According to Union Democrat on August 15th:

The aging water main where a fire hydrant lateral broke Thursday and unleashed an estimated 90,000 gallons of water in one hour, flooding hillside yards, laundry rooms and an apartment broke twice before in the past 10 years, Tuolumne Utilities District officials said Friday.

At its height, the broken hydrant lateral on North Shepherd Street allowed water to flow from the roughly 80-year-old cast iron main at a rate of 500 to 600 gallons per minute, David Andres, TUD interim general manager, and Don Perkins, TUD operations manager, said.

The two times the main broke before in the past decade were in September 2006 and September 2008, Andres and Perkins said. The hydrant lateral that broke Thursday is probably just as old as the cast iron main, Andres said.

“Clearly there’s a problem going on with that water main,” said property owner B.Z. Smith, whose daughter lives on North Shepherd near the spot where the hydrant lateral pipe broke Thursday afternoon.

“Why in the world has it happened twice in less than a decade that one of the major water mains for an entire city has gone out?” Smith asked.

Part of the answer is that, even though there have been multiple breaks on the same hillside system on North Shepherd resulting in losses of thousands of gallons of water, TUD has other pipes in Sonora that fail more often and lose greater amounts of water.

“It’s an unfortunate situation, and it’s unfortunate she’s had this occur more than once,” Andres said. “But this particular project, replacing that water main, would not rank as one of our top priorities because we have other water mains in Sonora that leak even more frequently. It really comes down to priorities. Not all of them result in the same damage to homes.”

Smith’s daughter, Wren Zuccaro, showed Friday where water rushed down both sides of her home, and where water an inch deep crept about 10 feet into her downstairs laundry room.

TUD’s human resources director went out to the flood-prone neighborhood and gave insurance forms to two property owners, Smith and Larry Leonard, who owns a building with apartments and storage rooms below Smith’s property.

Sonora firefighters helped clean up an apartment that flooded, and TUD personnel helped repair the landscaping, Leonard said, adding they both did a good job.

Zuccaro was home Thursday, heard rushing water outside and reported the flooding immediately, she said.

Andres said the first report about hillside flooding due to a break reached TUD at 3:40 p.m. and the first TUD crews arrived at 3:55 p.m. Water flow to the hydrant lateral was shut off at 4:40 p.m. and that stopped water flowing and flooding into the North Shepherd neighborhood, Andres said.

“How much water was lost, in the area of 90,000 gallons, plus or minus,” Andres said. “That’s just an estimate. It was 500 to 600 gallons per minute when it was peaking.”

The break on the lateral to the fire hydrant was isolated by TUD workers at the scene by turning off a valve to the hydrant, Andres said. No customers were without water service due to the shutoff. The break on the hydrant lateral has not yet been repaired.

The cast iron main that runs through the North Shepherd neighborhood has lead-packed joints and, in one of the breaks back in 2006 and 2008, it was initially one of the joints that leaked, Perkins said. When workers opened a hole to access the joint, the entire main failed and unleashed enough water under high pressure to wash two workers out of the hole, including one who weighed about 200 pounds.

“Typically these type of water mains would be put in the road, under the road,” Andres said. “But 80 years ago, whoever approved these water mains allowed them to be placed in people’s backyards and other locations that are not on main streets. What that results in, in some cases, houses are in low spots and that’s where the water’s going to run.

“We are concerned for our customers in respect to repairing those type situations, but because of the other pressing capital improvement needs in the district it is unlikely that this particular water main section would be replaced in the near future.”

Perkins said TUD responds to well over 300 leaks a year.

“There are pipes underground right now that are leaking that we don’t know about until they get big enough or come to the surface,” Andres said. “On the low end, you probably lose 5 percent of your water on a new system. Some might run 20 percent in losses due to leaks. That’s the way it is. You have water under high pressure in an underground system.”

It’s unclear how much water TUD loses due to leaks, Perkins said.

“We’re obviously losing more water than we should be, due to the bad water mains,” Perkins said. “No matter what we’re losing, it’s too much.”