MTBE found in new well
The South Tahoe Public Utility District just can’t get a break. Drilling a new well to make up for 12 of its 34 wells shut down because of MTBE, water officials found the last thing on Earth they wanted to find – MTBE.
The district Monday announced the additive is present in small amounts – below normal detection limits – in the aquifer STPUD had hoped to use for the well.
STPUD had planned to have the well up and running by Thanksgiving, but that has now changed.
“Needless to say, we will not be putting the well in service any time soon,” said Dawn Forsythe, STPUD information officer. “We’ve got to know how much is there, how it got there, whether we can strip it out. That’s probably going to take a month.”
Laboratories typically have a detection limit for MTBE at about 2 to 5 parts per billion. However, Forsythe said STPUD sent the water to two labs with “the most stringent tests known to man.” The results showed MTBE at levels between 0.1 and 0.2 parts per billion.
The new well was to be located at the same site where the district’s Arrowhead Nos. 1 and 2 were. The two wells – now destroyed because of MTBE contamination coming from the Meyers Beacon – took water from an aquifer much closer to the surface than the aquifer the new well was to access. The aquifers are separated by an aquitard, a non-porous layer of clay that should have protected the lower groundwater.
“Obviously, we’re going to do a lot more investigation,” Forsythe said. “Was there a hole in the aquitard? How was there intrusion into the lower aquifer?”
STPUD tested the water two months ago, without the stringent detection level, and found no MTBE.
STPUD will have to look at several options for the well, including installing an air stripper that could take the MTBE out of the water.
“Right now, abandoning the well and continuing to fix the well would cost about the same,” Forsythe said.
The Tata Lane No. 4 well, which was shut down in the summer, was contaminated by the plume coming from the USA Gas Station at the “Y,” but the water was successfully treated for several months by an air stripper. Because the well was pumping, however, the MTBE plume was drawn toward the well and MTBE levels rose to a point STPUD did not feel was safe.
STPUD has spent about $250,000 on the new well, and the total project is expected to cost up to $500,000. With 35 percent of its drinking water wells shut down, the district is in the process of finding a suitable site for another new well on State Route 89 near Camp Richardson. The Arrowhead well location already had the infrastructure for the new well, keeping the costs for building a new well low. The costs for the well on the highway likely will exceed $1 million.
“The water supply for the winter and spring is fine. We’re trying to get in shape for June,” she said.
For a large part of last summer, STPUD’s customers faced mandatory water-usage restrictions.
MTBE is classified by the U.S. Environmental Protection Agency to be a possible cancer-causing agent. California has set an action level at 35 parts per billion, but most people can detect it in water at levels much lower. It smells and tastes like turpentine.
No MTBE-contaminated water has ever reached STPUD customers.
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