Excavation Challenges In Riverside

By Loren Faulkner | September 28, 2010

MWD's Perris Valley Pipeline North Reach in Riverside, Calif., is a 2.7-mile placement of 97-inch and 109-inch-diameter water pipelines, part of an ongoing water delivery system upgrade involving two separate Southern California water districts.

Multiple Challenges

"It's probably as tough as a pipeline-laying job is going to get," said Wes Brodeur, project manager with W.A. Rasic Construction (WAR), the contractor on this portion, an approximately $40-million contract for labor and equipment.

"With MWD, there is always a high degree of proficiency needed to meet their strict requirements," says Brodeur. "It's also a dangerous environment, with unstable ground in certain areas; deep excavation, so, many safety control crews are on site; traffic control is a big issue as Alessandro Boulevard is a major artery to and from I-215 to Riverside and Orange/L.A. Counties; high ground water table; hard rock formations requiring rock drilling and excavation (FIRP)."

Two Cuts

109-inch steel CMLC pipeline domestic water main line for Metropolitan Water District (MWD) at the tie-in point at the Henry J. Mills Water Treatment Plant requires an open cut V excavation through extremely hard granite. There has been a limited use of blasting due to the limitations and restrictions of the blasting specifications and proximity to homes, utilities and traffic.

"We're using specialized 15-inch rock perforation (FIRP) drill technique. ECM company uses 15-inch rock drills to 'Swiss cheese' the rock so that breakers can perform the demolition work, rather than blasting.

"It took several months of drilling holes ahead of the pipeline excavation before using breakers to clear away the granite," says Wes Brodeur. A new Tramac 15-ton breaker, to be attached to a Hitachi EX800 excavator, is being used for the next level of heavy duty granite cracking.

The 9,000 linear feet of pipeline along Alessandro Boulevard that ties into the Mills Plant piping is a conventional excavation using a series of steel shoring cages. Trench shields are custom-made 12-inch-thick steel cages 50 feet by 10 feet by 8 feet wide. Excavation depths along Alessandro Boulevard average 20 feet to 26 feet.

Pipe Laying

MWD provides the 97-inch and 109-inch CMLC steel piping in 40-foot lengths. The 109-inch pipe is lined on site by a subcontractor, Spinello Company — 4/10-inch-thick steel, 1-inch coating of concrete, 3/4-inch concrete lining.

Birdseye is laid as bedding, compacted, and when pipe is installed is backfilled with more birdseye. Rasic uses approximately 75 tons of this material for each 40-foot length of pipe. A Kamatsu PC-1250 excavator is being used to set the pipes.


The Mills Plant pipe heading area and elsewhere required deep V excavating due to the available right of way. Normal installation of pipe bedding and zone with an excavator was impractical because of the reach required.

"We chose to use a GOMACO RTP-500 machine to lay down the pipe bedding and zone using birdseye fill," said Brodeur. "The conveyor reaches out over the cut exactly as we need it to do, to carry the birdseye fill to its place," he said. The machine was purchased from Terry Equipment Co., Fontana, California. At regular excavation areas, birdseye is installed using conventional equipment.


"We're now going to do a 100-foot tunnel at 30-foot depth where the Mills Plant ties into the Alessandro East connection to avoid overhead high power lines and buried utility lines that would cut power to entire neighborhoods and thousands of people, if interrupted. A road header will be used at this point since rock is not as hard," he added.

Two other tunnels will be constructed at the other end of the line — some 9,000 feet to the east — that will be 450 feet and 500 feet in length, respectively. These will be blasted and mucked out, Brodeur said.

At the east connection a 50-foot-deep tunnel access portal was constructed for the two — each 132-inch tunnel excavations. One tunnel goes east under a flood control channel and railroad tracks. The other goes northwest under Alessandro Boulevard, tying into the excavation there.

Brodeur said this portal required much blasting and off-hauling of some 5,000 cubic yards of rock that was then broken down as class II base. The existing 60-inch RCP storm drain pipe above the tunnel portal was secured with mining straps and rock bolts.

But design changes had to be submitted due to different soil and rock conditions than originally estimated. This caused a delay of some 30 days in finishing off the portal area, according to Brodeur. Special shoring included rock bolts.

A crew of 40 to 70 employees is working 10-hour days, including every other Saturday, to keep on top of a very aggressive MWD schedule, as environmental Storm Water Pollution Prevention Plan (SWPPP) procedures are being complied with, as well.

Work on the North Reach started in September 2007. The pipeline is scheduled to be functional in August 2008. W.A. Rasic's final street improvement, retaining walls, etc., will be completed in December 2008, according to Brodeur.

Project Fast Facts:

The entire Perris Valley Pipeline will consist of 6.5 miles of 96-inch pipeline from Metropolitan's Henry J. Mills Water Treatment Plant, east along Alessandro Boulevard and then south paralleling the 215 Freeway. EMWD is constructing a separate 4-foot diameter, six-mile long water pipeline that will connect its service area to the Perris Valley Pipeline at Cactus Avenue.

The Metropolitan Water District of Southern California, Western Municipal Water District and Eastern Municipal Water District are developing the $110-million project jointly. When completed, the pipeline will enhance the treated water delivery capacity in Eastern and Western's service areas by up to 150 million gallons per day. (Source: Perrisvalleypipeline.com)