Description of Services
As part of the design-build extension of the Massachusetts Bay Transportation Authority (MBTA) Green Line from Cambridge to Medford, Reliance Engineers provided geotechnical leadership during the early design phases of this major transit expansion. The project included approximately 8 kilometers (5 miles) of new surface track, eight at-grade stations, 4.8 kilometers (3 miles) of retaining walls, and 22 bridge structures, spanning a dense, urban corridor with varied ground conditions.
The geotechnical scope involved the planning, execution, and oversight of a comprehensive subsurface investigation program, valued in excess of $1 million, to support the design of multiple infrastructure elements. Reliance directed the development and quality control of this field program, including borehole drilling, laboratory testing, and in-situ testing required to characterize subsurface conditions across the corridor.
Reliance also led the geotechnical analysis and design for fourteen proposed bridge structures, each requiring tailored foundation recommendations based on local site conditions. Foundation systems evaluated and designed included driven piles, drilled shafts (caissons), and shallow spread footings, with attention given to settlement, lateral resistance, and constructability within tight site constraints. Several locations required the evaluation of existing foundations, to assess their suitability for reuse and compliance with current design codes for new superstructure loads.
The project presented multiple technical challenges, including construction near sensitive infrastructure, the need for staged construction sequencing, and limited access in constrained right-of-way areas. Reliance’s work supported the delivery of technically sound and economically feasible solutions for foundation design in a highly urbanized and operational transit environment.
