Emergency Modifications to the Clarendon Street Plaza of Back Bay Station

Location: Boston, Massachusetts
Contract: MBTA Contract S08CN17
Contract Value: $1,933,130
Project Dates: July 2003 - December 2003


The Clarendon Street Plaza is located directly above the MBTA Orange Line, Amtrak, and Commuter Rail Back Bay Train Station, and is supported on a structural concrete slab and steel girders.


The project involved extensive repairs to restore the busway plaza surfaces to a useable condition and eliminate water intrusion into the station below.

Work consisted of the removal of all materials above the structural slab and replacement with new construction.  Areas of deteriorated concrete were removed and replaced, and in some areas the steel deck was also repaired.

Certain areas had a layer of lightweight concrete placed directly above the existing structural slab, to ensure that the drainage composite was pitched towards the drains.

Waterproofing membrane was installed on top of the existing structural slab, together with a protection board and drainage composite, followed by lightweight concrete fill and reinforced wearing slabs or brick paving.

New catch basins were installed; repairs to the leaking drain lines within the station and installation of new conduits and electrical service to the existing lighting were also required.

Certain elements such as planters, lighting posts, walls and concrete bollards were left in place; other elements such as benches, signs, and granite curbs were removed and reinstalled.

The project site abutted Clarendon Street, and was directly overhead an operational MBTA station.  A complex shielding system was designed to prevent water, dust and debris from falling into the station below during the demolition and construction phases.

Work was carried out in two stages.  A system of temporary signage and lighting directed pedestrian and vehicular traffic to open roadway and sidewalks while work was performed in adjacent areas.  Access to the loading dock of the Red Cross building was maintained.  The station platforms and track were in operation at all times.