Stormwater Management Projects

Halfway Creek Regional

Conservancy Filter Marsh

Lee County Surface Water

The Brooks

The Conservancy: Filter Marsh Pollution Reduction

Within the Gordon River South sub-basin, in Naples, Florida, an existing drainage ditch allowed stormwater runoff to flow from a mall's parking lot, a major road, and adjacent residential areas with minimal or no treatment. The ditch bisects the Conservancy property before it discharges into the Gordon River. The purpose of the Conservancy Filtration Marsh Project was to reduce urban runoff pollution, while enhancing the wildlife and education values of the site.

This project was designed to intercept the stormwater flow in the drainage ditch and divert it into a wet detention pond, draining through a filter marsh before discharging into the river. The littoral shelf comprises a minimum of 30 percent of the surface area of the basin and is planted with native wetland vegetation. The shelf while reducing erosion, enhances the biological uptake of pollutants by plants, prevents re-suspension of sediments, and increases the habitat and aesthetic values of the filter marsh.

A new, large box culvert improved ditch flow characteristics and replaced an existing ineffective drainage culvert. The drainage ditch was analyzed with HEC-RAS to see the effects the improvements would have on the existing condition during the permitting phase of the project. The results of the analysis showed that upstream head conditions was reduced dramatically by removing the existing triple ERCP ditch culvert and replacing it with a smaller box culvert. These types of BMP improvements will reduce erosion of the ditch side slopes during high flow events, decrease the risk of upstream flooding, provide a littoral zone for further improved wildlife habitat/foraging, and provide additional treatment of the stormwater runoff.

Within six months of the end of construction, the filter marsh and sedimentation basins have proven to be a valuable habitat to small fish and wading birds