Friday, April 25, 2008
Con Edison Previews Toxic Remediation Plans for MCSM
As part of their presentation at the Isaac Newton MS PTA meeting on April 16, representatives from Con Edison, NYS Department of Environmental Conservation (DEC) and NYS Department of Health (DOH) previewed their plans for remediation of the toxic contaminants left buried under our school building from the manufactured gas plant that used to operate on our site.
After analyzing several of the alternative technologies currently available for removing the coal tars beneath the building, these organizations have concluded that no technology exists that can remove enough of the contaminants to eliminate the problem. By their estimation, any effort to extract these contaminants would leave half or more of them still beneath the school and with them, the same ongoing concerns for toxic vapors to enter the school building's indoor air. Removing the coal tars would require puncturing the holding tank beneath our school building in order to attempt vacuuming out those materials. In the DEC's judgment, doing so would risk making the contamination problem worse. As they stated in their presentation, "Any complete removal would require relocating the school." Consequently, they are "currently not planning on any source removal under [the] school."
This conclusion suggests that the toxic contaminants will remain on site, under the school building, until either a new removal technology becomes available or until our school building is closed and/or demolished.
According to the DEC and DOH, recent indoor air quality tests have suggested that the school basement's concrete floor has been working as an effective barrier against chemical gases entering the school. Con Edison and NYS are therefore proposing to leave the contaminants beneath the school building for the foreseeable future. However, to strengthen the barrier against vapor intrusion, they are proposing to install a "subslab depressurization" system during the next year. This system will create a vacuum area beneath the school's concrete basement floor. Any chemical vapors in the soil would then be pulled into this vacuum and vented away from the school, into the outdoor air.
Con Edison is currently preparing an Alternatives Analysis Report describing these findings and recommendations. This document will probably be presented in the early Fall and will include presentation at a public (PTA) meeting and a public comment period. A copy of their presentation to the Isaac Newton PTA on April 16 can be found on the Con Edison web site (www.coned.com/publicissues/manufactured_gas_plants.asp) or through the link on this website entitled "Information for MCSM Parents."