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USEPA MTBE Pilot Project Report

Objective 2 - Investigate Potential Sources of MTBE Contamination on Long Island That Could Impact Water Supplies or Environmentally Sensitive Areas

The report is available in parts as follows:

Methyl tertiary butyl ether (MTBE) was legally used as a gasoline blending component in New York State from 1979 (USEPA, 1998) until its statewide ban on January 1, 2004 (USEPA, 2004) (NYSDAM, 2004). The expanding use of MTBE in gasoline during that period (USEPA,1999) in conjunction with its physical and chemical properties (ITRC, 2005) resulted in significant MTBE impacts to the groundwater resource of Long Island (NYSDEC, 2000). Better understanding of the scope of the impact was of great importance to the New York State Department of Environmental Conservation (NYSDEC) as the Long Island aquifer system is the sole source of drinking water for over 2.7 million residents in Nassau and Suffolk Counties (US Census Bureau, 2007). Ninety-five percent of these residents receive their water from over 900 public water supply wells with the rest supplied by over 64,000 private wells (SCDHS, 2007).

Between December 2002 and December 2006, with funding provided by the United States Environmental Protection Agency (USEPA), the NYSDEC conducted a pilot study to better define the extent of MTBE contamination stemming from previously unidentified and/or unreported MTBE blended gasoline releases throughout the Long Island aquifer system. The study was intended to yield sufficient data to project the potential MTBE impacts upon drinking water source waters (groundwater) from unreported MTBE blended gasoline releases throughout the aquifers supplying the sole source of drinking water to the residents of Nassau and Suffolk Counties.

During the study, 52 gasoline retail stations in Nassau and Suffolk Counties (approximately 4.7% of the total number of stations in those counties) that had no known prior release of oxygenated gasoline underwent petroleum bulk storage inspections and groundwater sampling for MTBE. The study found that MTBE was nondetect or less than the New York State Department of Health drinking water standard and NYSDEC groundwater standard of 10 micrograms/liter (μg/L) at approximately 60% of sites investigated. Additionally, MTBE was found to have exceeded 10 μg/L at 34% and 53% of sites investigated in Suffolk and Nassau Counties, respectively. The MTBE concentrations in groundwater ranged from nondetect up to 240,000 μg/L in Nassau County and up to 63,000 μg/L in Suffolk County.

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