U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting Charleston South Carolina March 8-12, 1999--Volume 2 of 3--Contamination of Hydrologic Systems and Related Ecosystems, Water-Resources Investigation Report 99-4018B

Methyl Tert-Butyl Ether (MTBE) in Lakes in Byram Township, Sussex County, New Jersey, 1998 and Vulnerability of Ground Water in Lakeside Communities

By Otto S. Zapecza and Arthur L. Baehr

ABSTRACT

Water samples were collected from four lakes in Byram Township, Sussex County, N.J., in the summer of 1998 as part of an investigation of the occurrence of volatile organic compounds (VOCs) in domestic wells in lakeside communities. Cranberry Lake and Lake Lackawanna are surrounded by densely populated communities where the use of gasoline-powered watercraft is prevalent and water is supplied by lakeside wells. Forest Lake is surrounded by densely populated communities where the use of gasoline-powered watercraft is prevalent and water is supplied by lakeside wells. Forest Lake is surrounded by a densely populated community where the use of gasoline-powered watercraft is prohibited. Stag Pond is privately owned, is situated in a sparsely populated area, and is not navigated by gasoline-powered watercraft.

Samples were collected from Cranberry Lake in early summer and again in late summer 1998. Concentrations of the gasoline oxygenate methyl tert-butyl either (MTBE) ranged from 1.6 to 15.0 µg/L (micrograms per liter) on June 24 and decreased with depth. The depth-related concentration gradient is attributed to density stratification caused by the temperature gradient that is present in the lake during the early summer. MTBE concentrations ranged from 7.4 to 29.0 µg/L on September 8 and were uniform with depth, as was water temperature, indicating that the lake was vertically mixed. On the basis of these concentration profiles, the mass of MTBE in Cranberry Lake was estimated to be 15 kilograms on June 24 and 27 kilograms on September 8. These mass estimates are equal to the amount of MTBE in 52 and 95 gallons, respecitively, of gasoline that consists of 10 percent MTBE by volume. The increase in MTBE mass from June to September is a result of the net accumulation of this ether oxygenate in the lake during the summer season, when use of gasoline-powered watercraft is at its peak. Samples were collected from Lake Lackawanna on September 9. Concentrations of MTBE ranged from 3.7 to 14.0 µg/L. Like those in Cranberry Lake the previous day, VOC concentrations and water temperatures were nearly uniform with depth. The mass of MTBE in Lake Lackawanna on September 9 was estimated to be 6 kilograms, which is equal to the amount of MTBE in 21 gallons of gasoline that consists of 10 percent MTBE by volume. All VOC concentrations were less than 0.2 µg/L in samples collected from Forest Lake on September 8, 1998, and from Stag Pond on the following day.

Maximum MTBE concentrations measured in samples from several depths at one site on Cranberry Lake on November 5 and December 16, 1998, were 1.1 and 0.38 µg/L, respectively. The difference in MTBE concentrations in the lake between September 8 and November 5 is attributed to the decrease in MTBE mass input to the lake resulting from the significant decline in the use of recreational watercraft after Labor Day weekend and to natural volatilization processes.

Preliminary assessment of ground-water quality in 14 areally distributed wells around Cranberry Lake during November and December 1998 shows a high frequency of detection of MTBE -- approximately 93 percent. The extent to which Cranberry Lake functions as a nonpoint source of MTBE to wells and the effect of lakeside land use on ground-water quality is currently being studied. A regional assessment of the occurrence of MTBE and other VOCs in lakes and ground water is needed to determine the effect of the use of oxygenated gasoline on water quality in lakeside environments throughout northern New Jersey.