Two centuries ago, the aqueduct that funneled fresh water seven miles from the mountains to the San Buenaventura Mission was something of an engineering marvel -- a community lifeline built to an ancient Roman design by Chumash laborers under Spanish supervision.
Today, the last major surviving chunk of it is being considered for designation as one of the 11 most endangered historic sites in the United States.
Behind a locked chain-link fence on a gently sloping acre off Ventura's Canada Larga Road, the 100-foot-long, 10-foot-high ribbon of rock and cement is partly hidden by trees. Only a small, tattered paper sign marks the landmark, which is unknown even to some residents in the rolling ranchland nearby.
"It's just about invisible," said Kim Hocking, a senior county planner who for years has been involved in a quiet fight to keep the site intact.
His latest weapon comes courtesy of the National Trust for Historic Preservation, a Washington, D.C.-based group that lobbies to spare significant structures from blight and the bulldozer. Since 1988, the group has showcased various threatened treasures by listing sites from New Mexico's old adobe churches to New Jersey's Hackensack Water Works.
As a result, money has been raised, public indignation stirred, and, occasionally, a site restored. In 1994, McDonald's wanted to demolish an outlet in Downey that was one of the first hamburger stands operated by the McDonald brothers, who lent their name to the mega-chain. After the listing helped focus public attention on the pending demolition, McDonald's poured money into the restaurant, adding a museum and gift shop.
"Appearance on the list has led to just what was hoped for in many cases," said Dwight Young, a spokesman for the preservation group. "It's galvanized people at the grass-roots level to rally and keep historic places from being destroyed. In other cases, the negative value of being on the list has shamed public officials and private owners to do better by sites than they had been doing."
On the other hand, Young said, some of the highlighted historic places are about as endangered after their sudden fame as before. Only one -- Reno's stately old Mapes Hotel -- no longer exists. It was imploded and replaced by a parking lot in 2000.
Ventura's crumbling aqueduct will compete with about 100 other sites for inclusion among the 11 on the 2003 preservation list. The winners will be announced this spring.
"We seek variety," Young said. "We don't want them to be all old lighthouses, old houses, or old factory buildings. There's rich diversity in the American-built environment, and a diversity of threats that historic places face."
Last week, Hocking and volunteer Glenda Jackson let a couple of visitors in to see the fenced-off aqueduct, a huge, crumbling stonework with grass and even a sapling poking through its cracks.
In its roughly 200 years, the aqueduct has faced numerous threats, they said. They pointed to a gap caused by a rancher dynamiting it for easier access to his property. In 1978, it would have been razed by a developer if the county had not purchased the acre surrounding the aqueduct.
Now the biggest menace is natural. The aqueduct is perched on the bank of an arroyo that grows wider with each big storm. With another El Nino season predicted, Hocking, a staff member for the county's Cultural Heritage Board, is bracing for the worst.
Erosion has seriously damaged the aqueduct, he said. "It could just end up falling into the creek bed."
Hocking hopes to get $10,000 for an engineering study on minimizing storm damage to the site. He also envisions benches, a permanent sign and a roof over the aqueduct to keep rain from pooling in its crevices.
"We need some money to help save the site," he said. "If it makes the list, maybe it will catch the eye of a few benefactors."
Among other things, judges for the competition will consider the aqueduct's historic significance.
One of the oldest man-made structures in Ventura County, the aqueduct "represents the original colonization of the area," said Robert Lopez, a Moorpark College archeologist who has studied it exhaustively.
The early missionaries "knew immediately they had a problem," Lopez said. "They took water from the Ventura River to begin with, but at times it was so silty that it was unusable and at other times it dwindled to almost nothing."
In the late 1700s or early 1800s -- nobody knows for sure -- they began an ambitious project to tap San Antonio Creek, a stream that could range from trickle to torrent but that could be relied upon year-round.
The new aqueduct snaked through the mountains and down to the mission near Ventura's shore. Much of it was little more than a well-dug ditch. But in areas where the flowing water had to cross a canyon or climb a slope, the workers put up massive masonry structures. A covered tunnel inside narrowed the flow, allowing the force of the water to drive it uphill.
"That was one of the really nice engineering features," Lopez said.
At points where the water would rush downhill, threatening to overflow, workers slowed it with long S curves. Exploring what remains of some ditches associated with the system, Lopez found that at spots one edge was 10 centimeters higher than the other -- a way, he surmises, to keep water from splashing out.
Other California missions had similarly elaborate water-delivery systems.
Lopez said those systems were probably laid out by a Spanish hydraulics engineer named Pedro Colta, who drew his designs and building techniques from Vitruvius, a Roman architect who lived in the first century BC. A 1787 Spanish translation of a work by Vitruvius still sits in the library at the Santa Barbara mission.
"You can walk through Rome and find old aqueducts that are almost identical to this one," Hocking said.
In 1862, 60 consecutive days of rain permanently knocked Ventura's aqueduct out of commission. In the years since, chunks of the remaining masonry structures were blasted away for roads. Archeologists have found remnants of ditches and stonework between downtown Ventura and San Antonio Creek in Oak View.
An impressive remnant is the piece on the green, tree-shaded acre off Canada Larga -- a rock wall that resembles a ruin one might find in the hills of Tuscany.
When she isn't peering at hawks and mountain lions on the ridge above her nearby trailer, resident Lily McClintock looks after the site, chasing off interlopers and keeping the weeds down. "I see beauty there," she said. "Something in it calls out to me and I don't have the slightest idea why."