptual illustration of the Nereda process. Due to the challenges listed for an SBR and the lack of long-term operational experience in the United States, the Nereda process is considered not appropriate for the Pahala WWTP application. Pahala WWTP Revised PER Section 5 5-11 Figure 5-9. Nereda Process Courtesy: Aqua Aerobic Systems 5.2.4 Oxidation Ditch An oxidation ditch is a variation of the complete-mix extended aeration activated-sludge process. The process generally has a long solids residence time (SRT) and high mixed liquor suspended solids (MLSS) concentration, making it resilient to upset by peak organic loads. The typical SRT for oxidation ditches ranges from 15 to 30 days, and the MLSS is generally between 2,000 and 5,000 mg/L. Oxidation ditches are often oval in shape and have been called “racetrack” reactors. The depth of the ditch typically ranges from 4 to 12 feet. Mechanical aerators in the ditch provide aeration and mixing. Strategic placement of the aerators creates aerobic and anoxic zones within the oxidation ditch, for effective nitrification and denitrification. Biological phosphorus removal is also possible. Oxidation ditches are usually preceded by preliminary treatment, such as screening and grit removal. Primary settling is typically not included upstream of oxidation ditch systems. Return activated sludge (RAS) is pumped from the secondary clarifier back into the ditch. Figure 5-10 presents a schematic of an oxidation ditch. Typically, rotating brush or disc mechanical aerators are used to move mixed liquor around the tank and to provide aeration. The aerators help mix scum into the water column for treatment. The rigorous mixing action of the mechanical aerators can generate off-spray. Oxidation ditches are not available as packaged treatment systems. Because of the large footprint requirements and non-availability of packaged treatment units, the oxidation ditch process is eliminated from further evaluation. Pahala WWTP Revised PER Section 5 5-12 Figure 5-10. Typical Oxidation Ditch Schematic 5.2.5 Extended Aeration Activated Sludge Package Plant Extended aeration is a less-complex system which can operate without primary treatment or anaerobic digestion. The treatment provides a completely mixed process operated at long hydraulic detention times and high sludge age. The process uses larger aeration tanks with extended solids retention times (SRTs) of over 20 days. Careful consideration needs to be given to the capacities of motors, pumps, and compressors in order to ensure the process can handle variations in flow. The basic extended aeration process schematic is shown in Figure 5-11. Figure 5-11. Extended Aeration Process Schematic The process is generally limited to smaller WWRFs and is often used in prefabricated packaged plants. The range of typical SRTs on the mainland is 20 to 40 days, and the process generally operates with MLSSs between 2,000 and 5,000 mg/L. The long SRT and relatively high MLSS makes the process resistant to shock loading and stable but requires somewhat larger tanks and therefore incurs higher aeration costs for a given flow, compared to other forms of activated sludge. Sludge settling can be problematic in the tropics due to denitrification occurring in mixed liquor caused by the relatively high water temperatures. The process is similar to the oxidation ditch technology previously described but would use diffused aeration rather than mechanical aeration. The process is forgiving and resistant to shock loadings. Due to sludge settling challenges in the tropics this process will not be considered further. Pahala WWTP Revised PER Section 5 5-13 5.2.6 Activated Sludge with Anoxic Selector This process is similar to extended aeration but would employ a shorter SRT of less than 10 days and would operate at a MLSS concentration between 1,500 and 4,000 mg/L. Figure 5-12 shows a process schematic for this process. The Kihei WWRF and Wailuku-Kahului WWRFs on Maui operate with this process. The anoxic selector is typically sized to have a volume of approximately 10 to 30 percent of the total aeration basin volume. The process would not be as forgiving and resistant to shock loadings compared to the oxidation ditch and extended aeration processes due to the shorter SRT and lower MLSS concentration. But this option is available in a prefabricated package plants and would incur a smaller footprint than the oxidation ditch and extended aeration processes but would require operation and maintenance of blowers to provide air to the process. The fine bubble diffused aeration system would be more efficient than the mechanical aerators generally used in the oxidation ditch process. This process is retained for further evaluation. Figure 5-12. Activated Sludge with Anoxic Selector Process Schematic 5.2.7 Recirculating Gravel Filter Recirculating gravel filter technology is an effective technology to treat septic tank effluent wastewater. After collection and conveyance, the wastewater is treated, in this case using a recirculating pea gravel filter (RGF). RGFs are a relatively simple, but effective means to treat wastewater from small communities. RGFs have been used to treat flow rates up to 1.0 mgd. RGFs typically produce a nitrified effluent that contains less than 10 mg/L of BOD5 and TSS (Crites and Tchobanoglous, 1998). A schematic diagram of a RGF is shown in Figure 5-13. A septic tank is used to capture settleable and floatable solids. The septic tank effluent enters a recirculation tank. A dosing pump is used to apply wastewater in small doses to the top of the filter. The wastewater is treated as it percolates through the pea gravel media. A network of drainage piping collects the water at the bottom of the filter and returns it to the recirculation tank. A floating ball recirculation valve controls the return flow back to the recirculation tank or to the effluent disposal or reuse system. The dosing pump timer settings and recirculation tank volume are designed so that wastewater will typically flow through the filter for treatment an average of three to five times before being discharged. An example of a RGF system in use within a decentralized wastewater system can be found at the Stonehurst subdivision, located near Martinez, California (Crites, et. al. 1997). Effluent from the RGF is typically chlorinated for disinfection prior to discharge. Pahala WWTP Revised PER Section 5 5-14 For a community system with conventional sewers and Imhoff tank can be used in lieu of a septic tank. Imhoff tanks are designed to remove floatable and settleable solids, and also provides for some digestion of the removed materials. Figure 5-13. Recirculating Gravel Filter for Treatment of Septic Tank Effluent 5.2.8 Secondary Treatment Technology Screening Table 5-5 provides a screening evaluation of the secondary treatment technologies described above. MBR, activated sludge with anoxic selector, and recirculating gravel filter are carried forward as project alternatives in Section 7. Pahala WWTP Revised PER Section 5 5-15 Table 5-5. Screening of Secondary Treatment Options Criterion MBR SBR Nereda Oxidation Ditch Extended Aeration Activated Sludge with Anoxic Selector Recirculating Gravel Filter BOD5 ≤ 30 mg/L X X X X X X X TSS ≤ 30 mg/L X X X X X X X Nitrification X X X X X X X TN < 10 mg/L X X X X X Anoxic selector X X X Appropriate for remote island location X X X X X Appropriate for tropical climate X X X X X X Aeration tank size Small Moderate Low Large Large Moderate Not applicable Secondary clarifier size None None None Largest Largest Large Not applicable Energy requirement Highest Moderate Moderate Moderate Higher Moderate Low Operational complexity High High Moderate Moderate Moderate Moderate Low Available as packaged treatment system X X X X X Fatal flaw Proprietary control systems Limited full scale installations in U.S. Large footprint Large footprint Carry forward in evaluations X X X 5-16 5.3 Maintenance Chlorination The proposed effluent management system (subsurface drip irrigation disposal) does not require a disinfection process to protect human health and the environment because the treated effluent is dispersed below the ground surface. However, periodic maintenance chlorination of the subsurface drip system will be required to reduce biofilm fouling within the drip lines. Calcium hypochlorite is the solid form of hypochlorite used for disinfection. It can be found as a powder, granules, pellets, or as tablets in concentrations up to 70 percent. Calcium hypochlorite will degrade in strength at a rate of 3 to 5 percent per year. Once applied to the wastewater, the chemistry is similar to that for sodium hypochlorite. Calcium hypochlorite decomposes in an exothermic reaction if exposed to moisture. The solid can be directly applied to wastewater at very small WWTPs. Figure 5-14 shows a typical calcium hypochlorite feed system. Figure 5-14. Typical Calcium Hypochlorite Feed System The advantages of using calcium hypochlorite for disinfection at small, remote WWTPs is that it is available in concentrated form as powder, pellets, or tablets. This makes the transportation and storage of disinfectant optimal for small WWTPs. 6-1 Section 6 Solids Management This section evaluates solids management options for the Pahala WWTP. 6.1 Aerobic Digestion with Decant Thickening Aerobic digestion consists of aerating sludge in a tank for an extended period of time. Volatile solids are oxidized in the process, stabilizing the sludge and reducing the total mass of solids that must be managed by recycling or disposal. Pathogen densities are also reduced. The process does not produce biogas. The aerobic digestion process requires substantial energy input in the form of aeration blowers, and therefore is not typically used at larger (i.e., greater than 10 mgd) WWRFs. Many small (less than 5 mgd) wastewater treatment plants in the United States use aerobic digestion to stabilize solids, due to its relatively low capital costs, simplicity, and compatibility with the certain liquid treatment processes. Aerobic digestion with decant thickening is a two-stage process that can be achieved in the same basin. The first stage includes a period of aerobic digestion as described above. In the second stage the blowers are turned off for a period of time to allow sludge to settle and thicken. Supernatant is then decanted off the top. The blowers are turned back on to continue the aerobic digestion process. This process is repeated a few times until the sludge reaches approximately three percent solids. It is then pumped to the next process. Aerobic digestion with decant thickening is recommended for the proposed Pahala WWTP due to its simplicity, low cost, and effectiveness for small WWRFs. 6.2 Anaerobic Digestion with Biogas Use Anaerobic digesters are covered tanks equipped with mixing, heating, and biogas collection systems. Anaerobic bacteria in the digesters convert organic matter into methane, carbon dioxide, and water; pathogen densities are reduced; and a stabilized sludge is produced. Modern high-rate digesters are typically single-stage reactors. Mesophilic anaerobic digesters are typically operated at temperatures between 35 and 38°C. Mesophilic digestion systems produce a Class B biosolids product if the solids retention time (SRT) is greater than 15 days. Two-stage mesophilic anaerobic digestion, where digesters are operated in series, improves process performance. The second-stage anaerobic digester generally has less SRT than the first stage. The advantages of this process configuration are slightly improved volatile solids reduction, a product with reduced pathogen content, and less product odor potential. The anaerobic digestion process generates biogas that can be used for digester heating and generation of electricity. The mesophilic anaerobic digestion process requires primary sludge to operate effectively. Therefore, primary clarifiers are required for an anaerobic digestion process. WWRFs that do not have primary clarifiers must use other digestion technologies. Anaerobic digestion is cost effective for facilities larger than 5 to 10 mgd. Anaerobic digestion is not considered to be an appropriate technology for a facility the size of the Pahala WWTP. Pahala WWTP Revised PER Section 6 6-2 6.3 Screw Press Dewatering The screw press represents a relatively new technology for dewatering municipal wastewater solids, although the technology has been used successfully in industrial, pulp and paper production, chemical, and food processing applications. Figure 6-1 is a diagram of a screw press. Thickened sludge, conditioned with polymer, is introduced to the machine in the head box at the inlet end. The mixture is conveyed from the inlet end to the outlet end of the press by the rotating screw. As the material is conveyed along the length of the press it is squeezed between the tapered screw shell and the screen drums. The dewatered solids exit the press at the discharge end and fall down the discharge box. The adjustable pressure cone provides back pressure within the machine, particularly when the machine is initially filled. For municipal wastewater solids applications, the pressure cone is typically not needed after the machine is filled; the dewatered sludge provides sufficient back pressure. The liquid that was forced out through the screens is returned to the liquid treatment process. Figure 6-1. Screw Press Diagram The screw press operates at a very slow rotational speed. The screw rotation is usually one-half of a revolution per minute or less for municipal wastewater solids. Water is slowly forced from the sludge by squeezing action – similar to a belt filter press – but for much longer periods of time. The solids retention time in a screw press can be on the order of two hours. The simplicity of screw presses makes them practical for small wastewater treatment plants, such as the Pahala WWTP. 6.4 Disposal Dewatered solids, grit, and screenings would be trucked to the West Hawaii Landfill for disposal. 7-1 Section 7 Project Alternatives Evaluations Project alternatives are developed and evaluated in this section. 7.1 Project Alternative Descriptions Three Project Alternatives are developed below. All three include a new gravity collection system, WWTP, and subsurface drip effluent disposal system. 7.1.1 Project Alternative 1: Activated Sludge with Anoxic Zone Package Plants Project Alternative 1 is an activated sludge process with anoxic zone provided in the form of packaged treatment systems. A typical packaged treatment system of this nature would include: · Flow equalization · Anoxic treatment zone · Aerobic treatment zone · Secondary clarifier · Aerobic digester with decant thickening. Figure 7-1 is a sketch of Project Alternative 1. Wastewater would receive preliminary treatment in the headworks before flowing into the packaged treatment system. Two package treatment units would be provided, each with 50,000 gpd capacity. Effluent would flow into an irrigation equalization tank before being applied to the subsurface drip disposal system. Digested solids would be dewatered using a screw press prior to disposal at the landfill. Pahala WWTP Revised PER Section 7 7-2 Figure 7-1. Project Alternative 1: Activated Sludge with Anoxic Zone Package Plants 7.1.2 Project Alternative 2: MBR Package Plants Project Alternative 2 is similar to Project Alternative 1 but includes two MBR package plants to provide treatment. Figure 7-2 provides an outline of Project Alternative 2. The MBR technology would create effluent that could be recycled on nearby macadamia nut orchards, if desired in the future. However, recycled water distribution costs are not included in the evaluations below to allow all alternatives to be considered on an equal basis. Pahala WWTP Revised PER Section 7 7-3 Figure 7-2. Project Alternative 2: MBR Package Plants 7.1.3 Project Alternative 3: Imhoff Tank / Recirculating Gravel Filter Project Alternative 3 incorporates recirculating gravel filter treatment technology. Figure 7-3 provides a schematic of the project alternative. An Imhoff tank would be provided downstream of the headworks to remove grease and settleable solids prior to flowing into a recirculation tank. Recirculation pumps would distribute water from the recirculation tank over the surface of the pea gravel filter that provides secondary treatment. Water collected at the bottom of the filter would flow back to the recirculation tank. On average water would flow through the filter five times before disposal in the subsurface drip irrigation system as previously described. Pahala WWTP Revised PER Section 7 7-4 Figure 7-3. Project Alternative 3: Imhoff Tank/Recirculating Gravel Filter 7.2 Cost Evaluations Capital, operations and maintenance (O&M), and life-cycle cost evaluations are presented in this section. 7.2.1 Capital Costs Conceptual cost estimates were created for the three project alternatives. The cost estimates were developed using construction bids from similar projects, quantity take-offs, vendor quotes, and other sources. The costs were adjusted to account for economies of scale and construction inflation since the bid opening date. Where Hawaii costs were unavailable, U.S. mainland costs were used after adjustment to reflect Hawaii Island conditions. In accordance with the Association for the Advancement of Cost Engineering International (AACE) criteria, these are Class 5 estimates. A Class 5 estimate is defined as a Conceptual Level or Project Viability Estimate. Typically, engineering is from 0 to 2 percent complete. Class 5 estimates are used to prepare planning level cost scopes or evaluation of alternative schemes, long range capital outlay planning. Pahala WWTP Revised PER Section 7 7-5 Expected accuracy for Class 5 estimates typically ranges from -50 to +100 percent, depending on the technological complexity of the project, appropriate reference information and the inclusion of an appropriate contingency determination. In unusual circumstances, ranges could exceed those shown. Table 7-1 provides a summary of capital cost assumptions used. Table 7-1. Capital Cost Estimating Assumptions Description Value Estimate date February 2023 Engineering News Record 20-Cities Average Construction Cost Index 13,175 Electrical and instrumentation markup 25 percent Estimating contingency for unknowns 20 percent Table 7-2 provides a summary of the capital cost estimates, in current (February 2023) dollars. Detailed estimates can be found in Appendix A. Engineering costs were not included in the estimates. Table 7-2. Capital Cost Estimates Summary Description Alternative 1: Activated Sludge Package Plants Alternative 2: MBR Package Plants Alternative 3: Imhoff Tank/RGF Collection system $21.0 million $21.0 million $21.0 million Influent sewer $1.0 million $1.0 million $1.0 million WWTP $13.9 million $13.9 million $14.8 million Effluent disposal $1.4 million $1.4 million $1.4 million Totals $37.3 million $37.3 million $38.2 million AACE Class 5 estimate range $18.7 – $74.6 million $18.7 – $74.6 million $19.1 – $76.4 million As shown in the table, all three project alternatives have similar capital costs, and can be considered equal at this level of analysis. Pahala WWTP Revised PER Section 7 7-6 7.2.2 Operation and Maintenance Costs O&M costs estimates were developed for the three alternatives. The O&M cost estimates include collection system maintenance, plus estimates of labor, electricity consumption, chemicals, maintenance materials and solids disposal for the WWTP. O&M assumptions are listed in Table 7-3. The O&M estimates are based on the WWTP average dry weather flow capacity. Table 7-3. O&M Cost Assumptions Description Value Average dry weather flow 95,000 gpd Labor cost, loaded $100,000/year/full time equivalent Electricity cost $0.45/kWh Landfill tip fee $100/wet ton Maintenance materials 2 percent of equipment capital cost/year The O&M estimates for the three project alternatives are summarized in Table 7-4. Detail can be found in Appendix A. As shown in the table, Project Alternative 3: Imhoff Tank/Recirculating Gravel Filter incurs the lowest O&M cost, while Project Alternative 2: MBR Package Plants incurs the highest. Table 7-4. O&M Cost Estimate Summary Description Annual Cost Project Alternative 1: Activated Sludge Package Plants Project Alternative 2: MBR Package Plants Project Alternative 3: Imhoff Tank/RGF Collection system $40,000 $40,000 $40,000 Labor $200,000 $200,000 $200,000 Electricity $240,000 $270,000 $90,000 Chemicals $20,000 $25,000 $20,000 Maintenance materials $96,000 $96,000 $46,000 Solids disposal $51,000 $51,000 $51,000 Totals $647,000 $682,000 $447,000 7.2.3 Life-Cycle Costs An economic evaluation was prepared to assess the potential life-cycle costs associated with each project alternative. The economic evaluation consists of a net present value comparison. The net present value analysis includes capital, O&M, and equipment replacement costs. An appropriate inflationary factor and discount rate are applied to obtain the net present value over a 30-year planning period. The analysis assumes the capital costs are incurred in year 1, followed by 29 years of O&M. The net present value of an alternative represents the amount of money that would need to be set aside today (at a given interest rate) to pay the costs associated with the alternative over the entire planning period. The alternative with the lowest net present value is considered the most attractive from an economic perspective. The evaluation results are included in Appendix A. Pahala WWTP Revised PER Section 7 7-7 Table 7-5 summarizes the life-cycle cost evaluation assumptions. Table 7-5. Life-Cycle Economic Assumptions Description Value Year of analysis 2023 Planning period 30 years Inflation rate 3.5 percent Discount rate 5.0 percent Equipment replacement cycle 20 years Membrane replacement cycle 15 years Table 7-6 summarizes the results of the life-cycle cost analysis. Table 7-6. Life-Cycle Cost Analysis Summary Description Project Alternative 1: Activated Sludge Package Plants Project Alternative 2: MBR Package Plants Project Alternative 3: Imhoff Tank/RGF Capital cost $37.3 million $37.3 million $38.2 million Annual O&M cost $647,000 $682,000 $447,000 Equipment replacement cost (excluding membranes) $4.8 million $4.8 million $2.3 million Membrane replacement cost N/A $59,000 N/A Life-cycle cost $56.1 million $57.0 million $50.4 million Comparison to lowest cost alternative +11% +13% 0% Figure 7-4 shows the results in graphical form. As shown in the table and graph, the three project alternatives have similar capital costs. Alternative 3: Imhoff Tank/Recirculating Gravel Filter incurs the lowest life-cycle costs, largely due to lower O&M costs associated with the technology. Project Alternatives 1 and 2 incur similar lifecycle costs. At this level of analysis all three project alternatives can be considered to have similar lifecycle costs. Pahala WWTP Revised PER Section 7 7-8 Figure 7-4. Life-Cycle Cost Evaluation Results 7.3 Non-Economic Evaluation A non-economic evaluation was conducted to provide a qualitative comparison between the three alternatives. 7.3.1 Approach Non-economic evaluations are generally subjective by necessity. Quantifiable measurements are used when available, but lack of information or difficulty and expense of obtaining information requires subjective assessments. The project alternatives were scored in relation to one another and according to an evaluation matrix, described below. Each alternative was scored from 1 to 5 (5 = high/desirable, 1 = low/less desirable) for each evaluation criteria. The alternatives were not ranked in the scoring; alternatives could receive the same scores for any given criteria. The evaluation criteria were weighted to reflect their overall significance for the project. The scores were multiplied by the criteria weights to develop a non-economic score for each alternative. Pahala WWTP Revised PER Section 7 7-9 7.4 Non-Economic Evaluation Criteria Table 7-7 shows the non-economic criteria chosen for comparing the three alternatives. Table 7-7. Non-Economic Comparison Criteria Category Criteria Description Level of Service Measures Effluent quality The quality of the effluent produced with respect to BOD5, TSS, nutrients, and turbidity. Potential for capacity expansion Ability of the system to be expanded should additional capacity be required. Water recycling feasibility The relative extent of modifications that would be needed to create R-1 recycled water to support a future water recycling program. Public perception / community concerns The community’s impression of the project and the perceived support. Regulatory Monitoring complexity The relative difficulty of monitoring tasks required for the option chosen. Treatment adjustment potential The ability to increase treatment to comply with future permit requirements and/or growth. Safety regulations complexity The relative difficulty to comply with safety regulations including staff training, reporting, maintenance procedures. Environmental concerns The extent of the project’s potential environmental impacts should failures occur. O&M Factors Footprint The physical space that the processes will occupy (affecting land acquisition, subdivision, and permitting). Safe work environment Lost time accidents and the relative health and safety risk operation of given option will have on the employees; includes equipment access, chemical hazards, confined spaces, dust, etc.; the extent of measures required to ensure the health and safety of the employees. Maintenance complexity The relative intensity of equipment maintenance requirements. Operations complexity The relative intensity of the operations requirements. Island Factors Mainland delivery dependence The relative dependence on regular deliveries of equipment, supplies, or spare parts from mainland sources. Mainland servicing dependence The relative degree to which technology will require special servicing by mainland- based personnel. Power dependence The relative degree to which the treatment processes depend on electrical power for operation. Chemical dependence The relative dependence on chemical supplies, whether locally available or restricted by mainland delivery schedules and requirements. The categories and criteria were developed using best engineering judgment and our understanding of the project, and the County of Hawaii Department of Environmental Management goals and concerns. Pahala WWTP Revised PER Section 7 7-10 The weighting factors are listed in Table 7-8. Table 7-8. Non-Economic Comparison Criteria Category Criteria Level of Service Measures (25%) Effluent quality (30%) Potential for capacity expansion (20%) Water recycling feasibility (30%) Public perception / community concerns (20%) Category Total (100%) Regulatory (25%) Monitoring complexity (25%) Treatment adjustment potential (25%) Safety regulations complexity (25%) Environmental concerns (25%) Category Total (100%) Owner Factors (25%) Footprint (30%) Safe work environment (25%) Maintenance complexity (25%) Operations complexity (20%) Category Total (100%) Island Factors (25%) Mainland delivery dependence (25%) Mainland servicing dependence (25%) Power dependence (25%) Chemical dependence (25%) Category Total (100%) Overall Total 100% Pahala WWTP Revised PER Section 7 7-11 7.5 Non-Economic Evaluation Results A score of 1 through 5 was given for each criterion, with 5 being the most favorable, and 1 representing the least desired option. The complete non-economic evaluation is included as Appendix C. The non-economic evaluation results are summarized in Table 7-9. Table 7-9. Non-Economic Weighted Scores Alternative Score Rank Project Alternative 1: Activated Sludge Package Plants 3.80 2 Project Alternative 2: MBR Package Plants 3.96 1 Project Alternative 3: Imhoff Tank / Recirculating Gravel Filter 3.53 3 As shown in the table, Project Alternative 2: MBR Package Plants received the highest non-economic score. The higher score reflects the County’s desire to standardize on MBR technology to provide the highest level of treatment at WWTP facilities and to facilitate future water recycling programs. 7.6 Conclusions and Recommendation Figure 7-5 combines the economic and non-economic results into a single graph. As previously stated, the economic cost of the three project alternatives can be considered equivalent at this level of analysis. Project Alternative 2: MBR Package Plants has the highest non-economic score and is recommended for implementation if the County proceeds with a centralized sewer system and WWTP for the community. Figure 7-5. Combined Economic and Non-Economic Results 1 2 3 4 5 0 10 20 30 40 50 60Non Economic ScoreLifecycle Cost ($ million) Alternative 1: Activated Sludge Package Plants Alternative 2: MBR Package Plants Alternative 3: Imhoff Tank/Recirculating Filter 8-1 Section 8 Preliminary Design of Improvements A preliminary design of the recommended project is discussed in this section. 8.1 Site Plan Figure 8-1 is a preliminary site plan of the WWTP project. 8.2 Process Schematic Figure 8-2 is a preliminary process schematic of the proposed WWTP. GRIT REMOVAL INFLUENT AEROBIC DIGESTER TRUCK TO LANDFILL EFFLUENT SAMPLER RAS ANOXIC PRE- AERATION MEMBRANES SUBSURFACE DRIP ZONE 1 MBR PACKAGE PLANTS (2) PERMEATE CUT THROAT FLUME WAS PARSHALL FLUME MMAGNETIC FLOW METER IRRIGATION CONTROL TANK M M M M SUBSURFACE DRIP ZONE 2 SUBSURFACE DRIP ZONE 3 SUBSURFACE DRIP ZONE 4 EXISTING MACADAMIA NUT TREES (TYPICAL) CHLORINE (HYPOCHLORITE) MANUAL BAR RACK FINE SCREEN DISPOSAL Path: C:\bcpw\d3083617File Name: 152964-FIG_8-2 Plot Date: February 15, 2023 2:28 PM Cadd User: Richard SellonaFIGUREPAHALA WASTEWATER TREATMENT PLANT JOB NO: 152964 PROCESS SCHEMATIC 8-2 SCALE: NONE INFLUENT SAMPLER POLYMER M SUBSURFACE DRIP ZONE 5 M SUBSURFACE DRIP ZONE 6 SCREW PRESS DEWATERING Pahala WWTP Revised PER Section 8 8-4 8.3 Preliminary Design Criteria Table 8-1 lists preliminary design criteria for the proposed WWTP. Table 8-1. Preliminary Design Criteria Description Value Influent flow Average dry weather 95,000 gpd Peak day wet weather 312,000 gpd Peak hour wet weather 221 gpm Influent characteristics BOD5 300 mg/L TSS 300 mg/L TN 40 mg/L Odor control – granular activated carbon Airflow rate 6 air changes per hour H2S Inlet concentration 1-10 ppm H2S removal efficiency 99% Media type High-capacity carbon Mechanical screens Number of units 1 Type In-channel cylindrical Screen opening size 0.125 inch (3 mm) Maximum flow rate capacity Greater than 221 gpm Screening washing Integral Screening compaction Integral Bypass screen Type Manually-cleaned bar rack Bar spacing 1 inch Rake Fabricated to Interlock with bars Screenings receptacle Type 55-gallon drum or bags Screenings volume per million gallons treated 5 ft3/Mgal Estimated screenings quantity 0.5 ft3/day Disposal frequency 1/week Influent flow metering Type Parshall flume Maximum flow capacity Greater than 221 gpm Pahala WWTP Revised PER Section 8 8-5 Minimum straight upstream channel section 20 times the throat width Influent flow sampling Refrigerated automatic composite sampler Grit chamber Number of units 1 Type Aerated grit trap Volume 2,805 gallons Air supply 75 ft3/minute Removal Vactor truck Estimated average grit quantity 1.8 ft3/day MBR package plant Number of packaged treatment trains 2 Flow basis for biological design 50,000 gpd each Anoxic tank working volume (excluding membranes) 2,000 gallons each Aerobic working volume 7,000 gallons each Design SRT 5 days Waste sludge removal 1,500 gpd each Design MLSS concentration in bioreactor ≤ 8,000 mg/L Number of duty membrane blowers 1 per train Number of duty process aeration blowers 1 per train Aeration system type Coarse bubble diffused aeration Mixed liquor recirculation rate 4 x ADWF Membrane cleaning dosing systems Sodium Hypochlorite, Citric Acid, & Coagulant Sludge management system Number of units 1 Type Incline screw press Screw press capacity 45 gpm Polymer dose 20 lbs/dry ton Annual polymer use 475 lbs Average amount of dewatered sludge 0.54 wet tons/day Disposal frequency 1/week Maintenance Disinfection system Type Chlorine Form Calcium hypochlorite tablets Design chlorine dose 8 mg/L Irrigation equalization (control) tank Number of units 1 MAINTENANCE AND STORAGE ROOM SINK AND COUNTER SPACE ELECTRICAL ROOM 12' WIDE ROLL-UP DOOR DESK AND WORK SPACE GENERATOR ROOM WITH VENTILATION MOTOR CONTROL CENTER 6' MIN CMU BLOCKS SLUDGE DEWATERING EQUIPMENT BLOWER ROOM Path: M:\Projects\Projects\Hawaii, County Of (HI)\150440 COH Pahala WWTP\_CAD\0-PROJECT\FIGURESFile Name: 150440-FIG-OpsBldg Plot Date: February 15, 2023 2:57 PM Cadd User: Richard SellonaFIGUREPAHALA WASTEWATER TREATMENT PLANT JOB NO: 152964 OPERATIONS BUILDING PRELIMINARY FLOOR PLAN 8-3 SCALE: 3/16" = 1'-0" 0 2'8' SCALE: 3/16" = 1'-0" 4'12'1'3' 9-1 Section 9 Implementation Plan An implementation plan for the recommended WWTP project is presented is this section. 9.1 Implementation Approach The WWTP and collection system projects could be implemented using either a traditional design/bid/build (DBB) approach or a design/build (DB) approach, as discussed below. 9.1.1 Design Bid Build (DBB) Approach DBB is the traditional approach used by the County for implementing public works projects. The design is prepared by a consultant, and then bids are solicited from construction contractors. The County awards the contract to the lowest responsible bidder. Advantages of the DBB approach are that the County retains maximum control over the design process, ensuring the project will meet its needs. 9.1.2 Design Build (DB) Approach DB is an alternative delivery approach whereby the County would contract with an entity to both design and construct a facility that meets established project specifications. The combined WWTP and collection system projects are large enough monetarily for the County to consider a DB approach. The County would need to use a procurement process based on qualifications and cost to select the DB entity. The typical DB procurement process takes 9 – 12 months to complete. The DB bidders will need the County to complete the following prior to the DB procurement process: · Complete geotechnical report. · Environmental assessment. · Land use entitlements. · WWTP land purchase. Advantages of DB implementation are: · Possibility of reduced overall costs. · Design and construction can occur simultaneously, potentially reducing implementation time. · DB entity assumes the performance liability for the project, as defined in the project specifications. Disadvantages of the DB approach are that the County has limited experience with it, and the County would not have as much control over how the project is designed. 9.2 Implementation Schedules Planning level implementation schedules were developed for both approaches. 9.2.1 Recent Change in State of Hawaii Land Use Commission Policy The State of Hawaii Land Use Commission (LUC) recently changed its policy regarding the use of Special Permits for non-conforming uses. The proposed WWTP site is located in the Agricultural Pahala WWTP Revised PER Section 9 9-2 District as defined by the LUC. A WWTP is not an allowable land use in the Agricultural District. In the past the LUC has allowed Special Permits to be used for non-conforming uses. However, the LUC has recently changed its policy and now recommends that project proponents for permanent facilities (like a WWTP) pursue a District Boundary Amendment (DBA) from the LUC. The LUCs rationale is that permanent entitlement (i.e., a DBA) is more appropriate for a permanent facility like a WWTP, rather than a temporary entitlement like a Special Permit. Since the WWTP parcel is less than 15 acres the DBA can be processed by the County of Hawaii. However, the action will likely take longer to implement than a Special Permit. 9.2.2 Equipment Procurement Time to Impact Construction Schedule The COVID-19 pandemic continues to impact the construction industry due to increased time to deliver equipment and other materials. Most significantly, the time for the MBR package plant supplier to manufacture their equipment was quoted at 48 weeks instead of a typical pre-pandemic time of approximately 26 weeks. Similar delays are being experienced on other construction projects in Hawaii, and it is reasonable to assume that other equipment suppliers will quote extended supply times. As a result, we now suggest that a construction schedule of two years is a reasonable expectation. 9.2.3 Implementation Schedules Figure 9-1 presents implementation schedules for both approaches. At this time, both approaches may not enable the County to meet the AOC milestone schedule to close the LCCs. The DB approach offers greater potential to meet the milestone, because equipment procurement can possibly occur in parallel with design within a DB contract. 9.3 Recommendation Given the equipment procurement time impact to construction schedule, and the recent change in LUC policy towards the use of Special Permits for permanent facilities, it is unlikely that the County will be able to meet the Revised AOC deadline to close the LCCs. Using a DB approach to implement the project may offer better opportunity to meet the deadline, because a DB entity could initiate equipment procurement while design activities progress. Part B of this report evaluates using Individual Wastewater Systems to comply with the Revised AOC. 9-3 Figure 9-1. Implementation Schedules 10-1 Section 10 References Crites, Ron, Craig Lekven, Steve Wert, George Tchobanoglous (1997). A Decentralized Wastewater System for a Small Residential Development in California. The Small Flows Journal. National Small Flows Clearinghouse. Volume 3, Issue 1, Winter 1997. Crites, R. W. and G. Tchobanoglous (1998) Small and Decentralized Wastewater Management Systems, McGraw-Hill, New York. Department of Wastewater Management, City and County of Honolulu, State of Hawaii. Design Standards of the Department of Wastewater Management, Volume 1 and 2. July 2017. Hawaii Administrative Rules (HAR), Title 11, Department of Health Administrative Rules. Masa Fujioka & Associates. Letter Report, Probing for Large Cavities (Lava Tubes), Naalehu and Pahala Large Capacity Cesspool Sewerage System. January 9, 2007. M&E Pacific, Inc. Kau Sewer System Evaluation, Kau, Island of Hawaii, Hawaii. December 2004. SSFM International, Inc. Final Preliminary Engineering Report for Naalehu and Pahala Large Capacity Cesspool Conversion Projects, July 2007. University of Hawaii Agricultural Experiment Station, Growing Macadamia Nuts in Hawaii, Bulletin 121, , January 1959. USEPA. “Process Design Manual, Land Treatment of Municipal Wastewater Effluents”. EPA/625/R-06/016. September 2006. Water Environment Federation. Wastewater Disinfection, Manual of Practice FD-10. Water Environment Federation, 1996. Pahala WWTP Revised PER A-1 Appendix A: Cost Estimates County of Hawaii DEM Pahala Revised AOC PER Alternatives Net Present Value Analysis Agency: County of Hawaii DEM Sensitivity Adjustments (%)Results Project/Problem: Pahala Revised AOC PER Risk Premium Benefits Capital Costs Other Costs Capital Cost 30-year NPV Alternative 1 Package plant all new sewers $37,278,000 ($57,018,355) Alternative 2 Package plant use old sewers $23,598,000 ($45,221,554) Alternative 3 IWS management model 2A $17,400,000 ($26,445,670) Alternative 4 IWS management model 2B $17,400,000 ($26,810,306) Alternative 5 IWS management model 3A $17,400,000 ($26,605,508) Alternative 6 IWS management model 3B $17,400,000 ($28,694,426) Alternative 7 Alternative 8 Alternative 9 Alternative 10 Alternative 11 Alternative 12 Year of analysis: 2023 Note: "Status quo" refers to Escalation rate: 3.50% Alternative 1 Discount rate: 5.00% Make entries in yellow cells only All entries in dollars All entries in thousands of dollars Select one County of Hawaii Pahala WWTP Design-Post Design Alternatives Net Present Value Analysis Agency: County of Hawaii Sensitivity Adjustments (%)Results Project/Problem: Pahala WWTP Design-Post Design Risk Premium Benefits Capital Costs Other Costs Capital Cost 30-year NPV Alternative 1 RAS Package Plants / Subsurface Drip $37,242,000 ($56,054,039) Alternative 2 MBR Package Plants / Subsurface Drip $37,278,000 ($57,018,355) Alternative 3 Imhoff Tank / RGF / Subsurface Drip $38,147,000 ($50,381,465) Alternative 4 Alternative 5 Year of analysis: 2023 Note: "Status quo" refers to Escalation rate: 3.50% Alternative 1 Discount rate: 5.00% Make entries in yellow cells only All entries in dollars All entries in thousands of dollars Select one County of Hawaii Pahala WWTP Design-Post Design Alternatives Net Present Value Analysis Agency: County of Hawaii Sensitivity Adjustments (%)Results Project/Problem: Pahala Collection System Risk Premium Benefits Capital Costs Other Costs Capital Cost 30-year NPV Alternative 1 New Gravity Collection System $21,010,000 ($21,951,599) Alternative 2 STEP Collection System $18,608,000 ($22,210,229) Alternative 3 Reuse Existing Collection System $7,330,000 ($10,154,798) Alternative 4 Alternative 5 Year of analysis: 2023 Note: "Status quo" refers to Escalation rate: 3.50% Alternative 1 Discount rate: 5.00% Make entries in yellow cells only All entries in dollars All entries in thousands of dollars Select one Pahala WWTP Preliminary Engineering Report Alternative Solutions Cost Summaries Collection System TOTAL $21,010,000 $16,232,000 $37,242,000 ANNUAL O&M COSTS Electricity $240,000 Labor $200,000 Chemicals $20,000 Solids disposal $51,000 Maintenance materials $96,000 Gravity mainline maintenance $40,000 Total Annual Operating Costs $647,000 EQUIPMENT REPLACEMENT COST (20 YEAR)$4,776,000 Collection System TOTAL $21,010,000 $16,268,000 $37,278,000 ANNUAL O&M COSTS Electricity $270,000 Labor $200,000 Chemicals $25,000 Solids disposal $51,000 Maintenance materials $96,000 Gravity mainline maintenance $40,000 Total Annual Operating Costs $682,000 MEMBRANE REPLACEMENT COST (15 YEAR)$59,000 EQUIPMENT REPLACEMENT COST (20 YEAR)$4,800,000 Collection System TOTAL $21,010,000 $17,137,000 $38,147,000 ANNUAL O&M COSTS Electricity $90,000 Labor $200,000 Chemicals $20,000 Solids disposal $51,000 Maintenance materials $46,000 Gravity mainline maintenance $40,000 Total Annual Operating Costs $447,000 EQUIPMENT REPLACEMENT COST (20 YEAR)$2,283,000 Alternative #1 - RAS Package Plants / Subsurface Drip ALTERNATIVE #1 CAPITAL COST TOTAL Alternative #2 - MBR Package Plants / Reuse / Subsurface Drip WWTP TOTAL ALTERNATIVE #3 CAPITAL COST TOTAL WWTP TOTAL ALTERNATIVE #2 CAPITAL COST TOTAL Alternative #3 - Imhoff Tank / RGF / Subsurface Drip WWTP TOTAL Electrical & Instrumentation 25.0% Contingency 20.0% ENR CCI 13175.03 January, 2023 Pahala WWTP Capital Unit Costs Units Unit Cost Environmental protection, BMPs ac $11,000 Site clearing ac $20,000 Site roads, guard rails, pavement ac $92,000 Perimeter fence LF $150 Site grading ac $30,000 Site drainage improvements ac $18,000 Plant water catchment/collection system LS $75,000 Process yard piping LS $250,000 Headworks (includes site/civil, structures, equipment & piping)LS $1,011,000 Chlorine disinfection LS $150,000 RAS package plants LS $3,491,000 MBR package plants LS $3,515,000 Irrigation equalization tank gal $10 Subsurface drip irrigation line LF $10 Irrigation piping & valves LF $250 Imhoff tank LS $1,063,000 Recirculation tank LS $890,000 Recirculating gravel filter LS $2,541,000 Plant drainage system ac $40,000 Main generator (including process piping)LS $494,000 Maintenance/operations/electrical building SF $1,000 Influent sewer (16 inch) main along easement from Maile St LF $480 Phase 1 existing gravity collection system improve (Fukunaga)LS $4,880,000 Phase 2 new gravity collection system (Fukunaga)LF $16,130,000 Reuse existing gravity collection system LS $2,450,000 Sludge dewatering system LS $860,000 Pahala WWTP Unit Cost Estimates 1 of 2 Pahala WWTP Operation, Maintenance, & Replacement Unit Costs Unit Cost Units Equipment replacement cost 25%of process capital cost Package plant replacement cost 100%of package plant captial cost Maintenance materials 2%of equipment capital cost Gravity collection system maintenance cost $16,000.00 per mi Membrane replacement cost $1,950.00 per module + SH & install Solids disposal dumpster rental fee $300.00 per week Sanitary landfill tipping fee $116.00 per wet ton Hypochlorite tablet cost $8.00 per lb Dewatering polymer cost $3.00 per lb Diesel price $6.22 per gallon 2 of 2 Imhoff Tank Units Unit Cost Number of Units Cost Excavation CY $150 400 $60,000 Bedding & backfill CY $100 25 $2,600 Concrete CY $1,500 130 $195,700 Piping & valves LS $50,000 1 $50,000 Cover plates SF $200 70 $14,000 Odor control LS $500,000 1 $500,000 Epoxy Coating SF $80 3,000 $240,000 $1,063,000 Recirculating Gravel Filter Units Unit Cost Number of Units Cost RGF bed excavation CY $150 6,000 $900,000 Bed liner SF $8 40,000 $320,000 16 in PVC manifold pipe LF $160 300 $48,000 3 in PVC lateral pipe LF $30 7,100 $213,000 4 in PVC drainage & recirculation pipe LF $40 2,000 $80,000 Gravel media CY $150 6,000 $900,000 6 in sand media under liner CY $100 800 $80,000 $2,541,000 Recirculation Tank Units Unit Cost Number of Units Cost Recirculation tank excavation CY $150 1,000 $150,000 Bedding & backfill CY $100 200 $20,000 Concrete CY $1,500 200 $300,000 Handrail LF $100 200 $20,000 Pumps & valves ea $100,000 4 $400,000 $890,000 Pahala WWTP Lump Sum Cost Estimates TOTAL TOTAL TOTAL 1 of 2 Sludge Dewatering System Units Unit Cost Number of Units Cost 300 HP diesel dump truck LS $300,000 1 $300,000 Dewatering screw press LS $300,000 1 $300,000 Incline screw conveyor LS $80,000 1 $80,000 Polymer system LS $80,000 1 $80,000 Sludge feed pump & piping LS $100,000 1 $100,000 $860,000 Reuse Existing Gravity Collection System Units Unit Cost Number of Units Cost Inspection & cleaning LS $750,000 1 $750,000 Repair defects LS $1,500,000 1 $1,500,000 Archaeological monitoring LS $50,000 1 $50,000 BMPs LS $50,000 1 $50,000 Traffic control measures LS $50,000 1 $50,000 Pre- & post-construction inspections & documentation LS $50,000 1 $50,000 $2,450,000TOTAL TOTAL 2 of 2 Pahala WWTP Preliminary Engineering Report Cost Estimate Pahala WWTP Capital Cost Item Description Units General Unit Cost Number of Units COST 16 inch sewer main along easement from Maile St LF $480 1,700 $816,000 Subtotal $816,000 Contingency @ 20%$164,000 Influent Sewer Total $980,000 Environmental protection, BMPs ac $11,000 1.5 $16,500 Site clearing ac $20,000 1.5 $30,000 Site roads, guard rails, pavement ac $92,000 1.5 $138,000 Perimeter fence LF $150 3,000 $450,000 Site grading ac $30,000 1.5 $45,000 Site drainage improvements ac $18,000 1.5 $27,000 Plant water catchment/collection system LS $75,000 1 $75,000 Process yard piping LS $250,000 1 $250,000 Headworks (includes site/civil, structures, equipment & piping)LS $1,011,000 1 $1,011,000 Chlorine disinfection LS $150,000 1 $150,000 RAS package plants LS $3,491,000 1 $3,491,000 Plant drainage system ac $40,000 1.5 $60,000 Main generator (including process piping)LS $494,000 1 $494,000 Maintenance/operations/electrical building SF $1,000 2,150 $2,150,000 Sludge dewatering system LS $860,000 1 $860,000 Subtotal $9,247,500 Electrical & Instrumentation @ 25%$2,312,000 Subtotal $11,560,000 Contingency @ 20%$2,312,000 Wastewater Treatment Total $13,872,000 Irrigation equalization tank gal $10 20,000 $200,000 Subsurface drip irrigation line LF $10 52,000 $520,000 Irrigation piping & valves LF $250 800 $200,000 Subtotal $920,000 Electrical & Instrumentation @ 25%$230,000 Subtotal $1,150,000 Contingency @ 20%$230,000 Effluent Disposal Total $1,380,000 Alternative #1 TOTAL $16,232,000 Effluent Disposal Influent Sewer Alternative #1 - RAS Package Plants / Subsurface Drip Capital Cost Estimate Wastewater Treatment Pahala WWTP Preliminary Engineering Report Cost Estimate Pahala WWTP Capital Cost Item Description Units General Unit Cost Number of Units COST 16 inch sewer main along easement from Maile St LF $480 1,700.0 $816,000 Subtotal $816,000 Contingency @ 20%$164,000 Influent Sewer Total $980,000 Environmental protection, BMPs ac $11,000 1.5 $16,500 Site clearing ac $20,000 1.5 $30,000 Site roads, guard rails, pavement ac $92,000 1.5 $138,000 Perimeter fence LF $150 3,000 $450,000 Site grading ac $30,000 1.5 $45,000 Site drainage improvements ac $18,000 1.5 $27,000 Plant water catchment/collection system LS $75,000 1 $75,000 Process yard piping LS $250,000 1 $250,000 Headworks (includes site/civil, structures, equipment & piping)LS $1,011,000 1 $1,011,000 Chlorine disinfection LS $150,000 1 $150,000 MBR package plants LS $3,515,000 1 $3,515,000 Plant drainage system ac $40,000 1.5 $60,000 Main generator (including process piping)LS $494,000 1 $494,000 Maintenance/operations/electrical building SF $1,000 2,150 $2,150,000 Sludge dewatering system LS $860,000 1 $860,000 Subtotal $9,271,500 Electrical & Instrumentation @ 25%$2,318,000 Subtotal $11,590,000 Contingency @ 20%$2,318,000 Wastewater Treatment Total $13,908,000 Irrigation equalization tank gal $10 20,000 $200,000 Subsurface drip irrigation line LF $10 52,000 $520,000 Irrigation piping & valves LF $250 800 $200,000 Subtotal $920,000 Electrical & Instrumentation @ 25%$230,000 Subtotal $1,150,000 Contingency @ 20%$230,000 Effluent Disposal Total $1,380,000 Alternative #2 TOTAL $16,268,000 Wastewater Treatment Effluent Disposal Alternative #2 - MBR Package Plants / Reuse / Subsurface Drip Capital Cost Estimate Influent Sewer Pahala WWTP Preliminary Engineering Report Cost Estimate Pahala WWTP Capital Cost Item Description Units General Unit Cost Number of Units COST Influent sewer (16 inch) main along easement from Maile St LF $480 1,700 $816,000 Subtotal $816,000 Contingency @ 20%$164,000 Influent Sewer Total $980,000 Environmental protection, BMPs ac $11,000 2 $22,000 Site clearing ac $20,000 2 $40,000 Site roads, guard rails, pavement ac $92,000 2 $184,000 Perimeter fence LF $150 3,000 $450,000 Site grading ac $30,000 2 $60,000 Site drainage improvements ac $18,000 2 $36,000 Plant water catchment/collection system LS $75,000 1 $75,000 Process yard piping LS $250,000 1 $250,000 Headworks (includes site/civil, structures, equipment & piping)LS $1,011,000 1 $1,011,000 Imhoff tank LS $1,063,000 1 $1,063,000 Recirculation tank LS $890,000 1 $890,000 Recirculating gravel filter LS $2,541,000 1 $2,541,000 Chlorine disinfection LS $150,000 1 $150,000 Plant drainage system ac $40,000 2 $80,000 Main generator (including process piping)LS $494,000 1 $494,000 Maintenance/operations/electrical building SF $1,000 1,645 $1,645,000 Sludge dewatering system LS $860,000 1 $860,000 Subtotal $9,851,000 Electrical & Instrumentation @ 25%$2,463,000 Subtotal $12,314,000 Contingency @ 20%$2,463,000 Wastewater Treatment Total $14,777,000 Irrigation equalization tank gal $10 20,000 $200,000 Subsurface drip irrigation line LF $10 52,000 $520,000 Irrigation piping & valves LF $250 800 $200,000 Subtotal $920,000 Electrical & Instrumentation @ 25%$230,000 Subtotal $1,150,000 Contingency @ 20%$230,000 Effluent Disposal Total $1,380,000 Alternative #3 TOTAL $17,137,000 Wastewater Treatment Effluent Disposal Alternative #3 - Imhoff Tank / RGF / Subsurface Drip Capital Cost Estimate Influent Sewer Electricity cost $0.45 /kWh Flow ADWF:0.095 mgd 0.146987 cfs Labor (common across all alternatives) COH WWTP operator annual salary $100,000 including fringe benefits Number of employees/operators 2 2 Shifts: Wed - Sat / Mon - Fri Annual labor cost:$200,000 Electricity Equivalent Annual Alt 1 Alt 2 Alt 3 Duty Unit Motor Size Use Continuous Power RAS PP MBR PP RGF Load Count (hp)Factor Load (hp)(kWh)(kWh)(kWh)(kWh) Headworks Screens 1 2 20%0.4 2,613 2,613 2,613 2,613 Grit blower 2 5 100%10 65,323 65,323 65,323 65,323 Process tanks Anoxic zone mixers 2 5 100%10 65,323 65,323 65,323 N/A Aeration blower (main)1 27 100%27 176,373 176,373 176,373 N/A Aeration blower (flow equalization)1 13 100%13 84,920 84,920 84,920 N/A Imhoff tank odor control 1 2 100%2 13,065 N/A N/A 13,065 Recirculation tank pump 1 5 100%5 32,662 N/A N/A 32,662 Secondary clarifier Clarifier mechanisms 2 1 100%2 13,065 13,065 N/A N/A Membranes Membrane blower 2 5 30%3 19,597 N/A 19,597 N/A Permeate pumps 2 5 100%10 65,323 N/A 65,323 N/A Aerobic digestion Digester blowers 2 5 90%9 58,791 58,791 58,791 58,791 Sludge dewatering Screw press feed pump 1 5 30%1.5 9,798 9,798 9,798 9,798 Screw press 1 2 30%0.6 3,919 3,919 3,919 3,919 Cake conveyor 1 2 30%0.6 3,919 3,919 3,919 3,919 Pahala WWTP Preliminary Engineering Report O&M Cost Estimates 1 of 3 Miscellaneous Drainage return pumps 1 5 10%0.5 3,266 3,266 3,266 3,266 Plant water pumps 1 5 100%5 32,662 32,662 32,662 N/A Fans 2 1 100%2 13,065 13,065 13,065 13,065 533,038 604,894 206,422 $240,000 $270,000 $90,000 Chemicals Hypochlorite Tablets Daily chlorine demand @ ADWF 6.3 lbs/d assuming 8 mg/L dose, 15 min contact time @ PHWWF Annual hypochlorite demand @ ADWF 2,300 lbs/yr Hypochlorite tablet unit cost $8 per lb Total annual hypochlorite tablet cost:$18,400 common across all alternatives Dewatering polymer Daily dewatering polymer use 1.3 lbs/d assuming 20 lbs/dry ton dose Annual dewatering polymer use 475 lbs/yr Dewatering polymer unit cost $3 per lb Total annual dewatering polymer cost:$1,500 common across all alternatives MBR cleaning chemicals Sodium hypochlorite & citric acid cost:$5,000 per yr Alternative #2 only Membrane replacement (Alt #2) Membrane cost per module $1,950 material costs only Estimated additional costs per module $500 shipping & handling + installation costs Number of membrane modules 24 modules (12 per unit) Membrance replacement cost:$59,000 15 year life expectancy Maintenance materials Alt 1 Alt 2 Alt 3 RAS PP MBR PP RGF Package plant capital cost $3,491,000 $3,515,000 N/A Process equipment capital cost $5,140,000 $5,140,000 $9,129,000 not including package plant Equipment replacement cost factor 25.0%25.0%25.0%replace after 20 years process equipment replacement cost $1,285,000 $1,285,000 $2,282,250 not including package plant Total equipment replacement cost:$4,776,000 $4,800,000 $2,283,000 includes 100% package plant replacement Maintenance materials cost factor 2.0%2.0%2.0% Total annual maintenance materials cost:$96,000 $96,000 $46,000 Annual electricity consumption kWh: Annual electricity cost: 2 of 3 Sludge disposal Daily dewatering flow:517 gpd Daily dewatered sludge mass 0.54 wet tons/d West HI sanitary landfill tipping fee $116.00 per wet ton Onsite disposal roll off dumpster size 5.00 cu yds Dumpster rental fee $300.00 per week Annual dumpster rental fee $15,600.00 Disposal frequency 7.00 days Requires weekly disposal (once every 7 days) Diesel price (dollar per gallon)$6.22 per gallon Employee labor cost per hour $48.08 per hour based on 100K annual salary Distance Pahala to Landfill (roundtrip)189.4 mi per google maps Distance Pahala to Naalehu (roundtrip)24.8 mi per google maps Dump truck fuel economy 5.00 mpg Annual sludge disposal cost (truck to landfill) alternative Annual fuel cost $12,300 Annual landfill tipping fee $22,900 Annual Dumpster rental fee $15,600 Total annual sludge disposal cost:$51,000 Annual sludge disposal cost (No dewatering - truck sludge to Naalehu) alternative Storage capacity of dump truck 2000 gal Weekly volume of sludge 3,619 gal Required trips to Naalehu per week 2 count Required trips to Naalehu per year 104 count Distance traveled per year 2,600 mi Annual sludge disposal fuel cost $3,300 No dewatering polymer -$1,500 Total annual sludge disposal cost:$1,800 For informational purposes only New collection system maintenance (common across all alternatives) Gravity collection sewer mainline 2.5 mi Gravity mainline maintenance cost $16,000 Total annual mainline maintenance cost:$40,000 Reuse existing collection system maintenance Gravity mainline maintenance multiplier 3 Total annual mainline maintenance cost:$120,000 3 of 3 Pahala WWTP Revised PER B-1 Appendix B: DOH Variance Pahala WWTP Revised PER C-1 Appendix C: Non-Economic Evaluation Pahala WWTP Alternative Solutions Non-Economic Evaluation February 2023 Category Category Criteria Criteria Weight Weight Effluent quality 30%3 5 3 0.90 1.50 0.90 Potential for capacity expansion 20%5 5 2 1.00 1.00 0.40 Water recycling feasibility 30%3 5 2 0.90 1.50 0.60 Public perception / community concerns 20%3 5 3 0.60 1.00 0.60 Monitoring complexity 25%4 3 5 1.00 0.75 1.25 Treatment adjustment potential 25%5 5 3 1.25 1.25 0.75 Safety regulations complexity 25%4 4 4 1.00 1.00 1.00 Environmental concerns 25%4 5 3 1.00 1.25 0.75 Footprint 30%5 5 2 1.50 1.50 0.60 Safe work environment 25%4 3 4 1.00 0.75 1.00 Maintenance complexity 25%4 3 4 1.00 0.75 1.00 Operations complexity 20%4 3 5 0.80 0.60 1.00 Mainland delivery dependence 25%3 3 4 0.75 0.75 1.00 Mainland servicing dependence 25%3 3 4 0.75 0.75 1.00 Power dependence 25%3 3 5 0.75 0.75 1.25 Chemical dependence 25%4 3 4 1.00 0.75 1.00 ***Note : 5 = high/desirable, 1 = low/not-desirable Overall Score: 3.80 3.96 3.53 Alt #3 RGF Alt #1 RAS Raw Scores Weighted Scores Alt #1 RAS Alt #3 RGF Alt #2 MBR Alt #2 MBR Island Factors 25% Level of Service 25% Regulatory 25% O&M Factors 25% PART B: IWS Approach PART B Pāhala Individual Wastewater System Preliminary Engineering Report Prepared for Brown and Caldwell & County of Hawai’i, Department of Environmental Management March 2023 April 30, 2024 Yen Wen Fang Expiration Date of the License THIS WORK (PART B) WAS PREPARED BY ME OR UNDER MY SUPERVISION 4/30/24 Table of Contents Section 1 ...................................................................................................................................1 Preliminary Considerations .............................................................................................................1 1.1 Operational Considerations .....................................................................................................................1 1.2 Economic Considerations ......................................................................................................................5 1.3 Environmental Considerations ..............................................................................................................6 Cesspools: Prioritization Catagory by Block-Groups ..............................................................................7 1.4 Constructability ........................................................................................................................................8 1.4.1 Available Space Per Property ..............................................................................................................8 1.4.2 Site Slopes .............................................................................................................................................9 1.4.3 Traffic Area ...........................................................................................................................................10 1.4.4 Site Geology ........................................................................................................................................10 1.4.5 Percolation Test Results .....................................................................................................................11 1.4.6 Proximity to Bodies of Water .............................................................................................................12 1.4.7 Accessibility...........................................................................................................................................12 1.4.8 Landowner Engagement ....................................................................................................................13 1.4.9 Availability of Resources and Contractors ......................................................................................14 Section 2 ................................................................................................................................16 Project Timeline .............................................................................................................................16 2.1 Project Schedule .....................................................................................................................................16 2.2 Typical IWS Permitting and Construction process ...........................................................................17 Section 3 ................................................................................................................................19 Treatment Technologies ................................................................................................................19 3.1 Septic Tanks .............................................................................................................................................19 3.2 Aerobic Treatment Units ......................................................................................................................22 3.3 Passive Biofilters or Constructed Wetlands .....................................................................................24 Constructed Wetland Septic System .......................................................................................................24 3.4 Recirculating Biofilter ...........................................................................................................................25 3.5 Composting Toilets ...............................................................................................................................26 3.6 Incineration Toilets ................................................................................................................................27 Section 4 ...............................................................................................................................29 Disposal Technologies ..................................................................................................................29 4.1 Absorption beds .....................................................................................................................................29 4.2 Absorption trench..................................................................................................................................30 4.3 Combined Treatment and Disposal System ......................................................................................31 4.4 Seepage pit ............................................................................................................................................33 4.5 Subsurface drip irrigation ....................................................................................................................34 4.6 Greywater system ..................................................................................................................................35 Section 5 ...............................................................................................................................37 System Design ................................................................................................................................37 5.1 IWS Selection ..........................................................................................................................................37 References ............................................................................................................................39 Appendix A - LCC Closure Properties .....................................................................................................A-1 Appendix B - Additional Households ......................................................................................................A-4 Appendix C - Cost Calculations ...............................................................................................................A-6 Appendix D - Topography .........................................................................................................................A-11 Appendix E - USGS Soil Survey .............................................................................................................A-13 Appendix F - Ka'ū Gym Geotech Report ...............................................................................................A-21 Appendix G - YKE Geotechincal Data Report .....................................................................................A-23 Appendix H - Percolation Test Results .................................................................................................A-25 Appendix I - EZ Treat Recirculating Biofilter ........................................................................................A-31 Appendix J - Typical IWS Layout ............................................................................................................A-40 List of Figures Figure 1.1: The five management models for IWS maintenance ..............................................................2 Figure 1.2: Prioritization of Hawai‘i Island cesspools based on 15 site specific risk factors ..............7 Figure 1.3: Distribution of total acreage for properties to be served in Pāhala ...................................9 Figure 3.1: Side-view of a typical two-chambered septic tank ...............................................................19 Figure 3.2: Common septic tank materials and shapes in Hawai‘i ......................................................20 Figure 3.3: Side-view of typical aerobic treatment unit .........................................................................23 Figure 3.4: Effluent quality of septic systems vs. ATUs in Hawai‘i .......................................................23 Figure 3.5: Side-view of a typical constructed wetland following a septic tank ................................24 Figure 3.6: Side-view of a typical recirculating biofilter following a septic tank ................................25 Figure 3.7: Component view of a typical individual composting toilet ................................................26 Figure 3.8: Top view of a typical urine separating toilet ........................................................................26 Figure 3.9: Top view of a central composting unit .................................................................................27 Figure 3.10: Side view of a typical incinerating toilet ..............................................................................28 Figure 4.1: Typical absorption field installed following a septic tank ...................................................30 Figure 4.2: Typical absorption trench system installed following a septic tank .................................31 Figure 4.4: An example of a non-proprietary “layer cake” CTDS .........................................................33 Figure 4.5: Typical subsurface drip irrigation installed following a septic tank ................................35 Figure 4.6: Typical greywater reuse system installed in parallel with a septic tank ..........................36 List of Tables Table 1.1: County & homeowner responsibilities under variations of the EPA management models 4 Table 1.2: Installation cost estimates for a standard septic tank installed ............................................5 Table 1.3: The costs associated with four IWS management models ...................................................6 Table 1.4: DOH required setbacks for wastewater systems per HAR 11-62. ........................................9 Table 1.5: Percolation test results ...............................................................................................................11 Table 1.6: Percolation test results ..............................................................................................................12 Table 1.7: Proximity to bodies of water for properties in Pāhala with an existing cesspool ..............12 Table 2.1: Pāhala LCC Replacement Schedule .........................................................................................16 Table 2.2: Hawai‘i Permitting and Construction Process .......................................................................18 Table 3.1: Typical septic system performance in Hawai‘i .......................................................................20 Table 3.2: Advantages and Disadvantages of Septic Tank Materials ...................................................21 Table 3.3: Common single family home septic tank products in Hawai‘i ...........................................22 Table 5.1: An abridged selection of IWS options .....................................................................................38 Pāhala Individual Wastewater System Preliminary Engineering Report 1 1 Section 1 Preliminary Considerations 1.1 Operational Considerations An effective Individual Wastewater System (IWS) management strategy is crucial to ensuring distributed treatment systems are maintained and operated in a way that ensures they are functioning properly and effectively treating wastewater. This strategy may include but is not limited to: • Monitoring: Regular inspections of system components, such as septic tanks and drain fields, ensure they are functioning properly and identify and address any issues that may arise. • Maintenance: Proper maintenance of the system is also crucial, including regular pumping of septic tanks, cleaning and maintenance of the distribution systems, and proper maintenance of the treatment components. Regular maintenance can help prevent issues such as clogs and backups, which can lead to costly repairs and potential health hazards. • Regulatory Compliance: Necessary permits and licenses are obtained for the system, and required inspection and reporting schedules are met with the local regulator. • Community Education: Information and training on proper usage and maintenance of the systems are provided to homeowners, and any concerns or questions that may arise are addressed. In Hawai‘i, centralized wastewater treatment plants and cluster systems are regulated and inspected by the Department of Health (DOH) Wastewater Branch (Hawai‘i Administrative Rules 11-62). State-licensed WWTP operators are required for oversight to ensure that systems are inspected, operated, and maintained as required. A similar regulatory requirement does not exist for IWS in Hawai‘i. The State DOH Wastewater Branch is responsible for regulating IWS while operation and maintenance are currently the responsibility of the individual homeowner. If IWS were selected to serve Pahala Community, maintenance responsibilities could be distributed in a number of ways. In a 2003 resource, the EPA outlined five management models that can be used for the operation and maintenance of IWS (Figure 1.1). When selecting an appropriate management model for a network of IWS it is important to take into account the regulatory and cultural framework within which the IWS are situated. As it stands in Hawai‘i, IWS are currently managed using a combination of management Models 1 and 2 (DOH, 2016): • Model 1: Homeowner Awareness. The DOH allows septic systems to be managed under this model. Homeowners own and operate their own IWS and are responsible for keeping Pāhala Individual Wastewater System Preliminary Engineering Report 2 1 the system in good working order. • Model 2: Maintenance Contracts. The DOH requires that Aerobic Treatment Units (ATUs) are managed using this model. Homeowners are required to have an active service contract with a certified operator or factory certified representative, and a copy of that active service contract must be submitted annually to the DOH (DOH, 2016). Elevated regulation around the operation of ATUs is a reflection of their increased mechanical complexity and associated maintenance demands. Figure 1.1: The five management models for IWS maintenance (EPA, 2003) The Five Management Models Model 1 Model 2 Model 3 Model 4 Model 5 Homeowner Awareness: Maintenance Contracts:Operating Permits: Responsible Management Entity (R:ME) Operation and Maintenance:RME Ownership: specifies appropriate program elements and activities where treatment systems are owned and operated by individual property owners in areas of low environmental sensitivity. This program is adequate where treatment technologies are limited to conventional systems that require little owner attention. To help ensure that timely maintenance is performed, the regulatory authority mails maintenance reminders to owners at appropriate intervals. specifies program elements and activities where more complex designs are employed to enhance the capacity of conventional systems to accept and treat wastewater. Because of treatment complexity, contracts with qualified technicians are needed to ensure proper and timely maintenance. specifies program elements and activities where sustained performance of treatment systems is critical to protect public health and water quality. Limited- term operating permits are issued to the owner and are renewable for another term if the owner demonstrates that the system is in compliance with the terms and conditions of the permit. Performance- -based designs may be incorporated into programs with management controls at this level. specifies program elements and activities where frequent and highly reliable operation and maintenance of decentralized systems is required to ensure water resource protection in sensitive environments. Under this model, the operating permit is issued to an RME instead of the property owner to provide the needed assurance that the appropriate maintenance is performed. specifies that program elements and activities for treatment systems are owned, operated, and maintained by the RME, which removes the property owner from responsibility for the system. This program is analogous to central sewerage and provides the greatest assurance of system performance in the most sensitive of environments. Pāhala Individual Wastewater System Preliminary Engineering Report 3 1 The AOC stipulates that the County of Hawai‘i must administer a more active management strategy than is typical in Hawai‘i, either a Model 2 (Maintenance Contract) or Model 3 (Operating Permit) management strategy for a network of IWS at Pahala. These models reflect varying degrees of responsibility to the County and homeowner (Table 1.1). Four potential variations of these models are outlined here for implementation on this project: • Management Model 2A: Maintenance Contract with County In-House Staff The County employs and trains an in-house IWS management team; purchases and maintains its own pumping/hauling equipment; and administers the management program. The homeowner pays a monthly sewer fee that covers a portion of the costs. • Management Model 2B: Maintenance Contract with Third-Party Service The County administers the management program, keeps an operations and maintenance (O&M) schedule, and contracts out O&M activities to a third-party service provider. The homeowner pays a monthly sewer fee that covers a portion of the costs. Administration costs for this program can be mitigated with the use of an online asset management service. • Management Model 3A: Operating Permits with O&M by Users The County issues an operating permit to the homeowner; keeps an O&M schedule; and sends out maintenance reminders to homeowners. The homeowner is responsible for contracting a third-party service provider to conduct maintenance. An online asset management service with a portal for approved maintenance professionals to log service events is strongly recommended for the County to track homeowner compliance and levy fines, as needed. • Management Model 3B: Operating Permits with O&M Voucher by County The County issues an operating permit to the homeowner; keeps an O&M schedule; and sends out maintenance reminders with service vouchers to homeowners. The homeowner pays a sewer fee and is responsible for contracting a third-party service provider to conduct annual maintenance using the voucher. An online asset management service with a portal for approved maintenance professionals to log service events is strongly recommended for the County to track homeowner compliance and levy fines, as needed. These management strategies presented here are required by the AOC but are also unique to Hawai‘i and will present a number of barriers for implementation at the legislative, regulatory, and public levels. The Pahala Community and Hawai‘i’s stakeholders at large are accustomed to Management Model 1, which is the standard practice across the State of Hawai‘i. Pāhala Individual Wastewater System Preliminary Engineering Report Management Model Brief Description of Management Model County’s Responsibility Homeowner / User’s Responsibility Pros Cons 2A Maintenance Contract w/ County in- house staff • Funds design and construction of IWS • Purchase equipment & train IWS operator • O&M of IWS including trouble calls • Keeping record of O&M log • Send out notices and reminders to homeowners • Submit IWS inspection reports and variance renewals to State DOH • Report IWS problem to County • Cooperates and allows County staff to enter private property and provide maintenance of IWS • Maintain clearance to IWS for easy access 1. Best control on O&M schedule 2. Ensure best IWS performance 1. Highest cost 2. May not receive cooperation from some homeowners/users 3. Homeowner may have more trouble calls 4. Potential dispute between homeowner & County on plumbing repair cost & IWS repair cost 2B Maintenance Contract w/ 3rd Party Service • Funds design and construction of IWS • Select/prequalify certain 3rd party service provider (Pumper) • Issue PO to Pumper & plumber for annual inspection and trouble calls • Keeping record of O&M log • Send out notices and reminders to homeowners • Submit IWS inspection reports and variance renewals to State DOH • Report IWS problem to County • Cooperates and allows service providers to enter private property and provide maintenance of IWS • Maintain clearance to IWS for easy access 1. Better control on O&M schedule 2. Ensure better IWS performance 3. Less County staff to train 4. No pumping/hauling equipment to purchase & maintain 1. Higher cost 2. May not receive cooperation from some homeowners/users 3. Homeowner may have more trouble calls 4. Potential dispute between homeowner & County on plumbing repair cost & IWS repair cost 3A Operating Permits w/ O&M by Users • Funds design and construction of IWS • Keeping record of O&M log • Send out notices and reminders to homeowners • Enforce rules and regulations • Issues permit to homeowner to use, operate & maintain the IWS • Contracts with preferred pumper / plumber to maintain the IWS • Pay for the O&M service • Submit O&M record to County • Submit IWS inspection reports and variance renewals to State DOH 1. Least cost to County 2. No O&M staff or equipment 3. No trouble calls 1. Least control for IWS compliance & performance 2. Conflict with non-compliant homeowners 3. Highest cost to homeowner 3B Operating Permits w/ O&M Voucher by County • Funds design and construction of IWS • Keeping record of O&M log • Send out notices and reminders to homeowners • Enforce rules and regulations • Pre-select qualifying service providers • Issue vouchers to homeowners for annual inspections and pumping • Issues permit to homeowner to use, operate & maintain the IWS • Contracts with preferred pre- qualified pumper / plumber to maintain the IWS • Pay for the annual O&M service with voucher • Submit O&M record to County by pumper • Submit IWS inspection reports and variance renewals to State DOH 1. Reasonable control on O&M 2. Reasonable IWS performance 3. Less County staff to train 4. No pumping/hauling equipment to purchase & maintain 5. Trouble calls to be paid for by homeowner 1. High cost to County 2. Less control of all IWS Table 1.1: County and homeowner responsibilities under variations of the EPA management models 2 and 3 Pāhala Individual Wastewater System Preliminary Engineering Report 5 1 1.2 Economic Considerations When assessing the overall cost of a given system, it is important to consider the net present value lifecycle cost taking system lifetime and installation, maintenance, and operation costs into account. These costs can be affected by a variety of factors, including: • Type of treatment and disposal system: The selection of different types of treatment systems such as traffic rated tanks or aerobic treatment significantly affect overall installed cost. For disposal, seepage pits are significantly lower cost than absorption fields when it is possible to convert an existing cesspool. Site specific conditions will control which options are required. For traditional residential IWS installations subject to State procurement regulations, capital costs per household are typically in the range of $30,000-$100,000 (Table 1.2). Table 1.2: Installation cost estimates for a standard septic tank installed in conjunction with an absorption bed (left) and seepage pit (right). Figures are based on a 3-bedroom house and a percolation rate no slower than 5 min/inch. Standard Absorption Bed Seepage Pit Low (non-traffic) High (Traffic Rated) Low (non-traffic) High (Traffic Rated) Septic Tank 3,000.00 7,000.00 3,000.00 7,000.00 D-Box 750.00 2000 .00 –– Sewer pipe 250.00 250.00 250.00 250.00 Leach field-pipe/ chamber 500.00 3,000.00 –– Leach field-gravel 1,000.00 500.00 –– Cone. Ring ––3,000.00 3,000.00 Cone. Cover ––2,500.00 4,000.00 Soil replacement 1,500.00 1,500.00 –– Inspection ports 500.00 500.00 –– Misc. material 2,000.00 2,000.00 2,000.00 2,000.00 Material Total $ 9,500.00 $ 16,750.00 $ 10,750.00 $ 16,250.00 Labor / Equipment 7,500.00 15,000.00 7,500.00 15,000.00 Remoteness 5,000.00 5,000.00 5,000.00 5,000.00 Trucking for spoils 3,000.00 3,000.00 3,000.00 3,000.00 Tight working space 3,000.00 10,000.00 3,000.00 10,000.00 Relocate/reinstall/ repair 5,000.00 50,000.00 5,000.00 50,000.00 TOTAL $ 33,000.00 $ 99,750.00 $ 34,250.00 $ 99,250.00 Pāhala Individual Wastewater System Preliminary Engineering Report 6 1 • Operations and Maintenance cost: Operations and maintenance cost also play a big role in overall cost of IWS. Annual maintenance costs for a traditional septic system can typically run up to $400/year. Additional operations costs for aerobic treatment units are estimated to be $18,000/year to cover the electricity bill and contract operator cost. Annual maintenance costs to the County and homeowner vary depending on the management strategy. Here it is estimated that bringing maintenance in-house is the most affordable option (Table 1.3). However, the use of an efficient asset management tool could bring down cost redundancy in the following strategies. Annual costs over a 20-year service lifetime are further expounded in Appendix C. Table 1.3: The costs associated with four IWS management models, assuming septic systems with leach fields (Appendix A). Management Model Average Annual Cost to County Average Annual Cost to Homeowner Net Annual Cost to County Total Annual Dollars SpentThird-Party Service Provider In-House Third-Party Service Provider County Sewer Bill 2A: Maintenance Contract w/ County in- house staff –($956)-$6001 ($356)($956) 2B: Maintenance Contract w/ 3rd Party Service ($783)($572)-$6001 ($755)($1,355) 3A: Operating Permits w/ O&M by Users –($572)($733)-($572)($1,305) 3B: Operating Permits w/ O&M Voucher by County ($533)($572)-$6001 ($505)($1,105) 1.3 Environmental Considerations Properly designed and operated IWS are an effective means of wastewater disposal at a fraction of the cost compared to a centralized treatment facility. Conversely, poorly designed and maintained IWS are failing at rates between 25-70% nationally (Mohamed, 2009). Approximately 168,000 viral and 34,000 bacterial illnesses each year in the US can be traced to failing septic tanks (Ibid.). Septic tanks are also the second most common contributor to groundwater pollution and a contributing source in one-third of all harvest-limited ocean growing areas (EPA, 2003). Consequently, care must Pāhala Individual Wastewater System Preliminary Engineering Report 7 1 be taken in both the technical design and management strategy of IWS. The DOH Wastewater Branch has assigned priority levels to each of the 88,000 cesspools across the state of Hawai‘i (DOH, 2017). These priority levels ranged from Priority 1: Significant Risk of Human Health Impacts, Drinking Water Impacts, or Draining to Sensitive Waters to Priority 4: Impacts Not Identified. Priority 1 and 2 areas would be required to upgrade sooner and to higher levels of treatment. On Hawai‘i Island, the Hilo Bay, Kona, Puakō, and Kapoho were identified as priority 3 areas while Kea’au was identified as priority 2. Pāhala meanwhile fell under priority 4, the lowest of those available, as an area for which health and environmental risks had not been assessed or appeared low. Subsequently, a more comprehensive 2021 study that explored Hawai‘i’s cesspool prioritization, factoring in a total of 15 risk factors, reached a similar conclusion (Mezzacapo & Shuler, 2021). Figure 1.2: Prioritization of Hawai‘i Island cesspools based on 15 site specific risk factors (Mezzacapo, 2022) 2017 Priority Areas Priority 1 Priority 2 Prioirty 3 Cesspools: Prioritization Catagory by Block-Groups Pāhala Individual Wastewater System Preliminary Engineering Report 8 1 1.4 Constructability IWS are designed to treat and dispose of wastewater generated by individual homes. The design of these systems must take into account a variety of technical considerations to ensure the system functions as intended and protects public health and the environment: • System Size: The size of the system, including the number of bedrooms or the flow rate, can significantly affect the design of an IWS, particularly in space-constrained communities like Pāhala. • Site Conditions: The soil type, slope, drainage patterns, and accessibility of the site can affect the design and cost of the system. For example, a site with poor soil conditions may require more expensive treatment methods or additional site preparation. • Location: Factors such as labor and materials costs will increase due to the remoteness of the community and distance from major population and commercial centers. • Influent Characteristics: Pollutant types and concentrations can vary significantly from property to property. Wastewater produced from a single-family household is quite different from that of a restaurant, for example. • Level of Treatment: The desired level of treatment can also affect the design. If regulations require a higher level of treatment than a conventional septic system can provide, advanced treatment systems are required. The following section outlines the impact of these considerations on the constructability of a system of IWS to serve the Pāhala community. 1.4.1 Available Space Per Property Lots to be served in the community vary in size from 0.12 to 67 acres with a median size of 0.24 acres (Figure 1.3). Per Hawai‘i Administrative Rules, HAR 11-62-31.1 (2)(A), 10,000 ft2 (0.23 acres) of usable land must be available for each IWS. Of the 170 properties to be served in this project, 81 have less than 10,000 ft2 of total area. Space available for IWS installation on these properties is further limited by the presence of both permitted and unpermitted structures. Pāhala Individual Wastewater System Preliminary Engineering Report 9 1 Distribution of total acreageProperties to be served in PāhalaFigure 1.3: Distribution of total acreage (x-axis) for properties to be served in Pāhala under this project. The actual location of treatment and disposal infrastructure is limited by setback requirements. DOH-required setbacks are presented below (Table 1.4). From a system design perspective, it is recommended that systems should also be a minimum of 20 feet from any cut-face slopes present on a site to avoid surfacing of treated effluent. This is a particular constriction to heavily sloped sites. Table 1.4: DOH required setbacks for wastewater systems per HAR 11-62. Features Treatment Unit (ft)Seepage Pit (ft)Soil Absorption System (ft) Structure Wall Line 5 5 5 Property Line 5 9 5 Surface Water Body 50 50 50 Large Trees 5 10 10 Municipal Water Supply Well 1000 1000 1000 1.4.2 Site Slopes Slopes vary from site to site but the project as a whole has roughly a 10% grade (Appendix D). This is likely to affect the constructability of absorption beds as a method of wastewater disposal. Per HAR Pāhala Individual Wastewater System Preliminary Engineering Report 10 1 11-62-34, absorption beds shall not be installed on land with a slope gradient greater than 8%, while absorption trenches are permitted on a slope of up to 12%. . 1.4.3 Traffic Area It is generally not good practice to install an IWS under a trafficked or otherwise concreted area. The presence of concrete or traffic compresses the soil in distribution systems and affects the accessibility of the system for maintenance. However, it is sometimes unavoidable on particularly spatially-constrained properties. In this event, a system may be installed underneath a driveway or patio provided the system is designed to that end and traffic rated treatment components are used. These may include products such as concrete septic tanks and/or H-20 traffic related chambered disposal beds. 1.4.4 Site Geology The US Geology Survey was consulted for site soils information (Appendix E). The site is principally composed of Nā‘ālehu medial silty clay loam and Puueo-Nā‘ālehu complex. The surface of both compositions features silty loam, but the Puueo-Nā‘ālehu complex gives way to lithic bedrock at a depth of approximately 20-40 inches. This data was reinforced by the boring logs from a 2012 Ka’ū Gymnasium Foundation Investigation by Hirata & Associates and a 2021 Geotechnical Data Report by Yogi Kwong Engineers that found fresh to moderately weathered basalt extending to a depth of 15-25 feet. From Hirata & Associates (Appendix F): “The surface soil consisted of brown clayey silt derived from volcanic ash. Although the clayey silt/volcanic ash encountered in our borings appeared to be in a firm to medium stiff condition, laboratory testing indicated high compressibility characteristics. Underlying the surface volcanic ash at depths ranging from about 6 inches to 4.5 feet was gray, slightly to moderately weathered basalt. The basalt was in a medium hard to hard condition and extended to the maximum depths drilled (24.5 ft). A cavity was encountered within the basalt stratum in a boring at depths of about 11 feet, extending down to 14 feet” From Yogi Kwong Engineers (Appendix G): Basalt lava flows were encountered underlying the Fill or Tephra Deposits at an initial depth ranging from approximately 1.0 to 5.5 feet bgs through the explored depths of approximately 15.0 to 25.1 feet bgs. The encountered basalt lava flows ranged from fresh to slightly Pāhala Individual Wastewater System Preliminary Engineering Report 11 1 Measure 2022 EPI Pāhala LCC Replacement PER (min/in) 2012 Hirata & Associates Ka’ū Gymnasium Foundation Investigation (min/in) Test 1 10 @ 4 ft 8.5 @ 5 ft Test 2 10 @ 2 ft 18.5 @ 5 ft Test 3 4 @ 2.5 ft 23 @ 5 ft Test 4 10 @ 3 ft 16.5 @ 5 ft Test 5 –8.4 @ 5 ft weathered, medium hard to hard, intensely to occasionally fractured, and moderately vesicular to scoriaceous. The underlying basalt found at the site will significantly increase the size and installation cost of IWS. Further, it will be important to exercise caution during excavation due to the potential to encounter underground cavities and lava tubes. 1.4.5 Percolation Test Results IWS sizing is based on the percolation rate of the receiving soil. Percolation rates were estimated for the Pāhala community by two methods (Table 1.5): • Preliminary percolation tests were conducted to a depth of 2-4 feet at four sites distributed across the project (Appendix H). A tightly bonded gray basalt and volcanic ash soil layer was encountered in three of the four tests limiting the depth of the test. • 2012 records of percolation testing at the local Ka’ū Gymnasium were consulted (Appendix D). Similarly, gray basalt was encountered at a depth of 1-4 feet, however holes were drilled to a depth of five feet. Table 1.5: Percolation test results IWS traditionally take the form of a seepage pit or absorption field. Absorption fields disperse treated wastewater over a larger area using a buried network of gravity fed perforated pipes. Seepage pits, on the other hand, are deep holes, extending downward to achieve increased absorption area instead of horizontally. Absorption bed and seepage pit sizing for a typical three- bedroom home varies significantly with the percolation rate found on each property (Table 1.6). Pāhala Individual Wastewater System Preliminary Engineering Report 12 1 Table 1.6: Percolation test results Percolation Rate (min/in)4 12 20 Infiltration Area Required (ft2)345 525 630 Possible Absorption Field Length (ft) (W = 15 ft)23 35 42 Possible Seepage Pit Dimension (Diameter = 6 ft)12 19 22 Septic Tank Area Required (ft2)60 60 60 Total Footprint with Absorption Field (ft2)480 660 765 Total Footprint with Seepage Pit (ft2)120 120 120 1.4.6 Proximity to Bodies of Water An assessment for proximity to bodies of water found that all 170 of the properties in the Pāhala community exceed all required minimum DOH setbacks, avoiding any limitations to IWS installations (Table 1.7). Table 1.7: Proximity to bodies of water for properties in Pāhala with an existing cesspool from the Hawai‘i Risk Prioritization Tool (Mezzacapo & Shuler, 2021). Measure Min Med Max DOH Setback Distance to Surface Water (ft)400 1145 2073 50 Distance to Groundwater (ft)715 882 964 3 Distance to Municipal Well (ft)1155 2952 4536 1000 1.4.7 Accessibility The installation of an IWS can be a relatively invasive process requiring large equipment like excavators and cranes. Accommodating this equipment often requires the destruction of fencing, existing landscaping, and in some cases small structures. Building footprints as well as overhanging soffits must be considered in the design stage when approximating access path widths and selecting Pāhala Individual Wastewater System Preliminary Engineering Report 13 1 appropriate treatment system designs. Access should be considered for installation as well as future maintenance activities. Opportunities to resolve access issues include: • IWS Placement: Front-yard installations are recommended for homes without sufficient path widths to accommodate equipment access into the backyard. • Lightweight or Cast-in-Place Technologies: The use of a crane can be avoided by specifying cast-in-place concrete septic tanks instead of precast varieties for particularly inaccessible locations. Alternatively, plastic and fiberglass offer lightweight alternatives for simplified installation. • Alternate Access Routes: A property backyard may be accessed from a neighbors property by temporarily removing a fence. 1.4.8 Landowner Engagement The County of Hawai‘i has held meetings in both Pāhala and Nā‘ālehu in order to engage directly with community members about the status of the cesspool closure projects. Most recently, with the approval of the revised AOC, the County reinforced its commitment to the community and actively sought their engagement and support of the project. For example, all meetings follow important cultural protocols and are co-led by residents who are respected and speak on behalf of the community. Moreover, all meetings actively seek input from the community and provide updates on the project via PowerPoint presentations that provide a clear overview of new developments in the project. The following timeline provides an overview of important meetings and milestones that occurred in the past year: • In March 2022, a community meeting was held in Pāhala to gauge potential for community support. The EPA acknowledged revisions are needed to the 2017 AOC and reopens negotiations with the County. • In June 2022, the County signed the Proposed Revised AOC. DEM engages consultants. • In July 2022, the EPA signed the Revised AOC and circulated a draft for public comment. DEM begins work on feasibility studies, public presentation, and the project website. • On August 12, 2022, the website was launched. • August 22, 2022 is the effective date of the final Revised AOC. • On October 6, the first public meeting to discuss the final Revised AOC was convened. • In February 2023, a meeting was held in Pāhala to share the progress of the County’s most recent semi-annual report to the EPA. An update of the Feasibility Evaluation Report and the Preliminary Engineering Report are also shared via PowerPoint Pāhala Individual Wastewater System Preliminary Engineering Report 14 1 presentation. • The County recommits to the community by mailing notices to community members who have signed in. Notices are also posted to several local newspapers, the County webpage and the two community centers in Pāhala and Nā‘ālehu. Community buy-in is seen as especially important because the successful completion of this project necessitates that homeowners cooperate in the design and permitting process, the preparation of a simple floor plan, and of course during the construction process for access permission. On the surface, this project is a win for homeowners to be included in the project and the community. Their household cesspool or sewer connection will be upgraded to comply with the cesspool replacement mandate with government funding, a deal that most homeowners in Hawai‘i are not being offered. However, there are a number of sacrifices that homeowners will face: • New Operations and Maintenance Costs: Homeowners in Pāhala Community, currently connected to functioning individual cesspools, don’t currently pay annual operation or maintenance costs. Homeowners connected to the LCC are currently paying a reduced sewer fee representing about 50% of the standard sewer rate (Hawai‘i County, 2023). This project will either introduce a full-rate monthly sewer fee or a biannual bill for private maintenance of their new system. It is quite likely that some homeowners don’t see a need to upgrade from the current system. However, initial opposition to the project has largely been addressed through the County’s engagement efforts. • Property Destruction: Many homeowners are protective of their property. Permission is not trivial for a project that poses a risk to their landscaping, fences, and buildings. Homeowner satisfaction with the project will be closely linked with the speed and care with which their properties are upgraded and restored to pre-construction conditions or better. 1.4.9 Availability of Resources and Contractors As an island state, Hawai‘i faces unique challenges when it comes to the availability of IWS. The entire IWS market in Hawai‘i grew from 1192 units per year in 2018 to 1414 units per year in 2021. Based on permits issued, sourcing the 170 treatment units required for this project will require an increase in statewide treatment unit supply and workforce size by 14% (DOH, 2022). This will require advanced planning to overcome this logistic hurdle. Locally-based septic manufacturers include Jensen Precast on O‘ahu and Chemtainer on Hawai‘i Island. At present, Jensen produces approximately 40 concrete septic tanks per year. With that said, the company has stated that they have the capacity to build one septic tank per day to keep Pāhala Individual Wastewater System Preliminary Engineering Report 15 1 up with the needs of the project. The bottleneck to their current production rate has been cited as a shortage of inspectors, contractors, and engineers in the local market. Chemtainer manufactures polyethylene septic systems on Hawai‘i Island but was unwilling to share their annual production rates. Mainland treatment system manufacturers like Orenco and Infiltrator have significantly higher production rates but will also face increased shipping costs in transporting the units to Hawai‘i. In either scenario, it will be important to work with manufacturers from early in the design stage to reduce barriers and meet deadlines, and even then, it is possible that multiple suppliers will be required. Pāhala Individual Wastewater System Preliminary Engineering Report 16 2 2023 2024 2025 2026 ACTIVITY May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Design Topography Design Variance Permitting Procurement Advertise Bid Opening Award Contract Notice to Proceed Construction Pilot (1-10)Construction (1-10) LCC (11-109)Construction (11-20) Construction (21-30) Construction (31-40) Construction (41-50) Construction (51-60) Construction (61-70) Construction (71-80) Construction (81-90) Construction (91-100) Construction (101-109) Remaining (110-175)Construction (110-119) Construction (120-129) Construction (130-149) Construction (150-159) Construction (160-169) Construction (170-175) Regulatory Rule/Ordinance Change (by County)Construction (1-10) Kinetic Model 1 Section 2 Project Timeline 2.1 Project Schedule Phasing for this project should reflect deadlines as well as workforce and product availability. The AOC requires that the LCC be decommissioned and the 109 connected properties upgraded by the end of 2026, though the preliminary timeline projects completion by 2025. A 10-site pilot consisting of LCC connected properties is expected to be permitted and constructed by the end of 2023. Lessons learned will be integrated into the design and permitting of the next phase of 99 LCC connected properties, which will be completed before the end of 2024. Finally, the properties currently connected to individual cesspools should be permitted and constructed towards the end of 2024 and into 2025. For a single contractor, cesspools the IWS can be installed at a rate of one site per week on simple sites per week on simple sites, and one site every two weeks where soil conditions and accessibility are less favorable. In order to increase the pace of the project, multiple contractors will be awarded construction contracts in 10-lot bundles that may be completed simultaneously (Table 2.1). Table 2.1: Pāhala LCC Replacement Schedule Pāhala Individual Wastewater System Preliminary Engineering Report 17 2 2.2 Typical IWS Permitting and Construction process The permitting and construction process for IWS is largely standardized in the deliverables and timelines. First, the engineer prepares and submits a design package for DOH approval, which once received initiates the construction process. Once constructed, the engineer inspects the finished treatment system and files a final inspection report with the DOH. If everything is in order, the DOH returns an Approval for Use letter. The Pāhala LCC Replacement project will deviate from the standard process in three principal ways: • Properties to be Permitted in Bulk: The DOH has expressed the capacity to receive packages in groups of 10 or more properties. This will serve to expedite DOH review process. • Variance Requests: Due to preliminary data on percolation rates and property sizing, it’s expected that DOH variances to setback constraints will be required to accommodate absorption fields. Where space is still overly constrained, DOH variances will be required to allow for seepage pit installation. The procedure to receive a variance requires the rejection of the original design package and a subsequent variance application and review. This additional step usually adds approximately two months to the permitting process following design package review but the DOH has expressed willingness to allow the request for variance to be included with the initial design package. • Optioned Design: The geological conditions present at a given site will not be known until construction on that site commences. These conditions will have a significant impact on the disposal system design. To accommodate this uncertainty in the design and facilitate permitting, an optioned design package shall be submitted to the DOH to allow for a field determination according to the actual percolation rates and soil composition encountered. The timeline and deliverables for this procedure is outlined on the following page (Table 2.2). Pāhala Individual Wastewater System Preliminary Engineering Report 18 2 Step Timeline Party Deliverables Design Package + Variance Application Preparation 4-6 months Engineer • Site Evaluation/Percolation Test Result • IWS Calculation • Parcel map • Plot Plan • Simple Building Floor Plan for number of bedroom determination • IWS Layout • IWS Profile • IWS Details • Owner Certification form • $100 IWS Application Fee Design Package Review 2-4 weeks DOH Letter of Approval Variance Application Review 2 months DOH Letter of Approval for Construction Construction 1-2 weeks/property Contractor Completed IWS Inspection 1 day/property Engineer • Final Inspection Report (FIR) • As-Builts FIR Review 1 month DOH Approval for Use Table 2.2: Hawai‘i Permitting and Construction Process Pāhala Individual Wastewater System Preliminary Engineering Report 19 3 Section 3 Treatment Technologies 3.1 Septic Tanks Septic tanks are the most common conversion treatment technology in Hawai‘i. IWS contractors are familiar with the installation process and they operate without the need for electricity. A septic tank is an underground chamber made of concrete, fiberglass, or plastic, used for treating and disposing of household wastewater. The tank is filled with a mixture of wastewater and anaerobic bacteria, which break down the waste and separate it into three layers: a top layer of scum, a middle layer of liquid effluent, and a bottom layer of sludge (Figure 3.1). The liquid effluent flows out of the tank and into a means of disposal, where it is further treated and dispersed into the soil. The sludge and scum remain in the tank, and must be periodically pumped out by a professional septic service approximately once every two years, depending on usage. Figure 3.1: Side-view of a typical two-chambered septic tank (Carollo, 2021). Residential septic systems on their own remove about half of the organics in the wastewater stream and none of the nitrogen. The overall level of treatment is thought to be much higher when well- maintained and operating with a fully functional absorption bed (Table 3.1). Pāhala Individual Wastewater System Preliminary Engineering Report 20 3 Table 3.1: Typical septic system performance in Hawai‘i (Carollo, 2021). Contaminant Typical Raw Residential Wastewater 1 Typical Septic Tank Effluent Quality 2 Typical Effluent Quality Following Soil Absorption System 2 Total Nitrogen, mg N/L 4 14-40 39-82 ~1 TSS (mg/L)100-400 49-161 ~4 BOD (mg/L)100-400 132-217 <30 Fecal Coliform, MPN/100ml 3 ~106 1-106 ~13 1 From Table 2-1 (Water Resources Center (WRRC) University of Hawai'i-Manoa, 2008). 2 From Table 4-1 in the Onsite Wastewater Treatment Survey and Assessment Study (WRRC, 2008). 3 MPN/100mL = most probably number per 100 milliliters. There are several septic tank providers commonly used in Hawai‘i offering tanks of a variety of price points and materials. Septic tanks can be made from concrete, plastic, and fiberglass (Figure 3.2), each of which having its own set of pros and cons (Table 3.2). Where a septic tank is located beneath a vehicular traffic area, a traffic rated concrete septic tank can be used or a structural concrete slab designed for H-20 loading spanning a non-traffic tank may be used. Figure 3.2: Common septic tank materials and shapes in Hawai‘i (Carollo, 2021). Rectangular, Concrete Tank Oval, Concrete Tank Cylindrical, Concrete Tank Pāhala Individual Wastewater System Preliminary Engineering Report 21 3 Rectangular, Plastic Tank Fiberglass, Oval Tank Steel, Horizontal, Cylindrical Tank Table 3.2: Advantages and Disadvantages of Septic Tank Materials (Carollo, 2021). Septic Tank Material Advantages Disadvantages Concrete • Durable • Less susceptible to collapse and floatation • May be cast-in-place for custom shape • Precast tanks can be more expensive than plastic or FRP due to shipping and installation costs • Typically requires use of a crane for installation • Concrete may corrode over time due to acidic sewer gases Plastic (polyethylene) • Less expensive than precast concrete tanks (lower shipping and installation costs) • Variety of manufacturers and sizes for desired footprint • Plastics are typically resistant to corrosion • May not require a crane for installation • Plastic tanks may deform depending upon quality of the plastic and potential structural weaknesses of the material • If not installed properly, plastic tanks can float if flooded Fiberglass-reinforced polyester (FRP) • Less expensive than precast concrete tanks (lower shipping and installation costs) • Variety of manufacturers and sizes for desired footprint • Fiberglass is typically resistant to corrosion • May not require a crane for installation • More rigid and sturdy than plastic tanks • Less structurally strong than concrete tanks • If not installed properly, fiberglass tanks can float if flooded Pāhala Individual Wastewater System Preliminary Engineering Report 22 3 Ultimately, the choice of septic tank material will depend on availability, budget, and site constraints (Table 3.3). At a minimum, septic tanks in Hawai‘i must comply with International Association of Plumbing and Mechanical Officials (IAPMO) material and property standards for septic tanks. Further, sizing and installation criteria are regulated by HAR 11-62-33. The minimum septic tank capacity is 1,000 gallons for a household of 4 bedrooms or less and 1250 gallons minimum for households of 5 bedrooms. Septic tanks serving households greater than 5 bedrooms will require a variance from the DOH. Table 3.3: Common single family home septic tank products in Hawai‘i. Product Material Traffic Rated Capacity (Gal) Length (in)Width (in)Height (in) Weight (lbs) Local List Price Chem- tainer HDPE No 1250 96 58 62 400 $3,189 Infiltrator (via Ferguson) PP No 1287 127 62.2 54.7 320 $2,863 Orenco (via Custom Concrete & Septic) DCPD No 1500 168 72 64.5 620 $6,850 Jensen Precast Concrete Yes 1250 138 70 57 16,700 $6,850 3.2 Aerobic Treatment Units An ATU is a type of wastewater treatment system that utilizes oxygen and microorganisms to break down and treat household sewage. ATUs come in many proprietary shapes and sizes but at a minimum, systems typically include an aeration tank, where the wastewater is blended with air or oxygen while suspended microorganisms are able to grow and thrive and a settlement tank, where solids and other debris are allowed to settle out of the water (Figure 3.3). Pāhala Individual Wastewater System Preliminary Engineering Report 23 3 Figure 3.3: Side-view of typical aerobic treatment unit (Carollo, 2021) Ground FilterScum Sludge Primary Settling Basin Aerated Chamber Secondary Settling Basin To Effluent Disposal SystemAir Diffuser or Mixer Wastewater Motor or Blower The added complexity of the ATU system is responsible for higher treatment organic and nutrient removal rates that make ATUs optimal for operation upstream of sensitive receiving environments. Conversely, the added mechanical and electrical componentry leads to more frequent system downtime. Without an effective maintenance strategy, the performance of ATUs in Hawai‘i has been proven to be similar to septic tanks (Figure 3.4). ATUs are less affordable than septic tanks, as they have a higher up-front cost and a much higher O&M cost due to the requirement of contracting a certified wastewater treatment operator by the DOH. The ATU also expect a shorter service lifetime than septic systems due to its mechanical components (Babcock, 2019). Figure 3.4: Effluent quality of septic systems vs. ATUs in Hawai‘i (Babcock, 2012) Pāhala Individual Wastewater System Preliminary Engineering Report 24 3 3.3 Passive Biofilters or Constructed Wetlands A passive biofilter is a type of IWS that uses natural processes to treat and purify wastewater following a septic tank. It typically consists of a filter bed filled with a mixture of gravel, sand, and organic matter (such as wood chips or coconut fiber) that provides a habitat for microorganisms. These microorganisms break down the pollutants in the wastewater as it flows by gravity through the filter bed. The treated wastewater is then collected and can be safely discharged into the environment or reused for irrigation. Passive biofilters do not require electricity or mechanical parts, making them low-maintenance and cost-effective. Constructed Wetlands are very similar to passive biofilters except they are planted with native flora (Figure 3.5). These systems achieve high levels of nitrogen removal prior to disposal and often have a positive aesthetic impact on the site. However, they may require more space. The vegetation must also be regularly harvested to promote continued nitrogen removal and prevent clogging of the system. Both of these systems are considered secondary treatment works which the DOH requires to be operated and maintained by a certified wastewater treatment operator. Aside from the higher initial installation cost, the O&M cost can be up to 40 times that of the traditional IWS. Figure 3.5: Side-view of a typical constructed wetland following a septic tank (EPA, 2023) Constructed Wetland Septic System Pāhala Individual Wastewater System Preliminary Engineering Report 25 3 3.4 Recirculating Biofilter Recirculating biofilters are very similar to passive biofilters except the water is recirculated through the biofilter multiple times (Figure 3.6). On the first pass through the biofilter, ammonia is converted to Nitrate through nitrification. Returning this nitrified wastewater to the anoxic recirculation tank provides favorable conditions for denitrification, converting nitrate to inert nitrogen gas for total nitrogen (TN) removal. Expected TN removal rates vary from 50-70% before discharge. This improved treatment comes at the cost of increased installation cost, maintenance requirements, and electricity demand. Figure 3.6: Side-view of a typical recirculating biofilter following a septic tank (Babcock, 2019) In response to a request for a provisional design request made to several large-scale treatment product manufacturers, E-Z Treat provided an estimate and provisional design for their recirculating synthetic media filter units to serve the Pahala Community. The unit adds an additional $7,500 to $8,500 per household of material cost to a traditional septic system and improves effluent to meet stringent NSF 350 wastewater reuse standards. This solution is presented Appendix I. Maintenance demands are cited as an annual visual inspection of the system as there are no chemicals to add, filters to clean, or aerators to replace. However, similar to many ATUs, there’s limited precedent for the systems installation and performance in the State of Hawai‘i. Pāhala Individual Wastewater System Preliminary Engineering Report 26 3 • Individual Composting Toilets: These waterless toilets combine human waste with bulking material such as sawdust, leaves, or peat moss in a single chamber (Figure 3.7). The waste dries and composts in-situ until the container fills and is emptied into an outdoor composting pile to complete the composting process. Some composting toilets also use electrical or mechanical systems, such as an exhaust fan, to aid in the breakdown of waste and limit odors. These toilets do not require water or a connection to a sewer system, making them an eco-friendly alternative to traditional flush toilets. • Urine Diverting Toilets: Urine diverting toilets typically have two chambers: one for urine and one for solid waste (Figure 4.8). The urine is typically stored and used as a fertilizer, while the solid waste is broken down into compost. Figure 3.7: Component view of a typical individual composting toilet (Sun-Mar, 2023) Figure 3.8: Top view of a typical urine separating toilet (Separett, 2023) 3.5 Composting Toilets A composting toilet is a type of toilet that uses a combination of heat and aerobic microbial action to break down human waste into a nutrient-rich compost. Composting toilets typically come in three varieties: Pāhala Individual Wastewater System Preliminary Engineering Report 27 3 • Central Composting Units: These composters are installed outside the home and work in conjunction with pint-flush toilets. Toilet blackwater (along with a scoop of wood chips) flows through a 4” gravity sewer to the composter where its introduced to a horizontal drum that collects the solids and allows liquids to drain into the base of the enclosure (Figure 4.9). The drum must be rotated in the forward direction once every two days to fluff the retained solids and rotated in the reverse direction once every two months to drop the retained solids into an aging drawer where the composting process is completed. The outputs are a drawer of composted manure and the drained liquid. A single central composting unit can serve an entire home and solid wastes and any odors are kept entirely outdoors. Figure 3.9: Top view of a central composting unit (Sun-Mar, 2023) 3.6 Incineration Toilets An incineration toilet, also known as a thermal toilet, is a type of toilet that uses heat to turn human waste into ash (Figure 3.10). The waste is placed into a combustion chamber where it is heated to high temperatures, typically around 800-1000 degrees Fahrenheit, by a gas or electric burner. This process kills any harmful bacteria and viruses and reduces the volume of waste by up to 90%. The ash that is left can be safely disposed of in a landfill or used as a fertilizer. Incineration toilets do not Pāhala Individual Wastewater System Preliminary Engineering Report 28 3 require any water, making them suitable for remote locations or areas with limited water resources. They also produce very little smell and have no need for a septic system or connection to a sewer. However, they do require electricity or gas to operate, and can be relatively expensive to purchase and maintain. Further, they do not comprise a complete treatment solution. While the remaining household gray water can be disposed of with minimal treatment, a septic tank or other treatment unit is still required to treat kitchen blackwater, eliminating the economic advantage. No matter the variety, composting toilets and incineration toilet technologies are significantly cheaper than septic tanks and other IWS. Unfortunately, they do not comprise a complete treatment solution. While the remaining household gray water can be disposed of with minimal treatment, a septic tank or other treatment unit is still required to treat kitchen blackwater, eliminating the economic advantage. Figure 3.10: Side view of a typical incinerating toilet (Cinderella, 2023) Pāhala Individual Wastewater System Preliminary Engineering Report 29 4 Section 4 Disposal Technologies 4.1 Absorption beds Absorption beds are the most common form of IWS installed in Hawai‘i today. They consist of a network of perforated pipes, each a maximum of 100 feet long and laid in trenches 1.5-3 feet below the finished grade 4-6 feet apart (Figure 4.1). Each line is laid level to allow the gravity dispersal of treated effluent through the length of the pipe before it filters out and percolates down into the soil. A minimum of 6 inches of gravel is provided below each pipe. If the percolation rate is faster than one minute per inch, a depth of 3-foot soil replacement shall be installed to underlay the entire absorption bed. Soil replacement shall be washed #4 sand or cinder-soil mix with a percolation rate not faster than one minute per inch. These systems are easy to maintain when following an effective treatment system and microorganisms in the soil offer an added degree of treatment to the effluent as it filters through the upper oxic layers of the soil matrix. Absorption beds however have a significant space requirement with current Hawaiian regulations requiring a minimum of 350 sq ft for a 4-bedroom home. This space requirement increases with decreasing hydraulic conductivity of the soil as discussed in Section 4. Additionally, absorption beds can only be installed on a grade of less than 8%. While conventional perforated pipe adsorption beds are not traffic rated, companies such as Infiltrator offer a chambered dispersion product with an H-20 load rating that can also reduce the absorption bed space requirement by 17%. Usage Case: Used on typical lots without spatial, groundwater level, grade, or percolation rate constraints. Pāhala Individual Wastewater System Preliminary Engineering Report 30 4 Figure 4.1: Typical absorption field installed following a septic tank (Babcock, 2019) 4.2 Absorption trench An absorption trench is a type of subsurface wastewater disposal system that utilizes a trench filled with gravel or other porous material to filter and distribute household wastewater into the ground (Figure 4.2). Wastewater is distributed into the trench through a network of pipes, typically made of PVC or other durable materials. The gravel in the trench acts as a natural filter, allowing the water to slowly seep into the surrounding soil while also removing impurities with adsorbed beneficial bacteria. The trench may be lined with a layer of filter fabric to prevent the gravel from becoming clogged with soil or other debris. The percolation area of the system is calculated as the combined bottom area of the trenches. Individual trenches must be between 18 and 36 inches, with trenches more than 6 feet apart and suitable for installation on slopes up to 12%. Usage Case: Used on steeper lots with grades of 8-12%. Pāhala Individual Wastewater System Preliminary Engineering Report 31 4 4.3 Combined Treatment and Disposal System Combined Treatment and Disposal Systems (CTDS) combine chambered absorption beds with geo- textile fabric, and porous media to perform treatment and disposal in a single operation. One example of these systems consists of special 10 ft long by 12” diameter pipes embedded in a specific type of sand. The pipes contain ridges, perforations with skimmers, geotextile fabric, green plastic fiber mat, and fabric to support biofilm development (Figure 4.3). These components facilitate the distribution of water and development of a biomat along the length of the pipes. Without using any electricity or replacement media, CTDS following a traditional septic tank can offer BOD, TSS, and ammonia removal on par with aerobic treatment units. Unfortunately, there is little precedent for the use of CTDS in Hawai‘i to quantify their performance, lifespan, and design requirements for the State of Hawai‘i. Furthermore, this type of system is considered a secondary treatment system which requires a DOH certified operator to perform O&M. Usage Case: Used on lots with strict effluent quality requirements. Figure 4.2: Typical absorption trench system installed following a septic tank (Carollo, 2021). Pāhala Individual Wastewater System Preliminary Engineering Report 32 4 Figure 4.3: An example of a proprietary fixed-film CTDS (Infiltrator, 2023). An alternative CTDS involves a “layer cake” filtration system of 18 inches of sand and 18 inches of a sand and sawdust mixture (Figure 4.4). Aerobic processes take place in the oxic sand layer while an anoxic environment is created in the sawdust layer. This sequence of oxic and anoxic stages promotes TN removal rates from 50-90%. Pāhala Individual Wastewater System Preliminary Engineering Report 33 4 Figure 4.4: An example of a non-proprietary “layer cake” CTDS (Babcock, 2019). 4.4 Seepage pit Seepage pits are a vertical means of achieving the percolation area requirements for a disposal system. These systems typically consist of a 15-30-foot-deep pit lined with stacked precast perforated concrete rings or CMUs, to an internal diameter of 6-8 ft. Seepage pits are both less area intensive and less expensive than absorption beds, if converted from an existing cesspool (Table 9.1). A seepage pit must include a cover which extends at least 12 inches beyond the seepage pit excavation or over a provided concrete lining. An access hatch must be provided in the concrete cover to allow inspection and maintenance of the pit. The seepage pit may be designed to be traffic rated by providing the sufficient strength required in the design of the concrete lining and cover. The effective area of the seepage pit is equal to the vertical wall area corresponding to the effective depth of the pit. Slow percolation rates translate to a larger required absorption area and deeper pit (Appendix H). While seepage pits are an approved means of disposal in Hawai‘i, they are often only permitted when it can be demonstrated that an alternative means of disposal was not possible , i.e. insufficient land area, steep terrain (>12%) or very slow percolation rates (>60 min/inch). Where slow percolation rates present, seepage pits will need to be dug through the basalt rock layer to reach more porous soils or a variance will be required from HAR 11-62-34 d(1)b: Pāhala Individual Wastewater System Preliminary Engineering Report 34 4 Seepage pits shall not be constructed in soils having a percolation rate slower than ten minutes per inch (weighted average) or where rapid percolation through such soils may result in contamination of water-bearing formations or surface water. Usage Case: Used on highly spatially constrained, slope constrained, or geologically constrained lots where sufficient percolation rates can be achieved. 4.5 Subsurface drip irrigation Subsurface drip irrigation is an extremely water efficient means of wastewater disposal, slowly delivering effluent into the shallow subsurface and biologically active root zone of plants, promoting efficient uptake of nutrients by the microbes and plants in the soil medium (Figure 4.5). Installation of subsurface systems often requires less disruption to the absorption area though in Hawai‘i, they traditionally cost more. Regular maintenance is required to ensure the continued operation of the irrigation pump and manage biofouling in the distribution lines and the dripper clogs it causes. Disinfection is required following aerobic treatment as an added measure against biofouling and clogging of the distribution lines. Usage Case: Used on lots that prioritize wastewater reuse, are served by an ATU, and have a robust maintenance strategy. Pāhala Individual Wastewater System Preliminary Engineering Report 35 4 Figure 4.5: Typical subsurface drip irrigation installed following a septic tank (EPA, 2023) Drip Distribution Septic System 4.6 Greywater system Greywater systems are systems that collect and reuse wastewater from sources such as sinks, showers, and laundry machines. The collected water is then treated and can be used for irrigation or other non-potable uses such as toilet flushing. The use of separated gray water systems can help reduce the load on wastewater treatment units and conserve water through reuse. In Hawai‘i, the use of greywater systems is regulated by the State Department of Health, which sets guidelines for the treatment and reuse of greywater. Gray water systems can vary in complexity and cost. Simple systems, such as diverting water from a clothes washer to a garden, can be relatively Pāhala Individual Wastewater System Preliminary Engineering Report 36 4 inexpensive and easy to install (Figure 4.6). More complex systems may include treatment methods such as sand filtration, ultraviolet disinfection, or reverse osmosis. Overall, these systems are typically expensive to install and maintain as they are installed in addition to a traditional wastewater treatment system that’s still required to treat household black water. Usage Case: Used on lots with source separated plumbing that prioritize wastewater reuse. Figure 4.6: Typical greywater reuse system installed in parallel with a septic tank (DOH, 2009) Pāhala Individual Wastewater System Preliminary Engineering Report 37 5 Section 5 System Design 5.1 IWS Selection In 2019, Dr. Roger Babcock and the team at the Water Resources Research Center (WRRC) put together a report investigating the viability of cesspool upgrade options for 12,000 homes in upcountry Maui. In total, 38 options were evaluated, half of which used exclusively IWS methodologies, while the other half considered partial or full sewering of the community. The most applicable are presented in the table below (Table 5.1). The lifetime net present value assessments were made over a 60-year period using a discount rate reflective of public sector investment (2.8%). These treatment systems comprise a toolbox from which engineers can select site appropriate systems for individual property conditions. When making a selection, engineers should consider existing regulations, environmental concerns, site constraints, economics, and performance. Overall, each household IWS will cost $30,000-$100,000 to install and roughly $1,000 per year to operate and maintain. Based on the compiled data, this report points to the installation of traditional septic tanks with standard absorption beds. Where space and grading constraints prevent the installation of an absorption bed, the existing cesspool shall be repurposed as a seepage pit for disposal. This solution was selected for three reasons: • Passive Operation: The traditional septic IWS offers a passive operation with minimal O&M cost. While the ATUs offer the promise of improved performance, in practice in Hawai‘i, the added mechanical and electrical complexity and the operator requirement results in higher than average O&M costs or facing the risk of falling into similar treatment performance comparable to septic tanks. • Adaptive to Small Lots: The option of disposing to seepage pits allow septic systems to be installed particularly on spatially and geographically constrained lots. • Familiarity: Hawai‘i’s engineers, regulators, contractors, and septic pumpers are familiar with septic tanks, absorption beds, and seepage pits. The ATU and CTDS, on the other hand, are less known. Furthermore, the lack of certified wastewater operators throughout the State will result in higher cost and reduced performance for ATU and CTDS options. Pāhala Individual Wastewater System Preliminary Engineering Report 38 5 Treatment Disposal Estimated Nitrogen Reduction NPV Cost Per Property O&M Burden Usage Case Effluent Criteria Slope Perc Rate (min/in)Area Septic Seepage Pit 10%Low Low Low >12%<10 Low Absorption Field 47%Low Low Low <8%<60 High Absorption Trench 47%Low Low Low <12%<60 High Constructed Wetland 53%Med Med Med <8%<60 High “Layer Cake” CTDS 55%Med Low Med <8%<60 High Fixed-Film CTDS 78%Low Low Strict <12%<60 Med Septic + Recirculating Biofilter Seepage Pit 47%High Med Med >12%<10 Low Drip Irrigation 69%Very High Med Strict High Absorption Field 84%Low Med Strict <8%<60 High ATU Absorption System 53%Very High High Med <8%<60 High Constructed Wetland 58%Very High High Strict <8%<60 High ATU + Disinfection Seepage Pit 50%Very High High Med >12%<10 Low Drip Irrigation 71%Very High High Strict High Table 5.1: An abridged selection of IWS options from cesspool replacement analysis of upcountry Maui community (Babcock, 2019) Pāhala Individual Wastewater System Preliminary Engineering Report 39 R References Babcock, R., Barnes, M., Fung, A., Goodell, W., & Oleson, K. (2019). Investigation of Cesspool Upgrade Alternatives in Upcountry Maui Final Report. University of Hawaii Manoa. Babcock, R., Lamichhane, K. M., Cummings, M. J., & Cheong, G. H. (2014). Condition assessment survey of onsite sewage disposal systems (OSDSs) in Hawaii. Water Science and Technology, 70(6), 1083–1089. https://doi.org/10.2166/wst.2014.336 Carollo Engineers (2021). Cesspool Conversion Technologies Research Summary Report. Hawaii State Department of Health. Hawaii County Code, Chapter 21 Sewers (2016). https://www.hawaiicounty.gov/home/ showpublisheddocument/46/637032750278570000 Hawaii State Department of Business, Economic Development and Tourism. (2021). The State of Hawaii Data Book: A Statistical Abstract. State of Hawaii Department of Business, Economic Development, and Tourism. https://files.hawaii.gov/dbedt/economic/databook/db2021/ DB2021_final.pdf Environmental Protection Agency (2003). Voluntary National Guidelines for Management of Onsite and Clustered (Decentralized) Wastewater Treatment Systems. Environmental Protection Agency. https://www.epa.gov/sites/default/files/2015-06/documents/septic_guidelines.pdf Environmental Protection Agency. (2018) Types of Septic Systems [Overviews and Factsheets]. https://www.epa.gov/septic/types-septic-systems Environmental Protection Agency (2010). Code of Federal Regulations, 40 C.F.R §144.80 Title 40— Protection of Environment. https://www.govinfo.gov/content/pkg/CFR-2014-title40-vol23/ xml/CFR-2014-title40-vol23-part144.xml Evergreen. (2023). Separett Villa urine separating toilet. Evergreen. https://evergreen.eco/en-us/ products/urine-separating-toilet-villa-9020-12v-230v Hawaii State Department of Health. (2009). Guidelines for the Reuse of Gray Water. Hawaii Department of Health Wastewater Branch. https://health.hawaii.gov/wastewater/ files/2016/03/14_Gray_Water_GL.pdf Hawaii State Department of Health. (2016) HAR 11-62 Wastewater Systems. https://health.hawaii. gov/opppd/files/2015/06/11-62-Wastewater-Systems.pdf Hawaii State Department of Health. (2017). Relating to Cesspools and Prioritization for Replacement. https://health.hawaii.gov/opppd/files/2017/12/Act-125-HB1244-HD1-SD3-CD1-29th- Legislature-Cesspool-Report.pdf Pāhala Individual Wastewater System Preliminary Engineering Report 40 R Hawaii State Department of Health. (2022). IWS Final Approval Date Report (04/01/2017-04/01/2022). Hawaii State Department of Health Wastewater Branch. Incinerating Toilets Inc. (2023). Cinderella Comfort Incinerating Toilets. Incinerating Toilets Inc. https://incineratingtoilets.com/us/product/cinderella-comfort/ Infiltrator. (2023). Advanced Enviro-Septic. Infiltrator Water Technologies. https://www. infiltratorwater.com/products/presby-environmental/advanced-enviro-septic/ Lekven, C. (2019). Pahala Wastewater Treatment Plant Preliminary Engineering Report. Brown and Caldwell. https://www.epa.gov/sites/default/files/2020-03/documents/pahala_final_ea_ vol_2_508_2020-02-24.pdf Mezzacapo, M., & Shuler, C. (2021). 2021 Hawaii Cesspool Hazard Assessment and Prioritization Tool. University of Hawaii. https://health.hawaii.gov/wastewater/files/2022/01/ priortizationtoolreport.pdf Mohamed, R. (2009). Why households in the United States do not maintain their septic systems and why state-led regulations are necessary: Explanations from public goods theory. International Journal of Sustainable Development and Planning, 4, 143–157. https://doi. org/10.2495/SDP-V4-N2-143-157 Peterson, A. (2010, May 2). Plantation Era Is Gone, and Pahala Lives On: Historic Preservationist Julia Neal Uses Hammer and Wood to Pull the Community Together. Ke Ola Magazine. https://keolamagazine.com/community/plantation-era-gone-pahala-lives-on/ Pine Creek Structures. (2023). Excel NE Sun-Mar Composting Toilet. https://www.storageshedspa. com/sheds/other-products/17759/excel-ne-sun-mar-composting-toilet ShopTinyHouses. (2023). Sun-Mar Centrex 3000 Composting Toilet System. ShopTinyHouses.Com. https://www.shoptinyhouses.com/products/sun-mar-centrex-3000-central-composting- toilet-system A-1 A Appendix A - LCC Closure Properties A-2 A Pahala LLC Closure Absorption Field TMK#Owner Address Land Area (acres)# of Buildings # ofBedrooms Est. WW Gen.Septic Tank 1min/in.2min/in.Remarks dwg 9-6-014-053 Michael Munnerlyn 96-1335 Huapala Street 0.3315 1 3 600 1000 210 255 ok Y 9-6-014-054 Leroy Kenji Nagasako 96-1331 Huapala Street 0.3315 1 3 600 1000 210 255 ok Y 9-6-014-055 Edwin Mitsunaga 96-1325 Huapala Street 0.3315 1 3 600 1000 210 255 ok Y 9-6-014-056 Andrade Family Trust 96-1321 Huapala Street 0.3014 1 3 600 1000 210 255 ok Y 9-6-014-057 Ferdinand Capiral Ramos 96-3210 Hau Street 0.2861 1 5 1000 1250 350 425 432 Traffic rated Y 9-6-014-047 Domingo C Ramos JR 96-1305 Huapala Street 0.293 1 3 600 1000 210 255 ok Y 9-6-014-046 John Katchmar 96-1297 Haupala Steet 0.2435 1 3 600 1000 210 255 ok Y 9-6-014-045 Kandra Sanders 96-1289 Huapala Street 0.2479 1 3 600 1000 210 255 ok Y 9-6-014-044 Faith Derasin 96-1287 Huapala Street 0.168 1 3 600 1000 210 255 not fit fitted needs to be verified on site Y 9-6-014-043 Ramona Ponce 96-1281 Huapala Street 0.1674 1 3 600 1000 210 255 ok Y 9-6-014-042 Maria Hohnson 96-1277 Haupala Street 0.1674 1 3 600 1000 210 255 ok fitted needs to be verified on site Y 9-6-014-041 Kazuto Judalena 96-1275 Huapala Street 0.1681 1 3 600 1000 210 255 not fit fitted needs to be verified on site Y 9-6-014-040 Harold Kaneshiro 96-1271 Huapala Street 0.1666 1 3 600 1000 210 255 ok Y 9-6-014-039 Alfredo Asistin 96-1269 Huapala Street 0.1658 1 3 600 1000 210 255 ok Y 9-6-014-038 Dennis Andres 96-1265 Huapala Street 0.1658 1 3 600 1000 210 255 ok Y 9-6-014-037 Kelly Keoki Galimba 96-1261 Huapala Street 0.1674 1 3 600 1000 210 255 ok Y 9-6-014-036 Takeshi Kunihiro 96-1259 Huapala Street 0.1674 1 3 600 1000 210 255 ok Y 9-6-014-035 Zoe Alexandra Eustathiades 96-1257 Huapala Street 0.1627 1 3 600 1000 210 255 ok Y 9-6-014-034 Kenneth Yokota 96-1255 Huapala Street 0.1581 1 3 600 1000 210 255 ok Y 9-6-014-033 Philip Becker 96-1253 Huapala Street 0.1576 1 3 600 1000 210 255 not fit cut trees to fit Y 9-6-015-006 Hajime Ueda Trust 96-1252 A Huapala Street 0.3464 1 4 800 1000 280 340 ok Y 9-6-015-008 Sally Yamaguchi Trust 96-1258 Huapala Street 0.5667 1 3 600 1000 210 255 ok Y 9-6-015-009 Gloria Camba 96-1266 Huapala Street 0.6415 1 0 0 0 0 ok Y 9-6-014-052 Tsuruo Sumida 96-1334 Ilima Street 0.3073 1 3 600 1000 210 255 ok Y 9-6-014-051 Michael Kawachi 96-1326 Ilima Street 0.3315 1 3 600 1000 210 255 ok Y 9-6-014-050 Jeffrey Kekoa 96-1322 Ilima Street 0.3315 1 3 600 1000 210 255 ok Y 9-6-014-049 Rodney Takaki 96-1320 Ilima Street 0.3014 1 3 600 1000 210 255 ok Y 9-6-014-048 Estrella Ssuncion 96-3214 Hau Street 0.2861 1 5 1000 1250 350 425 ok Y 9-6-014-017 Lilybeth Orcino 96-3215 Hau Street 0.3083 1 3 600 1000 210 255 ok Y 9-6-014-018 Judy Jara 96-1300 Ilima Street 0.1609 1 3 600 1000 210 255 pls verify fitted confirm structure backyard Y 9-6-014-019 Longakit Family Trust 96-1298 Ilima Street 0.1561 1 3 600 1000 210 255 pls verify fitted confirm structure near septic tank Y 9-6-014-020 Stanley Lorenzo 96-1296 Ilima Street 0.1591 1 2 400 1000 140 170 ok Y 9-6-014-021 Ralphielyn Gaston-Lovell 96-1294 Ilima Street 0.1654 1 3 600 1000 210 255 pls verify have structures at the backyard Y 9-6-014-022 Lillian Oliveira Estate 96-1292 Ilima Street 0.1654 1 3 600 1000 210 255 pls verify have structures at the backyard Y 9-6-014-023 Amy Siva (Deceased)96-1290 Ilima Street 0.1652 1 3 600 1000 210 255 pls verify have structures at the backyard Y 9-6-014-024 Sixto Asuncion 96-1288 Ilima Street 0.1626 0 0 0 0 0 ok N/A 9-6-014-025 Saburo Fukunaga 96-1286 Ilima Street 0.1673 1 3 600 1000 210 255 ok Y 9-6-014-026 Alfred Galiza 96-1284 Ilima Street 0.1646 1 3 600 1000 210 255 pls verify have structures at the backyard Y 9-6-014-027 Jerry Villa 96-1282 Ilima Street 0.1644 1 3 600 1000 210 255 ok Y 9-6-014-028 Greg Mitsunaga 96-1280 Ilima Street 0.1673 1 3 600 1000 210 255 ok Y 9-6-014-029 Newton Ito 96-1278 Ilima Street 0.1684 1 5 1000 1250 350 425 not fit have structures at the backyard Y A-3 A 9-6-014-030 Iris Haugen 96-1276 Ilima Street 0.1641 1 3 600 1000 210 255 not fit have structures & trees at the backyard based on map and st view Y 9-6-014-031 Toshio Okamura 96-1274 Ilima Street 0.1626 1 3 600 1000 210 255 ok need to cut trees Y 9-6-014-032 CLH Trust 96-1272 Ilima Street 0.1615 1 3 600 1000 210 255 not fit could not fit with the existing structure on the backyard N 9-6-014-014 Frank Lorenzo J SR 96-1299Ilima Street 0.2154 1 3 600 1000 210 255 ok Y 9-6-014-013 Elizabeth Stone 96-1295 Ilima Street 0.2503 1 3 600 1000 210 255 ok 9-6-014-012 Steven Wroblewski 96-1293 Ilima Street 0.1814 1 3 600 1000 210 255 ok Traffic rated septic tank Y 9-6-014-011 Clement Andrade 96-1291 Ilima Street 0.1791 1 3 600 1000 210 255 not fit fitted front yard traffic rated septic tank Y 9-6-014-010 Patrick Kailiawa 96-1289 Ilima Street 0.1798 1 3 600 1000 210 255 not fit fitted backyard verify structures Y 9-6-014-009 Albert Ledergerber 96-1287 Ilima Street 0.1791 1 3 600 1000 210 255 ok Y 9-6-014-008 Deisha-Lyn Nurial-Dacalio 96-1285 Ilima Street 0.1798 1 3 600 1000 210 255 ok verify structures affected Y 9-6-014-007 Malia Panglao 96-1283 Ilima Street 0.1741 1 3 600 1000 210 255 ok Y 9-6-014-006 Young Elena Branch 96-1281 Ilima Street 0.1774 1 3 600 1000 210 255 ok Y 9-6-014-005 Young Elena Branch 96-1279 Ilima Street 0.1764 1 3 600 1000 210 255 ok Y 9-6-014-004 Sandra Polido 96-1277 Ilima Street 0.1798 1 3 600 1000 210 255 ok best fit might need to cut trees Y 9-6-014-003 Takamari Fukunaga 96-1275 Ilima Street 0.1781 1 3 600 1000 210 255 ok best fit might need to cut trees Y 9-6-014-002 Philip Alexander Becker Trst 96-1273 Ilima Street 0.1731 1 3 600 1000 210 255 ok best fit might need to cut trees Y 9-6-014-001 Barbara McBeath 96-1271 Ilima Street 0.1714 1 3 600 1000 210 255 ok best fit might need to cut trees Y 9-6-015-016 Ruby Manantan 96-1247 Hinano Street 0.2271 1 3 600 1000 210 255 ok Y 9-6-015-017 Chuck Higashi 96-1243 Hinano Street 0.2939 1 3 600 1000 210 255 ok Y 9-6-015-018 Hawaii Methodist Union 96-1239 Hinano Street 0.262 1 4 800 1000 280 340 ok Y 9-6-015-019 Wayne Nahinu Dacalio 96-1235 Hinano Street 0.2006 1 3 600 1000 210 255 ok fitted, need site verification Y 9-6-015-001 Stephanie Kawaauhau 96-1224 Huapala Street 0.2438 1 3 600 1000 210 255 ok Y 9-6-015-028 Keeane Kolekona Toriano 96-1250 Hinano Street 0.282 1 3 600 1000 210 255 ok Y 9-6-015-027 Morgan Dacalio 96-1244 Hinano Street 0.2939 1 3 600 1000 210 255 ok Y 9-6-015-026 Yokomizo Family Trust 96-1240 Hinano Street 0.3485 1 3 600 1000 210 255 ok Traffic rated Y 9-6-015-025 Kaitlin Marie Galimba 96-1236 Hinano Street 0.3829 1 3 600 1000 210 255 ok Y 9-6-015-024 Ned Nobuo Nishimura 96-3198 Hala Street 0.2443 1 3 600 1000 210 255 ok Y 9-6-015-023 Arthur Kaleohano 96-3196 Hala Street 0.3247 1 3 600 1000 210 255 ok Y 9-6-015-022 Hisako Yoshimura 96-3193 Hala Street 0.2879 1 3 600 1000 210 255 not fit best fit might need to cut trees Y 9-6-015-021 ShandonTamondong 96-3197 Hala Street 0.3544 1 3 600 1000 210 255 ok Y 9-6-015-020 Gary Tamondong 96-1218 Huapala Street 0.3253 1 3 600 1000 210 255 ok Y 9-6-016-039 Evelyn Barbara Baran 96-1212 Huapala Street 0.3017 1 4 800 1000 280 340 ok Y 9-6-016-040 Julia Neal 96-3186 Pikake Street 0.6606 1 5 1000 1250 350 425 pls verify best fit might need to cut trees Y 9-6-016-041 Bryan Davis-Natividad 96-3184 Pikake Street 0.6259 1 4 800 1000 280 340 ok Y 9-6-016-042 Tasha Tho Kaapana 96-3174 Pikake Street 0.6402 2 0 0 0 0 N/A 9-6-016-043 Don Francisco Dacalio 96-3172 Pikake Street 0.4293 1 4 800 1000 280 340 ok Y 9-6-016-044 John Ah San 96-3168 Pikake Street 0.4253 1 3 600 1000 210 255 ok Y 9-6-016-045 Julia Neal 96-3164 Pikake Street 0.3598 1 3 600 1000 210 255 ok Y 9-6-016-046 Ann Bertellotti 96-3160 Pikake Street 0.2523 1 5 1000 1250 350 425 ok Y 9-6-016-036 Michael Oldmen 96-3152 Pikake Street 0.4 1 4 800 1000 280 340 ok Y 9-6-020-001 Edmund Olson 96-1206 Kamani Street 0.1907 1 3 600 1000 210 255 ok Y 9-6-020-002 Michelle Ortega 96-3146 Pikake Street 0.184 1 3 600 1000 210 255 ok Y 9-6-020-003 Frank Ryder 96-3144 Pikake Street 0.1856 1 3 600 1000 210 255 ok Y 9-6-020-004 Pedro Gandalira 96-3142 Pikaka Street 0.1801 1 3 600 1000 210 255 ok Y 9-6-020-005 Dawn Rosales 96-3140 Pikake Street 0.1787 1 3 600 1000 210 255 ok Y 9-6-020-006 Rodrigo Evangelista 96-3138 Pikake Street 0.1789 1 3 600 1000 210 255 ok Y 9-6-020-007 David Souza JR 96-3134 Pikaka Street 0.1768 1 3 600 1000 210 255 ok y 9-6-020-008 Abdon Cabatingan 96-3132 Pikaka Street 0.1719 1 3 600 1000 210 255 ok y 9-6-020-009 Florendo Fuerte 96-3130 Pikaka Street 0.1733 1 3 600 1000 210 255 ok y 9-6-020-010 Edward Requlman 96-3128 Pikake Street 0.1699 1 3 600 1000 210 255 ok y 9-6-020-011 Felipe Aderinto 96-3120 Pikake Street 0.1661 1 4 800 1000 280 340 ok y 9-6-020-012 Wido Chalito Prtillo 96-3112 Pikake Street 0.1677 1 3 600 1000 210 255 ok y 9-6-020-013 Lester Matt Iverson 96-3104 Pikake Street 0.1633 1 3 600 1000 210 255 ok y 9-6-020-014 Sonny Gabini 96-3096 Pikake Street 0.203 1 2 400 1000 140 170 ok Y 9-6-020-018 Tristan Kaileo Oliveros 96-3109 Puahala Street 0.2215 1 3 600 1000 210 255 pls verify verify property line in front lawn Y 9-6-020-019 Michael Baldonado 96-3111 Puahala Street 0.1549 1 3 600 1000 210 255 ok verify property line in front lawn Y 9-6-020-020 Teofilo Villa 96-3115 Puahala Street 0.1495 1 3 600 1000 210 255 ok verify property line in front lawn Y 9-6-020-021 Lenor Lorenzo-Oleyte 96-3117 Puahala Street 0.1609 1 3 600 1000 210 255 ok Y 9-6-020-022 Dennis Santiago 96-3119 Puahala Street 0.1499 1 2 400 1000 140 170 ok Y 9-6-020-023 Apolinario Cabudol 96-3121 Puahala Street 0.166 1 3 600 1000 210 255 ok Y 9-6-020-024 Edward Andrade 96-3123 Puahala Street 0.1563 1 3 600 1000 210 255 ok Y 9-6-020-025 Mariano Delos Santos 96-3127 Puahala Street 0.1592 1 3 600 1000 210 255 ok Y 9-6-020-026 Freddie Penera 96-3131 Puahala Street 0.2018 1 3 600 1000 210 255 ok Y 9-6-020-027 Albert Louis 96-3133 Puahala Street 0.2044 1 2 400 1000 140 170 ok Y 9-6-020-028 James Yamaki 96-3137 Puahala Street 0.2079 1 3 600 1000 210 255 pls verify best fit might need to cut trees & shrubs Y A-4 B Appendix B - Additional Households A-5 B Pahala LLC Closure (additional properties)Absorption Field TMK#Owner Address Land Area (acres)# of Buildings # ofBedrooms Est. WW Gen.Septic Tank 1min/in.2min/in.Remarks dwg 9-6-021-001 Candrie Pascubillo 96-3198 Pakalana St 0.3129 1 3 9-6-014-072 Roy & Maybelle Okinishi 0.3777 1 3 9-6-014-071 Robert Rosario 96-1339 Huapala St 0.3444 1 3 9-6-014-015 Stanley Ballo 96-1303 Ilima St 0.2248 1 3 9-6-014-016 Raymond Ballio 0.1906 1 3 9-6-014-069 Berta Miranda 96-1315 Ilima St 0.2746 1 3 9-6-014-070 Darleen Iida 96-1319 Ilima St 0.3051 1 3 9-6-021-031 Vicki Paalulhi 96-1340 Huapala St 0.2924 1 2 9-6-014-067 Louisa & Harold Paaluhi96-1338 Huapala St 0.2928 1 3 9-6-014-066 Carmelita Ferreira 96-1334 Huapala 0.241 1 3 9-6-014-065 Rolando Lugtu 96-1330 Huapala St 0.241 1 3 9-6-014-064 Jose Abalos 96-1326 Huapala St 0.241 1 3 9-6-014-063 Felipe Aderinto 96-1322 Huapala 0.241 1 6 9-6-014-062 Tiffany Poncy 0.241 1 3 9-6-014-061 Gloria Camba 96-1314 Huapala St 0.241 1 3 9-6-014-060 Brenda Tacardon-Ortiz 96-1310 Huapala St 0.2755 1 3 9-6-014-059 Antonio Maltezo 96-1304 Huapala St 0.2755 1 3 9-6-014-058 Larson Mondina 96-1296 Huapala St 0.3879 1 3 9-6-015-031 Albert Galimba 96-1288 Huapala 0.2809 1 3 9-6-015-030 Carmen Belledo Trst 96-3198 Hapu St 0.271 1 3 9-6-015-029 Moses Espaniola 96-1256 Hinano St 0.3188 1 4 9-6-015-012 Annie Kaapana 96-1269 Hinano St 0.2258 1 3 9-6-015-011 Chris Kibler 96-1274 Huapala 0.2236 1 3 9-6-015-010 Kavelle Silva 96-1270 Huapala 0.2709 1 3 9-6-015-013 Patricia Pai 96-1259 Hinano St 0.1833 1 3 9-6-015-014 Rose Navarro 96-1255 Hinano St 0.2191 1 1 9-6-015-015 Prasert Chantrakul 96-1251 Hinano St 0.2271 1 3 9-6-015-007 Stanley Mizuno 96-1252 Huapala St 0.1662 1 0 9-6-015-005 Joyce Ibasan 96-1248 Huapala St 0.277 1 3 9-6-015-004 Jack Moses 96-1242 Huapala St 0.2565 1 3 9-6-015-003 Anderson Family Trst 96-1236 Huapala St 0.3 9-6-015-002 Madito Tamayo 96-1230 Huapala St 0.227 1 3 9-6-015-032 Huapala Lot 6 LLC 1.032 9-6-015-034 Michael Worthington 96-3232 Maile St 0.118 1 9-6-005-044 Edmund Olson 0.4937 9-6-016-011 Edmund Olson 96-3208 Maile St 0.7503 1 4 9-6-002-056 Julia Neal 96-3209 Maile St 3.421 1 5 9-6-002-016 PMK Capital Partners, LLC96-3207 Maile St 66.719 9-6-016-023 Rodney Freitas 96-3189 Pikake St 0.3437 1 3 9-6-016-024 Kathy Andrade 96-3187 Pikake St 0.3803 1 3 9-6-016-025 Paul Keim 96-3181 Pikake St 0.3522 1 3 9-6-016-026 Bryan Albert 96-3179 Pikake St 0.4579 1 3 9-6-016-027 Barry Beyer Trst 96-3175 Pikake St 0.3766 1 3 9-6-016-035 HH & S Inc 96-3167 Pakake St 0.1758 1 9-6-016-034 Edmund Olson 96-3163 Pikake St 0.9503 1 9-6-017-001 Corinna Salmo 96-3147 Pikake St 0.3751 1 4 9-6-017-002 Roman Catholic Church 96-3143 Pikake St 2.022 1 9-6-017-003 County of Hawaii 0.5257 9-6-018-001 Edgar Sales 96-1174 Holei St 0.3054 1 3 9-6-018-002 Hendrikus Dewaal 96-3133 Pikake St 0.2607 1 3 9-6-018-003 Adelaide Malepe 96-3109 Pikake St 0.2754 1 3 9-6-018-004 Martina Usman 96-3101 Pikake St 0.2476 1 4 9-6-018-028 Aloha Maria Dameg Gascon96-3093 Pikake St 0.3271 1 3 9-6-018-029 Alfred Ibarra 96-3077 Pakalana St 0.2874 1 3 9-6-020-015 Barbara Lee 96-3087 Pakalana St 0.2236 1 3 9-6-020-016 Joseph Aglia 96-3101 Puahala St 0.2478 1 3 9-6-020-058 Charles Doyle 96-3102 Puahala St 0.3429 1 2 9-6-020-057 Ernesto Abellera 96-3106 Puahala St 0.2465 1 2 9-6-020-056 Florentina Penera 96-3112 Puahala Street 0.294 1 3 9-6-020-017 Cristen Navarro-Vierra 96-3105 Puahala St 0.2208 1 3 9-6-020-034 Nathan Ortega 96-3118 Pauhala St 0.2527 1 6 9-6-020-033 Katherine Gacayan 96-3120 Puahala St 0.2255 1 3 9-6-020-032 Lester Ibasan 96-3124 Puahala 0.3072 1 3 9-6-020-031 Francis Woo 96-3126 Puahala 0.3139 1 3 9-6-020-003 Leland Janes Martin 96-3132 Puahala St 0.2392 1 3 9-6-005-008 State of Hawaii 96-3150 Pikake St 26.926 A-6 C Appendix C - Cost Calculations Pāhala Individual Wastewater System Preliminary Engineering Report A-7 C Year Tasks County O&M Staff Cost 0 IWS Installation Capital Cost/Household 0 Pumping & Hauling equipment 250,000.00$ 1,470.59$ 0 Personnel Training 50,000.00$ 294.12$ 1 Annual Inspection by & Trouble Calls by County staff - one IWS Operator / Plumber 822.00$ 2 Annual Inspection by & Trouble Calls by County staff - one IWS Operator / Plumber 822.00$ 3 Septic sludge pumping & disposal by County staff 1,250.00$ 4 Annual Inspection by & Trouble Calls by County staff - one IWS Operator / Plumber 822.00$ 5 Annual Inspection by & Trouble Calls by County staff - one IWS Operator / Plumber 822.00$ 6 Septic sludge pumping & disposal by County staff 1,250.00$ 7 Annual Inspection by & Trouble Calls by County staff - one IWS Operator / Plumber 822.00$ 8 Annual Inspection by & Trouble Calls by County staff - one IWS Operator / Plumber 822.00$ 9 Septic sludge pumping & disposal by County staff 1,250.00$ 10 Annual Inspection by & Trouble Calls by County staff - one IWS Operator / Plumber 822.00$ 11 Annual Inspection by & Trouble Calls by County staff - one IWS Operator / Plumber 822.00$ 12 Septic sludge pumping & disposal by County staff 1,250.00$ 13 Annual Inspection by & Trouble Calls by County staff - one IWS Operator / Plumber 822.00$ 14 Annual Inspection by & Trouble Calls by County staff - one IWS Operator / Plumber 822.00$ 15 Septic sludge pumping & disposal by County staff 1,250.00$ 16 Annual Inspection by & Trouble Calls by County staff - one IWS Operator / Plumber 822.00$ 17 Annual Inspection by & Trouble Calls by County staff - one IWS Operator / Plumber 822.00$ 18 Septic sludge pumping & disposal by County staff 1,250.00$ 19 Annual Inspection by & Trouble Calls by County staff - one IWS Operator / Plumber 822.00$ 20 Absorption bed replacement 30,000.00$ 20 Pumping & Hauling equipment Replacement 250,000.00$ 1,470.59$ 21 Annual Inspection by & Trouble Calls by County staff - one IWS Operator / Plumber 822.00$ Average Annual Maintenance Cost 956.44$ Based on $100000/175 = $572 Trouble calls, emergency repairs per IWS per year 250.00$ IWS Management Model 2A County In-House Maintenance Cost County WWD Admin Personnel Cost for Record Keeping and administering Pāhala Individual Wastewater System Preliminary Engineering Report A-8 C Year Tasks Outsource O&M Cost County Admin Staff 0 IWS Installation Capital Cost 1 IWS annual inspection & Trouble Calls 550.00$ 572.00$ 2 IWS annual inspection & Trouble Calls 550.00$ 572.00$ 3 Septic sludge pumping & disposal 1,250.00$ 572.00$ 4 IWS annual inspection & Trouble Calls 550.00$ 572.00$ 5 IWS annual inspection & Trouble Calls 550.00$ 572.00$ 6 Septic sludge pumping & disposal 1,250.00$ 572.00$ 7 IWS annual inspection & Trouble Calls 550.00$ 572.00$ 8 IWS annual inspection & Trouble Calls 550.00$ 572.00$ 9 Septic sludge pumping & disposal 1,250.00$ 572.00$ 10 IWS annual inspection & Trouble Calls 550.00$ 572.00$ 11 IWS annual inspection & Trouble Calls 550.00$ 572.00$ 12 Septic sludge pumping & disposal 1,250.00$ 572.00$ 13 IWS annual inspection & Trouble Calls 550.00$ 572.00$ 14 IWS annual inspection & Trouble Calls 550.00$ 572.00$ 15 Septic sludge pumping & disposal 1,250.00$ 572.00$ 16 IWS annual inspection & Trouble Calls 550.00$ 572.00$ 17 IWS annual inspection & Trouble Calls 550.00$ 572.00$ 18 Septic sludge pumping & disposal 1,250.00$ 572.00$ 19 IWS annual inspection & Trouble Calls 550.00$ 572.00$ 20 Absorption bed replacement 30,000.00$ 572.00$ 21 IWS annual inspection (repeat as Year 1)550.00$ 572.00$ Average Annual Maintenance Cost 783.33$ 572.00$ Based on $100000/175 = $572 Trouble calls, emergency repairs per IWS per year 250.00$ IWS Management Model 2B Outsource Maintenance Cost County WWD Admin Personnel Cost for Record Keeping and administering A-9 C Year Tasks O&M Cost to Homeowner/User County Admin Cost 0 IWS Installation 0 Capital Cost 1 IWS annual inspection & Trouble calls 500.00$ 572.00$ 2 IWS annual inspection 500.00$ 572.00$ 3 Septic sludge pumping & disposal 1,200.00$ 572.00$ 4 IWS annual inspection 500.00$ 572.00$ 5 IWS annual inspection 500.00$ 572.00$ 6 Septic sludge pumping & disposal 1,200.00$ 572.00$ 7 IWS annual inspection 500.00$ 572.00$ 8 IWS annual inspection 500.00$ 572.00$ 9 Septic sludge pumping & disposal 1,200.00$ 572.00$ 10 IWS annual inspection 500.00$ 572.00$ 11 IWS annual inspection 500.00$ 572.00$ 12 Septic sludge pumping & disposal 1,200.00$ 572.00$ 13 IWS annual inspection 500.00$ 572.00$ 14 IWS annual inspection 500.00$ 572.00$ 15 Septic sludge pumping & disposal 1,200.00$ 572.00$ 16 IWS annual inspection 500.00$ 572.00$ 17 IWS annual inspection 500.00$ 572.00$ 18 Septic sludge pumping & disposal 1,200.00$ 572.00$ 19 IWS annual inspection 500.00$ 300.00$ 20 Absorption bed replacement -$ 30,000.00$ 21 IWS annual inspection (repeat as Year 1)500.00$ 572.00$ Annual Average Cost 733.33$ 572.00$ O&M Cost to Homeowner / User includes trouble calls $300 + $200 = $500 County admin staff to provide recording keeping, regulation and enforcing Based on $100000/175 IWS Management Model 3A Operating Permit User O&M Cost Pāhala Individual Wastewater System Preliminary Engineering Report A-10 C Year Tasks Trouble call Cost to Homeowner/User County Voucher Cost (present value) 0 IWS Installation 0 Capital Cost 1 IWS annual inspection & Trouble calls 600.00$ 872.00$ 2 IWS annual inspection 600.00$ 872.00$ 3 Septic sludge pumping & disposal 600.00$ 1,572.00$ 4 IWS annual inspection 600.00$ 872.00$ 5 IWS annual inspection 600.00$ 872.00$ 6 Septic sludge pumping & disposal 600.00$ 1,572.00$ 7 IWS annual inspection 600.00$ 872.00$ 8 IWS annual inspection 600.00$ 872.00$ 9 Septic sludge pumping & disposal 600.00$ 1,572.00$ 10 IWS annual inspection 600.00$ 872.00$ 11 IWS annual inspection 600.00$ 872.00$ 12 Septic sludge pumping & disposal 600.00$ 1,572.00$ 13 IWS annual inspection 600.00$ 872.00$ 14 IWS annual inspection 600.00$ 872.00$ 15 Septic sludge pumping & disposal 600.00$ 1,572.00$ 16 IWS annual inspection 600.00$ 872.00$ 17 IWS annual inspection 600.00$ 872.00$ 18 Septic sludge pumping & disposal 600.00$ 1,572.00$ 19 IWS annual inspection 600.00$ 872.00$ 20 Absorption bed replacement -$ 30,000.00$ 21 IWS annual inspection (repeat as Year 1)600.00$ 872.00$ Annual Average Cost 600.00$ 1,105.33$ County voucher cost: $572 + $300 Based on $100000/175 IWS Management Model 3B County Voucher O&M Cost A-11 D Appendix D - Topography Pāhala Individual Wastewater System Preliminary Engineering Report A-12 D A-13 E Appendix E - USGS Soil Survey A-14 E Soil Map—Island of Hawaii Area, Hawaii Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/18/2023 Page 1 of 3212350021238002124100212440021247002125000212530021256002125900212620021232002123500212380021241002124400212470021250002125300212560021259002126200238500238800239100239400239700240000240300240600 238500 238800 239100 239400 239700 240000 240300 240600 19° 12' 45'' N 155° 29' 16'' W19° 12' 45'' N155° 27' 58'' W19° 11' 8'' N 155° 29' 16'' W19° 11' 8'' N 155° 27' 58'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 5N WGS84 0 500 1000 2000 3000Feet 0 200 400 800 1200 Meters Map Scale: 1:14,700 if printed on A portrait (8.5" x 11") sheet. SSooiill MMaapp mmaayy nnoott bbee vvaalliidd aatt tthhiiss ssccaallee.. A-15 E MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Island of Hawaii Area, Hawaii Survey Area Data: Version 15, Aug 30, 2022 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jan 3, 2019—Jun 28, 2022 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Soil Map—Island of Hawaii Area, Hawaii Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/18/2023 Page 2 of 3 A-16 E Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 517 Alapai hydrous silty clay loam, 10 to 20 percent slopes 0.5 0.1% 521 Naalehu medial silty clay loam, 3 to 10 percent slopes 163.8 18.0% 522 Naalehu medial silty clay loam, 10 to 20 percent slopes 178.1 19.6% 562 Akihi-Alapai complex, 10 to 20 percent slopes 0.0 0.0% 567 Puueo-Naalehu complex, 3 to 10 percent slopes 567.2 62.4% Totals for Area of Interest 909.5 100.0% Soil Map—Island of Hawaii Area, Hawaii Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/18/2023 Page 3 of 3 A-17 E Island of Hawaii Area, Hawaii 521—Naalehu medial silty clay loam, 3 to 10 percent slopes Map Unit Setting National map unit symbol: 2klhg Elevation: 0 to 1,200 feet Mean annual precipitation: 30 to 60 inches Mean annual air temperature: 70 to 75 degrees F Frost-free period: 365 days Farmland classification: Prime farmland if irrigated Map Unit Composition Naalehu and similar soils:100 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Naalehu Setting Landform:Ash fields on pahoehoe lava flows Landform position (two-dimensional):Backslope Landform position (three-dimensional):Side slope Down-slope shape:Linear Across-slope shape:Linear, convex Parent material:Basic volcanic ash over pahoehoe lava Typical profile Ap1 - 0 to 11 inches: medial silt loam Ap2 - 11 to 17 inches: medial silt loam Bw1 - 17 to 28 inches: hydrous silty clay loam Bw2 - 28 to 37 inches: hydrous silty clay loam 2Bwb - 37 to 44 inches: hydrous silty clay loam 3Bwb - 44 to 59 inches: hydrous silty clay loam Properties and qualities Slope:3 to 10 percent Depth to restrictive feature:More than 80 inches Drainage class:Well drained Runoff class: Low Capacity of the most limiting layer to transmit water (Ksat):Moderately high to high (0.57 to 1.98 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Maximum salinity:Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm) Available water supply, 0 to 60 inches: High (about 11.8 inches) Interpretive groups Land capability classification (irrigated): 3e Land capability classification (nonirrigated): 3e Map Unit Description: Naalehu medial silty clay loam, 3 to 10 percent slopes---Island of Hawaii Area, Hawaii Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/18/2023 Page 1 of 2 A-18 E Hydrologic Soil Group: B Ecological site: F161BY501HI - Kona Weather Ustic Forest Hydric soil rating: No Data Source Information Soil Survey Area: Island of Hawaii Area, Hawaii Survey Area Data: Version 15, Aug 30, 2022 Map Unit Description: Naalehu medial silty clay loam, 3 to 10 percent slopes---Island of Hawaii Area, Hawaii Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/18/2023 Page 2 of 2 A-19 E Island of Hawaii Area, Hawaii 567—Puueo-Naalehu complex, 3 to 10 percent slopes Map Unit Setting National map unit symbol: 2kljm Elevation: 0 to 1,200 feet Mean annual precipitation: 35 to 47 inches Mean annual air temperature: 70 to 75 degrees F Frost-free period: 365 days Farmland classification: Not prime farmland Map Unit Composition Puueo and similar soils:65 percent Naalehu and similar soils:35 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Puueo Setting Landform:Ash fields on aa lava flows Landform position (two-dimensional):Backslope Landform position (three-dimensional):Side slope Down-slope shape:Linear Across-slope shape:Linear, convex Parent material:Basic volcanic ash over aa lava Typical profile 2C1/A1 - 0 to 7 inches: extremely cobbly medial silt loam 2C2/A2 - 7 to 18 inches: extremely cobbly medial silt loam 2C3 - 18 to 30 inches: cobbles 2R - 30 to 40 inches: bedrock Properties and qualities Slope:3 to 10 percent Surface area covered with cobbles, stones or boulders:0.0 percent Depth to restrictive feature:20 to 40 inches to lithic bedrock Drainage class:Somewhat excessively drained Runoff class: Very low Capacity of the most limiting layer to transmit water (Ksat):Low to moderately low (0.00 to 0.06 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Maximum salinity:Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm) Available water supply, 0 to 60 inches: Low (about 3.1 inches) Interpretive groups Land capability classification (irrigated): 6s Land capability classification (nonirrigated): 6s Map Unit Description: Puueo-Naalehu complex, 3 to 10 percent slopes---Island of Hawaii Area, Hawaii Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/18/2023 Page 1 of 2 A-20 E Hydrologic Soil Group: A Ecological site: F161BY501HI - Kona Weather Ustic Forest Hydric soil rating: No Description of Naalehu Setting Landform:Ash fields on pahoehoe lava flows Landform position (two-dimensional):Backslope Landform position (three-dimensional):Side slope Down-slope shape:Linear Across-slope shape:Linear, convex Parent material:Basic volcanic ash over pahoehoe lava Typical profile Ap1 - 0 to 11 inches: medial silt loam Ap2 - 11 to 17 inches: medial silt loam Bw1 - 17 to 28 inches: hydrous silty clay loam Bw2 - 28 to 37 inches: hydrous silty clay loam 2Bwb - 37 to 44 inches: hydrous silty clay loam 3Bwb - 44 to 59 inches: hydrous silty clay loam Properties and qualities Slope:3 to 10 percent Depth to restrictive feature:More than 80 inches Drainage class:Well drained Runoff class: Low Capacity of the most limiting layer to transmit water (Ksat):Moderately high to high (0.57 to 1.98 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Maximum salinity:Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm) Available water supply, 0 to 60 inches: High (about 11.8 inches) Interpretive groups Land capability classification (irrigated): 3e Land capability classification (nonirrigated): 3e Hydrologic Soil Group: B Ecological site: F161BY501HI - Kona Weather Ustic Forest Hydric soil rating: No Data Source Information Soil Survey Area: Island of Hawaii Area, Hawaii Survey Area Data: Version 15, Aug 30, 2022 Map Unit Description: Puueo-Naalehu complex, 3 to 10 percent slopes---Island of Hawaii Area, Hawaii Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/18/2023 Page 2 of 2 A-21 F Appendix F - Ka'ū Gym Geotech Report A-22 F Pāhala Individual Wastewater System Preliminary Engineering Report A-23 G Appendix G - YKE Geotechincal Data Report Pāhala Individual Wastewater System Preliminary Engineering Report A-24 G © 2021 Yogi Kwong Engineers, LLC FINAL SUBMITTAL Geotechnical Data Report Pahala Community Large Capacity Cesspool (LCC) Replacement Project Pahala, Island of Hawai’i, Hawai’i PP rr ee pp aa rr ee dd ff oo rr :: Brown and Caldwell 2261 Aupuni St., Suite 201 Wailuku, Hawai’I 96793 NNoovveemmbbeerr 22002211 PP rr ee pp aa rr ee dd bb yy :: YOGI KWONG ENGINEERS 677 Ala Moana Blvd., Suite 710 Honolulu, Hawaii 96813 YYKKEE PPrroojjeecctt NNoo.. 1188002299 A-25 H Appendix H - Percolation Test Results A-26 H Wastewater Staff Disclaimer: Data provided and maintained by the Hawaii County Wastewater Division are subject to change at any time. The County of Hawaii does not guarantee the positional or thematic accuracy of the GIS data. Scale: 1:6,000 Current Time: 10/19/2022 3:59 PM 1 inch equals 0 miles Pahala - Percolation Test Sampling Pumeli St Huapala St P akalanaS tHinanoStIlimaSt 11 Huapala St P a a u auPlPikakeStK a umahanaStPuahalaStKoali S t P ak al a n a S t M aileStKamaniStOhiaStHoleiStKeahiStKokioStI liauStIlim aStPaauauSt11 Pahala Park and Community Center P A H A L A County of Hawaii IT Department, Esri Community Maps Contributors, © OpenStreetMap, Microsoft, Esri, HERE, Garmin, SafeGraph, GeoTechnologies, Inc,METI/NASA, USGS, EPA, US Census Bureau, USDA Street Centerlines Parcels (current boundary lines) 9-6-014: 052 9-6-014: 034 9-6-016: 040 9-6-020: 017 Approx. delineationline for soil types perNRCS Soil Map 4 lots are selected for the initial percolation sampling sites.These sites were selected based on their representing soil typeand relative elevations.It is not critical to be on the exact lot selected. Updated 11/03/22 96-3105 Puahala StreetCristen Dolly Navarro-Vierra 96-1334 Ilima StreetTsuruo Sumida 96-316 Pikake StreetJulia Neal & Michael Worthington96-1255 Huapala StreetKenneth & Los Yokota KAU GYM A-27 H Dense brown clay 4 48 A-28 H Very dense brown clay24Rock is encountered at 24" depth and cannot dig deeper. Digging is done using crowbar and shovel. 2 4 holes were dug at different locations in the property with similar result, encountering rock at 24 " depth A-29 H 2.5 30 Dense brown clay Note: Large impermeable rock encountered at depth of 30". Hole could not be dug deeper. Hole was dug with hand shovel and large crowbar. A-30 H 3 36 Very dense brown clay Note: Large impermeable rock encountered at a depth of 36". Test hole could not be dug any deeper. Hole was dug with a hand shovel and large crowbar. A-31 I Appendix I - EZ Treat Recirculating Biofilter A-32 I PO Box 176 Haymarket, Virginia 20168 March 25, 2023 To: James Roberts, Owner, The Wai Home From: Joelle Wirth, RS, E-Z Treat Incorporated Re: Pāhala Large Capacity Cesspool (LCC) Replacement Project EPA Grant XP-96942401 The following attachments are our proposals for the Pahala Large Capacity Cesspool Replacement Project. The first proposal was to address the Large Capacity Cesspool Replacement. EZ Treat has looked at the proposals and decided that the 190,000 gpd system is too large for us to consider. We typically handle flows up to 100,000 gpd effectively and competitively but greater than 100,000 gpd the other options identified would be more cost effective. I have included a flow diagram and a budget for a large system that can accommodate up to 53,300 gallons per day to give you an idea of the footprint and the associated cost for the equipment. In addition, we have put together several configurations of our system for use with single family residences. EZ Treat is NSF 40, 245 and 350 Certified. The configurations and a brief description follow: 1. D141 this model can accommodate flows up to 600 gpd. It requires a septic tank that is in front of a recirculation tank with EZ Treat Pod set to the side. The discharge could be gravity to a rehabilitated cesspool per Hawaii DOH standards or a drain field. Budget: $7450 includes freight 2 1000-gallon tanks $3500 A-33 I 2. D122 this model can accommodate flows up to 600 gpd. It requires a combination septic tank recirculation tank with the E-Z treat Pod set to the side and a pump discharging tank with EZ Treat Pod set to the side. The discharge could be gravity to a rehabilitated cesspool per Hawaii DOH standards or a drain field. Budget: $7450 includes freight 1 1500-gallon tank $2500 3. D118 this model can accommodate flows up to 600 gpd. It requires a septic tank followed by a field dosing tank with EZ Treat Pod set to the side. The discharge is pressurized and could be directed towards a rehabilitated cesspool or a designated drain field. Budget: $8472 includes freight 1 1000-gallon septic tank and 1 1500 gallon recirc/field dosing tank $4500 4. D149 this model can accommodate flows up to 600 gpd. It requires a septic tank that is in front of a recirculation tank with EZ Treat Pod set to the side. The discharge could be gravity to a rehabilitated cesspool per Hawaii DOH standards or a drain field. If p ressurized a combination recirculation-pump tank could be utilized to discharge to a drain field. Budget: $8472.00 includes freight Tanks two 1000-gallon tanks $3500 Total per household 11,972.00 The configurations are attached for your review. A-34 I PO Box 176 Haymarket, Virginia 20168 EZ Treat Technology EZ Treat treatment technology is designed to solve septic problems on most difficult sites by cleaning wastewater to very high levels before discharge to a leach field. E-Z Treat is a recirculating synthetic media filter. E-Z Treat is an affordable, high performing media filter. The media never needs to be replaced in comparison to other media such as peat, coco peat, foam or textile. The system is easy to install and has very low maintenance. E-Z Treat is one of the two black water onsite systems that tested and listed for NSF 350 through NSF. It is the 1st and only biological and non-chemical system approved for water reuse. NSF 350 allows for the reuse of treated effluent to be used inside residences and commercial facilities. Being able to produce a treated effluent that can now be used for expanded non potable activities such as toilet, flushing car washing, unlimited irrigation uses allows us the ability to rethink the water budget and be able to save and use water more efficiently. Treatment Process Septic tank treated effluent flows to the E-Z Treat Re-circulating Synthetic Filter where it receives passive biochemical treatment through and active bio-film matrix. The styrene media is very uniform providing ample surface area for biological growth. The styrene media contains many voids to accommodate optimum air and liquid flow. The re-circulation chamber contains a float bypass valve and re-circulation pump. The bypass connects to the 4” return line from the E-Z Treat Pod. The by-pass valve allows the effluent to be continually re- circulated through the styrene media. Treated effluent exits the bypass valve and flows into a gravity drain field, rehabilitated cesspool, or into a pump chamber for dosing to LPP, drip irrigation or other pressurized and non-pressurized drain fields. Effluent is suitable for reuse. UV disinfection may be required. A-35 I Leach Field Reductions In various states, EZ Treat has successfully requested and received approval for a reduction in the square footage of required leach field necessary to effectively dispose of EZ Treat-treated effluent. Approvals for reduction are based on empirical studies showing the correlation between acceptable loading rates and various soil types under a range of effluent quality, and the ability of time dosing to increase the infiltrative capacity of soils. Leach fields are designed with water loading rates to fit a variety of soil types considering the daily flow volume, depth to limiting factor, and strength of the effluent. When pretreatment produces a highly treated water, such as of the quality that EZ Treat can achieve, numerous studies have demonstrated that there is virtually no biological mat formation and effluent loading rates can approach natural soil infiltration rates. Residential Systems EZ Treat’s residential systems are available in a variety of sizes. Beginning with the residential models that treats up to three bedrooms and includes models that treat up to 6 bedrooms with one pod. Multiple pods may be used in series to acquire the desired flows. Residential systems also require a septic tank sized to existing state regulations. Commercial & Engineered Systems Commercial EZ Treat models include Models up to 5000 gpd per module. Commercial systems use the same treatment technology as the residential units and are set adjacent to reinforced concrete tanks sized according to flow volume and loading strength. EZ Treat has commercial systems installed and operating in schools, apartment buildings, restaurants, inns, retail stores, business parks, subdivisions, multiple-family housing units, breweries and more. Maintenance EZ Treat is designed to be operationally simple, the system is manufactured of non- corrodible materials and hardware, PVC piping, high-density polyethylene and fiberglass or precast concrete tanks, and industrial hardened electronics. All pumps have been selected to be of the highest quality and longest service life possible. There are no chemicals to add, filters to clean, or aerators to replace. As such, annual maintenance entails a review of the system, visual inspection of the treatment center and internal parts, a check of the effluent clarity to assure the system is operating at maximum efficiency, and a visual check of the disposal area. Experience EZ Treat has installed systems serving thousands of facilities. These include systems with flows ranging from 200-gpd to 100,000-gpd. In 23 years of being in the business, we have not had to replace the media in our filters. We pride ourselves for our reputation for consistent high-level treatment, innovation, versatility, and customer- friendly solutions to wastewater problems, with highly dependable operation and service. A-36 I A-37 I A-38 I A-39 I A-40 J Appendix J - Typical IWS Layout A-41 J A-42 J A-43 J