Survey confirms toxins in Lake Tahoe
MTBE and other gasoline contaminants are present in the Tahoe Basin’s lakes used by motorized watercraft, according to information released by the U.S. Geological Survey.
The August sampling conducted by USGS reinforces information the Tahoe Regional Planning Agency already has.
USGS studied Lake Tahoe and Lower Echo, Fallen Leaf and Upper Angora lakes. Only Upper Angora Lake, which has no motorized watercraft, had no synthetic compounds, which reinforced results of a 1997 study.
MTBE – methyl tertiary butyl ether – and the BTEX compounds – benzene, toluene, ethylbenzene and xylene – were found in varying degrees in the other three lakes.
MTBE – considered a possible cancer-causing agent by the U.S. Environmental Protection Agency – was detected at concentrations of 0.54 to 5.6 parts per billion at near-shore sites in Lake Tahoe. The highest concentration was detected at Emerald Bay. At a depth of 100 feet in the middle of Lake Tahoe, MTBE was detected at 0.31 parts per billion. In 1997 at the same site, it was detected at 0.26 parts per billion.
In Lower Echo Lake, USGS found MTBE at levels of 9.8 parts per billion.
USGS also detected MTBE in Fallen Leaf Lake, but found it in no lake tributaries.
No known regulatory levels for MTBE were exceeded, according to USGS, but California’s taste and odor threshold of 5 parts per billion was exceeded.
At that level, humans can begin to detect the additives presence in water; it smells and tastes like turpentine.
BTEX compounds were detected in all near shore locations of Lake Tahoe, with the highest concentration of benzene -0.44 parts per billion – in Emerald Bay. Benzene – a known human carcinogen – was also detected at 0.40 parts per billion in Lower Echo Lake and in very low concentrations at Incline Creek.
U.S. EPA has a drinking water standard of 5 parts per billion for Benzene. Health advisory limits exist for toluene, ethylbenzene and xylene, but no human carcinogenic effects are known at this time.
As part of the presidential commitment resulting from the 1997 Presidential Summit at Lake Tahoe, the study is part of an ongoing investigation done in cooperation with the Tahoe Regional Planning Agency.
Pam Drum, TRPA public affairs coordinator, said the bistate regulatory agency would soon incorporate the results with other studies being completed, including results from University of Nevada, Reno, and University of California, Davis, studies.
“In a few weeks, we hope to be able to draw some conclusions, once we’re able to compile all the data from all the agencies,” she said.
Contaminant concentration levels in basin lakes in parts per billion
Site benzene MTBE
Chambers Lodge * 0.97
Edgewood 0.21 3.4
Emerald Bay 0.44 5.6
Glenbrook Bay * 0.54
Incline Beach 0.17 1.0
Kiva Beach 0.17 2.5
Tahoe City 0.11 1.8
Tahoe Keys 0.18 2.7
TRG Buoy * 0.54
TRG Buoy (30 meters deep) * 0.31
Zephyr Cove 0.61 1.8
Upper Angora * *
Lower Echo 0.4 9.8
Fallen Leaf * 0.98
* denotes no contaminants were found at testing limits
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