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Project Experience: East Boston-Chelsea Bypass Project, Massachusetts

The Challenge

The Massachusetts Port Authority (Massport) proposed to construct a new bypass road primarily for commercial vehicles. The Project will consist of a 2,225 foot two-lane roadway in the existing abandoned railroad corridor connecting Frankfort Street (southern extent) to Chelsea Street (northern extent). The Project would provide an alternative to the existing roadway connections through Day Square, Eagle Square, and the Neptune Road Corridor. The Project should reduce vehicle trip volumes and alleviate congestion at these roadways and provide limited-access roadway connection between Logan Airport and the Chelsea Street Bridge.

The Solution

HMMH conducted an air quality study to support the environmental review of the project. The air quality study consisted of a mesoscale (e.g. qualitative) and microscale (e.g. quantitative) analysis of mobile source emissions in the project area. A mesoscale analysis was performed to assess the total volatile organic compounds (VOCs) and nitrogen oxides (NOx) in pounds per day (lbs/day) associated with motor vehicle emissions for the Preferred Alternative compared to the No-build condition for the year 2020. Since the Boston area is designated a non-attainment area for ozone, a mesoscale analysis was conducted to evaluate the regional impact of VOC and NOx (i.e. ozone precursors) emissions affiliated with the project. In addition, because the Project introduces a new roadway to the area, a microscale analysis was performed to evaluate the air quality impact at nearby residences along the new bypass roadway compared to the National Ambient Air Quality Standards (NAAQS).