High and Dry. Concrete lining of two canals will halt seepage of 93,900 acre-ft annually.

By the end of May, California’s Imperial Irrigation District will award contracts estimated at $136 million for construction of a 50-ft-deep, 23-mile-long canal to replace parts of a canal built in 1942. It is the largest part of a $219-million program to eliminate seepage in the transport of Colorado River water to Southern California’s Imperial and Coachella valleys. Completion of the program is set for 2008.

The program fulfills the provisions of the 2003 Colorado River Quantification Settlement Agreement between the U.S. Dept. of Interior, the state of California and four Southern California water agencies. It calls for concrete lining of 23 miles of new canal parallel to the 82-mile-long, earthen All-American Canal near the Mexico border and 37 miles of concrete-lined canal parallel to the 123-mile Coachella Canal already under construction. The agreement’s goal is to settle decades of water disputes and provide a means for the state to live within its 4.4 million acre-ft basic annual apportionment of Colorado River water.

“If we had done this four years ago when the price of fuel and concrete weren’t sky-high, we could have completed this at a fraction of the cost,” says Michael King, manager of the Imperial Irrigation District.

Lining the canals will save an estimated 93,900 acre-ft of water per year. DOI studies determined that building parallel canals would be more cost-effective than installing the lining in the existing canals using a submergible application process. The canals will tie in to the existing drop structures at road and river crossings.

“To minimize construction through the dunes, we moved the alignment south of the existing canal,” says Wayne Dahl, project manager and engineer of record for Bookman-Edmonston/GEI Consultants Inc., Boston, the engineering firm which, with MWH, Broomfield, Colo., designed the canals and is performing construction management for the Coachella Canal. The project requires moving 25 million cu yd of earth.

After excavating the canal prism, crews install the concrete lining. A paving train places the concrete, inserts the joints and applies a curing compound. As much as a half-mile of canal can be completed in a day, says Dan Charlton, project manager for Coachella Valley Water District.

“The climate conditions are extreme,” says Dahl. BE/GEI-MWH had to do a lot of dewatering because the canals had been leaking for many years. “The biggest challenge was keeping the water flowing while transitioning from the new canal to the existing canal,” says King. At eight canal junctions, contractors will drive 3-ft-wide, 60-ft-long sheet piles to divert water to one side of the canal while concrete is placed. When it has set, they will return the water and repeat the operation on the other side.

Not everyone is excited about the project. A consortium of Mexican and California-based environmental and economic-development groups sued for deprivation of water rights because seepage would no longer recharge the Mexicali Aquifer. Seven of the eight charges were dismissed by U.S. Chief District Judge Philip Pro on Feb. 8 for lack of standing. The judge did not set a date to hear arguments on the validity of the environmental documents.

The suits have not affected work progress. Bids will be opened March 22 on two sections of the All-American Canal and April 5 for the final section. “We might have to have two different contractors to get the best price,” says King. He predicts that as many as three of the 37 contractors who took bid packages will probably compete for the work.

Construction on the All-American Canal will start in June and should be complete by December 2008. The $83-million Coachella Canal will be complete in April 2007. m