NORTH COUNTY -- California's diverse park system is under siege from development all over the state, and nowhere is the threat more severe than in environmentally rich San Diego County, state officials and park supporters say.

Running out of room for building highways, sewer pipes and power lines on private property, developers and utilities are increasingly turning to state parkland -- which makes up 1.5 percent of California's land mass and about a quarter of San Diego's -- for their projects.

"San Diego County is kind of the epicenter of a series of very serious threats to California's state parks," said Elizabeth Goldstein, president of the California State Parks Foundation, an advocacy group, in a recent interview.

As a result, one of America's finest state park systems is in danger of being undermined, Goldstein said.

California's extensive system covers 278 parks and 1.5 million acres. The parks give visitors a chance to soak up the sun on golden beaches, feast one's eyes on colorful desert wildflowers, marvel at towering ancient redwoods and take a trip back in time at ghost towns.

San Diego County is home to several, including 600,000-acre Anza-Borrego Desert State Park, the largest state park in the continental U.S.

Others include San Onofre State Beach, with its famous Trestles surfing area and fifth-highest visitor total of all California parks; Old Town San Diego State Historic Park, which offers a glimpse into early county life; and Torrey Pines State Beach, one of two places in the world where the rare evergreens grow.

Roy Stearns, a spokesman for the California Department of Parks and Recreation in Sacramento, said there is no danger the system will disappear one day in the face of development pressure. But there is a risk, he said, that that pressure will steadily erode many of its best features.

"It's like we're starting to chip away at the system," Stearns said. "We're taking a little bit here and a little bit there, and once it's gone you never get it back. Once it turns into power lines and asphalt, nobody ever takes that stuff out."

The San Diego County threat

Park supporters in San Diego County are perhaps most concerned about the future of Anza-Borrego, where San Diego Gas & Electric Co. wants to plant 150-foot-tall metal towers in the sand and stretch fat 500-kilovolt wires across 23 miles of largely pristine landscape. The proposed Sunrise Powerlink transmission line would be visible from about one-sixth of the park, officials say.

Supporters also fret that little will be left of San Onofre state park if an Orange County transportation agency gets the green light to build a four-lane toll road -- with room for six lanes -- on it. The highway would cover 325 of the park's 2,000 acres in pavement.

Park supporters also fret about the U.S. government's plan to build another layer of the international-border barrier through Border Field State Park, forcing park visitors to line up to pass through a patrolled gate to frolic at a popular beach.

Sen. Christine Kehoe, D-San Diego, said she is deeply concerned about the proposals.

"In San Diego County alone, there are three major projects which propose to use park lands that were purchased and maintained with our tax dollars," Kehoe said. "Because open space is readily available, our parks are at risk of becoming the preferred corridors for infrastructure siting. Parks seem to have become the paths of least resistance."

For their part, proponents of the toll road and power line say they set their sights on state land only after surveys showed there was no other way to build their projects.

And not everyone agrees the projects will hurt the parks.

Gina Zari, spokeswoman for Assemblywoman Mimi Walters, R-Laguna Niguel, said the representative for coastal areas of southern Orange County and northern San Diego County backs the toll road and believes it actually will help the park, by providing money for improvements.

Still, park supporters maintain the developments will hurt the parks. And they say the proposals reflect an emerging attitude throughout the state that developed private property is more important to preserve than undeveloped parkland, supporters say.

"I heard one person refer to (state parkland) as underutilized open space," Stearns said. "What a tragic comment. Is that what Yosemite is? Is that what Yellowstone is? If that's what it is, why don't we just sell it today and put shopping centers on it tomorrow?"

No way around

SDG&E officials, however, say they highly value Anza-Borrego.

Because of that, said Jim Avery, vice president of electric transmission, the utility selected an existing power-line corridor as its preferred route for going through the park instead of proposing an entirely new one. Avery said SDG&E intends to minimize the Sunrise power line's footprint on the land by using compact H-frame towers -- with straight vertical poles and a cross-arm -- instead of erecting massive metal structures that some have likened to erector sets.

Avery said the utility would prefer to avoid the park, but it dominates the eastern side of the county and there is almost no way around it.

"There are basically two miles between the park and the Mexican border," Avery said.

Following the border would place the new line next to an existing one called Southwest Powerlink. Avery said that is an unattractive option because a wildfire could knock out both sets of wires at the same time and spark widespread power outages in metro San Diego.

Avery added that the utility cannot hide the line underground because 500-kilovolt wires cannot be buried.

SDG&E has said it plans to change out those for 230-kilovolt wires -- which can be buried -- at a proposed Warner Springs substation. Company officials say that will allow them to avoid homes in Ramona and Rancho Penasquitos.

When told of that strategy, state park Commissioner Caryl Hart, during a recent hearing in Borrego Springs, wanted to know whether 230-kilovolt wires could be used in the park, too, and placed underground.

"Theoretically, it's possible; economically, it's not justifiable," Avery said, saying that could boost the project cost well beyond the current estimate of $1.3 billion. As if on cue, the lights at the Borrego Springs Resort flickered at that moment.

Park commissioners held the meeting to gather information, in case they are one day called to make a decision. It is the California Public Utilities Commission that will determine, by January 2008, whether the line can be built. But, in its current form, the project would require eliminating 73 acres of designated wilderness in the park, and the Park Commission would have to approve that change.

San Onofre State Beach

As for the Orange County toll road, going through San Onofre on the other side of the county line is the only way to avoid drilling through San Clemente neighborhoods at huge cost and with great outrage, said Jennifer Seaton, a spokeswoman for the Foothill-Eastern Transportation Corridor Agency. She said alternate routes for the final four miles of Highway 241, which would connect the road to Interstate 5, would displace anywhere from 112 to 263 Orange County houses.

Going around the park by moving the route deeper into Camp Pendleton Marine Corps Base won't work because that would interfere with Marine activities, she said.

The park is on the base, and the state operates it under a 50-year lease with the military that expires in 2021.

Whatever the reasons for the route, Goldstein, the parks foundation president, said the highway would wipe out much of the park's inland reach. But Seaton said it would not affect the beach, where 95 percent of park visitors go.

That doesn't matter, Goldstein said.

"This is an intact environmental resource that no question has an extraordinary beach," Goldstein said. "But it also has an extraordinary inland unit. It is a long and narrow canyon that comes down to the beach."

The park experience

Goldstein said the highway would swing within a few hundred feet of San Mateo Campground. It won't offer much of a camping experience with a 16-foot sound wall to look at, she said.

Seaton suggested that experience already is compromised by the noise and ground shaking triggered by nearby military training.

Zari, of Assemblywoman Walters' office, said, "It's not Yosemite. It's very, very rundown."

Highway opponents also worry that its construction will compromise the world-class waves at Trestles Beach, a popular surfing spot. Seaton said the agency's studies prove that won't happen.

Goldstein remains skeptical. "The truth of the matter is, we won't know until it is too late to fix it," she said.

Farther down the coast, the now-pleasant day at the beach in Border Field State Park is in danger of being compromised. As part of the nation's bid to fortify the U.S.-Mexico border, a fence is to be built through the park.

"You're going to have to go through a gate to get down to the beach," Goldstein said. "And we all know that a lot of people in San Diego County are not going to feel comfortable doing that when there are Border Patrol agents inside that gate and on the beach. That's not exactly going to be a pleasant recreational experience for people."

Nor, said Goldstein, is looking at power lines going to be a pleasant experience for Anza-Borrego visitors. The wires would follow Highway 78, the main artery through the park, for several miles. And they would cross next to Tamarisk Campground -- one of two park campgrounds.

"It's in the heart of the park," she said. "It's really going to be visible from everywhere."

Contact staff writer Dave Downey at (760) 740-5442 or ddowney@nctimes.com.