Canal-Lining Could Bring Southland Water Bonanza

Using new technology that will permit them to pour concrete under water, engineers plan to line a short section of an earthen irrigation canal near here early next year in a $5.1-million experiment that could lead to a water bonanza for urban Southern California.

Working while water continues to flow in the large Coachella branch of the All-American Canal, a new machine will line the big ditch with a thin layer of plastic and cover the plastic with a 3-inch blanket of concrete, engineers said. The goal is to stop leaks without interrupting water deliveries. The experiment is scheduled to start in January.

If successful, experts said, the technique can be used to line nearly 70 miles of the old, federally built canals that deliver Colorado River water to the rich desert farming areas in Riverside and Imperial counties, saving 100,000 acre-feet of water a year that is now lost to seepage. The water saved would be sold to thirsty Southern California cities.

An acre-foot of water contains 325,800 gallons, enough to sustain two urban families for a year, or irrigate a third of an acre of cotton, experts said.

Urban water engineers report that the canal-lining project will be the first step in water conservation efforts that ultimately could recapture more than 400,000 acre-feet now being lost through seepage, inefficient water distribution and uncontrolled drainage.

That is enough water to supply the city of Los Angeles for six months, said officials of the Metropolitan Water District, the umbrella agency that provides water for 27 districts and water agencies serving 14.5 million Southern California residents.

The big urban agency is paying for a large part of the underwater canal-lining experiment. It has budgeted $150 million to line 30 miles of the All-American Canal and another 38 miles of the Coachella branch of that canal, in exchange for the right to take 100,000 acre-feet a year of the water saved by the project. The deliveries are guaranteed for 55 years. The MWD hopes to use the experimental technique for the entire 68-mile project.

Because these canals were built by the U.S. Bureau of Reclamation as part of the Boulder Canyon Project 50 years ago, a special bill had to be passed by Congress authorizing the unusual financial arrangement. That bill is on President Reagan’s desk for signature.

If the experimental method of lining the canals fails, it would run up the cost of the 68-mile project by as much as 40%, according to Thomas E. Levy, Coachella Valley Water District chief engineer. Because water is delivered through the canals year-round, an alternative delivery system would have to be built if the canals must be drained while they are lined with concrete.

Farmers in the Coachella Valley--on the north end of the Salton Sea--and the Imperial Valley on the south take 3.1 million acre-feet of water from the federal project, which draws water from the Colorado River above Yuma. When these unlined canals were built water was plentiful and little thought was given to waste.

Water Seepage

As much as 2,700 acre-feet of water a year is lost through seepage for every mile of the canal, experts say. Roughly one-third of the 2.8 million acre-feet delivered to the Imperial Valley drains into the Salton Sea, district official said. The state Water Resources Control Board has ordered the Imperial district to find ways to stop such waste.

And the state board last week warned MWD officials that their 2-million acre-feet water allotment from the state Water Project may have to be curtailed to the amount the agency took in 1985 because the state has to protect water quality in the Sacramento River Delta. The MWD took 700,000 acre-feet three years ago, but engineers said the district will need its full entitlement to meet growth in the next century.

The big district already faces the possible loss of half of its 1.2-million acre-foot entitlement on the Colorado River, according to MWD spokesman Jay Malinowsky. The district needs more, not less, water, because the population is growing by 400,000 people a year, he said.

“We’ve got to make up 650,000 acre-feet somewhere, and conservation is one part of making up that loss,” Malinowsky said.

In addition to the All-American Canal and the Coachella branch projects, the MWD and the Imperial district are putting the finishing touches on a second agreement that could net an additional 100,000 acre-feet of water for the MWD. The terms of this proposed contract call for the MWD to spend $115 million rebuilding the antiquated Imperial irrigation system.

The money would help line another 350 miles of secondary canals, build reservoirs and install 122 automatic canal gates, engineers report. The 17 proposed construction projects would save 100,000 acre-feet a year that the MWD could put into its own Colorado River delivery system, water engineers said.

If the historic agreement is approved by the MWD board next month, as expected, it will set a precedent for future conservation agreements that ultimately could save 350,000 acre-feet of Imperial Valley water for use in the MWD’s service area, according to Malinowsky.

Store Surplus Water

In addition, the district is also offering to pay Imperial Valley and Palo Verde Valley farmers not to farm in dry years so that their water would be available. The district also wants to store any surplus water it can buy in wet years in underground aquifers near Chino and in Kern County.

With the state facing a possible third straight dry year, water conservation is critical, most experts now agree. And the focus is on the new underwater canal-lining technology being developed by Kiewit Pacific Co. of Omaha. While similar liners have been placed in still ponds, the process has never been tried in flowing water.

“This has never been done before. . . . We’ve got to keep the water from diluting or eroding the concrete mix,” Kiewit engineer Conway Narby said. He would not disclose how the company proposes to solve this problem, saying, “We may want to patent the process.”

Machine Being Built

A huge machine to accomplish the task--a span of girders and conveyors that stretch across the canal like a bridge--is now being built in Iowa. Rollers for the plastic sheeting will be mounted atop the machine like paper towel dispensers. Big hoppers will extrude a 3-inch blanket of concrete atop the plastic as it is spooled out on the sides and bottom of the canal, Narby said.

The experimental liner will be placed in a 7,000-foot-long section of the Coachella branch, where it skirts the hills just above the Salton Sea. Here the canal is 103 feet wide at the top, 48 feet across at the bottom and 11 feet deep. The machine spanning the canal will be propelled by tractor treads that inch along the banks.

When the 38-mile section of the Coachella Branch is lined, most of the Coachella district’s delivery system will have been upgraded, according to chief engineer Levy. He said the Coachella district has contributed $350,000 to the experiment that is being financed primarily by MWD and the federal government. Sale of the 30,000 acre-feet of water saved by lining the last section of the canal will finance the project, Levy said.

Difficult Problem

The problems facing the Imperial district’s farmers are a bit more difficult. In addition to lining a 30-mile section of the All-American Canal--saving 70,000 acre-feet--the district has been ordered by the state to come up with plans by Jan. 1 detailing how it will save at least another 100,000 acre-feet.

The Imperial district’s tentative agreement with MWD would meet that deadline and open the way for additional agreements that could make another 250,000 acre-feet available to Southern California, according to Charles L. Shreves, general manager of the Imperial district.