PROJECT OF THE YEAR: ENVIRONMENT $25 MILLION–$75 MILLION
Alewife Stormwater Wetland Managing Agency: City of Cambridge, Massachusetts, Department of Public Works Primary Contractor: P. Gioioso & Sons, Inc. Primary Consultant: Kleinfelder/MWH/Bioengineering Group Nominated By: APWA New England Chapter he Alewife Stormwater Wetland project demonstrates how innovative approaches to science, engineering, and ecology can concurrently resolve infrastructure problems, enhance the environment, and provide new open-space resources to the community. Three engineering firms teamed with the client, the City of Cambridge Department of Public Works (DPW), the parcel owner, Massachusetts Department of Conservation and Recreation (DCR), and the project proponent Massachusetts Water Resources Authority (MWRA). This project is part of the federally mandated Boston Harbor Cleanup. The Cleanup and the MWRA’s Longterm CSO (combined sewer overflows)
Control Plan required Cambridge to provide sewer separation and stormwater management to protect the Alewife Brook and Little River from CSOs. This stormwater wetland and outfall was the cornerstone of the Alewife CSO plan. And what started as a creative solution to CSOs became a parkland gift to the community. The engineering team collaborated with state and local agencies to advance multiple, seemingly conflicting objectives. Project challenges included finding a suitable location for an outfall that would not exacerbate downstream flooding, destroy a shallow and friable river system, and then building the “solution” on state-owned land. This project enables the sewer separation and infrastructure renewal of the Concord/ Huron Avenue area (420 acres) in Cambridge and private property inflow reduction. It will enable the closure of the CSO regulator responsible for the greatest volume of CSOs to the Alewife Brook, thus increasing the level of sanitary sewer service for the neighborhood, and eliminating SSOs up to a 10-year storm event. The Alewife Stormwater Wetland attenuates and treats newly separated stormwater before it discharges into the Little River and maintains
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APWA Reporter
July 2014
preconstruction peak flows to reduce downstream flooding. The project was designed to simultaneously meet the DCR’s Master Plan goals for Alewife Reservation: to provide environmental and recreational enhancements that support the reservation’s health and usefulness. The hydrologic model showed that the volume required for stormwater storage was approximately 3.5 MG, but no municipal area existed for such a facility. A feasible parcel stood within the DCR Alewife Reservation. However, using state-owned land for a city project required legislative action. The team presented a unique approach: a constructed wetland that would be part of an urban parkland and incorporate DCR recreational facilities. Cambridge DPW and the engineering team collaborated with DCR to design features that provide public benefit and ecological value, meeting Alewife Reservation Master Plan goals: •
Improve water quality and restore natural hydrology
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Protect and enhance wildlife habitat
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Improve recreational, educational, and other cultural opportunities
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Provide for maintenance to minimize costs and maximize efficiencies