IMPERIAL BEACH, Calif. – On a temporary pier 15 feet above the Pacific Ocean, the worker guides a piling toward the template that will hold it in place for the crane to pound it into the water below.
One after the other, the pilings wend their way 300 feet out into the ocean, completing the westernmost extension of the border fence that separates Mexico and the United States.
The work presents a unique set of conditions markedly different from constructing the segments of the fence that are on land.
“It’s different working in a surf zone,” said Chuck Mesa, a coastal engineer with the Corps’ Los Angeles District. “You have to work with tides and sediment transport. The beach will change over time, and that affects project design and construction.”
There are winter storms, one of which, Mesa said, raised the sea level to within inches of the bottom of the pier, causing a temporary work stoppage for safety reasons. It also scoured about five to six feet of beach in the construction area.
In addition to weather and geophysical conditions, the contractor also faced some man-made obstacles that impacted construction.
“The design requires the contractor to drive the piles to a certain depth,” to ensure stability and longevity, Mesa said. “There are remnants of the previous border fence, and there are layers of clay beneath the sand. Both make it difficult to drive the piles and keep them in alignment.”
Robert Landreth is the project superintendent for Granite Construction Company. He said the work is an ongoing struggle, with the surf and debris from the old fence making it difficult at times to maintain the alignment.
“We’ve never built a fence out over the sea before, so we have to work with the design,” he said. “We have high surf, and the old forms debris at different elevations and are directly in line with where we’re placing this one.”
The 40-foot pilings are prepped, sandblasted, coated, and wrapped in fiber to give them a 30-year life expectancy. Compensating for the old fence and clay layers at times impacts the speed at which the pilings can be installed and their alignment and depth. Workers use levels to ensure the pilings are vertical.
“Other than that, the process is running very smoothly,” Landreth said.
Seung Yoo, the Corps’ construction rep for the project, said the surf fence project is essentially composed of two parts, the final 500 feet on land and an additional 300 feet into the Pacific Ocean.
Soo said when piling placement is completed, the contractor will grout the pilings and remove the temporary pier, in advance of environmental restrictions that protect endangered species in the area.