Saturday, January 2, 2010

Canal lining project through Imperial Sand Dunes nearly finished


Twenty-three miles may not seem like much.

But for a project to line a section of the All American Canal that snakes through the sand dunes west of Yuma, it's meant 20 years in the making, legal challenges and the expenditure of $285 million.

After nearly three years of construction by two contractors working simultaneously, the project is expected to be completed by spring.

The payoff is the conservation of an estimated 67,700 acre-feet of water a year once lost through seepage - enough to meet the annual needs of 500,000 people. Most of the saved water will be delivered to San Diego as part of an agreement by that city to help fund the project.

For Todd Shields, the project's executive program manager, it's a little more personal. During a recent tour of the canal, he related that his grandfather had worked on the original canal built in the 1930s.

"He had some stories to tell," Shields said of his grandfather. "When agencies pushed to line it, he said he always figured the part of the canal through the sand dunes would be lined eventually."

While the times and the equipment are very different today than when the canal was first built, both the original construction and today's lining project were crucial to the desert Southwest. The 82-mile All American Canal was built to control the flooding of the Colorado River and provide a reliable source of water to irrigate fields in Imperial County; today's project comes in the midst of a lingering drought even as growing cities need more water.

The lining project has consisted of actually constructing a new canal, lining its bottom and sides with concrete. That allowed for the continued delivery of the water through the original canal during construction.

A large portion of the new canal is now competed and carrying the diverted Colorado River water to Imperial County. The old canal is dry, except for portions that will continue to be used for temporary water storage.

Work now is focused on the "crossover" section where the old canal ties into the new one near the eastern edge of the lining project not far from Pilot Knob. The section of the canal that flows under Interstate 8 will remain unlined because of the cost, Shields explained.

Besides the concrete lining, a major difference between the old and new canals is that the new one is considerably narrower at the bottom, he said. That's because the new canal's concrete sides reduce the friction so it can carry as much water as the old canal even though it has less surface.

The canal carries about 3.1 million cubic feet of water a year to supply nine cities and irrigate thousands of acres of farmland.

There were a number of challenges to the project, Shields noted.

One was a legal challenge issued by environmentalists and businesses on both sides of the international border along which the All American Canal runs. They claimed that the seepage from the canal had become a vital water source for the Mexicali Valley aquifer.

That brought the project, first authorized by Congress in 1988, to a halt just as the contractors were mobilizing equipment in 2006. A year later, the lawsuit was dismissed and work began again in June 2007. The delays added $30 million to the cost, Shields said.

Another challenge was providing access for workers to the worksite, which required the construction of several miles of road - road that will be reclaimed by the sand dunes with the completion of the project, he said.

The project also required moving about 23 million cubic yards of dirt, which required a steady stream of dirt moving equipment, he said. Hundreds of wells had to be installed to pump groundwater and dry out the worksite.

The project also raised concerns about safety measures for those using the canal to cross illegally into the U.S. As a result, about 500 escape ladders were installed along alternate sides of the new canal, Shields said.

He noted there were 14 deaths in the All American Canal in 2009 - none of them in the lined portion. In 2008, there were 10 deaths in the canal, one in the newly lined section.

That was before the border fence was completed in the area, he said.