DWP Project Diverts Rainfall Into the Ocean : Ground water: Ironically, millions of gallons are being wasted because of a drought-inspired work in Sun Valley.

Hundreds of millions of gallons of rainwater that could be used to replenish city ground-water supplies instead are flowing into the ocean because a construction project made it impossible to divert runoff into spreading grounds in Sun Valley.

In an ironic twist, the water is being wasted because of a drought-inspired project to build a new pumping station at the Tujunga Spreading Grounds.

If the spreading grounds had been available for use during the recent storms, officials could have captured more than 800 acre-feet of water--about a year’s supply for 1,600 families--that instead flowed down Tujunga Wash to the Los Angeles River and on to the ocean.

The spreading grounds are a series of shallow earthen basins to which water is diverted during storms or when large amounts of snow are melting near the Owens Valley. The water percolates into the ground beneath the basins and slowly seeps southward toward city drinking water wells in North Hollywood and near Griffith Park.

The spreading grounds were put out of commission about two weeks ago when a contractor for the Los Angeles Department of Water and Power began work on a new pumping station. The work required cutting into the channel used to divert water to the spreading grounds.

A DWP official said the grounds will be out of commission about two more weeks, meaning that more water will be lost if rainy weather continues. Construction work is expected to continue until June, 1992, but the official said water can be spread in most of the grounds after two weeks.

Besides the Tujunga basins, other spreading grounds, including the Hansen and Pacoima grounds, are operated in the northeast San Fernando Valley to take advantage of porous sand and gravel, which quickly absorb water and act as natural filters.

An official with the county Department of Public Works, which operates the spreading grounds under an agreement with the city, said the shutdown was disappointing.

“When rain’s available, we fight hard to get everything we can,” said Don Nichols, chief of the department’s hydraulic and water conservation division. He estimated the loss at 800 acre-feet Tuesday morning, shortly before another heavy rain began to fall.

Nichols said county workers were preparing to divert water from the wash into the spreading grounds March 18 when they learned from the DWP about the construction in the channel.

DWP officials defended their decision to start work during the rainy season. They said the pumping station, part of $30 million in improvements to ground-water pumping capacity, itself is a key drought-busting measure that should not be delayed even for a few weeks.

Wells provide about 15% of the city’s water during an average year and potentially could supply much more during a drought or other emergencies.

But large-scale increases in pumping are limited by existing well capacity and chemical pollution that has shut down some wells.

In response, the DWP recently drilled a new string of wells near the Tujunga grounds and is constructing the pumping station and a chlorination reservoir for the water from the wells.

“I knew we were going to be second-guessed on this thing,” said Roger Menlove, manager of the Tujunga well field project for the DWP, referring to the timing of the construction work. But Menlove and others said the pumping station could not be delayed without abandoning the goal of having additional ground water available by the summer of 1992.

Walter Hoye, DWP director of water engineering, said the project has been on a fast track since planning began about 18 months ago.

“It’s turning out to be very fortunate that we will have it on-line, if all goes well, for a possible sixth dry summer,” Hoye said. He said it was better to risk losing “a modest amount of water” now to guarantee the availability of large supplies by next year.

Nichols, the county official, said hindsight is always perfect.

“Nobody thought it was ever going to rain again,” Nichols said. “Then it pours down rain the last couple of weeks and you say, ‘Uh-oh, did you really make the right decision?’ ”