Porous Alley Initiative
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.
This project will support implementation activities identified in the fecal coliform and draft 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.
The grant was accepted by the Council in 2013. Based on staff work loads, 2 alleys have been retrofit per year since then, with the final two scheduled for completion in 2015.
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:
*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 be 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.