HomeMy WebLinkAboutAgenda Item IV.2.a_Draft Wastewater Facilities Plan and Cesspool Conversion Evaluation EMC PresentationEnvironmental Management Commission Briefing
County of Hawaii, Department of
Environmental Management
Draft Wastewater Facilities
Plan and Cesspool
Conversion Evaluation
August 26, 2026
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Briefing Objectives
•Provide an overview of the Wastewater Facilities Plan
»Infrastructure condition and needs
»Required maintenance actions and capital projects
»Near and long-term capital improvement plan (CIP)
•Provide an overview of the Cesspool Conversion Evaluation
»Basis of analysis
»Range of conversion options
»Suggested County-led projects
•Discuss next steps
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The Facilities Plan and Cesspool Conversion Evaluation are key elements
of the Integrated Wastewater Master Plan required by the AOC
Cesspool Conversion Evaluation
Wastewater Facilities Plan
Integrated Wastewater Master Plan
Organizational Chart
Operations and Maintenance Manuals
Regional Plans
Sewer Service Expansion Program
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The Wastewater Facilities Plan and Cesspool Conversion
Evaluation are the result of a 3-year effort
•Contract number c.01120 between the County of
Hawaii and Carollo Engineers
»Contract executed June 27, 2023
»Notice to proceed issued July 10, 2023
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Analysis and findings are driven by several factors
Available
funding
Condition of
existing
facilities
Legally
mandated
wastewater
improvements
County’s
limited role
in cesspool
conversions
Total cost of all
wastewater needs
C A R O L L O . C O M
Overview of the Draft Wastewater Facilities Plan
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Agenda
Wastewater Facilities Plan
•Background and basis of the plan
•Overall condition of existing wastewater infrastructure
•Wastewater needs
»Maintenance actions
»Capital projects
•Proposed wastewater CIP
»Near term (10-year)
»Long term (20-year)
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Hawaii County Wastewater Roadmap
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Development of the Plan
Establish Requirements of Legal Mandates
Assess Wastewater Infrastructure Condition
Identify Total Potential Wastewater Needs
Establish Priorities Based on Funding Limitations
Develop Proposed Wastewater CIP
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Site visits were a key element in the condition assessment of
existing wastewater infrastructure
July 24-28, 2023 – site visits to all 6 existing WWTPs and 17 SPSs
April 13-15, 2026 – follow-up site visits to WWTPs and select SPSs
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Condition Assessment Methodology
Condition
Rating Scale
1.Excellent: Asset is in very good condition (no defects)
2.Good: Asset has minor defects
3.Fair: Asset has significant defects that will affect reliability or efficiency
4.Poor: Asset is highly unreliable or inefficient
5.Failed: Asset is no longer able to function in its current state
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Qualitative Summary of Overall Wastewater Infrastructure Condition
(2<CS<=3)
(3<CS<=4)
(1<CS<=2)
20% Good,
Minor Defects
50% Fair,
Significant Defects
25% Poor,
Unreliable
Failed 5%
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Identified Maintenance Actions from the
Condition Assessment
•General criteria
»Smaller in scale
»Enterprise funded
•48 maintenance action items
•Categorized as:»Urgent (ASAP)
»Near term (within 2 years)
»Long term (>2 years)
•Budget cost:»Small (<$100K)
»Medium ($100-$500K)
»Large (>$500K)
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Examples of Maintenance Actions
Kulaimano WWTP
Replace gate actuator
Honokaa WWTP
Remove vegetation from lagoon
Paukaa SPS
Replace hatch and ladder
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Summary of Maintenance Actions by Priority and Relative Cost
Urgent, 16,
33%
Near-Term, 19,
40%
Long-Term, 13,
27%
Small, 29, 49%
Medium, 23,
38%
Large, 8, 13%
Priority Relative Cost
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Identified capital projects are based on legal mandates and
the condition assessment
•General criteria
»Large in scale
»Debt financed
•70 potential projects
•Categorized by type of project
»Legal Mandates/Health and Safety
»Rehabilitation and Replacement
»Reliability and Redundancy
•Developed prioritized CIP based
on available funding
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Examples of Capital Projects Kulaimano WWTP
Failed Equipment
Hilo WWTP
Rehabilitation and Replacement
Kapehu WWTP
Safety and Code Violations
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Near-term (10-year) CIP is focused on highest priority wastewater
capital project needs
(2<CS<=3)
Note: Costs in 2025 dollars.
Priority
wastewater
needs $1.08B
Legal Mandates/
Health & Safety
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Long-term (20-year) CIP includes additional rehabilitation and
replacement projects
Note: Costs in 2025 dollars.
Priority
wastewater
needs $1.08B
20-year
wastewater
needs $1.59B
(Rehabilitation and
replacement &
reliability and
redundancy)
Legal Mandates/
Health & Safety
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Total wastewater needs amount to $2.3B, of which $0.7 billion are
unscheduled projects Priority
wastewater
needs $1.08B
20-year
wastewater
needs $1.59B
Total identified
wastewater needs
$2.29B
(Includes additional
unscheduled and unfunded
projects)
Legal Mandates/
Health & Safety
Note: Costs in 2025 dollars.
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Distribution of 20-Year CIP by Category (2025 dollars)
Priority 1: Legal
Mandates/Health &
Safety, $1.08 Billion
Priority 2: Rehabilitation and
Replacement, $0.26 Billion
Priority 3: Reliability and
Redundancy, $0.24 Billion
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Distribution of 20-Year CIP by Project Timing and Category
Note: Costs in 2025 dollars.
$-
$0.2
$0.4
$0.6
$0.8
$1.0
$1.2
$1.4
$1.6
$1.8
2026-2030 2031-2035 2036-2040 2041-2045
Bi
l
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s
Priority 3: Reliability and Redundancy Priority 2: Rehabilitation and Replacement
Priority 1: Legal Mandates, Health and Safety Cumilative CIP (20-year)
C A R O L L O . C O M
Overview of the Draft Cesspool Conversion Evaluation
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Agenda
Cesspool Conversion Evaluation
•Background and basis of analysis
•Full-range of potential cesspool conversion
options and projects
•Suggested County approach and priority sewer
extension projects
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Purpose: Address methodology and cost for converting all
48,600 cesspools in the County
Priority Category Number of Cesspools
1 4,170 (9%)
2 2,762 (6%)
3 41,651 (85%)
Total 48,583 cesspools
Conversions of more than 2,000 cesspools per
year is needed to meet the 2050 deadline
Hawaii County Cesspools
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Considers cesspool conversions by one of three methods
Conversion to a DOH-Approved Individual Wastewater System (IWS)New Decentralized or Cluster
Wastewater System
Connection to Existing County or
Non-County Wastewater System
https://gis.hawaiicounty.gov/arcgisportal/apps/webappviewer/index.html?id=9517e052e2464706bfc81165e35b7fcchttps://twri.tamu.edu/publications/txh2o/2022/winter-2022/bigger-is-not-always-better-decentralizing-texas-wastewater-infrastructure/https://www.epa.gov/septic/types-septic-systems
Kealakehe WWTP
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Driven by Hawaii Legislation
2017: Act 125 - Required all cesspools to
be converted by January 1, 2050*
2018: Act 132 - Formed the Cesspool
Conversion Working Group (CCWG)
•Technologies and finance studies
commissioned by the CCWG
2024: Act 217 - Required UH to develop
additional mapping and identify priority
areas
* Exemptions may be considered by DOH
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Approach to identifying cesspool areas for potential connection
to existing or new sewer infrastructure
Cesspool density analysis
»50 cesspools within 1/8 mile
»77 density groups identified
Combined groups where feasible
Wastewater flow generation
»CCH design standards
Proximity to Existing Infrastructure
»County
»Non-County
Available system capacity
»Development of sewer models for
County systems
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Extension of County-Owned Wastewater Systems
39 potential projects identified
•Hilo – 14
•Papaikou – 5
•Kulaimano – 3
•Honokaa – 5
•Kapehu – None
•Kealakehe – 10
•Pahala – 1
•Naalehu – 1
Summary
4,299 Priority 2 and 3 cesspools can potentially be connected to the Hilo sewer system.
Facility Existing Average
Annual Flow (gpd)Average Annual Flow Design Capacity (gpd)
Hilo WWTP 3,010,000 5,000,000
Projects Number of Cesspools Estimated Average Annual Wastewater Flow (gpd)
Gravity System LPS System
Hilo-1 423 178,000 127,000
Hilo-2 723 304,000 217,000
Hilo-3 47 21,000 15,000
Hilo-4 279 117,000 84,000
Hilo-5 153 50,000 35,000
Hilo-6 227 95,000 68,000
Hilo-7 397 167,000 119,000
Hilo-10 268 113,000 80,000
Hilo-11 145 72,000 52,000
Hilo-12 721 303,000 216,000
Hilo-13 669 271,000 194,000
Hilo-15 18 14,000 10,000
Hilo-161 18 8,000 5,000
Keaukaha2 211 89,000 63,000
Total 4,299 1,802,000 1,285,000
1 Prior EPA commitment area2The Keaukaha project is being developed by DHHL
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Extension of Non-County Wastewater Systems
•Waimea
»Parker Ranch WWTP
»246 cesspools
•Waikoloa Village
»Waikoloa Village WWTP (A-Plant)
»371 cesspools
•Kahaluu-Keauhou
»Heeia WWTP
»80 cesspools
•Puako
»Mauna Lani WWTP
»177 cesspools
Four potential project areas identified:
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Potential New
Decentralized
Wastewater
Facilities
26 projects identified
Project Number1 Community Development Plan Area Cesspool Priority Category Number of Cesspools
Average Annual Flow (gpd)
Gravity System LPS System
D-1 Puna 3 123 52,000 37,000
D-2 Puna 3 230 97,000 69,000
D-3 Puna 3 88 37,000 26,000
D-4 Puna 3 190 80,000 57,000
D-5 Hilo 3 3,079 1,293,000 924,000
D-6 Hilo 3 156 66,000 47,000
D-7 Hilo 3 92 39,000 28,000
D-8 Hamakua 3 135 57,000 41,000
D-9 Hamakua 3 86 36,000 26,000
D-10 Hamakua 3 136 57,000 41,000
D-112 Hamakua 3 126 53,000 38,000
D-12 Hamakua 3 335 141,000 101,000
D-13 North Kohala 3 181 76,000 54,000
D-14 North Kohala 3 180 76,000 54,000
D-15 North Kohala 3 822 345,000 247,000
D-16 South Kohala 3 199 50,000 36,000
D-19 Kona 3 1,609 676,000 483,000
D-20 Kona 3 273 115,000 82,000
D-21 Kona 3, 2 56 34,000 17,000
D-22 Kona 3 191 80,000 57,000
D-23 Kona 3 127 53,000 38,000
D-24 Kau 3 76 32,000 23,000
D-27 South Kohala 1 196 82,000 59,000
D-28 North Kohala 3 281 118,000 84,000
D-29 North Kohala 3 196 82,000 59,000
D-302 Milolii 3 42 17,640 12,600
D-312 Ocean View 3 697 292,740 209,100
1 Cesspools in project areas that are not deemed feasible should be converted to an approved IWS.2 Projects D-11, D-30, D-31 are areas of interest identified by the County.
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Conversion to Approved Individual Wastewater Systems
Project Number of
Cesspools
IWS Conversions in priority 1 areas 2,002
IWS Conversions in priority 2 areas 1,453
IWS Conversions in priority 3 areas 26,136
Total 29,591
Summary of Potential Conversions
to an Approved IWS
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Summary of Potential Cesspool Conversion Options
Conversion Method Number of Cesspools TotalPriority 1 Priority 2 Priority 3
County Sewer System
Extensions 1,620 1,201 5,591 8,412
Non-County Sewer System
Extensions 548 80 246 874
New Decentralized
Systems 196 28 9,678 9,706
IWS Conversions 2,002 1,453 26,136 29,591
Total 4,366 2,762 41,651 48,583
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Summary of Potential Cesspool Conversion Options
County Sewer
System
Extension,
8,412, 17%
Non-County
Sewer System
Extension,
874, 2%
Decentralized
System, 9,706,
20%
IWS
Conversions,
29,591, 61%
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Unit costs were developed to support project cost estimates
•May 2025 baseline
•Local costs from various
constructed projects
»Laterals
»Gravity sewers
»Force mains
»Low pressure sewers
»Grinder pumps
»Pump stations
»Decentralized systems
•DOH database and contractor quotes
»IWS
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Summary of Potential Cesspool Conversion Options (2025 dollars)
Conversion Method Number of
Projects
Number of
Cesspools
Cost(1)
($ million)
Cost per Cesspool
($ thousand)
County Sewer System
Extension 39 8,412 $783.6 $93
Non-County Sewer System
Extension 4 874 $122.2 $140
New Decentralized System 26 9,706 $2,923.4 $300
IWS Conversions ---29,591 $1,183.6 $40
Total Potential Cesspool
Conversions 69 48,583 $5,012.8 $103
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Total Potential Cesspool Conversion Costs (2025 dollars)
$784
$122
$2,923
$1,184
$5,013
$-
$1,000
$2,000
$3,000
$4,000
$5,000
$6,000
Connections to
County Systems
Connections to Non-
County Systems
Decentralized IWS Total
Co
s
t
(
$
M
)
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Suggested Cesspool Conversion Approach
•County led.
•Limited to Priority 1
cesspools and
previously identified
infill areas, if funded.
•Other projects
remain unplanned
and unfunded.
County Sewer
Extension Projects
Non-County Sewer
Extension Projects
New
Decentralized
Wastewater
Systems
Conversions to
DOH-Approved
IWS
•Led by private
owner/operator and
community.
•County assistance
limited to facilitation
with non-County
entities.
•Community led.
•County assistance
limited to facilitation
of project viability.
•Responsibility of the
property owner, working with DOH.
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Summary of Priority
County Sewer Extension
Projects
•10 Sewer system extension
projects
»Priority 1 cesspools and
previously identified infill areas
»Keaukaha (DHHL funded)
»3,066 cesspools converted
»$266M
»Based on availability of outside
funding
•Remaining projects unplanned
and unfunded
Project
Cesspool
Priority
Category
Number of Cesspools
Existing County Service
Extensions
Estimated
Capital Cost
($million)1
Cost per
Conversion
($thousand)
Hilo-3 3 47 $3.8 $81
Hilo-4 3 279 $18.9 $68
Hilo-16 2 18 $3.7 $206
Keaukaha2 2 211 $10.8 $51
Kealakehe-1A 1 9 $1.5 $167
Kealakehe-1B 1 9 $2.5 $278
Kealakehe-1C 1 19 $2.2 $116
Kealakehe-3 1 670 $58.0 $87
Kealakehe-4 1 97 $12.6 $130
Kealakehe-5 1, 2, 3 1,707 $162.8 $95
Priority 1 Total $131.1 $53
Priority 2 Total $58.0 $2,762
Priority 3 Total $77.0 $228
Total 3,066 $266.0 $93
1 Total cost assumes 50 percent gravity system and 50 percent LPS system.2 Cost is for informational use only and is not included in the total cost since the Keaukaha is being developed by DHHL.3 Costs shown include the collection system only. Costs do not include connection fees or “buy-in” costs to existing wastewater infrastructure, nor any WWTP costs.
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Priority County Sewer Extension Areas
Keaukaha (DHHL)
Hilo Service Area Kealakehe Service Area
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Revised Total Potential Cesspool Conversion Costs (2025 dollars)
$784
$122
$2,923
$1,184
$5,013
$266 $38 0
$1,814 $2,118
$-
$1,000
$2,000
$3,000
$4,000
$5,000
$6,000
Connections to
County Systems
Connections to Non-
County Systems
Decentralized IWS Total
Co
s
t
(
$
M
)
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Number of Cesspool Conversions
County
Sewer System
Extension,
8,412, 17%
Non-County
Sewer System
Extension,
874, 2%
Decentralized
System,
9,706, 20%
IWS
Conversions,
29,591, 61%
County
Sewer System
Extension,
3,066, 6%
Non-County
Sewer System
Extension,
177, 1%
IWS
Conversions,
45,340, 93%
Total Potential Suggested Approach
C A R O L L O . C O M
Next Steps
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Next Steps
AOC
Compliance
Date
January 31
EMC Briefing
August 26
Council
Committee
Briefing
September 15
C A R O L L O . C O M
Mahalo!