Projects

Stephens Associates Consulting Engineers (SA) performed geotechnical evaluation and engineering for elevator and lobby additions to Science Park Station on the MBTA Green Line.

The historic elevated station, located on the southern bank of the Charles River near the Museum of Science, was upgraded to meet current ADA accessibility requirements by adding two, three-story external elevators and lobbies at ground level. The elevators were designed as structurally isolated from the existing structure, resulting in eccentric loading of the foundation.

SA collected available geologic and geotechnical data from the Central Artery/Tunnel project, where underground viaducts pass beneath the station, as well as existing foundation data from the MBTA. SA performed subsurface explorations consisting of soil borings and vacuum excavation to evaluate subsurface conditions and identify existing buried structures.

In Phase I of our services, SA evaluated suitability of shallow foundations for structural support by analyzing bearing capacity and potential construction and long-term settlement under the eccentric loading. Based on the analysis results, SA consulted on options for deep foundations in consideration of the nearby adjacent above- and below-grade structures, limited site access because of the busy rotary surrounding the station, and potential capacities of various deep foundations. In Phase II of our services, SA evaluated deep foundation capacity for drilled micropiles, drilled shafts, and helical piles, and consulted with the Structural Engineer.

SA structurally and geotechnically designed micropile foundations and prepared construction specifications for geotechnical instrumentation and micropile foundations. During construction, SA responded to Contractor requests for information and reviewed submittals regarding foundations and geotechnical instrumentation, observed construction of deep micropile foundations on-Site full time, observed, reduced and interpreted static tension load test data, observed installation of geotechnical instrumentation, and monitored vibrations and groundwater at the structure.