The most technically challenging highway project ever undertaken in the US is well underway. Officially called the Central Artery/Tunnel Project, but referred to locally as the Big Dig, the project will replace Boston's aging six-lane elevated Central Artery with a modern eight-to-ten lane underground expressway while keeping the existing artery and surface roads open to traffic. Under the direction of the Massachusetts HIghway Department (MHD), the Big Dig is managed by Bechtel Parsons Brinckerhoff.

The contract involves rebuilding five major highway interchanges and constructing a landmark cable-stayed bridge over the Charles River, north of the city. The first element ­ the Ted Williams Tunnel stretching beneath Boston Harbor to link the city with Logan Airport ­ opened in December 1995.

Committed to employing Best Management Practices (BMP) in the project, MHD was concerned about pollutants washing off the roadway surface, as environmental studies forewarned. One of the concerns was the challenge of removing Total Suspended Solids and petroleum-based products. Traditional BMPs to deal with the problem of runoff pollution proved impractical due to factors such as limited rights-of-way, high land values, highly-variable soil conditions and the existing complex infrastructure.

The MHD solution was to install deep-sump hooded catch basins in all entrances to the underground storm drainage system, conveying the flow to a series of Canadian designed Stormceptor units which will trap and remove suspended solids and petroleum-based products. Discharged water will flow to stormwater pump stations, located near the entrances to depressed highway sections. In addition, the Stormceptors will protect the pumps by removing floatables, grit and fine materials, as well as acting as a primary treatment device to trap suspended solids and petroleum products from surface roadways. This combination will remove 80% of Total Suspended Solids.

To date, the Federal Highway Administration has funded 21 Stormceptor units for the roadway system north of Boston; MHD has committed to another 35 units in other areas of the project.