Marlette water system enters 21st century
Tribune News Service
CARSON CITY, Nev. – The Marlette water system was an engineering marvel when it was built nearly 140 years ago, using gravity to move water up and out of the Tahoe Basin, down the Sierra and into the Virginia Range to Virginia City.
It still is, providing water to both the Comstock and Carson City through an inverted siphon that doesn’t need power. But, during the past five years, the system has gone high-tech. Instead of as many as nine water tenders who lived on the mountain in the old days or, more recently, workers who drove up the hill practically daily to make sure everything was working, a computer system communicating with remote sensors at nearly every site in the system keeps track of everything.
“All the people who had to be up there have all gone away,” said system manager Mike Leahy. “One person can do it.”
He said that when the control valves are finally added to the monitoring equipment at Hobart Reservoir, he will be able to not only keep tabs on but control everything without leaving the office. In fact, using a smartphone, he doesn’t even need to be in the office.
“This way, we know all the time what all the sites are doing,” he said. “We’re more accurate, more precise.”
The controls also give him the ability to better measure how much water is available.
“You could never measure that before,” he said.
When originally built, water flowed out of Marlette Lake into a flume that wound around the mountain on the Tahoe side, through a 4,000-foot-long tunnel to the Carson City side of the Sierra to Red House. There, that water joined water from a half dozen springs on the east slope and from Hobart Reservoir. From there, it flowed through another wooden flume to the storage tanks above Lakeview.
Leahy says that’s where the inverted siphon begins. The water plunges more than 2,000 feet down an 11-inch-wide pipe, building to a pressure of more than 650 pounds per square inch. It crosses beneath U.S. 395 and, using that pressure, climbs 1,500 feet up into the Virginia Range, where it empties into Five Mile Reservoir above Virginia City.
That high pressure was obvious several years ago when the pipe sprung a leak just a few yards from the highway, producing a geyser more than 40 feet high.
The flumes were abandoned after the old tunnel collapsed in the 1960s. Pipes replaced them but that meant hauling a diesel-powered pump up the mountain each summer to pump water from Marlette when the flow from Hobart and the springs wasn’t enough.
The old pump is mothballed now, replaced by a permanent generator system that powers an electric pump submerged in a well 10 feet from the shore of Marlette.
Not only is it more efficient, it’s nearly silent, unlike the old generator that pretty much destroyed the solitude of the alpine lake when it was running. Not only can Leahy control it from his office at the base of the mountain, it eliminated the dangerous task of hauling the diesel pump up and down the rugged, narrow road that snakes along the side of the mountain every summer.
In addition, the new pump doesn’t overheat and need a rest every few hours.
“We can run it all day, all night – run it for months,” Leahy said.
In a normal year, system managers pump from July through September. Because of the weather, the diesel had to be removed from the hill at that point.
This year, he said, there’s so much water on the mountain that pumping hasn’t been necessary at all. Ample snow and rain this year has made the mountain lush.
“I’ve seen growth equivalent to what we normally see in two or three years,” he said. “It was just a vegetation boom.”
Over the past five years, he said, the state has spent a lot of money installing the pump, generators, electronic monitoring and new pipes. When a new pipe from Red House to the Lakeview tanks is put in next summer, the total will reach $10.5 million.
But he saved several hundred thousand dollars by not installing 1,000 feet of pipe above Hobart. After it’s pumped over the crest of the mountain, Marlette water still flows in an open stream to Hobart.
That saved money and eliminated the need to dig a pipeline right through the habitat of the rare mountain beaver, which lives between the lake and the reservoir. That species, the aplodontia, is more than 40 million years old and considered by scientists to be a living fossil.
And it doesn’t hurt the quality of the water, which Leahy describes as some of the purest in the world.
The system supplies all of Virginia City’s drinking water and about 10 percent of Carson City’s water.
“This water really improves the quality of Carson City’s water,” he said.