David Knowlton, City Engineer/Department of Public Services Director,, City of Salem, MA
Sections of coastal Salem, MA have endured frequent flooding for over a century, made worse by development and encroachment into the floodplain. To address this, Salem initiated a $50 million flood mitigation project to reduce flooding along Canal Street, a densely developed section of downtown. After a comprehensive mapping and survey effort, extensive modeling to delineate flooding extents for different size storms was conducted. Based on the results, 13 flood mitigation strategies were identified and prioritized by cost and expected performance under selected design storm conditions. These included several construction projects including installation of upsized drain lines in the affected areas; a new seawall at Forest River Park, earthen berm improvements along Rosie’s Pond Brook including composite sheet pile walls; upgrades to the Ocean Avenue West Stormwater Pump Station; and a 14 MGD pump station and a 4-million-gallon underground stormwater facility. Limited available open space meant that major elements of the project had to be located on Salem State University property. This required close collaboration and was facilitated through an agreement with the State of Massachusetts’ Division of Capital Asset Management and Maintenance. In addition to the pumping and storage infrastructure, the city used the restoration of a public park as an opportunity to integrate green infrastructure that provides stormwater treatment. The program leveraged federal grants and offers a model other cities can adapt to their needs to improve stormwater quality while mitigating the impacts of potential future flooding. The presentation will outline the complexities and considerations for negotiating a Memorandum of Understanding and Easement Agreements with State Agencies to facilitate public works projects. Attendees will learn how to identify appropriate urban flood mitigation strategies for their communities and develop strategies for incorporating water quality improvement measures into flood mitigation projects.