Stormwater Pipe Repair and Replacement Program

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As of October 2017
Phase: Construction underway

2017 Stormwater Pipe Replacement Project

The City of Shoreline is actively constructing for the 2017 Stormwater Pipe Replacement Project at three locations: Whitman Avenue N between N 145th Street and N 149th Street, 8th Avenue NW just south of NW Richmond Beach Road and 11th Avenue NW north of NW 190th Street. 

Construction is scheduled for 11th Avenue NW work in September. This page will be further updated as the project progresses.

11th Avenue NW location: Expected start date September 11, 2017. The Storm Creek Basin Plan identified a priority need to replace a failed stormwater pipe running down the hill slope to the west of 11th Avenue NW between the properties at 19031 and 19041 11th Avenue NW. The level of difficulty and disturbance required to replace this pipe in-place necessitate replacing it with a new storm drain pipe and catch basin alignment running south for approximately 400 linear feet (LF) along the west side of 11th Avenue NW to NW 190th Street within the public right-of-way. The old pipe will be capped at the upstream end and abandoned in place. Other improvements will include minor reconfiguration of the contributing system and installation of new asphalt berms and a shallow roadside asphalt swale to help collect roadway runoff and convey it away from downslope private properties. This flyer was provided in July 2017 to neighbors along 11th Avenue NW to provide information and solicit feedback.

Temporary construction impacts at these sites may include short-term loss of selected on-street parking and two-way travel. Local access will be maintained at all times. Other temporary impacts may include but are not limited to disturbances to landscaping and paving within the right-of-way, and mailbox impacts (not to affect delivery of mail).

Work substantially completed by early September 2017 at Whitman Ave N and 8th Ave NW locations:

Whitman Avenue N location: This postcard was mailed to neighbors. The Boeing Creek Basin Plan identified a priority need to replace multiple failed sections of concrete stormwater pipe within the public right-of-way of Whitman Avenue N at four locations on the east side of the street and one location on the west side between 14550 and 14817. Open cut replacement methods will be used to selectively replace damaged portions of pipe in place and connect them to existing undamaged pipe. One new catch basin will be installed to provide a standard connection for a large lateral pipe.

8th Avenue NW location: This postcard was mailed to neighbors. The Puget Sound Drainage Basin Plan identified a priority need to replace a severely failed section of concrete stormwater pipe crossing 8th Avenue NW south of Richmond Beach Road. Overall poor conditions of this pipe warrant complete structure-to-structure replacement. 8th Avenue NW traffic will be detoured for no longer than 5 days according to a traffic control plan. Advance notice of this closure will be given by means of temporary readerboard signs.

 Stormwater Pipe Repair  3-17-15
Open Cut-Style Pipe Repair. Damaged pipe is exposed by cutting a trench, then removed and replaced with new pipe. Couplings are used to connect new to existing pipe.

Overview and History

The City owns and maintains approximately 140 miles of stormwater pipes in active use. A majority of these pipes were installed more than 50 years ago and are nearing or have already exceeded their original design lifespan.

In order to address this aging stormwater infrastructure issue, the City has systematically assessed the condition of stormwater pipes (typically in conjunction with basin planning efforts) since 2013. The Stormwater Pipe Repair and Replacement Program (SWPRRP) repairs and replaces the failing stormwater pipes identified during the condition assessment video inspections.

The SWPRRP proactively ensures public safety, reduces flooding, decreases maintenance demands, and protects critical infrastructure and public and private property. Pipes identified as seriously deficient are prioritized for repair and replacement based upon estimated likelihood of failure and potential consequences of failure.

The preferred repair method is to install a durable composite pipe liner (known as cured-in-place pipe or CIPP); open cut trench pipe replacement is used for pipes too badly damaged to repair with CIPP. These chosen repair methods provide optimal value by means of extending the lifespan for existing stormwater infrastructure (as an alternative to much more expensive complete replacement).

Cured-In-Place Pipe (CIPP) is a trenchless pipe repair method utilized for rehabilitating damaged pipes by installing a flexible liner that is inserted through an existing pipe end and then quickly and permanently cured into a hard, durable composite material fully lining the complete pipe length. Lack of excavation and other surface disturbance means that crews can work quickly and without lengthy impacts to traffic and neighbors. Potential impacts at a given location are typically limited to temporary traffic revisions (lasting one or two days), and some minor noise and odor associated with the steam-curing process (which lasts a few hours and dissipates immediately upon completion). Uncured CIPP resin as well as condensate and rinse water from the curing process are strictly controlled to minimize potential water quality impacts. The CIPP pipe repair method provides optimal sustainability by extending the lifespan of the City’s existing stormwater infrastructure without the expense and high level of disturbance that comes with extensive excavation.

Previous Pipe Repair and Replacement Projects

  • 2014 was the initial year of the Stormwater Pipe Repair and Replacement Program. Construction repaired 13 pipes at locations within the Storm Creek and Boeing Creek Basins, which included installing 780 linear feet (LF) of CIPP repairs and 86 LF of open cut-replaced pipe.
  • The 2015 Stormwater Pipe Open Cut Repair Project implemented repairs at 11 locations, including installation of over 300 LF of new or replaced stormwater pipe and 11 new or replaced catch basins.
  • 2016 CIPP Stormwater Pipe Repair Project repaired over 3,000 linear feet (LF) of failing stormwater pipes at 21 separate locations, generally concentrated in the northeastern area of the city within McAleer and Lyon Creek Basins.

    2014 and 2015 Stormwater Pipe Repair and Replacement Program work was funded in part by the King County Flood Control District Sub-Regional Opportunity Fund.

Cured In Place Pipe RepairSM
Cured-In-Place Pipe (CIPP) pipe repair. Damaged pipe receives a new permanent liner of a hard, composite material. The liner is pulled through the pipe then cured using steam heat and pressure. This photo shows the inflated liner protruding from the existing catch basin, and a vent pipe for curing steam.

Pipe Interiors Before and After Repair


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