June 11, 2002 -- The American Academy of Environmental Engineers (AAEE) recently presented MWH and SEA Consultants, Inc. an Honor award at the 2002 Excellence in Environmental Engineering competition for its innovative design and construction of the Crescent/Carver Sewer separation and stormwater improvements project in Cambridge, Mass.
The $8.6 million program brought immediate relief from flooding problems to the neighborhood. The program also introduced an aggressive public outreach program that positively addressed the community about construction issues.
The design of the $8.6 million Crescent/Carver Sewer Separation and Stormwater Management Program involved sewerage and drainage system improvements within a 31-acre parcel of the 410-acre sewershed catchment located in northwest Cambridge.
Located within the upper portion of the catchment are parts of Harvard University and Lesley College, and an extremely dense complex of residential homes and apartment buildings. Severe surface flooding and sewer surcharging above street level was occurring during major storm events when the existing 48-inch by 54-inch combined trunk sewer became overwhelmed.
The S E A/MWH team recommended the construction of 44-acre-feet of underground stormwater storage facilities with an optimized storm water conveyance system to provide 25-year, 24-hour storm protection for the entire area.
Widely successful in Europe, this concept combined with sewer-flushing vaults and a new large diameter storm drain proved to be an ideal and affordable solution with minimal impact to the surrounding, heavily congested community.
The team also incorporated innovative automatic flushing systems to cleanse sediments within flat sanitary sewers. During rainstorms, collected flows from several catchbasins are directed into small vaults connected to sewers. Once the rains have passed and the existing downstream pipe has sufficient capacity, a hydraulic gate is activated and the collected stormwater is rapidly discharged as a flush wave down the sanitary sewer causing erosion and scour of accumulated sediments. This unique feature minimizes the need for manual cleaning.
The elimination of flooding and wastewater backups along the areas serviced by the new sewer area has improved water quality of the Charles River and eliminated public health concerns from wastewater backups.
This project demonstrated that innovative thinking and use of proven technologies in other parts of the world can be used successfully in this country and in particular, Cambridge, one of the nation's oldest and most historic cities.
Over the last year, the Crescent/Carver area has endured a number of severe storms without any street flooding. The tanks have filled, emptied and been quickly re-readied for the next storm. SEA and MWH completed the entire project in 29 months, ahead of schedule and on budget.
