November 28, 2005
Mr. Jay Rourke, Project Manager
Boston Redevelopment Authority
One City Hall Square
Boston, MA 02201-1007
Subject: Simmons College School of Management Building DPIR
Dear Mr. Rourke:
Thank you for the opportunity to comment on the Draft Project Impact Report for the Simmons College School of Management project. As you know, the Boston Groundwater Trust was established by the Boston City Council to monitor groundwater levels in areas of the City where building foundations are threatened by low groundwater levels and to recommend solutions to the problem. As such, my comments are limited to groundwater related issues.
In my July 14, 2005, comment letter on the PNF for this project, I raised concerns related both to the construction phase and to the long term operation of this very deep excavation. Unfortunately, the information in the DPIR does not completely allay those concerns.
While the foundation design calls for a concrete slurry wall, there is no information about the waterproofing of that wall. There is no response to my request that there be an annual certification of no removal of groundwater from the site. The DPIR asserts that the amount of water to be removed from the building’s underdrains will be minimal and not have any effect on groundwater levels; it neither quantifies this nor speaks to potential leakage through the slurry wall. In response to my comments requesting construction with no underdrains, the DPIR asserts that it is "not reasonable" to expect a structure with such a deep excavation to be constructed without them. However, such construction has been employed in Boston on projects dating as far back as 500 Boylston Street in the 1980’s, and is a well proven technique.
I appreciate the proponent’s commitment to coordinate with the Trust on measures to maintain adequate groundwater levels, as requested by City and State reviewers. I look forward to working with them to determine the best locations for the wells. The proponent’s intention to turn over wells on public property for ultimate incorporation into the Trust’s network, as typically required by the Public Improvements Commission, is commendable. However, I see no indication of a commitment to provide information to the Trust on well readings to be taken before and during construction, nor to continue to monitor wells on the campus after construction and provide information to the Trust. Preconstruction monitoring for a period of six months prior to commencement of work to establish a baseline has been required on multiple projects and should be required on this one; the information is provided to the Trust. In addition, the project should be required to provide the monitoring data to the Trust during construction so that the public can be assured that no unintended lowering of groundwater levels is occurring; this has also been required on recent projects with significant excavations.
I was also taken aback to read that "Should the groundwater observation wells indicate a depression in the groundwater levels due to dewatering activities, the groundwater level may (my emphasis) be recharged by reintroduction of the pumped water into the subgrade". This recharge should be mandatory in case groundwater levels drop.
I appreciate the intention to consider recharge through a perforated pipe. As the Authority considers the establishment of recharge requirements for projects in its proposed Groundwater Conservation Overlay District, similar requirements on this deep excavation project make sense.
This project is located in a critical area near wood pile supported structures including both the Gardner Museum and the college’s own main campus building. It is vitally important that this deep excavation be constructed and monitored in a way that assures that it will not cause groundwater problems either during construction or operation.
Very truly yours,
Elliott Laffer
Executive Director
Cc: John Walser, BRA
Maura Zlody, BED
