Baxter Boulevard Combined Sewer Overflow

Planning and design of the BBNSC began in the summer of 2011 with the selection of the design team to include Sebago Technics, Inc (Lead Consultant), AECOM, Jordan Environmental and S.W. Cole Engineering.

Planning & Design

A design approach was selected to include gravity dewatering and approximately 2 million gallons of storage split between Baxter Boulevard (CSO-007) and Payson Park (CSO-006). This approach allowed for controlling CSO’s at all three CSO locations without having to construct a storage system at CSO-005 which would have resulted in deep excavation, dewatering and overall higher costs. Through a comprehensive modeling and calibration effort, an integrated design was developed to reduce CSO’s at 006 and 007 in a manner that compensated for and reduced CSO’s at 005 without the need for physical storage at CSO-005. Once the design was solidified, a Computation Fluid Dynamic (CFD) analysis was completed to assess the performance of the diversion structures and solids deposition/re-suspension. To optimize flow performance, a V-bottom channel was incorporated in the storage conduit along with bending weirs and a baffle system inflow regulator CSO 006 and 007.


Project bidding was completed in the late fall of 2012 followed by the award of the contract to Sargent Corporation at a bid price of approximately $9.7 million. Construction work was initiated in late January 2013 and completed by the end of July 2013 well in advance of the December 2013 mandated completion date. At its completion, The BBNSC project reduced the total overflow volume on CSO’s 005, 006 and 007 to less than 15 MG during the typical rainfall year of 1966 which represents a more typical average year of rainfall.

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Project Details

City of Portland
Portland, ME
Date Completed:
Civil Engineering and Planning and Permitting
AECOM, Jordan Environmental, S.W. Cole Engineering, Inc.