Cambridge Underground: Challenges of Sewer Separation and Stormwater Management

Cambridge is an old city that is seriously in need of the infrastructure improvements that are now being implemented. Sewer separation and stormwater management projects will alleviate the problem of flooding and threats to public health caused by untreated wastewater discharged to low-lying neighborhoods and the Charles River during heavy rainstorms. Since 1998, S E A Consultants Inc. and Montgomery Watson Harza (S E A/MWH) have been working with the Cambridge Department of Public Works to pinpoint problems within the existing system; develop ways to achieve the program objectives; and plan, design, and oversee construction of over $325 million in city-wide infrastructure improvements over the next 15 years. Unconventional construction methods in heavily developed urbanized areas such as use of large underground storage tanks, maximizing use of surface storage potential, use of best management practices to reduce floatables and sediment discharges to the Charles River, and applications of trenchless technologies to minimize construction disruptions while improving the infrastructure have been highlights of the program. The paper describes various aspects of the Cambridge sewer separation and stormwater management program, the condition of the existing infrastructure, improvements needed to support future growth, and innovative techniques used to address water quality and quantity considerations. Planning, design, construction, utilities, traffic and pedestrian management, and community participation will be explained as they relate to this program.