Canal lining failure along the East Branch Aqueduct.

The Repair Side

 The task of designing repairs to SWP’s aging facilities falls to DWR’s Division of Engineering. DOE’s staff must determine what kinds of methods and materials to use that will best do the job. “Engineering staff design the repairs, prepare the plans and the specifications, and package them with contract documents for public works contracts,” says Les Harder, Chief of DOE.

When the repair begins, Engineering staff oversee the construction and inspect the work and can reject it if they feel it doesn’t meet the contract’s requirements. DOE’s inspectors work out of two offices, one in Sacramento and another in Lancaster. A temporary office in Yucaipa is associated with the construction of the East Branch Extension Project.

The repairs include just about every part of the Project—buildings, pumps and generators, roads, tunnels, pipelines and more. However the most visible ones, those often covered by the media, have been along the California Aqueduct. Harder says that considering its large size, length, and the many difficult geologic conditions it traverses, the aqueduct has performed well over the years.

Repair at mile 56 was a planned outage in 1990. Canal lining is underway.
However the canal is now more than 30 years old, and it is experiencing more distress from settlement, seepage, hydrocompaction, and foundation solutions, all of which can result in canal slippage or failure. In the past decade, there have been 16 major repairs, which added up to more than $40 million.

The aqueduct was originally constructed with unreinforced concrete lining about 3-4 inches thick. The lining reduces seepage, provides a smooth surface to reduce friction and thus conserves pumping energy, and prevents erosion of its slopes. Since then, technology has changed and created new methods and materials that strengthen the canal slopes by keeping water from leaking into the soil. Now plastics and rubberized asphalt materials are used to reduce seepage distress.

What method is selected is sometimes determined by how much of the embankment needs to be removed and what is the cheapest but most effective repair. DOE has recently used both a spray-on geomembrane (trade name Liquid Boot) in conjunction with a plastic geotextile material, then covered with a two-inch layer of shotcrete and an asphatic elastometic geomembrane (tradename Teranap), which can be rolled over the canal prism. The Teranap rows are overlapped and sealed by applying heat to the edges of the rolls, and also covered with a 2-inch layer of shotcrete.

Before and during repairs, environmental concerns are always a priority, especially when borrow sites or spoil areas are required that might disturb habitat. When dewatering a canal repair section, fish are often stranded within that canal section, and DOE must work with Department of Fish and Game staff to remove the fish safely.

Repair work along the aqueduct also involves working with O&M to schedule outages for dewatering the canal and stopping water deliveries beyond that section. As demands by the SWP contractors for water increase, timing is everything in terms of when and how long the repair takes. For DOE, that means working around the clock at an accelerated pace.

A 23-year DOE veteran, Harder says more surveillance and preventive work are needed if emergencies are to be prevented. In recent years DOE and O&M staff have carried out several preventative repairs to deter problems escalating into true emergencies. But as contractors’ water requirements rise, there will be fewer opportunities for outages to do repairs. “We’ll just have to find more inventive ways to do the job.”