While emphasizing that Don Pedro Reservoir remains a safe — but aging — facility, Turlock Irrigation District is hoping to secure another 50 years of successful operation with three major refurbishment projects in 2017.
“It’s up to current standards and it’s passed every single thing we’ve thrown at it,” said Chief Dam Safety Engineer Peggy Harding. “It’s an excellently constructed and maintained dam. There’s absolutely nothing I can think of that this dam needs aside from routine maintenance.”
“The chances of dam failure are very low. It’s one of the best designed facilities out there,” added Assistant General Manager of Power Supply Administration Brian LaFollette.
These three major projects will cost about $7 million, according to LaFollette, who said that the costs are included in next year’s budget for the Don Pedro Reservoir. The TID Board of Directors is slated to make a final decision on the budget on Dec. 13.
Power Plant Engineering Department Manager Robert Bohrisch said that after staff repaired corrosion of an emergency cooling water basket at the facility in 2010, they began to look “with a critical eye” at where there might be other issues within the facility that may present different, long term issues for the power plant.
All three projects for next year will take place in the Power Tunnel, which is one of two major tunnels at Don Pedro Reservoir that feeds into the Power House to generate electricity. The other major tunnel, the Diversion Tunnel, was the originally installed tunnel at the reservoir and recently underwent refurbishment work of its own.
The work on the Power Tunnel will be completed in two phases, with the first phase beginning before the irrigation season in February with the bulkhead gate installation and turbine shutoff valve replacements. The second phase, which is expected to begin after the irrigation season in October, will include the fixed wheel gate installation. Each phase is slated to take about 45 days to complete.
“They served us well for the last 45 years, but after 45 years of having been underwater, it’s the appropriate time to do some refurbishment work,” said LaFollette. “Between those two outages, we hope to complete all three projects and we will have restored our gates for another 50 years of operation.”
Completed in 1971, the Don Pedro Reservoir has a capacity of 2,030,000 acre feet, making it the sixth largest reservoir in California. The reservoir is licensed by the Federal Energy Regulatory Commission and jointly held by TID and the Modesto Irrigation District. It undergoes frequent regulator inspections by the State Division of Safety of Dams and the FERC Regional Engineer Office, as well as an independent engineer report every five years.
During their meeting Tuesday, TID Board of Directors also received information regarding current hydrological conditions from Utility Analyst Jason Carkeet, who reported that the Tuolumne River Watershed received nearly three inches of precipitation during this weekend’s storm.
The month of October wrapped up with 5.96 inches of precipitation, which is four more inches than the historical monthly average. The precipitation year, which starts in September, now stands at 5.99 inches, which is 235.8 percent of the historical average of 2.54 inches for this date.