In 2013, the Pierce County Department of Public Works and Utilities Surface Water Management Division installed a stormwater filtration system to treat stormwater from 0.6 acres of impervious surfaces that was discharging into Rody Creek, a main tributary to Clarks Creek. The intent of the project was to improve dissolved oxygen levels in Clarks Creek by meeting a TMDL goal from the Washington State Department of Ecology (WSDOE) through reducing sediment loads. Achieving this goal would improve the overall health of the Rody Creek watershed and accelerate the recovery of salmon populations in Clark Creek and its tributaries.
The engineer of record selected a competitors spiral filter system based on the fact it was a WSDOE GULD listed product and the public bid process. A few months later, the county complained the competitor’s system had clogged twice since it was installed (middle picture). The City tried to work with the manufacturer to solve the performance issues, but the City and the manufacturer could not agree on what was causing the system to fail. The City then contacted WSDOE who awarded a grant to get approval to retrofit the system with a Stormwater Management Stormwater Management StormFilter, a stormwater treatment device that uses rechargeable, media-filled cartridges which trap particulates and absorb pollutants such as dissolved metals, hydrocarbons, and nutrients.
Contech worked extensively with the county to develop a solution utilizing StormFilter cartridges. Being a retrofit, it was crucial for Contech to provide an accurate flow kit and cartridge placement. In addition, the project was located in a residential area, so quick installation was key. Contech provided proposal drawings, specifications, and installation documentation. This streamlined the process and provided a solution that was installed in just two days.
One of the unique features of the StormFilter is its patented surface cleaning mechanism that helps restore the permeability of the filter surface between storm events and prevent clogging. After 6-months of installation, the system was operating at full capacity and had not required any additional maintenance. When maintenance is needed, Contech offers a maintenance and certification program that has been well received by Pierce County and other WA jurisdictions.