The Gwynns Falls Water Quality Management Plan — A Case Study

Abstract

Parsons Brinckerhoff (PB) lead a team of water resource engineers and environmental scientists to develop a comprehensive water quality management plan for the Gwynns Falls Watershed. The headwaters of the 171 square kilometer (66 square mile) Gwynns Falls watershed begin in Baltimore County and drains through Baltimore City, into the Middle Branch of the Patapsco River and ultimately into the Chesapeake Bay. This project was a joint effort between Baltimore County Department of Environmental Protection and Resource Management (DEPRM) and Baltimore City Department of Public Works (DPW) as a first inter-jurisdictional, regional cooperative restoration effort and initiative. The goals of the water quality management plan were: Identify and evaluate non-point source stormwater pollution and stream degradation; Determine management measures for the reduction of nonpoint source pollution and reestablishment of stream stability; and Provide a watershed restoration framework for Baltimore City and Baltimore County. One of the major plan components was the stream assessment. Field crews walked, collected data and photographed over 214 kilometers (133 miles) of stream within the Gwynns Falls. The streams were divided into approximately 900 individual reaches averaging 227 meters (750 linear feet) each. The large number of reaches and data to be collected presented a unique challenge for the assessment team. Other key assessment features include GIS data management; water quality modeling using EPA SWMM; stormwater assessment that included 48 stormwater management facilities and 82 storm drain outfalls; and a forest patch assessment. The results of the field assessments were used to develop cost estimates and rankings for more than 120 projects within the watershed. Each project was ranked based on cost, water quality and habitat benefit, land availability, public acceptance and educational opportunities. The final product is a list of management recommendations and a prioritized list of restoration projects for incorporation into the City and County’s capital improvement programs.