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Washington County Government Center Stormwater Management Planning

The Washington County Government Center campus was in need of expansion to accommodate population growth and additional services. Using their redevelopment and expansion plan, SRF developed a Stormwater Management Plan after completing a hydrologic and hydraulic evaluation of the site and stormwater conveyance systems. This plan addressed discharge, detection, and elimination; construction site runoff control; post-construction site runoff control; and pollution prevention/good housekeeping items. In addition, the project needed to meet non-degradation criteria as measured by phosphorus loading. The total drainage area treated was approximately 75 acres, with more than 34 acres associated with the campus itself.

From several alternative concepts, the Stormwater Management Plan selected by Washington County included a wet pond for pre-treatment and bioretention basins, which function as partial recharge basins allowing for the infiltration of the first ½-inch of runoff from impervious surfaces. SRF prepared construction plans for these improvements.

Located in the southeast corner of the campus, the design of the stormwater facilities removed overgrown and invasive vegetation and replaced it with a native plant palette. This, along with a new walking trail that weaves through the stormwater basins creates an attractive open space for campus employees and adjacent neighborhood residents to stroll through for exercise and native habitat enjoyment.

SRF also provided full-time construction inspection services, including testing of the bioretention soils to confirrm design parameters. Staff also monitored the plant establishment and worked with the contractor during the three-year establishment period.

Washington County Highway Department
Stillwater, Minnesota
Construction Administration
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