SE 31st Street RetrofitMarion County | November 2012
With construction of the SE 31st Street Retrofit, Marion County addressed a long-standing problem of untreated stormwater reaching the aquifer by draining into a large sinkhole. The formerly untreated stormwater drained from a 26-acre watershed just south of Ocala and flowed directly to the sinkhole via an upland cut ditch. This project attenuates peak flows and improves water quality before the stormwater discharges to the large sinkhole.
Jones Edmunds assessed the site to determine vegetation community types and to determine if jurisdictional wetlands, surface waters, or listed wildlife species are present. The project site is in the Sensitive Karst Areas Basin and contains five sinkholes in the north portion. Results of the ground-penetrating radar evaluation found approximately 13 anomalies, indicating that a subsurface feature such as a sinkhole may be found at this location. A majority of these anomalies are close to the existing sinkholes. These data were used in the design process to avoid excavating in these areas.
Jones Edmunds designed and permitted a lined 2.3-acre constructed wetland with a forebay and a small bioretention area that treated highway runoff before entering the wetland. Jones Edmunds also secured a permit from SJRWMD, prepared bid documents and specifications, and provided construction services. The wetland and the bioretention area were constructed in uplands throughout the central and east portion of the project site. The emergent marsh treats the remaining suspended solids and dissolved organics, nutrients, and metals and provides water attenuation and wildlife habitat. The bioretention area treats runoff from a 0.9-acre area of US 441 and its right-of-way and overflows to the forebay and wetland. Among its numerous benefits, this stormwater treatment system achieves the following:
- Remove pollutants such as nitrogen, phosphorus, and heavy metals that typically occur in stormwater
- Improve the water quality that discharges to the on-site sinkhole
- Attenuate peak discharges
- Maximize stormwater detention time within the constructed wetland
- Create additional wildlife habitat