The report said that groundwater samples analyzed from two monitoring wells installed on the lots revealed no hazardous concentrations in prospective building areas.
Vetere said that the moderately contaminated soil can be disposed of safely, but at a cost. Charts showed that disposal costs for the west lot would be about $345,000 and for the east lot, about $230,000, if the land is not paved over on another part of the property.
The NRA would not pay those costs; instead, a developer would be responsible. NRA members said last night the financial estimates will benefit construction companies who want a ballpark figure on getting rid of contaminated earth.
The removal of earth is part of another engineering challenge: creating underground parking. The NRA members have said that parking for residential units would have to go beneath the surface. GZA findings show that excavation for underground parking can be done, and still be within the guidelines of the 100-year flood plain elevation.
An executive report stated, “The parking garage can be constructed below the 100-year flood plain, provided that measures to protect the garage from flood are incorporated in the building design.”
Such protective measures could include “waterproofing of the exterior walls and subslab, installation of sump pumps, basement drainage systems, site grading to prevent water from entering the garage and the installation of watertight entry doors that can be closed when flood conditions are imminent,” according the executive summary.
It was said that earth removal to the depth of 12 feet would accommodate “the excavation needs for the sub-level parking.”
The executive report said that the 100-year flood plain elevation at the site is about 13 feet, which is an acceptable depth.
Vetere said that the NRA must take numerous steps before any construction is even considered, including ordering a formal risk assessment report and developing cost estimates.