Active Capital Improvement Projects

18-2 International Blvd. SR 509 Rd Improvements

The Washington State Department of Transportation (WSDOT) proposes to extend the SR509 freeway from S 188th St to Interstate 5 as part of the Connecting Washington and the Puget Sound Gateway projects.  WSDOT anticipates selecting a contractor by the end of 2020 who will design and construct the project.  The overall project is scheduled for completion by 2026; however, the recent impact of Covid 19 may delay the State's schedule and/or reduce scope.

 WSDOT's design requires a freeway overpass for International Blvd S (ILB) at SR509 near S 206th St.  Sound Transit (ST) simultaneously plans for the Federal Way Link Light Rail to cross ILB in the same general vicinity.   Because ST will construct their infrastructure first, WSDOT contracted with ST to construct the overpass on their behalf during the light rail construction.  The effort help avoid multiple contractors working in the same general area on separate Public Works contracts.



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18-5 34th Ave S Water Main Replacement

In August 2018, the City of SeaTac informed the District of their plans to improve the road along 34th Ave S from S 160th St to S 166th St.  The City plans to install curb, gutter, sidewalk, new storm drainage and add on-street parking.  The City will also overlay the road upon completion.  Construction was originally scheduled for spring 2020 but was delayed due to Covid and ROW acquisition.

The District maintains approximately 1,850 LF of 6-inch AC water main within this section of road.  The existing main conflicts with the City's improvements.  The project includes replacing the existing main with a new 12-inch diameter DI pipe and connect an existing 12-inch main on each end of the project limits, thereby eliminating a bottleneck.  In addition, by replacing this main, the District would eliminate additional aging AC pipes, prevent the need to disturb the newly constructed road, and avoid the cost of an overlay at the District's expense. 


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19-2 2020 Water Main Replacement (Manhattan CI Replacement)

Highline Water District maintains several small diameter cast iron (CI) water mains in the general location of 2nd Place SW between SW 171st St and SW 176th St in the Maple Lane subdivision of Normandy Park.  Typically, CI mains are not the District's highest priority for replacement; however, these unlined, 6-inch diameter pipes were constructed in the late 1950's by the Normandy Park Water Company.  Over the years, the inside of unlined pipe corrodes and the buildup of rust deposits (tubercles) causes flow restrictions and water quality issues.  This area is one of the few locations of record where the District has unlined, cast iron pipes still inservice.

Most of these pipes are within easements in undeveloped, sensitive areas with limited valving and redundancy.  One pipe crosses under a seasonal stream tributary to Miller Creek.  Many pipes cross private property under steep banks, trees or retaining walls.  The District experienced previous ruptures and the location complicates repairs due to limited access.


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20-1 Star Lake Military Road Water Man Relocation

Highline Water District owns an existing 12-inch cast-iron water main from S 272nd St to Star Lake Road along the west side of Interstate 5.   The main is primarily on private property within easements granted to the District.

The proposed Sound Transit Link Light Rail Federal Way Extension conflicts with the existing main and will limit future access.  Sound Transit did not include this work as part of their original DB Contract and requested the District to evaluate and propose acceptable alternatives to address the removal of this main.



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21-1 24th Avenue S Water Main Replacement (2022 AC Project)

The City of Des Moines informed the District that it proposes roadway improvements along 24th Ave S from S 223rd Street to Kent-Des Moines Road.   The City plans to widen the road, install sidewalks and storm improvements on the east side of 24th Ave S.  The proposed City schedule is for design and ROW acquisition in 2021 and construction beginning in early 2022.

The District maintains an existing 10-inch AC watermain along the section of road.   The water main conflicts with the proposed road improvements.   The District must relocate the main in accordance with the terms of the franchise agreement with the City.  The proposed water work will include approximately 2,500 LF of 12-inch DI water main along with new hydrants and services.

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21-2 32nd Avenue S Water Main Replacement (City of SeaTac)

In late summer 2020, the City of SeaTac informed the District of an upcoming road improvement project scheduled for design and construction in the next two years.   The project has two parts: roadway reconstruction and replacement of curb, gutter and sidewalk improvements along 32nd Ave S from S 170th St to S 176th St; and pedestrian improvements along 32nd Ave S from S 176th St to S 180th St and along S 180th St to the Bow Lake Trailer Park.   The project is part of the City Council's goal to improve multimodal transportation within the City.

The District operates approximately 5,000 LF of various sized water mains throughout the corridor.  The mains are either cast iron or AC and may prove beneficial for the District to replace the mains as part of the City's work.   It is unclear of the magnitude of direct conflicts with District infrastructure as the City has only recently begun the planning and design stage. During the preparation of the budget, the City provided a limited description of their overall project scope.  There is possibility of a reduction in the scope for the District work depending on the City's design.


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21-3 Manison Hill 2.5MG Reservoir Int/Ext Recoat and Safety Improvements

The District will complete the Sound Transit improvements at the Mansion Hill tank site in 2021.  The previous work included completion of the new, 4.5 MG reservoir and Pump Station No 9.  The next phase of work will include retrofitting the existing 2.5 MG 490 Zone ground reservoir.

 The existing 2.5MG reservoir was constructed in 1959.   The tank was last coated in 2002 and the coatings are nearing the end of their useful life.   The base layer of the exterior contains lead and has been top coated several times in the past.   The recoating effort will require a complete removal of the exterior with lead abatement and surface preparation for a full recoat on the interior and exterior.  The exterior color will match the new 4.5 MG reservoir.



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22-1 King County Lake to Sound Trail Relocation

Project 22-1 King County Lake to Sound Trail Relocation

King County, in partnership with the cities of Burien and SeaTac, plans to construct a new trail from S 200th St to S Normandy Road and Des Moines Memorial Drive.  The trail will connect the Des Moines Creek trail to the regional trail network operated by King County.

 In early 2021, the District received notice by the City of Burien to relocate an approximately 1,200 LF of existing 16-inch cast iron water main in conflict with several retaining walls.   The proximity of the main prevents the excavation to form the wall foundations. 

 The District retained Parametrix, the same consultant who is designing the trail, to facilitate design of the relocation.   The work will be a bid schedule on the County construction contract.  In early 2022, Highline and King County will need to negotiate an ILA to include the work.

 The anticipated project cost is $805,000; however, the full scope of the necessary work is still in development.   Work is tentatively scheduled for 2022; however, King County may delay the project until the 2023 construction season. A detailed budget will be prepared prior to construction.  The work will be funded by existing rates and capital reserves. 

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22-2 2023 AC Water Main Replacement (Hunnington Park)

Project 22-2 2023 Water Main Replacement (Huntington Park)

Huntington Park is a private community, condominium-type property located in Des Moines. The Huntington Park Homeowners Association reached out to the District inquiring our intent to replace existing water infrastructure in the future.   The Association plans to overlay the existing roads in the next several years.

 The District owns and operates several small diameter AC water mains in Huntington Park.   Highline inherited these mains when Water District No 56 dissolved and was incorporated into the District. The neighborhood is located on several tax lots and the existing water mains are within inherited easements.

 The District has an excellent opportunity to replace the aging infrastructure in partnership with the Homeowner's Association.  It allows for updating the existing easements and upgrade the water system with modern materials and construction techniques.

 The project includes replacing approximately 10,000 LF of AC mains, including valves, hydrants, and services.  Design and easement acquisition would commence in 2022, with construction following in 2023-2024.

 Project 22-2 includes $200,000, $2,400,000, and $800,000 for years 2022 and 2023 and 2024, respectively.  A detailed budget will be prepared once the project is fully scoped in design.  The District will fund the project by rates and capital reserves.


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22-3 SR 509 Phase 2 Water Main Relocaton

Project 22-3 SR509 Phase 2 Water Main Relocation

As part of the Connecting Washington and Puget Sound Gateway Project, WSDOT proposes to construct a new tollway connecting Interstate 5 and SR509.  Phase 1 (Project 18-2) includes constructing a 4-lane highway between Interstate 5 and 24th Ave S in SeaTac.   The second phase (this project) includes completing the freeway from 24th Ave S to Des Moines Memorial Dr and S 188th St where SR509 currently ends.

 The District has identified three locations of potential conflict with the new tollway:

  • At Des Moines Memorial Drive and S 188th St, WSDOT proposes two onramps/offramps/round-a-bouts that conflict with an existing 16-inch cast-iron water main. 
  • At S 192nd St near Des Moines Memorial Drive, WSDOT will construct a new overpass for the city street, severing an existing 8-inch water main and requiring it to be affixed to the new bridge.  
  • At Des Moines Memorial Drive near S 196th St, a new stream culvert will require an 8-inch water main to be relocated.


The full scope, budget and schedule for the project has yet to be determined.   The District included $25,000 for design services in 2022 and allocated $1.55M in subsequent years.   A full scope and budget will be prepared once additional details are provided by WSDOT.


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Contact Us

Highline Water District
23828 30th Ave. S.
Kent, WA 98032
Phone: 206-824-0375
Emergency: 206-824-0375
FAX: 206-824-0806
Hours: M-F 7:00-4:00

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