Too Much Water Endangers Pipes That Deliver It : Storms: Emergency repairs are under way to prevent the heavy rainfall from exposing and rupturing crucial lines. Sand-mining companies are also getting some blame for the erosion.

The storms that have brought much-needed rain to San Diego County have also endangered the pipelines through which most of the county’s water is delivered, eroding the San Luis Rey River bed and threatening to expose--and possibly rupture--the underground pipes, water officials said Thursday.

At a special meeting Thursday of the San Diego County Water Authority board of directors, chief engineer Ergun Bakall said that three of the authority’s pipelines that were once buried 20 feet below the river are now less than 3 feet down. He said $150,000 in emergency repairs have begun in an attempt to build a mini-dam to slow the river flow and shore up the pipes.

On Thursday morning, dozens of residents of the Rancho Monserate Mobile Home Park just west of Interstate 15 received a letter from the County Water Authority warning that noisy, round-the-clock construction would begin immediately.

“Should a pipeline be uncovered, it could fail,” the letter warned. “Since these pipelines carry the imported water that makes up 95% of the county’s total supply, a failure would cause serious, if temporary, difficulties for San Diegans.”

Jeanne Ray, a resident of the mobile home park, said the construction of the steel and rock dam sounds like thunder. As she spoke, her dog barked in the background.

“Every time they hit a rumble, she goes crazy,” Ray said, noting the irony of the situation in light of the drought. “You want it to rain, and then it does, and you need a way to turn it off.”

At the water authority meeting, director Bob Stevens of the city of Del Mar drew attention to the sand-mining companies whose operations have been said to contribute to the erosion.

“Is there a liability on the part of the sand miners up there?” he asked. The authority’s legal counsel said that has not been evaluated.

But Ray said that, litigation or no litigation, she holds the sand miners responsible.

“The sand miners have changed this channel completely. Big huge lakes in the riverbeds. It’s destroyed,” she said. “They have really screwed up. I call them greedy guts. And they are.”

In February, the board received the results of a study that found that extensive sand- and gravel-mining operations around the river threatened the integrity of the pipelines, especially during floods. But, when the study was presented to the board, the thought of rain seemed largely hypothetical.

Now that recent rainstorms have caused the predicted problems to come to pass, attention is focusing more in earnest upon the four active companies that operate around the river: the L.E. Morrison Sand Plant, California Sand, the H.G. Fenton Materials Co. and J.W. Sand & Materials.

Even if all expansion of the sand mining business was halted, the study found, the existing operations are enough to pose a serious threat.