Status

As of February 2018
Phase: next project (2019 construction) in planning

Overview and History

The City owns about 140 miles of stormwater pipe. Most of these pipes are over 50 years old and have exceeded their expected lifespan. Older pipes can become damaged over time. Damaged pipes can cause serious problems such as flooding or sinkholes. In 2011 we started a program to inspect all pipes by video camera to identify damage.

The Stormwater Pipe Repair and Replacement Program (SWPRRP) fixes damaged pipes. We prioritize repairs based on the severity of damage and importance of pipe. Our preferred repair method is to install a durable liner inside the existing pipe. Pipes too badly damaged to repair by lining are dug up and replaced. We seek to maximize the number of repairs we can do by choosing the lowest-cost reliable methods.

In 2014 and 2016 we installed a pipe liner type known as Cured-In-Place Pipe (CIPP). A CIPP flexible liner is inserted through existing pipe ends without any digging. The inflated material is then quickly cured into a hard, durable liner. CIPP crews can work without lengthy impacts to neighbors. Traffic revisions may last one or two days. The steam curing process creates minor noise and odor which lasts only a few hours. Potential water contaminants from installation and curing are strictly controlled. Overall, CIPP liner pipe repair is cost effective with minimal disturbance.


Pipe repair by CIPP liner. This photo shows the steam venting end of the inflated liner protruding from an open catch basin.

Previous Pipe Repair and Replacement Projects

  • 2014 was the first year of the Stormwater Pipe Repair and Replacement Program. 13 pipes were repaired within Storm Creek and Boeing Creek Basins. Work included 780 linear feet (LF) of CIPP liner repair and 86 LF of open cut replaced pipe.
  • 2015 Stormwater Pipe Open Cut Repair Project repaired pipes at 11 locations. Replacement work included 300 LF of pipe and 11 catch basins.
  • 2016 CIPP Stormwater Pipe Repair Project installed over 3,000 LF of CIPP liner. Work was done at 21 locations mostly McAleer and Lyon Creek Basins. 
  • 2017 Stormwater (Open Cut) Pipe Replacements Project completed work at three general locations. Replacement work included 700 LF of pipe and 10 catch 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.

Open Cut-Style Pipe Repair. A trench is dug to remove the damaged pipe. The new pipe is installed as a partial replacement. Couplings are used to connect new to existing undamaged pipe as shown.

 Pipe Interiors Before and After Repair