Written by Carol Frank Friday, 18 March 2011 00:00
The investigation of the Exxon Mobil leak at 788 Middle Neck Road that has released MTBE into the aquifer is on-going as experts are trying to “map” the plume of contamination to determine its size, shape, direction of flow, and levels of concentration. The New York Department of Environmental Conservation (DEC) provided the Record with the results of the probes so far.
Spokesperson Bill Fonda emailed the following information: Water from the Poplar Court area has been analyzed and showed that at 5 feet below the water table, MTBE was detected at 186 parts per billion (ppb). At 10 feet below, nothing was detected, but at a depth of 15 feet, the analysis discovered 17,100 ppb of MTBE.
When the information about the leak came to light, the official report was that MTBE was found at 10,500 ppb concentrations on the site of the service station. Obviously, the numbers were greater since 17,100 ppb have been discovered off-site.
The state groundwater standard considers 10 ppb of MTBE to be acceptable, although the Water Authority of Great Neck North cleans drinking water to a “non-detectable” level.
At Old Tree Lane, less MTBE was found. No detectable MTBE was found at the 10, 15 and 20-foot depths; however, probes at 25 feet below the water table found 3,340 ppb and at 30 feet below found 5,720 ppb.
Mr. Fonda wrote, “As you can see as the plume travels it drops, with more uncontaminated water above contaminated water. In addition, the order of magnitude decreases as well. Based on this trend, we would expect the plume to decrease when the next set of wells are put in, but that will only be proven once we have test results.”
As reported last week, the Village of Kings Point is being asked for permits to drill monitoring wells on Gilbert Road.
Mr. Fonda emphasized once more that with the contamination so deep underground, air testing is not deemed necessary.
A letter was hand-delivered to the residents of Poplar and Old Tree Lane from Exxon Mobil on Nov. 10, 2010 explaining the situation and asking for their patience while the monitoring wells were being drilled. The letter also added that if residents needed additional information, they could call Charles Kolb at 239-4654.
Methyl tertiary-butyl ether (MTBE) is a gasoline additive that was banned in New York State in 2004 because it had been implicated as a human carcinogen. It is difficult and costly to remove MTBE from the water supply once it has entered the aquifer and reaches public supply wells. MTBE is a volatile, flammable and colorless liquid that has a turpentine-like smell. It mixes readily with water and, unlike many other contaminants, can move as quickly underground as water does, usually at a rate of one foot a day.
The conversion of 17,100 ppb is the equivalent of adding 22 gallons of MTBE to an Olympic-sized swimming pool.