All News Releases By Date
EPA Proposes Modifications to Groundwater Cleanup At the Nyanza Chemical Superfund Site in Ashland, Mass.
Release Date: 08/22/2006
Contact Information: David Deegan, (617) 918-1017
(Boston, Mass. - August 22, 2006) – The U.S. Environmental Protection Agency is proposing to alter the cleanup strategy for contaminated groundwater at the Nyanza Chemical Superfund Site in Ashland, MA. Since the interim cleanup decision was issued in a 1991, EPA has gathered additional information about the site which makes it necessary to modify the original cleanup plan to ensure the protection of human health and the environment.
EPA is issuing an "Explanation of Significant Differences" (ESD) to provide public notice and formally document the differences from the 1991 interim Record of Decision (ROD). This document also addresses potentially unacceptable inhalation risks by eliminating exposure to vapors migrating from the more contaminated portions of the groundwater plume to the indoor air of overlying structures through the installation of vapor mitigation systems. Additional air sampling and groundwater monitoring will be performed to assess the need to install mitigation systems in other nearby buildings.
This modified remedy, detailed in a document called Explanation of Significant Differences (ESD), addresses this newly identified ongoing source of contamination. The significant differences between the remedy as presented in 1991 and the action now being proposed include:
1. Extraction of "dense non-aqueous phase liquid" (DNAPL) with off-site treatment and disposal;
2. Performance of routine groundwater monitoring to assess any changes in plume concentrations and migration;
3. The installation, on a voluntary basis, of vapor mitigation systems in approximately 40 to 50 structures (mostly homes) located in the northeast portion of the plume, in an area generally bracketed by Tilton Ave. and Water St. to the west, the Sudbury River to the north and to the east, and the rai road tracks to the south;
4. Performance of additional air testing, on a voluntary basis, at approximately ten (10) to fifteen (15) additional homes and businesses located above remaining areas of the plume, generally described as areas immediate west of Forest St and southeast of the Town Hall along Main St.. These homes and businesses have not yet been selected;
5. Installation of small diameter monitoring wells in the areas generally described in #4 above to more accurately determine the extent of the shallow groundwater plume.
In addition, this ESD provides clarification on the use of institutional controls to prevent exposure to contaminated groundwater.
Groundwater monitoring was initiated in 1998 on a semi-annual basis to further assess the contamination and continued until the Fall of 2003 and EPA has concluded that the "dense non-aqueous phase liquid" (DNAPL) present in the aquifer beneath the northern portion of the Site continues to be a source to the larger dissolved contaminant plume in groundwater. DNAPL is highly-concentrated liquid product that has sunk to the bottom of the aquifer. It is denser and more contaminated than the groundwater. The results of the semi-annual groundwater monitoring prompted EPA to undertake indoor air sampling programs in 1998 and 2004 to determine if contaminants in the groundwater were volatilizing and migrating into homes and businesses at levels that might affect public health.
Staff from the EPA, the Massachusetts Department of Environmental Protection and the Ashland Health Department canvassed the neighborhood earlier this week to talk with residents about the groundwater contamination and next steps. EPA will finalize plans after talking with residents and obtaining further information about the construction of the homes.
EPA has also scheduled a public meetings at Ashland High School, 65 East Union Street, to provide an update on groundwater and indoor air actions for neighborhood residents on Thursday, Sept. 21, 2006 at 7:00 pm. A second meeting to provide an overall Nyanza site update on groundwater, indoor air, and the Sudbury River is scheduled at Ashland High School on Thursday, Oct. 26, 2006.
The Explanation of Significant Differences (epa.gov/region1/superfund/sites/nyanza) is available for public review through September 22 online or at the locations listed below:
U.S. Environmental Protection Agency
One Congress Street
Boston, MA 02114
Monday through Friday 9:00 am. to 5:00 pm.
Ashland Public Library
66 Front Street
Ashland, MA 01721
(508) 881- 0134
SUMMER HOURS - Tuesday through Thursday 10:00 am to 8:00 pm. Friday 2:00 pm to 5:00 pm. Saturday 10:00 am to 5:00 pm.
# # #