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Design of a treatment wetland for the North Acton Recreational Area, Acton, MA

The Assabet River, part of the Assabet River Basin in Massachusetts, is in a eutrophic state due to nutrient loading, particularly phosphorus, coming from various sources along the river. The Town of Acton, a community located in the Assabet River Basin, is interested in using urban best management practices (BMPs) to reduce NPS phosphorus loading to an adjacent Assabet River tributary. In an effort to publicly demonstrate the advantages of using BMPs to improve local water quality, this paper will evaluate the use of a constructed wetland to reduce phosphorus loading to a swimming pond in the newly constructed North Acton Recreation Area (NARA). Since the swimming pond eventually discharges into the Assabet River Basin, improved water quality of the swimming pond is directly related to improved water quality of the Basin. The proposed wetland will consist of two swales to channel storm water runoff to the wetland area, a detention or sedimentation pond, two emergent marsh cells, and a micro pool. The phosphorus removal methods used in the wetland are sedimentation, microbial uptake, and plant uptake. On average, the wetland will reduce the phosphorus concentration in storm water runoff from 0.35mg/L to 0. 12mg/L. After the treated runoff mixes with the swimming pond water, the final phosphorus concentration in the swimming pond is expected to be around 0.043 mg/L, below the 0.05 mg/L permissible concentration. In addition to serving as a phosphorus removal mechanism, the wetland will also provide many auxiliary benefits such as providing a wildlife haven, serving as an educational tool for local citizens, and enhancing the overall aesthetic value of the park. Thesis Supervisor: Harold F. Hemond Title: Professor of Civil and Environmental Engineering