February 13, 2008
Mr. John FitzGerald, Project Manager
Boston Redevelopment Authority
One City Hall Square
Boston, MA 02201-1007
Subject: 4-6 Newbury Street
Dear Mr. FitzGerald:
Thank you for the opportunity to comment on the Small Project Review Application for 4-6 Newbury Street. The Boston Groundwater Trust was established by the Boston City Council to monitor groundwater levels in sections of the City where the integrity of building foundations is threatened by low groundwater levels and to make recommendations for solving the problem.
As acknowledged in the Supplemental Document Geotechnical Report, the project is located in the Groundwater Conservation Overlay District and is subject to the requirements of Article 32 of the Zoning Code. I am pleased that the proponent has committed to presenting plans that will meet the GCOD recharge requirements.
I was pleased, as well, to read that the finished floor of the single level of underground parking would be at approximately Elevation 8 BCB, above the level generally thought to be critical for groundwater in the Back Bay. However, the building section shows that an elevator will be used for garage vehicle access, with its attendant pit located below the finished floor. This pit should be fully waterproofed in order to prevent any groundwater intrusion. In addition, the foundation design should be such that no groundwater is drained offsite from below the building. As required by the GCOD zoning, the proponent should "demonstrate by certification from a Massachusetts registered engineer or other expert or authoritative body recognized by the Board of Appeal" that the project "result in no negative impact on groundwater levels within the lot in question or adjacent lots".
While the proponent has committed to meeting the recharge requirements, no site has been identified for the recharge system. Since the building will extend to the property line along the alley, selection of the site may be more difficult than for many other projects.
As noted in the geotechnical report, the adjacent buildings to the east and west are believed to be supported on wood pile foundations. The closest groundwater observation well to the site, located in front of 10 Newbury Street, has often registered groundwater elevations noticeably lower than those of nearby wells. Both of these factors argue for the project to pay particular attention to groundwater related issues. It would be helpful if the proponent could suggest potential causes for the low readings, and particularly if he could investigate the existing structure to see if there is a sump pump or other possible source of drawdown.
I look forward to working with the proponent and the Authority to make sure that this project can only have a positive impact on groundwater levels in the Back Bay.
Very truly yours,
Elliott Laffer
Executive Director
Cc: Kathleen Pederson, BRA
Maura Zlody, BED
