Ban helped lake over summer, researchers say
There was as much as a 90 percent reduction in the amount of MTBE and other gasoline compounds in Lake Tahoe’s waters last summer compared to years past, indicating that the first-year ban on certain types of watercraft significantly helped the lake’s water quality, according to scientists.
“I was just absolutely delighted with the results,” said Jim Baetge, executive director of the Tahoe Regional Planning Agency, the bistate authority which implemented the ban. “I expected positive results; you would have expected a substantial reduction. But to now tell us there was an 80 to 90 percent reduction, that lends a lot of credibility to what we did.”
The University of California, Davis Tahoe Research Group announced Tuesday that samples taken in August show that MTBE and toluene, a compound often used as an indicator for other gasoline contaminants, had been reduced 50 percent in many places, and sometimes as much as 90 percent.
To some extent, the recent increase in the amount of MTBE-free gas available at Tahoe played a part, researchers said, but there was a significant reduction in other compounds as well, indicating it was primarily the absence of carbureted two-cycle motors leading to the improvement in water quality.
“Comparisons of data collected during this study with that of previous years shows a dramatic decrease in MTBE concentration at both offshore and near-shore locations, 86.7 percent and 95.8 percent respectively. This demonstrates that programs to eliminate MTBE from Lake Tahoe are having an effect,” states a report by UC Davis researchers Brant Allen and John Reuter.
“… A comparison of the decreases in ambient MTBE and toluene concentrations was done to determine which corrective action was having the greatest impact on Tahoe water quality. … If the new boating regulations were having the greatest impact, both MTBE and toluene concentrations could be expected to drop.
“Indeed both mean MTBE and mean toluene concentrations dropped significantly, 95.8 percent and 88.3 percent respectively, indicating that the elimination of the highly polluting two-cycle engines is having a clear impact on water quality.”
TRPA took action to institute the ban more than two years ago, and it was finalized this spring. During that time, the agency held multiple hearings, was sued, resolved the lawsuit out of court and had a team of scientists from U.C. Davis, University of Nevada, Reno and U.S. Geological Survey and other agencies involved in extensive research to reinforce the regulation.
TRPA and research officials claim two-stroke engines cause more pollution than other engine types, dumping about a quarter of their fuel into the water unburned. The ban eliminated most of the engines powering Jet Skis and personal watercraft, with only a couple of models of acceptable personal watercraft available over the summer.
There were other exemptions: Sailboats utilizing two-stroke engines as auxiliary power and watercraft powered by two-stroke engines rated at 10 horsepower or less are exempt for three years.
TRPA crews patrolled Lake Tahoe’s waters and marinas this summer to make sure boaters were complying with the new carbureted two-stroke engine ban and the two-summer-old 600-foot no-wake zone rule. The bistate regulatory agency issued 525 written warnings for violations of the rules and filed one lawsuit against a concessionaire who allegedly repeatedly violated the ordinance.
Baetge attributed the success of the watercraft ordinance largely to the cooperation of the research agencies involved.
“This would never have happened if UC Davis, UNR, USGS, (Desert Research Institute), (California Air Resources Board) and all the other contributors hadn’t all concentrated on the watercraft issue,” Baetge said. “That’s the way it should work for all environmental preservation efforts at Tahoe.”
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