Town Hall Bioretention Retrofit, Mooresville, NC

WK Dickson conducted survey and developed design plans for two stormwater best management practice (BMP) bioretention (a.k.a. rain garden) locations for the Mooresville Town Hall property. The project was a retrofit effort, with one location adjacent to North Church Street and one adjacent to the Post Office building and Town Hall. These bioretention measures were designed to capture stormwater runoff from asphalt parking lot and the Town Hall roof to infiltrate storms up to the 1-inch of runoff, reduce peak flows during frequently occurring storms and to optimally remove key pollutants, including Total Suspended Solids, Total Nitrogen, Total Phosphorus, Heavy Metals and Pathogens. The Internal Water Storage (IWS) zone design modification was implemented for both bioretention designs in order to maximize the Total Nitrogen removal potential while increases the overall infiltration capacity. Another critical component to the overall design was the educational component, where the bioretention sites were carefully selected to provide public access and educational opportunities.

Design challenges included maximizing the capacity of the bioretention measures within practical limitations of the existing site, as well as connecting to shallow existing storm drainage system, which was accomplished using the IWS design modification. Scope included design, field surveys, utility coordination, geotechnical subsurface investigations, design and construction plans, and construction administration and observation.