In the summer of 2007, the City constructed a new water quality facility that is made up of a series of underground vaults located within the parking lot of Luke McRedmond Landing Park.

This facility collects stormwater from watershed 540, 15.01 acres of urban commercial development. Some additional area of the watershed is non-pollution generating park and roof areas that bypass the water quality facility.

This facility uses an innovative media filter to capture pollutants within the filter prior to discharge to the Sammamish River.

What is a Media Filter?

A media filter is a type of filter that uses a bed of sand, compost, crushed granite or other material to filter water for drinking, swimming pools, aquaculture, irrigation, stormwater management and other applications. Media filters can be effective at removing pollutants in stormwater such as suspended solids, dissolved metals, oil & grease, and phosphorus. Sand was the first widely used filter for stormwater. These sand filters were later amended with compost, zeolite, perlite, granular activated carbon, and other media to improve removal of various pollutants. Filters have been modified using various mechanical configurations to improve flow rates and reduce maintenance requirements. Porous concrete is a media that has recently been explored for use in stormwater treatment.

For this project, the City selected an emerging technology known as the ecoStorm plus, manufactured by Royal Enterprises. The product had recently received approval from the Washington State Department of Ecology for pilot use in Washington.

How does it work?

The ecoStorm plus is a system that combines a porous concrete filter with a vortex / swirl concentrator to remove sediment and other pollutants. The system is designed to promote sedimentation by directing stormwater through a centrifugal swirl pattern. Water then flows through a porous concrete filter designed to promote precipitation of dissolved metals and the natural filtration as the water flows through the concrete.

Design Information

This product was selected for this site as a pilot project based on substantial lab scale data demonstrating pollutant removal efficiencies. As a pilot project, the system was constructed to allow for monitoring of water quality, and the system was constructed with some redundancies. The Design of this project is documented in KPG's Design Report and As-Built Drawings.

But, does it work?

As part of Ecology's approval process, pilot studies are required for new technologies. Pilot installations are monitored using Ecology's TAPE protocol. This technology evaluation program reviews engineering reports on the performance of new technologies and reports the results at Ecology's web site. Test protocols have been developed for permanent stormwater treatment systems and for construction sites. These protocols specify sampling criteria, site and technology information, quality assurance and quality control measures, target pollutants, and evaluation report content.

The McRedmond Water Quality Facility has been subject to monitoring since it was installed. The City is working closely with Ecology and the manufacturer to confirm that it works in real world conditions. Should the facility receive approval from Ecology, it will be considered for use at other proposed facilities in Redmond.

Contact:  Anisha Prasad at 425-556-2722