With grant funding from the Department of Natural Resources (DNR), Howard County, Maryland awarded $1,000,000 to SMC to treat stormwater runoff on nonprofit properties that have entered into a Nonprofit Partnership. SMC first screened the properties in the nonprofit partnership to identify viable opportunities for treatment and determine the amount of impervious acres to be treated for the total fee.
SMC identified existing stormwater management ponds for retrofit to provide a total of 15 acres of impervious acre credits toward the County’s MS4 requirements. The retrofits add a gabion sand filter sandwich to existing detention ponds to provide water quality treatment for at least the first inch of runoff.
SMC provided design, permitting, and construction services while community outreach was provided by a subcontracting partner. Design elements included SCD coordination, attainment of long term access agreements with property owners, preliminary and final design of project elements, performing preliminary hydrologic and hydraulic computations, surveying, and final permit attainment through the redline plan revision process. Once final permits were obtained, SMC constructed the facilities.
Construction activities included the installation of erosion and sediment control measures, site excavation and grading, installation of gabion baskets, geotextile fabric, and sand to create the sand filter. Once the filter was completed the infiltration bed was constructed. The bed consisted of underdrain pipe tied into an existing outfall structure, sand filtration media and stone filtration media. Final site grading and stabilization was completed to ensure long term success as SMC will provide aesthetic maintenance for 2 years and functional maintenance for 5 years following construction acceptance.