Salmon-killing chemicals can be treated with bioretention, but King County says no

Photo of a bioretention facility in the Town of Mill Creek. (Photo by the author)

Bioretention was approved over six years ago by the Washington State Department of Ecology for use as a stormwater treatment facility. Yet King County is slow to accept it for use.

Bioretention is a versatile stormwater management facility and the only known water quality treatment method to treat 6PPD, a pollutant that research has linked to dead coho salmon. 6PPD is an additive to promote the life of car tires. The toxic pollutant was discovered in runoff that enters our waterways.

Other water quality facilities such as sand filters, grass lined swales and retention ponds have not been shown to be able to treat 6PPD.

Bioretention consists of a mixture of imported soil, plants and mulch installed to create a shallow depression in which stormwater collects. Its purpose is to capture and filter rainwater runoff, which results in a decrease in the level of pollutants leaving the system.

King County Executive Dow Constantine takes pro-environment stances, generally speaking, and seeks to be a climate leader and advocate for iconic species like coho and killer whales. However, on the issue of bioretention, he let the county fall behind.

As a civil engineer, I have specified bioretention for use in many jurisdictions in the Puget Sound region because it is an environmentally friendly and environmentally friendly way to treat stormwater runoff that is better suited for the protection of salmon runs compared to conventional stormwater treatment systems. I’ve used it in Snohomish County, Town of Mill Creek and Bellevue.

For a design I prepared in unincorporated King County, I proposed vehicular access to a new home, via a circular drive and an interior bioretention system. I was pleased to provide a design that harmonizes the functional use of bioretention to capture and treat runoff from the proposed driveway, while providing an aesthetically pleasing landscaping feature for the homeowner.

An aerial view of the bioretention design submitted to King County for permit review by the author.

King County has elected to publish its own King County Stormwater Management Manual (KCSWMM). Additionally, cities in King County can adopt the KCSWMM or use the Washington State Department of Ecology’s Stormwater Management Manual for Western Washington. The City of Sammamish has adopted the KCSWMM and the City of Bellevue uses the state manual.

The KCSWMM is a design document to ensure that stormwater runoff from new landscaping surfaces is mitigated by installing approved stormwater management facilities. The manual provides details and applicability standards for stormwater designs.

Although I have provided several stormwater system designs in King County, the design I submitted in early 2019 was the first time I had offered a bioretention system for water quality control. water in unincorporated King County.

The wet stormwater pool and combined retention system allows sediment to settle to the bottom of the pond. (Credit: Environmental Protection Agency)
A sand filter bioretention facility. (Credit: Chesapeake Stormwater System)

I was surprised when my design was rejected and returned with a comment that bioretention is not permitted for use as a water quality treatment facility in the unincorporated county of King. Of the more than 25 municipalities in which I provide design services to clients, King County is the only jurisdiction I know of that does not allow water quality treatment through the use of bioretention .

So I asked King County staff what authority they had to prohibit its use. I met with Department of Permits and Environment and Review (DPER) staff in 2019 and was unable to get a satisfactory response. This is a system that has been tested by the Washington State Department of Ecology and meets the standards required by the Federal Clean Water Act.

Several DPER staff were surprised to see the verbiage included in the King County mManual and said they would ask the Land and Water Resources Division of WRLD staff about it.

Later in 2019, I spoke with John Taylor of the King County Local Services Department and he revealed that in 2014 Land and Water Resources Division (WLRD) staff met and checked with each other and determined that King County would not allow bioretention. for use in their jurisdiction, which is unincorporated King’s County.

In May 2022, after the Covid-19 shutdown was interrupted, sought to make progress once again and corresponded with Curt Crawford, Storm Water Service Section Manager at WLRD and WRLD Division Director Josh Baldi. I highlighted the new 6PPD research and the requirement that all jurisdictions be required to use Department of Ecology (DOE) approved water quality facilities.

The excerpt below is from the 2019 DOE Stormwater Management Handbook and includes an explanation of Washington State law that requires all jurisdictions to use DOE-approved water quality facilities.

In August I met again with WRLD, including Curt Crawford, and despite the relevant and compelling information discussed, the staff stuck to their position that they have no intention of reconsidering the use of bioretention facilities for use in King County as water quality treatment. ease. I mentioned that the county is legally obligated to accept “all reasonable technologies known to be available” and that bioretention is uniquely suited to treat pollution from 6PPD tires, thereby protecting salmon runs, but it only served to nothing.

King County’s position to ban the use of bioretention is illogical, ignores applicable law, and could have devastating effects on long-term salmon migrations.

Even though King County presents itself as an environmental leader, it appears staff are making their own policy decisions that are inconsistent with these leadership goals.

King County was contacted for comment but did not provide a response until this article was published.

Information from the Zoom meeting of August 17, 2022 can be corroborated by:

  • Lisa Harbert, PE, (Professional Engineer) Harbert Engineering
  • Haim Strasbourger, PE City of Sammamish, Development Review Engineer

For those wishing to participate, ASCE, (American Society of Civil Engineers), Seattle Chapter Committee has next meeting on September 21.

Donna Breske (guest contributor)

Donna Breske is a licensed Professional Engineer in Washington State. She owns Donna Breske & Associates and, along with her staff, provides land use and civil engineering design advice for numerous infill projects in multiple jurisdictions in the Puget Sound area. She holds a Bachelor of Science in Civil Engineering from the University of Washington and an MBA from Seattle University. She is married to her husband Fred with whom they share two adult children. She grew up in Seattle and is passionate about breaking down absurd barriers to departmental authorization and ensuring consistent, predictable results.


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