Wednesday Feb 27 2013
UPDATE: New blueprint to reduce Tahoe lake pollution gets Placer supes OK
By: Gus Thomson, Reporter/Media Life columnist
UC Davis study shows clarity levels at lake best in a decade
Placer County has signed on to a $750,000 plan intended to reduce the amount of pollution going into Lake Tahoe.
The project, costing $750,000 over the next five years, includes work to reduce sand and grit flowing into the lake, was approved Tuesday by the board.
The county Board of Supervisors’ approval of the project Tuesday comes at a time when researchers say clarity levels are the best in a decade.
Required under a recently updated federal permit regulating storm-water runoff from Placer and El Dorado counties, plus the city of South Lake Tahoe, the plan is the latest in a series of efforts to keep Tahoe blue since water clarity started to become a concern in the late 1960s.
The county decision came on the same day that University of California Davis researchers and the Tahoe Regional Planning Agency jointly announced
Lake Tahoe’s clarity improved in 2012 for the second year in a row, and its waters were the clearest in 10 years.
Supervisor Jennifer Montgomery, whose District 5 includes the Placer portion of Lake Tahoe, said the problem over decades has been trying to stop fine sediment reaching Lake Tahoe.
The sediment comes from dirt and sand that mix with rain and snow to form polluted runoff that can reach the lake. Nitrogen and phosphorus, another pollutant that Placer plans will attempt to reduce, are found in fertilizers that are used to help add green to landscaping during the short growing season around the lake.
“The approval of this plan gives us specific goals for pollutant reduction,” Montgomery said. “Attaining these goals will take work, but that is necessary to not only stop the decline in the lake’s clarity, but to improve it as well.”
Over the past decade, the county has completed 16 water-quality improvement projects to reduce the amount of pollution reaching the lake.
Last year’s average annual clarity level in Lake Tahoe was 75.3 feet, or a 6.4-foot improvement from 2011, according to data from UC Davis Tahoe Environmental Research Center scientists.
The lake’s clarity is measured by the depth at which a 10-inch disk, called a Secchi disk, remains visible when lowered beneath the water’s surface. The measurements have been taken since 1968, when the Secchi disk could be seen down to an average of 102.4 feet.
The annual clarity level is the average of 22 individual readings taken throughout the year. The highest individual value recorded in 2012 was 107 feet and the lowest was 57 feet.
Two of the new sediment-reduction proposals are for Kings Beach’s commercial core improvement project and the Lake Forest Panorama Project. Both will treat runoff that flows into the lake or streams that flow into Tahoe.
As well, Placer County is planning to change its sand that it uses on roads to increase vehicle traction during storms. Plans are to switch to a less-fine sand mix and reduce the amount of fine sediment reaching the lake by nearly 5,000 pounds a year.
The county is also buying a high-efficiency road sweeper to further control the sand flow. The vacuum sweeper will be used in both winter and summer to remove pollutants from roads before they are carried away by rain, snow or wind into the lake, the county said in a statement issued Tuesday.
County cost over five years for the Placer Lake Tahoe Pollutant Load Reduction Plan is an estimated $750,000 – or $150,000 a year.
Geoffrey Schladow, Environmental Research Center director, said improvements in both summer and winter clarity during 2012 are very encouraging.
“The lake will continue to be subjected to a range of disturbances, each of which has the potential to impact clarity,” Schladow said. “There is now growing belief that managing for clarity is possible.”