BWSC Contract 4

We worked with the Boston Water & Sewer Commission (BWSC) to provide engineering design services related to the separation of sanitary and storm sewers in a portion of South Boston and in North Dorchester/Lower Roxbury. Due to the size of the project areas and overall construction cost, the project was divided into four Construction Contracts.

The South Boston Interceptor (SBI) conveys flow from the tributary areas that are eventually treated at the WWTP on Deer Island and are influenced by tide elevations. As part of the proposed improvements, stormwater from this area was directed to the Fort Point Channel to outfall BOS072 through the existing SBI that runs beneath Gillette where the height of the tide can affect the drainage systems.

As part of the preliminary design phase for this project, we have compiled and reviewed record information for existing water mains within the project area. The information included age, material, and soil conditions. It was used to develop the basis of design for water main rehabilitation and replacement as part of the sewer separation work for this contract. The basis of design criteria for water main replacement included new pipe material and class, minimum depth of cover over new pipe, insulation requirements, and vertical separation from invert of the water main to the crown of sewer in which the sewer is below.