Cost for Tahoe clarity could be $2 billion
October 31, 2007
INCLINE VILLAGE – Bringing Lake Tahoe’s clarity back to a midway bench mark of 75 to 80 feet in 20 years could cost anywhere from $1.8 billion to $2 billion, according to a report recently presented at a Pathway 2007 Forum.
The clarity of Lake Tahoe is measured by sinking a white disk below the surface. At this point, the disk can be seen 67.7 feet below. Lake clarity is measured against a 1968 standard of 97.4 feet.
Three different scenarios to increase lake clarity were presented by the Lahontan Regional Water Quality Control Board at a Pathway Forum meeting. Each scenario represented a different level of compliance required in four environmental categories around the lake to reduce the amount of fine sediment.
Fine sediments are particles smaller than a human hair that enter the lake and reduce clarity.
Scenario A focuses on retrofitting and enhancing current lake practices to deal with atmospheric, urban and ground water sediment. At a $1.8 billion price tag for capital costs, this plan suggests a 31.7 percent reduction in particles to improve clarity by almost 11 feet to a 78.6 feet clarity level in 20 years.
Taking it a step further, scenario B also includes new innovations and suggests 78.7 feet of lake clarity for $1.5 billion.
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The most rigorous possibility is scenario C which exceeds the 20-year bench mark with 81.5 feet of clarity at $2 billion.
The purpose of creating the scenarios was not to create a requirement, but rather to start a conversation about methods to improve lake clarity, said Robert Larsen, an environmental scientist with the Lahontan water board.
“We’re going to keep working on this information,” he said.
The scenarios stemmed from research completed in the Total Maximum Daily Load Pollutant Reduction Opportunity report. While the original report assumed 100 percent compliance across the lake, these three proposals take a more realistic approach, according to Doug Smith the Lake Tahoe daily load unit chief for the Lahontan water board.
“We were looking for the most reasonable pollutant control opportunities,” Smith said.
The Lake Tahoe Total Maximum Daily Load Technical Report complied by scientists and researchers with 30 years of data, concluded that Lake Tahoe’s clarity will be most responsive to a decreases in fine sediment.
To increase clarity, it makes sense to focus on those areas that produce fine sediment, Larsen said.
From that conclusion, fine sediment production was broken down into four areas – atmospheric, forest upland, stream channel and urban and ground water – and examined by teams of experts. These groups studied each area for possible improvements and methods that could be applied.
Those groups then took their findings to focus teams, including local experts experienced with putting environmental policies into place, that reviewed the plausibility of the information.
Finally, the Lahontan water board took that information and complied it into three different possibilities to achieve lake clarity.
Breaking it down
All three scenarios recommend continuing stream restoration and supporting current methods to support sediment reduction from the forest.
“What they are doing makes sense and is cost effective,” Larsen said.
Atmospheric and urban and groundwater proposals vary between each option from minor to major changes.
To reduce the amount of atmospheric fine sediments, scenario A requires weekly or bi-weekly street sweeping, reducing the number of wood-burning stoves and graveling or paving 80 percent of the unpaved roadways in the Tahoe Basin.
“We are extending what we already do by pushing the limits of gravity-driven filtration and best management practices,” Larsen said.
Scenarios B and C build on scenario A by including weekly fine-particle-effective street sweeping.
Scenario A advocates a more rigorous enforcement of private property best management practices and constructing wet basins or wetlands to deal with urban and ground-water particles.
“The most significant source is urban runoff,” said Jack Landy, U.S. Environmental Protection Agency Lake Tahoe Basin coordinator. “The most significant projects call for storm water pump and treatment facilities – basically a storm water collection system.”
To deal with those fine sediments, scenarios B and C advocate advanced mechanical or chemical treatments. The difference between the two options is how many major urban watersheds around the basin would be eligible for pump and treat.
The Lahontan board introduced the possibilities and numbers to the forum to get an idea of the reaction to the costs, Larsen said.
Costs start at $1.8 billion for capital improvements and an additional $11 million to $15 million in annual operations and maintenance costs. In the past 10 years about $500 million has been spent in total on lake clarity, Larsen said.
Capital costs would be covered by mostly federal and matching state monies, and operational and maintenance costs would be the responsibility of the local districts, Larsen said.
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