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DEC Releases Horseblock Road Groundwater Report

Investigation Links Elevated Levels of Contaminants to Management of Vegetative Waste.

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Yaphank, NY - July 23rd, 2013 - The New York State Department of Environmental Conservation (DEC) today released a report containing the results of an investigation into groundwater quality in the Horseblock Road area in Yaphank, Suffolk County.

The report found elevated levels of certain contaminants in a residential well and several groundwater monitoring wells downgradient of the Long Island Compost/Great Gardens facility, indicating that the facility appears to be the primary source of the contamination.

The investigation, a cooperative effort involving DEC, the New York State Department of Health (NYSDOH), and the Suffolk County Department of Health Services (SCDHS), was prompted by the detection of elevated levels of manganese in a private well at a residence on Horseblock Road. The residence is located adjacent to the LI Compost/Great Gardens facility, which manages leaves, brush, land-clearing debris, grass, food waste and compost. The residence has been connected to the public water supply, and another residence in the immediate vicinity that uses a private well has also been connected as a precaution. Since most homes in that area are connected to the public drinking water supply, there should be no exposure to groundwater or increased health risks. Groundwater quality investigations are underway and groundwater monitoring will continue.

The initial investigation was expanded to include sampling of groundwater, surface water and compost materials from a number of other facilities in Suffolk County that manage vegetative wastes to determine whether the groundwater impacts documented in the Horseblock Road area are unique to the area or related to management of vegetative wastes generally. Groundwater samples were analyzed for metals, inorganics, volatile and semi-volatile organic compounds and radioactive contaminants (radionuclides).

The study found that manganese and very low levels of naturally occurring radioactive materials, the primary contaminants of concern in the Horseblock Road study area, appear to emanate from the Long Island Compost/Great Gardens facility in Yaphank. These contaminants were also found in samples collected at other sites in Suffolk County that accept vegetative wastes.

DEC and Long Island Compost recently resolved a longstanding permit dispute through an agreement under which the company will undertake changes to its operating practice, which are expected to reduce the potential for groundwater impacts. The agreement also requires that the company implement a groundwater monitoring plan to track any changes in water quality below the site.

Groundwater impacts appear to be attributable to organic matter that has migrated into the soil and changed the groundwater chemistry. Decomposition of organic material can cause naturally occurring elements such as manganese to leach into the groundwater. The presence of radionuclides in groundwater also may occur due to the breakdown of organic material and the leaching process. However, the report found that additional investigative research should be undertaken to determine the actual mechanisms that cause the changes in groundwater quality.

Although contaminants in some groundwater samples collected as part of the study exceeded drinking water standards, no imminent threat to public health is indicated because no pathway exists for humans to become exposed to the contaminants.

"The study pointed out a number of steps that can be taken to reduce potential groundwater impacts from vegetative waste facilities," said DEC Region One Director Peter A. Scully.

Among the next steps identified in the report are:

  • Continue an ongoing investigation into groundwater impacts from vegetative waste facilities on Long Island.
  • Determine if operational changes implemented at the Long Island Compost/Great Gardens facility have resulted in an improvement in groundwater quality by re-sampling wells in the Horseblock Road area.
  • Consider adding groundwater characterization and monitoring requirements, as well as best management practices for stormwater, as part of the permitting process for large-scale vegetative waste operations.
  • Develop a study, preferably in conjunction with a regional university, to determine the actual release mechanism(s) to guide DEC's regulatory revision process.

The study was conducted jointly by the New York State Departments of Environmental Conservation and Health along with the Suffolk County Department of Health Services. All samples were collected and analyzed by the SCDHS. Selected samples were analyzed by the NYSDOH.

A copy of the Horseblock Road Assessment Report can be found on the DEC website.