PL-INT-2023-005630 06.30.23 ELEMENT ENVIRONMENTAL LLC CAT PL.5

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E2 determined the maximum allowable headworks loading (MAHL) for the NAVFAC Hawaii Wastewater Treatment Plant (WWTP). E2 performed an assessment of the impacts of the non-domestic discharges on the NAVFAC Hawaii WWTP,the fate of non-domestic waste streams, sludge impacts (including disposal and potential reuse considerations), whole effluent toxicity impacts and WWTP removal efficiencies. Considering these assessments as well as outfall dilution, water quality standards in the Hawaii Water Quality Standards, and pertinent regulations specified in the National Pollutant Discharge Elimination System (NPDES) Permit, E2 will develop the MAHLs for chemical and biological pollutants of concern and provide recommended revisions to indirect discharge limitations. ➢ Waimanalo Wastewater Treatment Plant R-1 Reuse Feasibility Study. Waimanalo, Oahu. Hawaii. A Feasibility Study (FS) was completed for the United States of America Army Corps of Engineers and City and County of Honolulu to assess the technical, environmental, and economic feasibility of producing R-1 water at the Waimanalo Wastewater Treatment Plant for reuse in the Waimanalo community. The first component of the FS was a market survey that was completed to identify potential users in the community. The survey identified available potable and irrigation water sources; gauged interest from the potential users; gathered user concerns with R-1 water use; and identified potential R-1 water demands. The results of the market survey indicated strong interest in R-1 water reuse from the Olomana Golf Links,Waimanalo District Park, Waimanalo Beach Park, Honolulu Polo Club, and Waimanalo Wastewater Treatment Plant (WWTP).A conceptual design for the first phase of improvements was completed and identified the WWTP improvements,the distribution system improvements, and the end user improvements. ➢ Large Capacity Cesspool Closure.Hickam Field. Oahu.Hawaii. E2 completed the closure design for five Large Capacity Cesspools (LCCs) located within the former Hickam AFB portion of JBPHH. These active LCCs are located at Buildings 2115, 3510, 3220, 3004, and 3435. The design services included determining the closure requirements for the LCC, determining the alternative disposal method (i.e., replacement with septic tank/leach field, or connection to existing wastewater collection system, development of construction drawings, specifications, and detailed cost estimates for the closure of the LCCs as well as completion of draft LCC closure applications for the State of Hawaii Department of Health. The project included historical document review, topographic surveys, geotechnical investigations, and engineering services. E2 interviewed building tenants regarding their operations to determine the average and peak design flows for the new wastewater facilities. Percolation tests were completed at the three LCC sites that were determined to require leach fields. One of the challenges for the project is the shallow groundwater table that is present at several of the sites located near the shoreline. The shallow groundwater requires the use of packaged pump stations to pump effluent from the septic tank to an elevated leach field. The relatively low flows (about 15 gallons per minute [gpm]) also required the design of packaged low flow progressive cavity pump stations. Waianae Agricultural Park Drainage Improvements. E2 completed the design of miscellaneous improvements to the drainage system at the Waianae Agricultural Park. The improvements included slope stabilization of drainage ways, diversion of runoff into an infiltration basin, design of overflow protection drainage intakes for the infiltration basin, and repairs to existing concrete drainage swales. During large rain events, debris being carried by stormwater has caused the primary drainageway intake to clog and flows to overtop the drainage system causing washout of the access road and drainageway slopes. To mitigate the blockage of the drainage intake, E2 designed diversion structures that will route stormwater into an infiltration basin.The diversion structures will allow for stormwater to enter the infiltration basin even with heavy debris build-up. An elevated backup drainage intake was also designed in the infiltration basin that will collect stormwater overflow and prevent overtopping of the drainageway. Other improvements included riprap stabilization of drainageway slopes. ➢ Pier 21 WWPS. Honolulu Harbor. Oahu. Hawaii. E2 prepared construction documents for the replacement of the existing packaged pump system at the Pier 21 WWPS with a new aboveground pumping system. The Pier 21 WWPS provides wastewater service to industrial facilities located along Pier 21 in Honolulu Harbor.The design included installation of new pumps and related appurtenances while allowing continued use of the existing influent wet well manhole present at the site. The design also included the replacement of the existing force main from the WWPS to the wye connection, which connects the force COUNTY OF HAWAII-FY24- PAGE 47