May 13, 2013 Retrofitting existing stormwater ponds

For years, the municipal NPDES permits have required stormwater control for new development, redevelopment, and construction sites.  However, to really improve water quality, retrofit of existing areas will likely be needed.

A report prepared by Parametrix and Bissonette Environmental Solutions for Puget Sound Partnership states “greater than 90 percent of developed land in Puget Sound discharges undetained, untreated stormwater, and retrofit of these existing untreated areas has been suggested as an important next step toward progress in reducing stormwater impacts to Puget Sound.”  The new 2013-2018 Phase I Municipal Stormwater Permit includes the retrofit of existing treatment and/or flow control facilities as one of the minimum performance measures under Structural Stormwater Controls (section S5.C.6).

One new resource to help plan for stormwater retrofits is the Kitsap County Stormwater Pond Retrofit Design Guidance Manual. The manual provides a framework to prioritize which stormwater ponds should be retrofitted, as well as what kind of retrofit will provide the most benefit. Let us know if you have used the manual – outside of Kitsap County – or if you have other retrofit resources or case studies that would be useful to share.

  • Retrofitting existing stormwater retention facilities seems to me to be of little use now, as they are new installations. Retrofitting old direct storm drains (& storm/sewer mixed systems) is a MUCH more valuable activity! This is the 90% the Parametrix report is speaking about. It is much more costly (than designing it in begin'g) but with all the alternatives now being studied & developed, retrofit'g is often possible.

    Posted Feb 21, 2015 by Jim Citizen Hendrickson
  • Storm water ponds are of great interest to me and my group the Olympia Mycelial Network, we are very interested in knowing how we can contribute some viable mycelium to the goals of storm water filtration, and storm water ponds seem like an ideal start!

    Posted Apr 12, 2017 by Ava Arvest

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