St. Johns County implemented this project to reduce nutrient loads to the Lower St. Johns River (LSJR) to meet the Total Maximum Daily Load (TMDL) compliance goals of the LSJR Basin Management Action Plan. Jones Edmunds prepared a Preliminary Engineering Report (PER). We also helped with the design, permitting, and construction-phase services for the Masters Tract Regional Stormwater Treatment Facility.
Masters Tract is a 272-acre parcel owned by St. Johns County adjacent to Deep Creek, a tributary of the LSJR. Agricultural uses negatively impact stormwater runoff from upstream areas, resulting in high nutrient loads to Deep Creek. As a result, the design focused on optimizing nitrogen removal through multiple treatment methodologies. These include wet pond construction, stormwater harvesting, infiltration canals, and constructed wetland communities. Jones Edmunds completed extensive wetland field investigations to delineate all on-site wetlands, identify wetland mitigation areas, and determine wetland creation design elevations using Deep Creek floodplain wetlands. We also provided a Phase I Environmental Assessment and soil nutrient for the County.
The project included routing incoming creek flows to a stormwater pump station that discharges to a regional stormwater basin for initial treatment and nutrient removal. We then route the water to agricultural irrigation, two large emergent marsh flow-ways, or a series of three 13+-acre treatment wetland cells for further water-quality polishing. Furthermore, we use excess stormwater for irrigation of a nearby farm that currently uses groundwater.
In addition, the project provides 21 wetland mitigation credits generated by the constructed wetlands to offset the future County Capital Improvement Program wetland impacts. These mitigation credits result in a value of approximately $2.1M. Jones Edmunds assisted the County in securing $2.9 million in grant funding and is providing grant administration and construction services.