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Backup reservoir considered for flume

Board also rescinded the mandatory 21 percent water conservation target


Guy McCarthy / Union Democrat Tuolumne Utilities District’s water supply depends on a wooden flume and ditch system that originates below Lyons Dam. The flume and ditch are susceptible to wildfire and other foreseeable hazards.

Fire-proofing the vulnerable flume-ditch system that carries water for people served by Tuolumne Utilities District, acquiring land for a backup reservoir in case the flume burns or sustains other damage in foreseeable circumstances, and rescinding the district’s mandated 21 percent conservation level were among issues dealt with Tuesday by TUD’s board of directors and staff.

The vital wood flume-dirt ditch system below Lyons Reservoir is owned and maintained by Pacific Gas & Electric Co., and it is the vulnerable link TUD and its customers depend on for water supply.

Last year, TUD officials described the PG&E Main Canal of flumes and ditches as Tuolumne County’s “Achilles heel.” But a proposal to seek $28 million for tunnels to bypass the disaster-prone wooden flumes that date back to the Gold Rush era and carry most of Tuolumne County’s water was pulled from consideration for entry in a national disaster resiliency competition.

‘Fire break’

Now, the short-term plan includes seeking multiple grants totaling about $700,000 for a 4-mile-long, 500-foot-wide fire break to clear canopy fuels and understory fuels on each side of the flume-ditch system between Lyons Dam and Twain Harte, Tom Haglund, TUD’s general manager, said Tuesday.

“It’s dense, it’s overgrown,” Haglund said of the unburned watershed the flume-ditch system passes through. “It presents a danger to us.”

There is no such fire break along the flume-ditch system right now. Healthy trees, dead trees and dying trees stand next to the flume, which is basically an aqueduct on wooden stilts built on steep mountain terrain.

Partners TUD staff are working with to build the fire break include PG&E, the Forest Service and Sierra Pacific Industries, the logging giant that’s interested in harvesting timber in the same area.

“We want to reduce the canopy and reduce the understory so that any fire that comes through there will be low intensity,” Haglund said. “We’re trying to cobble together funding sources for fire protection of the flume.”

‘Fire draft points’

In addition to the fire break, TUD staff have identified 20 to 25 spots along the flume-ditch system where tanks holding up to 20,000 gallons of water each can be located as “fire draft points,” Haglund said.

The proposed tanks are intended to help Tuolumne County and other fire agencies deal with fire when it comes, to protect forest lands, private property and water quality.

“We’ve provided these potential sites along the ditch system for Cal Fire to evaluate,” Haglund said.

The final number of tanks utilized will be up to Tuolumne County, Haglund said.

Backup reservoir

Knowing a foreseeable catastrophe could take out the flume-ditch system and shut down water to tens of thousands of residents, TUD staff and elected board members have over the years pursued a backup reservoir at Sierra Pines outside Twain Harte.

District staff have budgeted $150,000 for fiscal year 2017 to continue evaluating the site for a proposed reservoir that could hold 350 acre-feet to 850 acre-feet of water, enough to supply six to 12 weeks of water for customers in the event of catastrophic loss of flume sections on the Tuolumne Main Canal.

A timeline presented Tuesday starts August 2016 and ends September 2018 with acquisition of about 22 acres from PG&E. Cost of the land has not been budgeted, and Haglund said he did not want to “telegraph” the land’s worth. Multiple appraisals of the land’s market value will be expected before any purchase is pursued.

Asked how long it could take before the district has the backup reservoir built and filled with at least 350 acre-feet, Haglund said he hoped it could happen inside the next 10 years.

The district has been discussing the plan with PG&E for several years, but has not been in a financial position to move forward with feasibility and environmental studies until now, TUD staff said in a report. The project is part of TUD’s capital improvement plan, which the district put together last year to show customers why five years of rate increases adopted in November 2015 are necessary.

The TUD board voted 4-0 to approve the timeline for completing a feasibility study at Sierra Pines. Directors Ron Kopf, Kent Johnson, Jim Grinnell and Ron Ringen were present, and John Maciel was absent.

Mandatory 21 percent rescinded

The wettest winter in five years has ensured TUD has more than sufficient water supply to deliver potable water to all its customers through the remainder of this year, according to TUD staff.

Haglund recommended Tuesday the board of directors rescind the district’s 21 percent water conservation level it adopted earlier this year. That 21 percent target was a reduction from 24 percent conservation mandated last year for TUD by the State Water Resources Control Board.

People who get their water from TUD must still abide by end-user water conservation mandates, Haglund said.

Mandatory requirements mean people must avoid:

1) Using potable water on outdoor landscapes in a manner that causes runoff onto adjacent property, non-irrigated areas, private and public walkways, roadways, parking lots or structures.

2) Using hoses and potable water to wash motor vehicles, except where the hose is fitted with a shut-off nozzle or similar device.

3) Running potable water on driveways and sidewalks.

4) Using potable water in a fountain or other decorative water feature, except where the water is part of a recirculating system.

5) Using potable water on outdoor landscapes during measurable rainfall or within 48 hours of measurable rainfall.

6) Irrigating with potable water ornamental turf on public street medians.

7) Irrigating with potable water on landscapes outside newly-constructed homes and buildings in a manner inconsistent with regulations or other requirements established by the California Building Standards Commission and the Department of Housing and Community Development.

The TUD Board of Directors voted unanimously to rescind 21 percent conservation and retain mandated end-user water requirements.