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Home My WebLink AboutReg 2026-03-02 Item 5D - Resolutions - 2025 Water & Sewer Comprehensive PlansCity mfTukwila Thomas McLeod, Mayor Marty Wine, City Administrator A �� u��x� ILL UTE NO, ��.��K� ��. Agenda Item Adopt the Comprehensive Water System Plan Update and the Comprehensive Sewer Plan Update Sponsor Adib Altallal, Utilities Engineer Legislative History Recommended Motion February 23.202G Transportation & Infrastructure Services Committee March 2, 2026 Regular Meeting, Consent Agenda O Discussion Only XAction Requested MOVE TOapprove the resolutions adopting the Comprehensive Water System Plan and Comprehensive Sanitary Sewer Plan Updates. EXECUTIVE SUMMARY Council action is requested to adopt the updated comprehensive plans for the City's water and sanitary sewer utilities. These plans document existing conditions, evaluate future needs, and identify system improvements that may be needed over the planning horizon. Long range plans are required to be adopted by the City for regulatory compliance. A resolution has been prepared for each Plan for Council's consideration. DISCUSSION The Water System Plan Update documents the current status cfthe Cby's water system and analyzes future needs. Maintaining u current plan is required for Department ofHealth compliance. The plan received a SEPA Determination ofNon-Significance and has been reviewed by all required agencies. The Sanitary Sewer Plan Update provides a 20-year outlook for managing the collection system and accommodate projected growth, including the recommended capital improvement plan and potential funding strategies. It received a SEPA Determination of Non -Significance and notes that any future projects will go through all required reviews as they advance. The plan has been submitted to the Department of Ecology for review and received concurrence. ATTACHMENTS A. Comprehensive Water Plan Update Executive Summary added after O2/3377SMtg B. Resolution toAdopt Comprehensive Water System Plan C. Comprehensive Water System Plan Update (September 2O25) D. Comprehensive Water Plan Update Executive Summary - added after 02123 TIS Mtg E. Resolution toAdopt Comprehensive Sanitary Sewer Plan F. Comprehensive Sanitary Sewer Plan Update (Ueoember2024) G. Minutes from the 02/23/2026 Transportation & Infrastructure Services Committee Meeting - to be distributed separately 43 Comprehensive Water Plan Update �� x��no��x� � � Ct EXECUTIVE SUMMARY The City ofTukwila (City) prepared this Comprehensive Water System Plan (CVVSP)todocument the status and analyze the future needs of the water utility system. This CWSP is largely an updated version of the City's 2015 Plan. The purpose of this CWSP is to document changes to the City's water system, to identify required system modifications' and to appropriately outline capital improvement projects to resolve existing deficiencies and concerns aswell as meet future water demands. Maintaining a cunentCVVSP is required to meet the regulations of the Washington State Department of Health (DOH) and the requirements of the Washington State Growth Management Act. This CWSP complies with the requirements ofDOH as set forth inthe Washington Administrative Code NVA[) 246'290'100\ Water System Plan. AweU'deve|oped planning document will be a living document and tool that the City staff can use to anticipate the capacity, the timing, and the cost of improvements necessary to accommodate growth. An integrated plan will provide staff with the tools to quickly and knowledgeably answer questions from the City Council and the public about the costs ofgrowth and how topay for it. The data used for this CWSP was developed from May 2020 through February 2021. This CWSP will be used as a guide in maintaining and improving the water system in the short-term over the next ten years and also provide a planning framework over the long-term 20-year planning horizon. This CWSP contains timeframes, which are the intended framework for future funding decisions and within which future actions and decisions are intended to occur. However, these timeframes are estimates, and depending onfactors involved inthe processing ofapplications and project workandovai|abi|ityof funding, the timing may change. The framework presented in this CWSP does not represent actual commitments by the City. Key points of the CWSP including analysis results and recommendations are emphasized below, with more detail provided in the chapters. The City water system isowned and operated bythe City. The system currently consists ofsix pressure zones, one reservoir, one pump station, nine pressure reducing valves, thirteen check valves,and approximately 44 miles of transmission and distribution pipelines. The City maintains total of1U interties with five adjacent water purveyors. As of January 1, 2004, the City's sources of water are supplied mostly by the Cascade Water Alliance (Cascade). Cascade, formed in April 1999, is a group of eight municipal water utilities and districts formed to provide water supply for the current and future demands of the utilities and districts involved. Cascade currently receives most of its water from Seattle under a declining block contract, with the first block of 30.3 million gallons per day (mgd) extending through December ]1'2O23. The existing water system map showing the City's water system facilities, retail water service area, and pressure zones is presented in Figure El1. Figure ES2 presents the hydraulic profile ofthe system. CITY opmmWILA COMPREHENSIVE WATER SYSTEM PLAN UPDATE ES-1 44 EXECUTIVE SUMMARY EPTEMBER 2025 / FINAL / CAROLLO Seattle Intertie (E. Marginal Way at North City Limit) X0 PRV S CLOVELE ST SS 10 (East Marginal) & PRV 10 KCWD 125 Intertie (131st pi.) 51361HST, S 142ND ST S 1466TH ST S 148TH ST S 1501'11 3 S 152ND ST S 154TH ST 98TH ST S 2001H ST S 144TH ST S GRAHAM ST S OTIIRL S KFNYON ST. S 'HENDERSON ST Seattle Intertie (47th Avenue S and Victor Street) .,.......,; Seattle PRV 9 S BANGOR ST S RYAN ST SS 169 (Ryan Hill) North Hill Pump Station},--, Reservoir & PRVu SS 13 (South Center)d& PRV 5 160TH S T yyE SS 16 (Crystal Springs) &,PR.V 16 S164THST 5 1661Ii Sr e,, S 168TH S( S 170TH ST S 172ND ST 73RD ST S 175TH ST S 776TN S 184ND ST Highline Interties S 190TF1 4TH ST S LANGSTON RD euend 0 Check Valves 0 Supply Station 0 Back-up Supply Station L PRV X Emergency Intertie Reservoir & Pump Station Roadways Modeled Pipeline by Diameter 6" or Less °^^°°--^ 10" - 12" - 16" or Greater Retail Water Service Area Pressure Zones Pressure Zone 320 (North Boeing Field Zone) Pressure Zone 340 (Lower Ryan Hill Zone) Pressure Zone 360 (City Zone) Pressure Zone 380 (Crystal Springs Zone) Pressure Zone 400 (North Hill Zone) Pressure Zone 465 (Upper Ryan Hill Zone) Mlles 0.28 0.55 Data Sour., City of Tukwila, approximateKing County GIS, ESRI DisclaLmer features shown ID,. figure are for planning purposes and resent Lngineering nd/osurvey r locations Is not implied 5152ND ST SO9SUNSE SW 7TH ST SS 15 (Christensen) & PRV 15 SW 16TH ST SS k14 (West Valley) & PRV 14 Renton Intertie SW43RD ST :Kent Intertie R405 FNN SW 27TH S[ 34TH .ST SW 41ST ST Figure ES.1 Existing System CITY OF TUKWILA COMPREHENSIVE WATER SYSTEM PLAN UPDATE 45 (RYAN HILL) 465 ZONE - UPPER RYAN HILL ZONE 340 ZONE - LOWER RYAN HILL ZONE 13 CHECK VALVES / BETWEEN 360 AND 400 • 360 ZONE - CITY ZONE SEATTLE INTERTIE 47TH & VICTOR (BACK-UP) SEATTLE INTERTIE E. MARGINAL WAY , (BACK-UP) -2WAY INTERTIE 320 ZONE - NORTH BOEING FIELD ZONE o_ 400 ZONE - NORTH HILL ZONE 380 ZONE - CRYSTAL SPRINGS ZONE , I , 1050 1050 4000 480 480 GPM GPM GPM GPM GPM NORTH HILL PUMP STATION pw:\PHX-POP-PW.Carollo.local:Carolio\Documents\Client\WA\Tukwila\8472B00\Deiiverables\Chapter 4\FIGURE 4.2.dgn SS 13 (SOUTH CENTER) SS 14 (WEST VALLEY) SS 15 (CHRISTENSEN) SS 16 (CRYSTAL SPRINGS) m SS 10 (EAST MARGINAL) 0_ KOWD 125 DU VAMISH INTERTIE (EMERGENCY) KOVVD 125 (131ST PL) IINTERTIE (EMERGENCY) KENT (NTERTIE (.EMERC-31ENCY) RENTON IINTERTE (EMERGENCY): PRESSURE ZONE 340 ZONE - LOWER RYAN HILL ZONE MAXIMUM MINIMUM CUSTOMER CUSTOMER ELEVATION jETLELEVATIONAFT) 196 21 465 ZONE - UPPER RYAN HILL ZONE 320 ZONE - NORTH BOEING FIELD ZONE 366 112 42 15 380 ZONE - CRYSTAL SPRINGS ZONE 400 ZONE - NORTH HILL ZONE 360 ZONE - CITY ZONE 235 140 267 112 207 10 SUPPLY STATION SS 169 (RYAN HILL) SS 10 LEAST MARGINAL) OXBOW (PRV 10A) SS 13 (SOUTH CENTER) SS14 (WEST VALLEY) CONTRACTUAL FLOW (GPM) 70 900 300 800 BACK-UP SS15 (CHRISTENSEN) 840 SS16 (CRYSTAL SPRINGS) 20 SEATTLE INTERTIE 47TH AND VICTOR BACK-UP [ SEATTLE INTERTIE E. MARGINAL WAY BACK-UP Note: Contractual flows are as stated in the "2nd Amended and Restated Declining Block Water Supply Agreement between the City of Seattle and the Cascade Water Alliance (Including Management Agreements #7 dated 7/15/2013 and #9 dated 3/27/2014). FIGURE ES.2 EXISTING SYSTEM HYDRAULIC PROFILE Comprehensive Water System Plan City of Tukwila t. 46 EXECUTIVE SUMMARY .C~ S (�*� ^_r.t r~ The City guides the development and financing of the infrastructure required for water services and ensures consistency in service levels and customer relations. While the City has discretion in setting the performance, design criteria, and standards for its water system, these must meet or exceed the minimum standards for public water supplies set by DOH through WAC 246-290. Together, policies and criteria provide the desired level of services to utility customers. The policies that govern the City's water system are based on City policies as defined inthe City ofTukwila Comprehensive Plan (2015) and the water system design criteria as defined by the City. The policies and criteria relevant tothe [ity'swater system are summarized inChapter 3 Policies and Criteria and are organized according tothe following categories: Service policies. Source criteria. • Booster pump station (BPS) criteria. = Distribution storage criteria. • Fie flow requirements. • Financial policies. t r � Projecting future water demand is a key part of the water system planning process. Demand projections are used to identify the system improvements required for supply, pumping, storage' and piping infrastructure. Historical water purchase and consumption and Puget Sound Regional Council (PSRQ demographic projections datavveeusedtndeve|npthedemandp jectinnparametersusedtoestimate the[ity's water demands through the planning period. Historical supply and consumption data showed fairly constant values, therefore, only one demand scenario was developed for this CVVSP. Between 2015 and 2019 (excluding 2017 and 2018 data), the City's average day demand (ADD) was approximately 1.93 mgd. During that time, historical maximum day demands (MDD) were approximately 3.2 mgd. On average, the City's typical Single -Family household consumes 147 gallons per day (gpd). For this analysis, water demand projections weedeve|opedusingthefoUowingstepc 1. Grow historical water service accounts for each pressure zone and customer category bvthe zone - specific popu|ationandemp|oymentgrnwthratesfromacnmbinationofthedemogephicana|ysis using PSR[data and the [it/svacant parcel data. 2. Convert water service account projections into equivalent residential unit (ERU) projections. l Convert ERU projections to ADD projections using demand projection parameters derived from historical data consisting of the [ity's ERU value, distribution system leakage (DSU, other authorized use, and large consumer data. 4. Apply the k4DDtoADD peaking factor to convert ADD to K4DO. Figure ES.3 also summarizes these steps. CITY opmmmLA COMPREHENSIVE WATER SYSTEM PLAN upmxTs ES-4 47 EXECUTIVE SUMMARY For each pressure zone - Start with Historical number ofWater Connections Gro�w un|ngTRPC Growth Rates Convert toADD using Projection Parameters ~ = Demand Projections Apply Peaking Factor to get MOD Y Pressure zone Demands =Total System Demand FiquneES.3 Demand P .enUonMethodology Numerous factors and assumptions affect the accuracy ofprojected future water demands. Tn project the [ity'sfuture ADD and WDC\ several parameters were used, which are listed in Table ES1.These parameters include ERU value, DSL, other authorized use, and the VIDD/ADD peaking factor. Table ESA Water Demand Projection Factors Parameter Value . ERUValue (god/ERU) - DSL of Purchase) Other Authorized Use (Percent ofConsumption MDD/ADD Peaking Factor 147 5.4% 0.8% 1.77 Historical Historical Average - --------- Histohoa|Averago Historical Average Figure ESA shows agraph nfCity-wide demand projections. The[hx'sADOwssp jectedtobe221 mgd in2O2O.|nZ044 itisestimated tobe3/45mgd.|nZ044 K4DDisestimated tobe6]0mgd.These demands are the basis for the water system evaluation presented in Chapter S System Analysis. CITY opmmmLA COMPREHENSIVE WATER SYSTEM PLAN UPDATE 48 EXECUTIVE SUMMARY 2015 = � Figure ESA Projected Water Demands 2025 2030 2035 *ist^rica|xxoo ~~ — pmjectedMmo The system analysis identified potential future system deficiencies in the City's water distribution and based on the analysis results, improvements to the system were recommended. The pipeline capacity evaluation was conducted using the City's updated and calibrated WaterCAD hydraulic model. The supply, pump station' and storage capacity evaluations were conducted in Microsoft Excel, Improvements identified in the system analysis are summarized in the Capital Improvements Program (C|P) in Chapter 9. ES~51 St,ipp)V/\V4Ysis The supply analysis compared the [it/scontractual flows from Cascade with the projected demands. Based on the results of the supply analysis, it is recommended that the City work with Cascade to increase its contractual flow by 1.5 mgd to improve supply reliability »othat contractual flows are sufficient to meet the Cit/s projected K4DDvvhi|e concurrently refilling the fire suppression storage. ES.5-2 PWr0ping Analysis The pumping analysis compared the [hv's existing pumping capacity against the [it's pumping criteria. There were no recommendations based on the pumping capacity evaluation, but it is recommended that the City add back-up power to the North Hill pump station for pumping reliability and system resiliency. CITY opmmmm 49 EXECUTIVE SUMMARY ES,5-3 Dist6bWtio0 SVsterD Analysis The calibrated WaterCAD model of the City's distribution system was used to analyze the system for future planning horizons bvadding projected systemdemand»forthe20Z0.2O34.andZO44p|anning years. Key parameters evaluated with the model included system pressure during normal operations and fire flow conditions and system velocities. During normal operations, the minimum pressure criteria was set at 30 pounds per square inch (psi) in the distribution system during IVIDD and peak hour demand and 20 psi during afire event, The [ity'»goal istoprovide amaximum uf12Opsi. Improvements such as pipeline upsizing and main looping were recommended to address identified deficiencies. Each nfthe recommended improvements requires afurther site -specific and project -level engineering analysis before implementation. Distribution pipeline recommendations are shown in Figure EI5. CITY opmmmLA COMPREHENSIVE WATER SYSTEM PLAN upOATs ES7 50 SEPTE EXECUTIVE SUMMARY ER 2025/FINAL / CAROLLO S 96TH ST Seattle Interne (E. Marginal Way at North City Limit) Fs x0 PRV 8 S SULUVAN ST , S 00NOVAIV ST S93RD51 s Loon sir S 101ST ST S104THST � F 51201_sr_ a 5 1241.H ST S 72&TH ST S 140TH ST 6 S 156'fH 5T S 1.92ND S"r AY 5116PH ST 5 136TH ST S 142ND Si, 5 146fH ST S 188TH ST S 200TH ST S 138TH SF )YRTLE Sr WILLOW ST a 5 OTH4LO ST .5 HOLDEN ST S KENY(N,/, S THFSI E ST LGy 4. S CLOVERDALE, ST 9sk 1'L s�S S HENDERSON ST F`S 5 ROX BURY SI Oxbow (PRV 10A) Seattle Interne (47th Avenue S S NcwaLI6 and Victor Street) [ Seattle S RYANST, PRV 9 S $ANGOR ST SS 10 (East Marginal) & PRV 10 o. SS 169 (Ryan Hill) } - LEO ST 5 AVON ST S 148TH 5T q' $ 150TH Sr 2 S 252ND ST 'IMH ST S 1.44TH Si North Hill Pump Station*' Reservoir & PRV till SS 13 (South Center) & PRV i' 5 160Ti I ST SS 16 (Crystal Springs) & PRV 1 6. s1641HSr S 166TH Si 73RD ST S1.E8TH ST , S 170TH Si 5172ND ST, S 172ND PL S 176fH ST S 175TH Sr S 198TH ST S LANGSPON S 133RD Sr S178TH 5379 S 182ND $T o Highline Interties 4THST, S 190TH SY Q S S99THPL H SS Check Valves 0 Supply Station 0 Back-up Supply Station I, PRV X Emergency Intertie Reservoir & Pump Station ^^^^• Pipeline Improvements Modeled Pipeline by Diameter 6" or Less 8" - 16" or Greater Roadways Retail Water Service Area Water Body Pressure Zones Pressure Zone 320 (North Boeing Field Zone) Pressure Zone 340 (Lower Ryan Hill Zone) Pressure Zone 360 (City Zone) Pressure Zone 380 (Crystal Springs Zone) Pressure Zone 400 (North Hill Zone) Pressure Zone 465 (Upper Ryan Hill Zone) Feet 0 1,500 3,000 Kis. City of Tuknin King County GLs, rSRI figuie are for purposfs and represert rou mate tions Lrigneering Pna/or surrveyaaccuracy is not ,mpl:ed ST S1347H SliF SUNSET -0LVO SS 15 (Christensen) o, & PRV 15 SW 16TH ST SS44 (West Valley) & PRV 14 SW 27TH ST W 34TH ST Renton Interne 'z SW 39TH.y�, SW 41ST ST SW 43RD ST Kent Intertie S 146TH Si Figure ES.5 Pipeline Improvement Projects CITY OF TUKWILA COMPREHENSIVE WATER SYSTEM PLAN UPDATE 51 EXECUTIVE SUMMARY ES,5-4 Storage.- Analysis The City currently operates a 2 million gallon (MG) storage tank at North Hill (15045 57th Avenue South). The tank is the sole storage facility for the City. The City's water storage volumes are comprised of five components Operational storage. Equalizing storage. Standby storage. Fire -suppression storage. Dead storage. Storage deficits were identified in all the City's service levels. The City has different options to consider for meeting their storage requirements. Five options were compared, potential storage sites were identified, and proposed alternatives were evaluated with the hydraulic model. Four site locations and five system configurations were developed, including: Alternative 1A North Hill Gravel Site with BPS to465Zone. Alternative 18 North Hill Gravel Site with Separate 465 Tank Alternative Beacon Ave Reservoir. Alternative Ryan Hill 2Acre Site Resenxoir. Alternative Ryan Hill 065Acne Site Reservoir. Potential layouts and simplified schematics were created for each alternative. Figures El6 and ES7 show examples of these figures for Alternative 2. The [ity's hydraulic model was then used to confirm the sizing of the new infrastructure, including pump station and transmission pipelines. Two representative storage sites (three system configurations)were carried forward tothe [|Pfor cost development: Alternative 1A North Hill Gravel Site with BPS to465Zone. = Alternative 1B North Hill Gravel Site with Separate 465 Tank Alternative Beacon Ave Site. • Alternative Ryan Hill 2Acre Site. CITY opmmmLA COMPREHENSIVE WATER SYSTEM PLAN upOATs E6'8 52 EXECUTIVE SUMMARY SEPTEMBER 2025 / FiNAL / CAROLLO Legend Proposed Storage Facilities Proposed PRV Proposed Check Valve Proposed Pipeline Water Main by Diameter 6" or Less 8.. emusalan. 10" - 12" oisemii 16" or Greater MOMMONE= Feet 0 500 1,000 ,s,A414k *.N'Att:k 311, cesika, e,acon eser ,for MG PRV to Figure ES.6 Storage Alternative 2 Beacon Avenue Reservoir - Potential Layout CITY OF TUKWILA COMPREHENSIVE WATER SYSTEM PLAN UPDATE FS 10 53 EXECUTIVE SUMMARY Supply Stations +' 3601400/320 Zone Beacon Ave Tank Domestic Pump oeacmx Ave PS Fire Pump I Figure ES7 Storage Alternative 2 Beacon Avenue Reservoir-Simp|ified Schematic � t r �s "id c Since the inception ofCascade in2U04 the City operates under Cascade's Water Conservation Program. Cascade's mission is to produce regional water conservation program that benefits the ratepayers of Cascade Members and provides long-term sustoinabi|itynfwater resources. Cascade included conservation as a key factor in the 2019 update to the Transmission and Supply Plan Extension (TPSB.Amajor resu|tofthechangesdeschbedinthe2019TPSEistopostponetheneedto develop the Lake Tapps Reservoir a»a municipal water supply for at least another 10yeao. In 2019, Cascade adopted a savings goal of 0.4 mgd on an average annual basis from 2019 to 2022, as outlined in the 2019 TPSE. The program objectives for Cascade's 2019-2022 Regional Water Efficiency program include the following: 1. Achieve the necessary savings to meet Cascade's adopted Water Use Efficiency Rule savings goal. 2. Pursue cost-effective program measures that provide the greatest benefit for the greatest number of ratepayers. l Offer program measures that represent all Cascade members in the distribution of program resources. 4. Create innovative and impactful education opportunities and campaigns that promote the value of water and the conservation ethic. S. Enable high -volume peak season water users to help themselves use water more efficiently and integrate sustainable landscaping techniques. The [it's historical DSLva|ues have been lower than the DOH requirement to achieve a standard of no more than 10 percent water loss (the average DSL from 2015, 2016, and 2019, as noted in Chapter 4, is 5.4peoent). Similarly, the City's historical ERU values have been lower than DOH's general value of 200 gpd/ERU, which is to be used by utilities without detailed water use data (the average ERU from 2014 through 2019 is 147 gpd/ERU, as noted in Chapter 4). The City will continue its conservation efforts and CITY OpmmWILA COMPREHENSIVE WATER SYSTEM PLAN UPDATE E3'1l 54 EXECUTIVE SUMMARY follow Cascade's goals and recommendations through participation in Cascade's Water Conservation Program. Cascade provides water efficiency programs and services on behalf of its members. In 2019, Cascade administered more than a dozen conservation program measures or activities including the following: Rebates for EnergyStar and WaterSense labeled showerheads, clothes washers, and faucets. Showerheadand aeration installation atmultifamily accounts. Free conservation items delivered upon request to multifamily properties and Cascade members for distribution tocustomer. Participation in 16community events tnpromote the value nfwater and the "We Need Water Because —^ campaign (also provided through media). These programs and services promoted water efficiency and water stewardship resulting in approximately 25.000 direct customer interactions representing all Cascade members. The City Water Department conducts a leak detection survey of the entire distribution system annually as part of its valve and hydrant maintenance program in order to identify and repair leaks. To further reduce demand. the City promotes the use of reclaimed water in the portion of the service area where it is available. To assist the City's customers in conserving meter, each month after the meter reading cycle, the City generates a list of accounts with higher than normal consumption based on historical information and visits these properties to notify customers mfpotential leaks. t r lit The City benefits from the inclusion in the City of Seattle's (Seattle) Regional Monitoring program for many current water quality regulations. Per the Cascade Interlocal contract, Cascade is responsible for source water quality that meets all State and Federal requirements at the point ofdelivery from Cascade to the Oh/. However, ultimately the responsibility for compliance resides with the City. The City is directly responsible for the quality within the distribution system; the [VVSP, therefore, provides a summary of distribution system water quality only. The City isin compliance with all current regulatory requirements, including monitoring and reporting requirements. It is recommended that the City monitor the future total co|iform rule and update their co|iform monitoring plan per the new rules to maintain future compliance. The City prepares anannual Water Quality Report ([CK)that documents regulated contaminants detected during monitoring to ensure consumers know what's in their drinking water. The [ity'sWater Quality Monitoring Reports from 2010-2019 showing compliance are included in Appendix Q. � � Jl�l �0,? The City's Public Works Department is responsible for water, sewer, drainage, construction, engineering, construction inspection, fleet and facilities, and street functions. The mission statement of the [it's Water Utility department is to provide for the efficient, environmentally sound, and safe management of the existing and future water system within the [ity's service area. CITY opmnWIm COMPREHENSIVE WATER SYSTEM PLAN UPDATE E3'12 55 EXECUTIVE SUMMARY The operations and maintenance (]8<K4) responsibilities and tasks outlined in Chapter 8—Operations and Maintenance include: Inspections, Preventive Maintenance, Repair and Replacement. Water Quality Operations, Cross Connection Control Program. Emergency Response Operations. Department Coordination. Records Documentation. Standard Plans and Specifications. Chapter also summarizes future operations and maintenance needs and the remaining useful life analysis, which was previously performed during the 2014 pipeline asset management study. Minor edits were made to ensure consistency with the City's latest G|S database. Figure ES.8 present the total length of pipeline reaching the end of its assumed useful life by decade. Figure ES.8 Length of Pipeline Replacement by Decade .t r � V � r 41, The various projects recommendedintheP|anweresummahzedinaozmpnehensive[|P.VViththis[|P, the City will have a guideline to plan and budget for the water system over the next ZOyears. as well as the recommended timing and cost estimates for each identified project. P jectphasingisdeschbedas short term (0 to 5 years, which corresponds to 2021-2025), medium -term (5 to 10 years, which corresponds to2O26'203O)orlong term (10toZOyears, which corresponds tn2O31'2040. CITY nrmmwm COMPREHENSIVE WATER SYSTEM PLAN UPDATE 56 2S'13 EXECUTIVE SUMMARY The P|an's capital projects are categorized by the following infrastructure: Distribution pipeline (P), Pump Station (PS). Storage (ST). Supp|y(S). ° General (S). Several distribution pipeline projects (P)mereidentifiedtoaddress fire flow deficiencies inthe distribution system and are shown inFigure ESA 1.One pump station project (PS)vvasidentifiedtoaddback'uppower tothe North Hill BPS, which isalso shown inFigure ESA 1. The main storage project (ST)indudesconst/uctingo/acquihngaminimumofl0K4Gofadditiona| storage in the 360 pressure zone (PZ) and/or the 465 PZ to mitigate storage deficiencies identified in the storage analysis. Four site locations and five system configurations were reviewed as part of the storage alternatives evaluation. Since the recommended storage project doesnntindudestumgeforthe380PZ two options for addressing the storage deficiency in the 380 PZ were also identified as part of the CIP. Two supply projects (S) were also identified, but no costs are associated with the projects. General projects (G) include annual pipeline replacement programs based on high priority and medium priority pipes identified in the remaining useful life analysis, as shown in Figure El12.Additiona| general projects include large meter replacements, intertie projects, and water system plan updates. Tables ES2 and EI2 summarize the [|P projects by project type and category, respectively. Figures ES.9 and ES.10 summarize the percent ofeach project identified by project category and project type, respectively. Specific project details can be found in the Detailed OPTab|e in Appendix R. The total Water [|Pcost over the next 2Uyears i»approximately $109S million, which equates to approximately $S.Smillion annually incurrent dollars. Ofthe total cost, $46'4million isbudgeted for the short'te/m'$21.6miUionisbudgetedforthemedium'term'and$41.5miUionisbudgetedforthe long-term. When considering OPcost byproject type.asshowninTab|eES2andFiguneE5.9'appvoximatek/ 57percent ofthe [|Pcosts are repair and replacement projects. |mpnovementp jectsmakeup approximately 24percent nfthe OPcosts, and capacity projects makeupabout19percentoftheOP costs. When considering C|Pcosts by project category, as shown in Table ES3 and Figure El10\ 58 percent of the [|P costs are general projects, mostly from the pipeline repair and replacement pno8rams, and approximately 38percent mfthe C|Pcosts are storage projects. Oisthbutionpipe|inep jectzmakeup approximately three percent ofthe {|Pcosts, and the pump station project makesupthenemainingone percent ofthe C|Pcosts. CITY opmmmLA COMPREHENSIVE WATER SYSTEM PLAN UPDATE ss|4 57 EXECUTIVE SUMMARY Table ES.2 CIP Summary by Project Type �Pn�edTvoe � ' '. Total C|PCost Estimate C|PPhohhzation Short-term Medium -term � $62,715,500 |— $25'8885OO �$2U,88O,0U0 r—'------- Improvement � $2S,889,SO0 � � 236% � Figure EG.9 C|PSummary bvProject Type �$12.353.OUO �11.218.5UU - |$17,4S2'5OU $0.069'000 $10'505'U00 $4'315'000 '$4G.37U.5DO $21.802.500 `—' — ------'------- u Repair & Replacement CITY opmmmLA COMPREHENSIVE WATER SYSTEM PLAN UPDATE 58 ES'15 EXECUTIVE SUMMARY SEPTEME3ER 2025 / FVNAL / CAROLLO Table ES.3 CIP Summary by Project Category Project Category Total CIP Cost Estimate CIP Prioritization Short-term (2025-2029) Medium -term Long-term (2030-2034) (2035-2044) Distribution Pipeline (P) Pump Station (PS) Storage (ST) Supply (S) .............. .............. General (G) Total Cost Average Annual Cost General $63,498,000 58.0% $2,991,000 $1,301,000 $41,695,000 $0 $63,498,000 $109,485,000 $5,474,250 $1,437,000 $0 $33,065,000 $0 :........ ....... $11,870,000 $46,372,000 $9,274,400 Distribution Pipeline $2,991,000 3% Figure ES.10 CIP Summary by Project Category $1,554,000 $0 $8,630,000 $0 $11,417,000 $21,601,000 $4,320,200 Storage $41,695,000 38.1% $0 $1,301,000 $0 $0 $40,211,000 $41,512,000 $4,151,200 Figure ES.11 illustrates the locations of the specific projects identified and their project priority by timeframe. Figure ES.12 shows the locations of pipeline included in the Annual Pipeline Replacement Program projects. CITY OF TUKWILA COMPREHENSIVE WATER SYSTEM PLAN UPDATE ES-16 59 EPT EXECUTIVE SUMMARY ER 2025 / FINAL / CAROLLO Seattle Intertie (E. Marginal Way at North City Limit) 2,24, 2,CH fCAGO ST S SULLIVAN ST q, 5 6QNOVA4 ST PRV 8 OIL ST S WILLOW ST 22' )YRTLE ST 5 oTHE120 ST S HOLDEN ST KENY(N,52, 4 S LHFST'LE ST 4Gy B. S CLOVERDALE. ST S HENDERSON ST S 93RD ST z �t U ! A 9eT9/ST sROXBURYsr s �sr Oxbow (PRV 10A) 5 10olii N iOTST ST a'" ° sNORsou<Sj S '2j i Seattle Intertie (47th Avenue S 4104TH 5T .6v KQS. 1 and Victor Street) 'W SSeattle S RYAN ST a. S 120TH Sr z SS 10 (East Marginal)] & PRV 10 S 1161'H Si' +✓'�' KCWD 125 Intertie 5 1247E ST S 128TH ST S 140TH ST 156121 WAY S156THST S 192ND S'(' 5 136TH ST S 1.42ND ST 5 1.465H ST SR S 188TH ST 5 200 T H ST S$ANGOR5T„ SS 169 (Ryan Hill) 5190 ST 5 AVON ST iL KCWD 125 Intertie (131st pl.) S 135TH S( ?'2TH ST S 144TH ST S 148TH 5T 5150TH S 52ND ST SS 13 (South Center)&PRV 5 160TH ST SS 16 (Crystal Springs) & PRV 16 S 164TH Sr S 165TH S1' S 168TH ST 5170TH ST 72ND ST, 51.72ND PL 5 176TH ST S 175TH ST 5 1987E ST 179'TH 552 S 182ND Si 5 178TH ST S 190TH 57 2194TH 51' Project Priority - RUL - Greater than 15 Years RUL ---- Low Priority Medium Priority --- High Priority Check Valves Supply Station S Back-up Supply Station PRV Emergency Intertie Reservoir & Pump Station Roadways Retail Water Service Area Pressure Zones S LANGSTON 1 S 133RD ST S 135TH ST 9H/SUNSET. 5799TH PC s: 595, DSw Pressure Zone 320 (North Boeing Field Zone) Pressure Zone 340 (Lower Ryan Hill Zone) Pressure Zone 360 (City Zone) Pressure Zone 380 (Crystal Springs Zone) Pressure Zone 400 (North Hill Zone) Pressure Zone 465 (Upper Ryan Hill Zone) IIM=1=1=1Feer 1,250 2,500 ata Sources City of Tula King County GIS, [SRI Disclaimer Features uhown in this figure are for planning gnmaamaane Engineering und/or gunfuy acuurauy is nut tugged Hsi 132ND ST SS15 2 (Christensen)2 5`u loT &PRV 15 51,1 S W_15TH ST 55114 (West Valley) & PRV 14 Renton Intertie SW 43RD ST !Kent Intertie S196TH ST 60 Figure ES.11 Project Priority - RUL Analysis CITY OF TUKWILA COMPREHENSIVE WATER SYSTEM PLAN UPDATE S EDDY ST EPT EXECUTIVE SUMMARY ER 2025 / FINAL / CAROLED Seattle Intertie (E. Marginal Way at North City Limit) 5sCH1CAGO ST, SULLIVAN ST S DONOVAN 5T PRV 8 S GRAHAM ST S MORGAN ST YST S'WILLOW ST TEE ST S OTHELLO s S HOLDEN ST "�8. Y a M 5 KENYON ST M Vp9 5 'Gl 1 93RD ST v. 20TH ST S 140TIi ST 5156TH WAY S 156TH ST, 5 192ND ST S 2062H 5T S 116TH ST 136TI I ST S THISTLE Sr, S CLOVSRDAI 2 ST 5 I-IENDERSON ST Legend Remaining Use Life CIP Projects w,-- G-1 (High Priority RUL) G-2 (Medium Priority �— RUL) Low Priority or Greater than 15 years RUL Check Valves U Supply Station 05 Back-up Supply Station I PRV X Emergency Intertie Reservoir & Pump Station Roadways S ROXBURY, ST 'A En Retail Water Service Area Oxbow (PRV 10A) &qT - - - -ch Pressure Zones ii SS 10 (East Marginal) & PRV 10 -KCWD 125'. ntertie (quwamis"h) `'s KCWD 1251 133RD ST Intertie (131st pl.) X, 4 959 S 1,42ND ST S 146TH ST S ].98TH ST S 2001H Sr S 148TH ST S 1.50111 Sl" S 152ND Si," S 154TH ST S 144TH ST TAF Seattle Intertie (47th Avenue S and Victor Street) Seattle S RYAN ST PRV 9 S0 44 1R ST Name Pressure Zone 320 (North Boeing Field Zone) Pressure Zone 340 (Lower Ryan Hill Zone) Pressure Zone 360 (City SS 169 (Ryan Hill) ' Zone) S LED ST Pressure Zone 380 (Crystal Springs Zone) North Hill Pump Station, Reservoir & PRV sout,i -R 55 13 (South Center),& PRV S 160TH 5 SS 16 (Crystal Springs) & PRV 16 5 164TH Sr ' S 166TH ST S 198TH ST z . S 1701H ST 1 5 172ND ST 5 1739D Sr S 172ND PL 176TFl 51 S 1751H 1t ¢e wS. S178Tjysp A S 182ND ST Highline Interties 1901FI S1991 PL 4TH ST (1 Pressure Zone 400 (North Hill Zone) Pressure Zone 465 (Upper Ryan Hill Zone) Feet 0 1,500 3,000 Data Sources City of Tukvdla, 1,,r19 County GI,S, FSN S LAN0STON qp '' Approximate locations and/or survey a vary SW SUNSET- • *1 L-y, SS 15 "it; )Christensen)p, & PRV 15 SW 1671) ST SS`14 (West Valley) & PRV 14 Renton Intertie I. 5W 43RD ST 'Kent Intertie S 196TH Sr 921 SW 27iH ST _"' SW 41ST ST Figure ES.12 Remaining Useful Life CIP Projects CITY OF TUKWILA COMPREHENSIVE WATER SYSTEM PLAN UPDATE 61 EXECUTIVE SUMMARY .1 � The City water utility is accounted for separately from other City departments and is operated in a self-sufficient manner. The Public Works Department manages the system, the Finance Department manages the billing, collection, and accounting services, and the two departments jointly prepare and monitor the annual budget. The water utility has been meeting the operating expenses and debt repayment in each year and has been maintaining a level ofreserves for emergency and future replacement. Chapter 10 represents the financial program, including financial history, outstanding debt, fees, and charges, and capital improvement funding. The [ity's 1Oyear water financial plan proposed in Chapter 10 includes a 9 percent annual increase from 2025 to 2029, followed by a 5 percent increase in 2030 for monthly residential rates for [|P' positive cash f|ovv, and to rebuild the reserves. CITY opmmmLA COMPREHENSIVE WATER SYSTEM PLAN upOATs B-19 62 Attach ent Washington Resolution. No. A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF TUKWILA, WASHINGTON, ADOPTING THE 2025 COMPREHENSIVE WATER PLAN, AND PROVIDING FOR WATER SERVICE POLICIES FOR THE CITY, AND REPEALING RESOLUTION NO. 1857. WHEREAS, the City of Tukwila is an Optional Municipal Code city, subject to the duties imposed under the provisions of Chapter 35A of the Revised Code of Washington; and WHEREAS, the Comprehensive Water Plan identifies specific actions and strategies to manage and control the quality of the water system in Tukwila; and WHEREAS, the City Council of the City of Tukwila has deemed it desirable to adopt a Comprehensive Water Plan in accordance with the provisions of WAC 246- 290-100; and WHEREAS, the City Council of the City of Tukwila adopted the 2015 Comprehensive Water Plan via Resolution No. 1857 on April 20, 2015. NOW, THEREFORE, THE CITY COUNCIL OF THE CITY OF TUKWILA, WASHINGTON, HEREBY RESOLVES AS FOLLOWS: Section 1. The 2025 Comprehensive Water Plan and Appendices, dated September 2025, prepared by Carollo Engineers, are attached hereto and are hereby adopted by this reference as if set forth in full. Section 2. The Comprehensive Water Plan shall be revised every ten (10) years to reflect changes in the City of Tukwila's Capital Improvement Program, which requires facility modifications, as it relates to the standards outlined in WAC 246-290-100. Section 3. Repealer. Resolution No. 1857 is hereby repealed. 2026 Legislation: Water Comprehensive Plan Version: 02/13/2026 Staff: A. Altallal Page 1 of 2 63 PASSED BY THE CITY COUNCIL OF THE CITY OF TUKWILA, WASHINGTON, at a Regular Meeting thereof this day of , 2026. ATTEST/AUTHENTICATED: Andy Youn-Barnett, CMC, City Clerk Armen Papyan, Council President APPROVED AS TO FORM BY: City Attorney Filed with the City Clerk: Passed by the City Council: Resolution Number: Attachment: 2025 Comprehensive Water Plan and Appendices dated September 2025 2026 Legislation: Water Comprehensive Plan Version: 02/13/2026 Staff: A. Altallal Page 2 of 2 64 Attach ent C c u Exhibit A 2025 Comprehensive atePlan ON FILE WITH CITY Can be accessed electronically here: • Lin / ctr. nic s x oc 65 Comprehensive Sanitary Sewer Plan Update Attach �� v��u��nn r � Cti EXECUTIVE SUMMARY The City nfTukwila (City) islocated inthe central Puget Sound region, 12miles south ofthe City of Seattle, 17 miles north ofthe City mfTacoma, and directly east ofthe Seattle -Tacoma International Airport. The City collects wastewater from the residential, commercial, institutional, and industrial dischargers within the service area and has an agreement with King County Wastewater Treatment Division (WT[) for conveyance and treatment of its collected wastewater. The City's wastewater collection infrastructure includes over38.5 miles of pipelines ranging in diameter from 4to 24 inches, and 10 lift stations (L5). The primary goal of the City of Tukwila's Comprehensive Sanitary Sewer Plan Update (Plan) is to develop a clear and logical path to manage the collection system. The plan covers the next 20'yeartimeframe to maintain the system and to accommodate projected growth inthe sewer service area. Key elements addressed inthe Plan include: Develop a basis for planning for the overall system by establishing the service area goals and policies. Develop ademographic analysis summarizing the population, employment, and land use projections for the City. Develop aflow monitoring program to characterize existing system flows and calibrate hydraulic model for the City. Develop accurate flow projections for the sanitary system to forecast future expansion needs. = Describe and inventory the [ity'swastewater collection system. = Assess the existing system's ability to meet the needs of the existing and forecasted population in the [it/s sewer service area through a system analysis. = Summarize the system improvements identified through the system analysis. • Develop the recommended Capital Improvement Plan ([|P)for the City. • Develop a funding strategy that will provide financial strength and viability of the City to implement the schedule of capital improvements. • Support the City with the State Environmental Protection Act (SEPA) process. ES, 1.1 Sewer Service Area A map of sewer service area through the planning period is presented in Figure ES.I. CITY opTuwWILA 66 Manufacturing Industrial Center Riverton 5 146i5 51 Sly 5 200TH ST Ryan Hill McMicken 70TH ST Segale Foster Point Tukwila Hill Central Business 'o District 5 212TH 5T DECE EXECUTIVE SUMMARY ER 2024 / FINAL / CAROLLO eoend Roadways 2 Tukwila City Boundary • • y Tukwila Sewer Service Area Water Body Parcels Feet 0 1,500 3,000 Data Source, City of Tukwila. King County GIS. ES.R.I D4sclaimer.,e.atures shown in this figure ale for planning purposes and present Engmeeong approximate n,�yacuacy not implied. Figure ES.1 Sewer Service Area CITY OF TUKWILA COMPREHENSIVE SANITARY SEWER PLAN UPDATE 67 EXECUTIVE SUMMARY � � r A temporary flow monitoring program was developed to characterize existing dry and wet weather flows for select portions of the [ity's sanitary sewer system. Measured flows were analyzed for use in subsequent hydraulic model calibration efforts and for preliminary characterization nfinflow and infiltration (|/|)within the monitored portions of the system. The temporary flow monitoring program collected data for a period of approximately 90 days between November 12, 2020, and February 9, 2021.The City of Tukwila Temporary Flow Monitoring November 20Z0 February 2027report prepared hyADS Environmental Services (ADS) summarizes the flow monitoring program. A copy of the report is included in Appendix D. Seven flow monitoring sites were identified for the flow monitoring program. Flow monitoring sites were selected to monitor portions of the system to the north and south of Interstate 405 (1405). Figure ES.2 shows the flow monitoring sites and the associated flow monitoring basins within the [ity's overall system. Average dry weather flow (ADWF) was developed using dry weather conditions from the flow monitoring period. Rainfall data was used to identify five significant rainfall events and evaluate rainfall response at each of the flow monitoring locations. F|nvv monitoring data was evaluated for each of the five storm events identified in Chapter 2 to observe collection system response to wet weather events. CITY opmmmLA COMPREHENSIVE SANITARY SEWER PLAN UPDATE ES'3 68 DECE EXECUTIVE SUMMARY ER 2024 / FINAL / CAROLLO S D6NOVAN ST S APO ST S 96TH ST S 190TH ST, S 101Sf S S 104TH ST S 1121H Sr 116TI T `o rn, 5 12€1TH ST u, S 140TH Si S 136TH ST S 133(1T ST, S 13STH S 142ND ST S 146TH ST S HOLDEN ST 4 S MY12TI.E ST NYON ST SOTH o_ STH[STLF. ST - 2, z ey FrT 5 CLOV[Rp,4LE Si .ry 5'HENDERSON ST S BOE G • Commercial Cente Lift Station (do. 9 S 2 S148TH.ST 'ST? S thSOTH. 6TH WAY S 152ND St® 5 1.64TH ST S 188TH ST 44TH ST S,ROXBURY ST uJ S NORFdl..;v S S RYAN ST BANGOR ST `t SLEETS S AVON SF • Allentown Lift Station )No. 10) soul- • S 158TH ST S .. eseeeew S7GOTH SI• S 162ND ST • 164FH ST ,S 166TH ST m •♦ S 1681H ST Q Q Tr, S 170TH ST `r m S172ND ST ry�jy" S173RD ST 5.172ND Pl.�a. 5 %7GI"h1 STS 175111 ST 182ND ST S 12469\ ST. Foster Poin Lift Station (No. B) �,;, • InterurbaniPS (King Countay) Station No. 12 s i98THST S 2007H ST S i.99TH PL SE 72NL1 S T�TAFT 2.7DH ST I` S 128TH ST S LAN6S1'ON RD. S 13tITH Sf 8 132ND. '347y R3STH ST )4TH ST S 2127H ST Stado SW SWes . Syln eoend Roadways —•y Tukwila Sewer Service —"" Area Tukwila City Boundary Water Body n Flow Monitor Connection to King County King County South Treatment Plant King County Lift Station King County Sewer Main ▪ Tukwila Lift Station ��•. Tukwila Force Mains Tukwila Gravity Sewer Pipelines by Diameter 6" or Less — 8" • 10" or Greater Unknown Diameter Monitoring Basin Flow Monitoring Basin i Flow Monitoring Basin 2 Flow Monitoring Basin 3 Flow Monitoring Basin 4 Flow Monitoring Basin 5 Flow Monitoring Basin 6 Flow Monitoring Basin 7 .. .:. Unmetered Feet O 1500 3,000 PP, of Tukwila, • CO., GlS,[ II Lng,neem, a./or survey acct., is not m0. SW 16TH ST S55 19TH ST 27TH ST , er SW 34TH ST SW 39TI?sT SW 41ST ST S 192ND ST S 208TH ST r31ST S SDTH ST Figure ES.2 Flow Monitoring Basins and Locations CITY OF TUKWILA COMPREHENSIVE SANITARY SEWER PLAN UPDATE 69 EXECUTIVE SUMMARY nsceMoemzna4/FINAL /cAnouo ES.3 Flow Projections Existing average dry weather flows developed from the flow monitoring program, described in Chapter 2, were used to determine flow factors for the [it/s existing land uses in each flow monitoring basin. The flow factors were utilized to develop existing, 1 0-year, and build -out dry weather flows for use in hydraulic modeling efforts. Accurate estimates of the future quantity of wastewater generated are critical in maintaining and sizing sewer system facilities. Table ES.1 presents the total projected AOVVF and peak wet weather flow (PVVVVF) for the three planning periods for the modeled system and whole collection system. Modeled system peak flows were estimated as the peak hourly rate during the design storm. The January 1 toJanuary 4' 2021 storm event distribution was used as the basis for the City's custom design storm. The 2.5'inch National Oceanic and Atmospheric Administration (NOAA) 5'year, 24'hourdesign volume was applied to the [ity'scustom design distribution to produce the custom design storm. The peaking factor, a ratio of PVVVVF to ADVVF was used to calculate the PVVVVF for the total system, which includes areas outside ofthe model. Table ES.1 Flow Projection Summary Planning Year k"D^Fhnod ' -- - -' ' Peaking Factor � Existing Modeled System ' Existing Total System 10-YearModeled System 10-Yeo Total System Build -Out Modeled System Build -Out Existing Total System 9.08 5.2 !13.08 52 9.94 4.9 1471 |4�9 ��---- —�---i'- 13.43 4.9 20.42 /4.S ESA Existing System The sewer system within the City's sewer service area is owned, maintained, and operated by the City. The system is divided into 20 drainage basins, with 1y6'3SSfeet ofgravity pipe, 10 lift stations with 22tnta| pumps, and 5'064 feet of force main. The City maintains a total of 25 connections with King County VVTD trunk lines. Wastewater from the City is conveyed to King County trunk lines to ultimately be treated at King County'» South Wastewater Treatment Plant (WWTP).The City also discharges to the Seattle Public Utilities (SPU) collection system where flow is routed to the King County system. The existing sewer system, including the pipelines, LSs' King County connections, and drainage basins are presented in Figure ES3and Appendix H. CITY opmmmLA COMPREHENSIVE SANITARY SEWER PLAN UPDATE ES-5 70 DECE EXECUTIVE SUMMARY ER 2024 / FINAL / CAROLLO S 128TH .ST, S 136TH ST 51.42ND 5T $ OTHELLO Sr, S KENYON 5T S CLOV'ERDALE' Sf LENOERSON Sr Commercial Center Lift Station (,0.9)�. 5 144TH ST S 146TH ST S 148TH ST s k597H $1.. 56TH 159 S 152ND 5%4 5 S4TN Sf i S 188TH ST S 192ND ST S 2007H ST 168TH ST S 170TH s;, S172NL1 ST "y 73RD ST; : • 5 175TH ST S 176TH ST S 282ND ST , S RYAN ST ANGOR ST anon (No. 8) . Interu b nips (King Cont(uy Station No 2 204TH ST S LANGSTON RD 5132ND S12 SW SUNSET Q{yQ Station A ri3a 3RD ST Lift Station No. 4 27T eoend Roadways Tukwila City Boundary � 1 Tukwila Sewer Service Area Water Body ® Connection to SPU Connections to King County King County South Treatment Plant King County Lift Station King County Sewer Main Tukwila Lift Station Tukwila Force Mains Tukwila Gravity Sewer Pipelines by Diameter 6" or Less 8" 10" or Greater Unknown Diameter Drainage Basin 4 5 6 7 8 9 0 12 14 16 20 22 23 24 2/18 Feet 0 1,500 3,000 Data Sources y of Tukwila, King County GIS, Doclairoce psham, le this fiqurc erspanpnq purposes and represent Enymeenno approximate survevaarOe., SW 41ST S1' S 208TH ST S 212TH ST Figure ES.3 Existing Sewer System CITY OF TUKWILA COMPREHENSIVE SANITARY SEWER PLAN UPDATE 71 SIS EXECUTIVE SUMMARY Asystem analysis was conducted for the [it/spumping and wastewater gravity collection systems. The analysis identified existing condition issues and capacity deficiencies associated with current and projected future use and recommend improvements toalleviate any identified concerns. The collection system was evaluated for the three planning scenarios: N Existing. = lO'Yeac Build -out. For the conveyance system, the design criteria and performance criteria are outlined below: Performance Criteria: During PVVVVFfor the design storm, water levels should not surcharge (maximum depth to diameter flow ratio [d/D] of 1.0). Pipes and manholes that surcharged and exceeded ad/Dof1are considered deficient. Design Criteria: Sewers shall be designed to flow at maximum d/D of0.8 at peak flow rates for both existing and build -out conditions. The [ity'slift stations should have sufficient firm capacity to pump the PWWF during the design storm. The maximum force main pipe velocity should be below 8 feet per second (ft/s) during PWWF for the design storm. The design ofnew force mains should keep the minimum velocity above Zft/stominimize E S .5A GraVih/C-oKUectio0 SYsteBl Evaitiation For each planning scenario, the PWWF was routed through the hydraulic model. The peak hydraulic grade line in manholes and gravity pipelines was compared to the established performance criteria. In general, the modeled collection system has sufficient capacity to convey existing flows during the design storm. The existing deficiencies are relatively minor, and their locations are identified with red in Figure ES.4. E S. 5 .2 Lift Static O DaDd Force Main EVa}uaf`*n The City's hydraulic model includes six lift stations out of the 10 lift stations located in the collection system. The estimated current and future PVVVVFsvvee compared tnthe six lift station firm capacities. All stations had adequate capacity, and none were deemed deficient. The maximum modeled velocity in each of the lift stations force mains was below 8 ft/s. Therefore, no force mains were deemed deficient. ES parallel or relief sewers can be constructed. Table Eproject details. S.2 summarizes the recommended improvement .5.3 Re[oNm ended Improvements When an increase in capacity is required, existing sewers can beupsize6 to larger diameter pipe, or CITY opmmmLA 72 EXECUTIVE SUMMARY nsceMoemzna4/FINAL /cAnouo Table ES.2 Recommended Pipe Capacity Projects �Pn�e� �U]' � Type Improvement Description Basin ID Existing Proposed Size 8bo .enoth Phase feet) Reasoning—� P-1 G-1 / Gravity General Upsizing along NWFargo St 22 between NVV23n1and NVV10bAve �------------- —[ �Upsizing near Division {t 22 between NYV10hand �NVV11MhAve | Programmatic surveying n[ All adverse sloped pipesinCity GtS Notes: |D 'idondfioaUnn; N/A' not . _,,_— 8 44 �238 | System Surcharging System Surcharging System Surcharging CITY opmmmLA COMPREHENSIVE SANITARY SEWER PLAN UPDATE B'G 73 EXECUTIVE SUMMARY 1281151 5T S 1.36TH ST s oruritio sri s urNYON ST S CLOVERDALE,ST S HENDERSON SF 13 ,t.N. • # ''..4,, ' '.4%,7#••••lio•Rio,...mon 4 ,5 6,pEING N, . _ .. It i 5 I, 'a • s). ii.„. i4ill Ai s ,NE AlleNown Lift *Statict),INo. 10) ‘,..• :.. vas: _ Lift Station (Flo. 9) * Y 1, ▪ r r 8 ... Lift StatiOri li"is Foster Point* • • to • -:--; InterurlikniPS • F.":" (King Coon.ty) S 142ND ST . • • , . G„.... N • 016'5,16'56516 S 146TH ST 4s, Commercial tenter Csi N,N S BANGOR ST REN404, =, S LANSTON RD -NONNO Sr 5 SW SUNSET 861-0 -7NI" • S 146TH ST g4„.. s *soTH s, 8 . z , K.,,, S 156TH WAY S 152ND .S%,,,, Lift‘. ..... • i S 1S4TH ST • SB54 a? fir S 188TH ST es • • • • • • El • mi. Ns Nisi.1,441L • I 14 S ILTd,1.S; .., . _ jiii. " . Area 7 657 651 ...a •,,, 1.?" R5 S 168TH ST • 66 -NH , • • / ° # • 8 S 172ND ST S 173ND ST 5 • # S 175TH sir : S 176TH st r. 9 ; i • S 192ND ST S 2007H ST S 182ND 5T, a Lift Station No:3 * Lift Station :No. 4 k , ift Station...wane...x.4 190TH51 s .104TH ST 1313 S 212TH ST S 1.67.1-1 ST DFOEMBER 2024 / FINAL / CAROLLO Legend Roadways 117:2 Tukwila City Boundary Tukwila Sewer Service A Water Body O Deficient Manhole 4.9,99. Surcharged Pipeline Unsurcharged Pipeline Lift Station Force Main Feet 1,500 3,000 Data Sourte, City of Tukwila, King Cnunty GIS, ES121 Disclaimer Features showr in this figure are tor planning purposes a. represent approximate locnons Lngneenng and,,, s. not imDlied 5W 7TH ST SW 27TH ST .,•L=i' SW 34TH ST SW 41ST ST S 208TH ST cAS s ciu40 ‘1'° 74 Figure ES.4 Build -out System Capacity Deficiencies CITY OF TUKWILA COMPREHENSIVE SANITARY SEWER PLAN UPDATE EXECUTIVE SUMMARY nsceMoemzna4/FINAL /cAnouo ES.6 Operations and Maintenance Chapter 6 provides an overview of the City's Sanitary Sewer Utility organization and operational procedures. The purpose of this documentation is to identify areas where improvements or changes could enhance existing system operation. The Public Works Department sewer operations and maintenance staff appear to possess or be able to access all of the equipment and supplies required to adequately perform the responsibilities assigned. However, the lack ofsufficient labor to adequately address the many responsibilities of sewer operations and maintenance was a recurring issue during past years. Based on the analysis of the adequacy of existing staffing levels in Sewer Operations and Maintenance work programs, the City determined that an additional two full time employees (FTE) would be required for sewer maintenance and operations activities. A portion of additional staff time would be devoted to implementing a grease interceptor inspection program. ES,7 Capital Improvement Plan The purpose of this CIP is to provide the City with a guideline for planning and budgeting of its wastewater system. Planning -level cost estimates were developed for each of the recommended projects in 2021 dollars and are based on an Engineering News -Record Construction Cost Index (ENK[C|) 20'dty average of 12,112 (June 2021). To estimate the construction costs, the following mark-ups were applied to the direct costs: 30 percent for contingency, 10 percent for general conditions, 15 percent for contractor overhead and profit, and 20 percent for engineering, legal, and administrative fees. Design and construction for all projects was assumed to occur within 1 year except when noted. Table El3 and Figure ElS provide a summary of the recommended [|P. Additional details on the [|P are provided in Chapter 7and Appendices ] and K. TableE8.3 Capital Improvement Plan �U] Short -Term Medium -Tenn Lift Station Projects LS-1 Pipeline Projects - -------- - P-1 P-2 ---- --- P-3a General Projects E-1 G-2 - G4 Total , /v4'000'000 $1200,000 $1,200,000 000,000 ^- ---- $4,000,000 `$1U.2OO'OOU $190,000 $30,000 - $4,000,000 $lU0U�OO $4,000,000 :$8,000,000 $150,000 � $200,000 $21'88O.UOQ $200,000 -------- $1O.420.00O onqpmmmLA 75 5127.TH ST 5 128TH 5T S LANGSION RD S DONOVAN ST °3R6 ST 5 96TH ST 6 s 1Q6Tt t ST S Toss ST 5104TH SW S 112 FH St 6lrr 116TH.ST 5'ND 5 120TH ST u, S 140TH ST. S 136TH Sr S 138TH S'i 51.42ND ST q S 146TH ST EXECUTIVE SUMMARY DECEMBER 2024 / FINAL / CAROLLO S MYRTLE ST > SE 72 S OTH S HOLDEN ST , NYON ST o, STHtSTLF. ST 5 CLOV[Rb,4L[ Si .ry Roadways 4.. ••• Tukwila City Boundary Tukwila Sewer Service r� Area Water Body Recommended Lift Station Projects 5 HENDERSON ST 1.22ND Commercial Center Lift Station )do. 9) 44TH, SFm..1 S 2 S 148TH ST • R RS�.4, S FSOTH ST o .5136TH WAY ,S 15;NO 4.: `ABN S 154TH Sr , 4911TH'e S 18811-1 sF Recommended System Improvements 6 ROXBURY ST P-2 S NC7RFOL.;v ST 6P �`. «ter p_g 5 (iYAN 5T TAFf n ...,.�. Recommended Surveying a (G-1) aANGOR ST a Other Lift Stations Force Mains S LEq ST - - ? - -[ OF' Gravity Pipelines wi "517:H 5T' .S AVON ST Feet N 0 1,500 3,000 Data Sources City of Tukwila, King County GIS, ES2, Disclaimer Features shown IP th,s. < J RENF Q fn9uur for pl,nnn9 purposes and n tIoes own Lift `E' Engine r nresent q pndio survey ace., cu' e ion (No. 10) rs net implied • 1 q 5 162ND ST • i 164FH ST 166TH S ,r �+ S 168 Di ST ,2 z 5 170TH S(' �� A `r .m S 172ND ST S 173RD ST S 172ND f'L••d• s 120f sl Foster Poir Lift Station (No. Lift Station No.12 lift Station No. 2 ISIN.ER 5 1901H 62 S 2007H ST a 12P - S OOTH PL S 204TH ST 5212TH ST, oTH SR :.r4rri sp STO31N ST 5 435TH ST SW SUNSFT' $U,n :.�3STQNR S2ND ST N e!/,Q '0R0 P2 D S3R!?ST SSTHS 76 < SW 77"N ST ` S 7TIi St SW 16RH ST . 5' I9T H ST SW 3411i ST SW 39THAB SW 41ST ST S 102ND ST S 1967ri 5T 5 208TH S1" p31ST SOTH ST 76 Figure ES.5 Recommended CIP Projects CITY OF TUKWILA COMPREHENSIVE SANITARY SEWER PLAN UPDATE Attachment E Washington Reso fon No. A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF TUKWILA, WASHINGTON, ADOPTING THE 2025 SANITARY SEWER COMPREHENSIVE PLAN AND PROVIDING FOR SANITARY SEWER SERVICE POLICIES FOR THE CITY, AND REPEALING RESOLUTION NO. 1827. WHEREAS, the City of Tukwila is an Optional Municipal Code city, subject to the duties imposed under the provisions of Chapter 35A of the Revised Code of Washington; and WHEREAS, the Sanitary Sewer Comprehensive Plan identifies specific actions and strategies to manage and control the quality of the sanitary sewer system in Tukwila; and WHEREAS, the City Council of the City of Tukwila has deemed it desirable to adopt a Sanitary Sewer Comprehensive Plan in accordance with the provisions of WAC 173- 240-050; NOW, THEREFORE, THE CITY COUNCIL OF THE CITY OF TUKWILA, WASHINGTON, HEREBY RESOLVES AS FOLLOWS: Section 1. The 2025 Sanitary Sewer Comprehensive Plan and Appendices dated December 2024, prepared by Carollo Engineers, are attached hereto and hereby adopted by this reference as if set forth in full. Section 2. The Sanitary Sewer Comprehensive Plan shall be revised every ten (10) years to reflect changes in the City of Tukwila Capital Improvement Program requiring facility modifications, as it relates to the standards outlined in WAC 173-240-050. Section 3. Repealer. Resolution No. 1827 is hereby repealed. [signatures to follow] 2026 Legislation: Sewer Comprehensive Plan Version: 02/13/2026 Staff: A. Altallal Page 1 of 2 77 PASSED BY THE CITY COUNCIL OF THE CITY OF TUKWILA, WASHINGTON, at a Regular Meeting thereof this day of , 2026. ATTEST/AUTHENTICATED: Andy Youn-Barnett, CMC, City Clerk Armen Papyan, Council President APPROVED AS TO FORM BY: City Attorney Filed with the City Clerk: Passed by the City Council: Resolution Number: Attachment: 2025 Sanitary Sewer Comprehensive Plan and Appendices dated December 2024 2026 Legislation: Sewer Comprehensive Plan Version: 02/13/2026 Staff: A. Altallal Page 2 of 2 78 Attachment F :// c Exhibit A 2025 Comprehensive Sanitary Sewer Plan ON FILE WITH CITY Can be accessed electronically here: u • Lin / I ct • nic • CI 0 79