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FIRM OVERVIEW AND BACKGROUND <br /> Sand Island Wastewater Treatment Plant and <br /> Sewer Basin Facilities Plan <br /> tI6, " t," ` t,-.1.1 "'xif'' CITY AND COUNTY OF HONOLULU,ENVIRONMENTAL SERVICES,HONOLULU, HAWAII <br /> „— _ '"--1 C--' I� fi <br /> r Client Reference: <br /> ---., _ Mr.Wesley Yokoyama,Chief,Wastewater Engineering and Construction, <br /> City and County of Honolulu <br /> 808.768.8790 / wyokoyama@honolulu.gov <br /> The City and County of Honolulu's Sand Island Sewer Basin(SISB)is Climate Change Vulnerability Evaluations <br /> the largest in the system and extends from Kuliouou at its eastern end <br /> to the Salt Lake/Aliamanu area at its western end.It encompasses the The climate change,storm surge,and tsunami analysis has a <br /> downtown and Waikiki urbanized areas and consists of two primary planning horizon through 2100 and is a key element of the planning <br /> sub-basins:the Ala Moana(or East Basin)and the Hart Street(or West effort.The analysis takes into account the Mayor's Directive,as well <br /> as the latest climate change science related to sea level rise and o <br /> Basin).Wastewater facilities within the SISB service area include a z <br /> network of more than 600 miles of gravity sewer lines and force coastal erosion.Risks,triggers,and impacts to critical wastewater z <br /> mains,17 wastewater pump stations,and the 90-mgd Sand Island collection and treatment assets within the basin will be identified. o <br /> Wastewater Treatment Plant(SIWWTP).The Fort Shafter military Vulnerable facilities will be prioritized,and potential improvements I <br /> base effectively adds a 18th pump station to the system and delivers hardening and/or relocation scenarios will be developed.The work a <br /> wastewater from the base directly to the SIWWTP. also includes an assessment of the ability of the CCH to effectively 1 <br /> implement recovery efforts following a disaster,such as extreme z <br /> flooding due to a hurricane or tsunami. 2 <br /> Project Goals and Elements o <br /> m <br /> Carollo is preparing a comprehensive facilities plan for the SISB with ^'' �s1� {r '� [ <br /> the goal of setting a long-term vision and direction related to the �; "; m <br /> most cost-effective,reliable,and sustainable strategies for future * k �i" z <br /> wastewater collection,treatment,and disposal.Necessary capital a H' " %, <br /> improvements will be identified through the year 2045. / A'.;- 117A ' 4'lia, m <br /> mw <br /> Key elements of the plan include: n <br /> U) <br /> m <br /> • Evaluation of the impacts of climate change,storm surge, Sand Island Wastewater Treatment Plant .a <br /> and Sewer Basin Facilities Planta <br /> and tsunamis. m <br /> • Projection of future flows and loads based on Climate Change Vulnerability % N <br /> recent land use trends. Assessment and Resilience P � t �"�:Thr4:11., tiFINAL I Januar 2021 `■ Identification of potential regulatory scenarios. Y <br /> r <br /> bkni A <br /> • Detailed collection system evaluation,including strategies ` i', , '° o <br /> for reduction in inflow/infiltration,salinity sources,and <br /> system storage. ' w{ rpm , z <br /> a.�. .�. <br /> • Viability of decentralized treatment given the impacts of climate D <br /> change and sea level rise. z <br /> 2 <br /> • Evaluation of liquid and solids handling processes at the SIWWTP13 <br /> and the associated ocean outfall. K <br /> D <br /> m <br /> Volume 1 of 2 4orcaro0 <br /> FINAL REPORT a a nw ..wa Myr+w Mrd ww wx. D <br /> m <br /> D <br /> O <br /> z <br /> CAROLLO / QUALIFICATIONS / JUNE 2023 10 <br />