Integrated Water Management

Little Mystic Channel (BOS019) CSO Storage Facility


Little Mystic Channel (BOS019) CSO Storage Facility

Charlestown, MA


About this Project

The Little Mystic Channel (BOS019) CSO Storage facility, the MWRA's first offline CSO storage/pumpback facility, was constructed as part of the Authority's Long-term CSO Control Plan. This facility will reduce CSO activations in a typical year from 16 to 2 by storing up to 670,000 gallons for pumpback after the storm subsides.

FST improved upon the 1997 Facilities Plan scheme by designing twin 10-foot by 17-foot box culverts over 250 feet long to store more flow in an extremely confined site without affecting the adjacent Tobin Bridge. Strict criteria were included in the specifications for support of excavation, underpinning the retaining wall of the Chelsea Street Bridge and installation of instrumentation to monitor the effectiveness of the trench support in preventing ground movement.

The Pumpback/Odor Control Building is over 50 feet deep. It contains 800 gpm dry pit submersible pumps and an 8000 cfm activated carbon odor control system. The Influent Gate Structure includes a hydraulically operated flushing gate system to clean deposits from the conduit floor. Construction of the $10 million project was completed by the court ordered deadline.

More Information

Owner: Massachusetts Water Resources Authority (MWRA)

Location: Charlestown, Massachusetts

Highlights: This project met each Federal District Court ordered milestone since FST began design.