Green Line extension (gLX) Retaining walls and noise barriers

Steere performed design for over 1,600 feet of retaining walls and over 1,300 feet of noise barrier walls as part of the Green Line Extension (GLX). The 4.3-mile extension serves to reduce traffic congestion, support municipal plans for sustainability and urban redevelopment, and create an additional transportation route between the densely populated municipalities of Somerville and Medford. The project included the design and construction of a vehicle maintenance facility, administration buildings, a light rail viaduct, six new stations, one relocated station, six highway bridges, and a community path extending from Cambridge to Medford.

Steere was responsible for the design of over 1600-feet of retaining walls and over 1300-feet of noise barrier walls. The wall supports a cantilevered concrete slab carrying the community path and therefore was designed as a pedestrian bridge. The retaining and noise walls consist of several different wall types: soldier pile and lagging, soil nail, steel sheeting, modular precast block, and mechanically stabilized earth. The wall heights range from approximately 8-feet to 26-feet and have been designed for light rail surcharge, where applicable.

Retaining Wall MW-5 is a 20+ foot high cantilevered soldier pile wall designed to serve as part of a pedestrian bridge carrying the Community Path with cast-in-place slabs supported on concrete pile caps. Due to Right-of-Way constraints, the slab cantilevered a maximum of 7-feet beyond face of wall.

Location: Cambridge & Somerville, Massachusetts

Owner: Massachusetts Bay Transportation Authority (MBTA)

Timeline: Design Completed in 2019; Construction Completed in 2021