August 11, 2005
Mr. Mark McGowan
Boston Redevelopment Authority
One City Hall Square
Boston, MA 02201-1007
Subject: 1330 Boylston Street
Dear Mr. McGowan:
Thank you for the opportunity to respond to the Additional Materials submitted by the proponent on this project.
I was disappointed in their response to my previously submitted comments. While I appreciate their commitment to installing observation wells around the site, I remain concerned about the long term impact of their design.
The flowable fill with which they propose to backfill around the excavation hardens to a relatively brittle material. If it is impossible to use impervious clay as the backfill, as suggested in my letter, there should at least be a five foot plug of clay at the bottom of the wall. The flowable fill should, in that case, be a water barrier mixture that contains bentonite. The proponent should clearly indicate what material they plan to use and how effective it will be as a water barrier. They should also make clear how they plan to waterproof the below ground sections of the building. There is concern that, over the life of the building, the steel sheet piling may develop leaks that could lead to a groundwater drawdown.
I was also disappointed in the proponentŐs resistance to the use of a waterproofed reinforced concrete mat slab. If they continue to plan to use an underdrain system, they should indicate how much water they expect to be drained from the site over time. They should indicate as well what mechanism can be used to verify the amount of water being removed and what remedy will be offered if the amount removed exceeds projections.
The proponents should also demonstrate clearly why they cannot install a recharge system. Any project can make the statement that drainage from its roof will not have a significant long term impact on the problem, but taken together, recapture from as many sources as possible will help to raise groundwater levels throughout the area of concern.
Because their additional information does not adequately address these issues, I feel that it is very important that the proponents be directed to proceed to a DPIR. We continue to be committed to working them and the Authority to agree on a project that will have no negative impact on groundwater levels and the potential to make a positive impact.
Elliott Laffer
Executive Director
Cc:
John Walser, BRA
Maura Zlody, BED
