T-38 - 216 Ave SE Water Quality Improvements

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The City of Maple Valley constructed four (4) Modular wetland systems as part of the roadway Improvements project completed in Fall 2016, along a 3,300 foot stretch of 216th Avenue SE.  This is a type of green stormwater infrastructure.  These roadside modular wetlands will treat previously untreated stormwater runoff prior to discharge into Cranmar Creek. 

Formerly, storm water along 216th Avenue SE (a north/south minor arterial on the South end of Maple Valley) sheet flowed untreated off of the roadway and made it way into the treasured Cranmar Creek.  Cranmar Creek flows year round benefiting from natural springs and is a tributary to the regional Jenkins Creek. 

This project will now collect the untreated surface water and utilize both traditional and low impact development (LID) methods to assure that water being discharged will not degrade our natural resources.  The project installed new curb and gutter on the east side of the roadway and four (4) Department of Ecology approved Modular Wetland Systems with downstream infiltration chambers.   These systems are designed to remove over 80% of Total Suspended Solids that currently make their way into our natural resources.  Both creeks provide critical habitat for Coho salmon smolt.

The improvements will not only improve water quality for the drainage basin(s) along 216th Avenue SE between 272nd and the Southern City Limits of Maple Valley, it will protect this service area in the case of unexpected spills and unforeseen erosion.  In addition, this project will be installing landscaped medians to reduce the overall pollution generating impervious surface area.  This project was funded in part by the King County Wastewater Treatment Division.

Any questions, please contact Kim Scattarella, 425-413-8800.

T-38 216th Ave SE - MWS vegetation - 111816
November 18, 2016 - MWS Vegetation