Bus Facility Shoreline Stabilization and Yard Improvements
The MBTA’s largest bus facility is located along the tidally influenced Mystic River, separated from the water by a deteriorating sheet pile seawall.
Behind the seawall exists a 345kV buried transmission line that is a major electrical trunk line for eastern Massachusetts. Considering the transmission line, the poor soils, and the life cycle costs of a new steel bulkhead, the MBTA ruled out a replacement of the seawall and designed a new natural shoreline constructed over stabilized subsurface soils. The stabilization consists of a vast grid of soilcrete columns installed via jet-grouting techniques into the deep clay layers under the river. Atop the soilcrete columns, a new shoreline embankment will be constructed of natural stone lifts with geosynthetic fabrics and geogrid panels. The project also includes upgrades to the drainage system, dredging of the river bottom, and the construction of a new flood wall to provide hurricane resiliency to the facility.
2020 – Perfect Record
By the Numbers
25K CY
Jet Grouted Soilcrete
23K CY
Soil Reinforcing Geogrid
21.5K CY
Temporary Steel Sheeting
167.2K SF
Geogrid
32.5K CY
Excavation & Dredging
32K CY
Fill Material
6.4K CY
Contaminated Soil Disposal
$36.6M
Project value
Scope of Work
- Soil improvements
- Dredging river sediments
- Drainage repairs & upgrades
- Flood resilient seawall
- Excavating existing bulkhead & landside fill
- Temporary cofferdam
- Shoreline stabilization, backfill, & restoration
Unique Challenges
- Tidal changes up to 12 ft in height
- Dewatering of 1,200 ft cofferdam
- Contaminated soils & groundwater
- Maintaining daily bus facility operations
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