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THE POWER OF TRI-DAM

Built & paid for without a penny of state or federal financial help

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THE POWER OF TRI-DAM

Donnell is the highest Tri-Dam Project on the Stanislaus River.

Photo contributed/


POSTED August 31, 2016 12:50 a.m.

Ron Berry is what one might call a power player when it comes to basketball.
It’s not that the longtime manager of the Tri-Dam Project plays hoops. He deals in water.
And the best way to describe the water that flows from the reservoirs he oversees on the Stanislaus River Middle Fork and irrigates 114,000 acres of farmland, flows through taps serving 180,000 urban users, and is providing the revenue needed to install state-of-the-art farm irrigation systems and ultimately lower power costs in Manteca, Ripon, and Escalon by 15 percent is by using basketballs.
“People have a hard time grasping what cubic feet per second means when it comes to water,” Berry told Manteca Rotarians gathered at Ernie’s Rendezvous Room earlier this month. “So we tell them to think of basketballs.”
It takes 685 cubic feet of water dropping per second — or the volume of 685 basketballs passing a point in a given second  — in a penstock or tunnel to spin the generators at Donnells Reservoir that generates 72 megawatts of electricity. That’s over half of the power the project that is jointly owned by South San Joaquin Irrigation District and Oakdale Irrigation District generates.
The clean electricity from the Tri-Dam Project is being used to power some of the tech industry’s fabled firms. Under a deal that runs through Dec. 31, 2023, the Santa Clara-based Silicon Valley Power Company is buying all Tri Dam power.
Money from power sales after the initial 50-year PG&E contract expired more than a decade ago and the $52 million bonds issued in 1955 to build the three reservoir project were retired, has allowed as much as $12 million a year to flow into SSJID coffers as its 50 percent split of annual Tri-Dam “profits.”

Tri-Dam will make
cheaper electricity
possible in Manteca,
Ripon & Escalon
The Tri-Dam proceeds allowed SSJID to conduct four years of capital improvement projects into one year to take advantage of lower construction prices during the Great Recession and generate jobs, install state-of-the-art drip irrigation systems in Division 9 south of Manteca, and to fund undertakings such as research to protect the fish on the Stanislaus River.
It has also covered the hefty bills SSJID has piled up pushing toward its goal of harnessing Tri-Dam proceeds to lower electricity rates 15 percent in Ripon, Manteca and Escalon. That could become a reality within three years as SSJID deals with the final stretch of obstacles to acquire the retail system from PG&E.
Independent consultants hired by the San Joaquin County Local Agency Formation Commission analyzing the SSJID retail power plan emphasize the Tri-Dam receipts is what makes it possible for the SSJID to accomplish its goal of lower power rates across the board 15 percent.
So in a way, it makes Berry the man who oversees the proverbial printing press that churns out dollars for SSJID and OID.
But as far as he is concerned, he is simply the keeper of the vision that started shortly after the dawn of the 20th century when the two districts had the foresight and wisdom to purchase water rights  the middle fork of the Stanislaus River and build the Goodwin diversion dam above Knights Ferry.
That put in place the first wave of economic prosperity in Manteca and other SSJID communities. With the arrival of irrigation water in 1914, Manteca farming and the community itself more than tripled in five years.
The partnership built the original Melones Reservoir in 1926 with a storage capacity of 112,000 acre feet of water.
Berry turns to football to help people picture an acre foot of water.
“Think of a football field covered with a foot of water,” he said. “That’s an acre foot.”
Melones twice saved the communities SSJID and OID serve from economic disaster as it allowed the delivery of irrigation water in the late 1920s and 1930s when severe drought crippled farmers elsewhere in California.
Plans for Tri-Dam Project were drawn up in the 1930s consisting of three dams — Donnells, Beardsley, and Tulloch — as well as three power plants and a seven-mile tunnel carved through rock.
Construction didn’t start until 1955. When it was completed the district had three times the water storage than what the original dams provided. They also had a reliable source of income to pay for the system’s operations and maintenance as well as to retire bonds over 50 years via power that they sold to PG&E.
What was considered remarkable at the time — and even today — is the fact the Tri-Dam system was planned, financed, and constructed entirely by SSJID and OID without a penny from the state or federal governments.

New Melones
was made possible
by deal with SSJID, OID
New Melones Reservoir with its 2.4 million acre foot capacity was made possible after the two districts agreed to allow Melones Reservoir to be inundated. It is why the two districts have the legal rights to the first 600,000 acre feet of water that flows into the Bureau of Reclamation facility every year.
New Melones was completed in 1979.
When Donnells was completed in 1958 it was the fifth highest concrete arch dam in the western United States with an exposed dam face of 317 feet. It was topped by Hoover Dam at 726 feet built in 1936, O’Shaughnessy Dam in Yosemite National Park at 430 feet built in 1923, Arrowrock Dam on the Boise River at 350 feet built in 1915, and Parker Dam on the Colorado River at 320 feet built in 1938.
“The beauty of a double arch concrete dam is they get stronger as you put more water behind them,” Berry said.
That’s why Donnells peak water elevation is 4,916 feet — a foot below the top of the dam. Other dams such as the earth-filled Beardsley Reservoir that is part of the Tri Dam Project have ultimate water elevations significantly lower than the top of the dam. At Beardsley the top water elevation is 3,297 feet as opposed to the dam’s elevation of 3,405 feet.
Donnells holds 64,325 acre feet of water but was at 34,808 acre feet as of Aug. 24. Beardsley holds 97,802 acre feet of water. It was at 83,100 acre feet on Aug. 24.
Tulloch Reservoir holds 64,332 acre feet of water behind a dam with an elevation of 5007 feet.
Tri Dam is headquartered in Strawberry off of Highway 108 in Tuolumne County.

To contact Dennis Wyatt, email dwyatt@mantecabulletim.com

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