Buildup on Coastal Sands a Take-Care Operation : Bridge construction: Workers make effort to avoid disturbing the fragile wetlands and nests of the rare least tern.

On the hot sand, the buildup continues. Military-style heavy equipment and vehicles scuttle under the searing sun.

No, it’s not Saudi Arabia. It’s the mouth of the Santa Ana River, between Huntington Beach and Newport Beach. A three-year, $15-million bridge construction project is under way.

The mammoth work is complicated by a number of factors: workers must keep traffic from grinding to a halt on busy Pacific Coast Highway, deal with building on and around a turbulent waterway, and try not to disturb the nesting site of a rare bird, the least tern.

The fragile Huntington Beach Wetlands that are host to the least tern are among the environmentally sensitive areas involved in the huge construction puzzle. Trucks, cranes, bulldozers and scores of workers must weave in and out of the area, while trying to avoid harm to the wetlands, the river, the ocean, Huntington State Beach and the nests of the least tern.

The least tern is an endangered species. Although almost driven to extinction, the birds, paradoxically, still like to nest on a stretch of beach that is heavy with human activity. The nesting site is only about 150 yards from the traffic on Pacific Coast Highway and is at the eastern edge of Huntington State Beach, one of California’s most popular state parks.

Even though the tiny birds have grown accustomed to highway noise, the state Fish and Game Department worried about what would happen to them once the massive bridge project got under way.

“We built sound walls (around the nesting site) to keep noise of construction away from the birds,” Decker said. “Also, we’re not allowed to go inside the fenced area, so we work around that area.”

State Fish and Game Department officials said last week that the least terns have been somewhat disrupted in recent months, but it is not clear if the construction activity is solely to blame. “The exact cause is unknown,” said department spokesman Kurt Taucher. “It may be due to many factors.”

Yet another difficulty lies in replacing the one existing bridge with two new structures.

“We’re not just building one bridge,” said Bill Decker, engineer for Caltrans District 12. “We’re building two: one over the Santa Ana River and the other over a new Talbert Channel that’s going to be built to the wetlands.”

Decker was referring to the Huntington Beach Wetlands, a newly restored ecological area between Brookhurst Street and the Santa Ana River, immediately north of Pacific Coast Highway. The wetlands receive ocean irrigation through a channel that connects to the river mouth. Decker said a new channel to the wetlands will go beneath Pacific Coast Highway and connect directly to the ocean--hence the need for a second bridge.

The new bridges are being built because the existing one is too narrow and dangerous, Caltrans officials said.

The existing bridge carries four lanes of traffic--two northbound, two southbound--on a structure that is only 45 feet wide. The new bridges will be 106 feet wide. And unlike the one being replaced, the new bridges will have a raised center divider to prevent northbound and southbound traffic from colliding.

“There’ve been a lot of accidents at that old bridge,” said Huntington Beach Police Chief Ronald E. Lowenberg. “So we’re glad that this new construction is making the bridge safer.”

Since construction work began in October, 1989, traffic along the bridge area has been forced to flow through a series of plastic cones and other temporary street dividers. The bridge has thus become even narrower and potentially more dangerous.

But, ironically, accidents have decreased since construction started, said Lt. Roger Parker, commander of the Police Department’s traffic division, although exact numbers were unavailable.

“I think what is happening is that drivers see all the construction and they say to themselves, ‘Uh-oh, I’m going to have to pay more attention to my driving,’ ” Parker said.

Decker said work on the new bridges is just about on schedule, despite disruptions during the February oil spill off Huntington Beach that caused much construction work to be stopped or delayed.

“We’re just about on time, and it looks like we’ll be completed in March, 1992,” Decker said.