Porous Alley Initiative

Project Complete

More than 60 of Puyallup's alleys are impervious gravel-paved surfaces - contributing to stormwater pollution runoff including sediment, oils, and more. The Porous Alley Initiative concept started with funding from a Department of Ecology Capacity grant, allowing for one gravel alleys to be retrofitted with porous asphalt. These retrofits reduced the volume of stormwater runoff and related pollutants as well as reduce annual maintenance requirements by City crews such as grading and re-graveling of the alleys.

Efforts of the Public Works Engineering Stormwater Division have secured additional grant funding to expand the program, and continue retrofitting gravel alleys in Puyallup's Clarks Creek and Puyallup River basins - supporting both stormwater management and water quality improvements.

Grant Funding Expands Initiative

The City was awarded a grant from the Washington Department of Ecology Statewide Stormwater Grant Program that will allow for the replacement of several impervious, gravel-paved alleys within the city with porous asphalt pavement. The Porous Alley Initiative project removed 4 alleys, just over 42,000 square feet of impervious cover in the Clarks Creek and Puyallup River basins, effectively reducing untreated stormwater runoff to our local streams and river by 1 million gallons of stormwater annually.

This project supported implementation activities identified in the fecal coliform and sediment-dissolved oxygen total maximum daily load (TMDL) documents for which the City is obligated by Ecology to implement projects to meet requirements. In addition, when replaced with porous asphalt, the alleys will no longer require annual maintenance by City crews to re-grade and re-gravel. Instead, they will be maintained as part of the existing street sweeping schedules in the project area.

Project Alleys

This project identified eight (8) alley and street locations for replacement based on need as well as other factors impacting placement of permeable pavements. The project sites anticipated for construction include:
  • 6th Avenue SW - Roadway paving completed: June 28, 2013. Final touch-up items completed August 2013.
  • Wilson Loop Drive NW - Construction completed August 2013.
  • Wilson Loop Drive NW - west end porous shoulder completed September 2013
  • 8th Avenue NW Alleys, between 11th and 9th Street NW - completed September 2015
  • Safeway Alley - south of 4th Avenue SE, off of 2nd Street SE (to-be completed by City crews*)
  • Holly Hotel Alley (to be completed by City crews*)
*Based on feedback from the funding organization for this grant-funded project (Department of Ecology), additional testing and design was required prior to approval of the plans. As a result, construction was postponed while a geotechnical expert was contracted to complete PIT tests and archeological reviews of the sites. In addition, the additional geotechnical costs and delays created a shift in the method of construction for the final two alleys - these will now be completed by City Staff and on-call contracts.