Permanent fixes for indoor air pollution at the MBTA’s Back Bay Station could be costly, according to a consulting engineer’s report.
The repairs could climb from $800,000 to $6 million.
The MBTA commissioned Westwood-based Hatch Mott MacDonald to study the decades-old ventilation system as part of a $32-million station renovation project being led by developer Boston Properties. For years, diesel exhaust from commuter rail locomotives has lingered on station platforms and filtered up to the concourse.
The most expensive option – installing capture hoods above locomotives’ exhaust pipes – could cost up to $8.5 million, the report said. The second-costliest repair – replacing a half-dozen 84-inch reversible fans with 96-inch fans – would cost $6 million, according to a report issued July 24 by Hatch Mott McDonald and provided to Banker & Tradesman this week by the Massachusetts Department of Transportation (MassDOT) under a public records request.
Other options include installing eight supplemental jet fans at a cost of $3 million to $4 million and installing a second set of doors at the top of the stairway to the concourse and additional ventilation for $800,000.
More comprehensive computer modeling is needed to determine which option should be designed, the report said. As an interim solution, the engineers recommended installing doors at the top of stairways 5 and 6 to reduce the flow of air from the platform to the concourse.
MassDOT spokesman Jason Johnson said the MBTA will adopt the report’s recommendation of creating a modeling assessment that would include detailed engineering. The model is expected to be completed by the end of winter.
In December, MassDOT selected Boston Properties to take over management and maintenance of the 28-year-old station in a privatization agreement.
The Back Bay project would include a new facade facing Dartmouth Street, more retailers and food vendors and capital improvements including the ventilation repairs.
The lease was amended effective Aug. 1 after Boston Properties discovered several problems as the result of its due diligence, including a missing certificate of occupancy for the station and hazards to pedestrians from the busway’s expansion joints.
Boston Properties now has the right to terminate its lease to operate the station by February if the MBTA has not obtained a temporary certificate of occupancy.
The ventilation system was originally supposed to be fixed as part of the Columbus Center development, an $800-million mixed-use project involving air rights over the Massachusetts Turnpike that has been repeatedly delayed due to lack of financing.
Boston Properties last year presented conceptual plans to build a large mixed-use development including offices, residences and retail above Back Bay Station. That project is subject to negotiation of an air rights agreement with MassDOT and a major project review by the Boston Redevelopment Authority.
