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Agate Bay Phase 2

Bellingham, Washington


Whatcom County


Wilson Engineering


Oceanside Construction, Inc


August 2019

Technical Description:

  • (3) Stormwater Management StormFilters®

Lake Whatcom is a large natural lake in Whatcom County in Washington. The northwest end of the lake lies within the city of Bellingham, and 22 small watersheds drain into the lake. The lake serves as the drinking water source for about 96,000 people in the Bellingham area and is popular for recreation. The lake has been threatened by declining water quality, and in 1998 was put on the state’s list of polluted water bodies. The Agate Bay Stormwater Improvement Project, Phase 2 is a part of a two-year effort to provide stormwater treatment in the Agate Bay region.

The primary water quality concern is low levels of dissolved oxygen (DO) as a result of increased levels of phosphorous and fecal coliform bacteria. A lack of oxygen threatens the survival of fish and aquatic plants. Stormwater is the chief source of this phosphorous. 

Whatcom County submitted and received grant funding from WA Ecology to address and retrofit the existing stormwater system within a particular drainage area of the lake’s watershed.

The project included replacing failing pipes and culverts, installing new pipes and catch basins and reducing ditch erosion. The project also included the installation of three 8’ x 11” Stormwater Management StormFilters. The three StormFilters contain media cartridges filled with PhosphoSorb®, a lightweight media that removes total phosphorus (TP) by adsorbing dissolved-P and filtering particulate-P simultaneously. The vaults were oversized to allow for additional capacity in the future.

The StormFilter was selected because Whatcom County estimated the StormFilter with PhosphoSorb media provides the lowest cost per pound of phosphorus removal as compared to alternative treatment systems.

WA Ecology imposes a very strict window for construction activity in the watershed. Contech coordinated extensively with the installing contractor throughout the process to ensure timely execution and delivery within that window.  Failure to do so would have caused the project to shut down until the following year.

This was one of several projects that Contech has provided treatment systems for in the Lake Whatcom watershed. Contech provided the most efficient treatment system to help meet the stringent requirements imposed by WA Ecology on Lake Whatcom.  The Contech team provided support throughout the process, helping to ensure that the contractor and County met their construction schedule. The new stormwater improvements provide immediate water quality treatment of stormwater discharging into Lake Whatcom.

Technical Description:

  • (3) Stormwater Management StormFilters®

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