Winds can restrict North Tahoe water supply

Several weeks ago, the perfect storm clogged the intake pipes for the North Tahoe Public Utility District’s ultraviolet water treatment plant off of National Avenue in Tahoe Vista — restricting water capacity for 2,600 district customers.
But officials say the storm passing through the Basin this week shouldn’t pose any challenges for the plant, which was first built as a lake pumping station in 1969. The district converted the station to a water treatment plant in 2001 and 2002 and was the first municipality in California to use the ultraviolet technology.
“I look at it as one of the shining stars that the [North Tahoe Public Utility District] has,” said the utility district’s Board President Lane Lewis.
While the waters on Lake Tahoe were rough Sunday afternoon through early Monday morning, Public Works Director Lee Schegg reported that the treatment plant met typical evening demands for water, at times pumping up to 1,600 gallons of water per minute.
“Generally speaking, we don’t have these kinds of events very often,” Schegg said. “And so we really don’t have to worry about it too much.”
The early January blizzard, however, blew in gusty southwest winds for prolonged periods of time, churning up enough sand and lake sediment to block the underwater pipes’ screens.
“It’s been a highly efficient plant,” Lewis said. “But there’s still areas that we need to get worked out in the plant.”
The screens are made up of holes, 25 millionths of a meter in diameter, which strain out any unwanted particles. A self-cleaning process automatically pushes backwater through the screen when too many particles build up.
But the self-cleaning cycle couldn’t keep up with the intensity of that particular storm, which slammed into the lake in the first week of January. If the cycles repeat too quickly, the system will initiate continual backwashes and automatically shut down the entire treatment plant, Schegg said.
Prompted by the early-January conditions, the public utility district operated the treatment plant at a low capacity — only 600 gallons per minute — significantly diminishing the amount of water pumping through the system.
With the holidays still in full swing and demand for water at high levels, the Placer County Office of Emergency Services sent out a notice on Jan. 4 to customers living in the Kings Beach area notifying users to limit their water usage for the remainder of the storm and avoid using high-water appliances, such as the dishwasher and the washing machine.
“[The notice] was aimed at trying to keep the system as normal as possible,” Schegg said. “Without having to into those storage reserves.”
The main North Tahoe water system stores 1.62 million gallons of water in their reserves, Schegg said. Plans to increase the water storage capacity by another 1.4 million gallons of water are outlined in the district’s five-year capital improvement plan.

Ultraviolet water treatment, at a glance The North Tahoe Public Utility District was the first to use ultraviolet technology to treat water in the state of California. And while it took almost seven years to get approval from the Department of Health Services, board President Lane Lewis said the district is very satisfied with their investment. “It’s been an incredible plant,” Lewis said. The plant uses superior technology that efficiently cures lake water for drinking. And it has saved the district millions of dollars in operating and construction costs, Lewis said. The plant uses two disinfectants to treat the water, said Public Works Director Lee Schegg — chlorine and ultraviolet light. “Ultraviolet is extremely effective against all the pathogenic organisms,” Schegg said. “Like Giardia and Cryptosporidium.” It’s compact size and lack of operating equipment cut down on the plant’s cost of operation, Schegg said.