|The Edwards Branch Watershed Project is a multi-phased approach to addressing storm water runoff and improving overall water quality in a small, primarily residential, 1 square mile watershed. Structural and non-structural BMPs as well as stream restoration and buffer preservation projects have been implemented to study the effectiveness of the multi-BMP approach. Completed in 2002, the wetland project was the first structural BMP of this overall project. An arched footbridge was constructed over the wetland to maintain connectivity with an adjoining park and to allow for public education and interaction with the wetland.
Stream restoration at Edwards Branch
Other phases of the Edwards Branch Watershed Improvement Project focused on street flooding, channel erosion, and storm water pollution control.
|Edwards Branch Wetland
The design of a storm water wetland is similar to the design of wet ponds except that wetlands are much shallower and therefore, their flood control ability is limited. The main body of the wetland consists of high and low areas, which encourage a variation in vegetation type across the wetland.
The wetland at Edwards Branch is designed to remove pollutants through gravitational settling, wetland plant uptake, absorption, physical filtration, and biological decomposition.
The wetland at Edwards Branch
The wetland is monitored to determine its efficiency at removing Total Suspended Solids (TSS), bacteria and many other pollutants commonly found in storm water runoff within the context of this particular scenario.
Testing of water moving into and out of the wetland indicates that the wetland has the ability to effectively treat a number of pollutants including sediment, nutrients, and some forms of metals.
Summary report for test results
Recent tests conclude that the wetland removes 35% Total Nitrogen, 45% Total Phosphorus, and 55% Total Suspended Solids respectively. Total nitrogen and total phosphorus removal by the Edward's Branch wetland, 45% TN and 45% TP. The Edward's Branch wetland exhibited high removal of copper (57%) and zinc (71%) and the moderate removal of lead (32%). The Edward's Branch wetland was very successful in removing E. coli
and fecal coliform, achieving removal rates of greater than 90% for E.coli
and 99% for fecal coliform entering the wetland.