Man-Made Wetlands’ Future Starts to Dry Up : Despite initial success, biologists say a site near the Simi Valley-Moorpark freeway interchange will be choked by silt within 20 years.

When the concrete curve connecting two key freeways tore right through ecologically sensitive wetlands along the Arroyo Simi, Caltrans engineers told conservationists not to worry.

A new, larger patch of wetlands would be created out of nearby pastureland to make up for the six acres of damp grasses and cottonwood trees lost at the spot where the Simi Valley Freeway meets the Moorpark Freeway.

It was an expensive undertaking that carried a price tag of nearly $1 million, but state regulators considered the effort important, since 90% of state wetlands had already been lost to development.

Five years later, the wetlands east of Moorpark appear to be thriving with golden grasses and myriad wildlife.

But there are ominous signs of trouble.

Many of the cottonwoods are covered with a type of rust that indicates stress. The native grasses have not taken hold as biologists had hoped. And most important, the stretch of wetlands is losing its most essential element: water.

A system built to take water in from the nearby Arroyo Simi and carry it to the wetlands was poorly designed, California Department of Transportation biologists say. Nearly four feet of sediment has built up in five years, a condition that will gradually choke off the water supply to the wetlands.

Within 20 years, biologists say, the 18 acres will be wetlands no more.

“Like most biologists in the state and nation, I firmly believe that creating wetlands should be a last-ditch alternative,” said Paul Caron, a Caltrans biologist who inherited the project after it was built. “A lot of people seem to think it’s easy to do. But it is extremely detailed and complex.”

Standing on a bridge that crosses the Arroyo Simi, Caron pointed to the chaparral and brush on the dry hillside behind the man-made wetlands.

The wetlands would have had a better chance of survival had they been built inside the curving elbow of the water, rather than on its backside.

“There is a reason there is nothing back there,” he said. Caron said the water delivery system could be fixed with an infusion of as much as $100,000. But in current economic times, no money is forthcoming for the project, which Caltrans considers complete.

“Our obligation to this project is essentially over,” he said. “We’ve satisfied our mitigation requirements.”

Caltrans attempted to create the wetlands to make up for land sacrificed for the connector. Before Caltrans built the concrete curve that sits 100 feet above the arroyo and train tracks below, traffic from both freeways dumped onto city streets in Moorpark.

The community strangled in the black diesel smoke of tractor-trailers as well as exhaust from cars and commuting traffic.

National policy signed into law by President Bush said there would be no “net” loss of wetlands. The U.S. Army Corps of Engineers granted Caltrans permission to build the freeway on the condition that it replace the wetlands nearby.

However, creating wetlands proved more difficult than believed at the time. The practice is still experimental, said Cat Brown, a U.S. Fish & Wildlife Service biologist stationed in the Ventura field office.

“Creating an ecosystem is extremely difficult,” she said. “There are billions and billions of bits of information in a wetlands. How can we figure out what they are or even figure out what the most important ones are?”

Since the 2.2-mile connector was conceived, Caltrans has taken a new tack to most of its wetlands mitigation projects. Now, rather than trying to create a wetlands on adjacent parcels, Caltrans and other developers can use a “wetlands bank” to give up some acreage and help restore or create wetlands elsewhere.

Approaching wetlands conservation as a collective effort rather than saving small parcels piecemeal is the strategy for the future, said Ted Durst, regulation program manager for the South Pacific region of the Army Corps of Engineers.

“It makes more sense to preserve a watershed rather than save the same amount of acreage by putting a chain-link fence around a parcel in the middle of a parking lot.”

While there is a park-and-ride lot near the 18-acre wetlands south of the Simi Valley Freeway and just east of the connector, the wetlands seem remote from the traffic barely 10 or 20 feet into the vegetation.

The soil, a type of clay that is dry on the surface and cracked into shapes that look like puzzle pieces, is moist and damp only four inches below. The din of the freeway is almost drowned out by the sound of cottonwood leaves fluttering in the steady breeze and the music of warblers and other songbirds that lilts in the air.

As the brush grows more dense farther into the wetlands, insects are prevalent and the air becomes noticeably humid. A small lizard scurries past Caron’s feet.

“It’s called a microclimate,” Caron said. It’s part of what makes a wetlands ecosystem so complex. In addition to acting as a natural filter for water, wetlands also attract and support plants and wildlife that grow in no other type of ecosystem.

Three years ago, biologists considered the wetlands project a success with 23 bird species using the area. Even an endangered least Bell’s vireo was seen there. But since then, silting problems have become evident.

Caron points out a willow trunk where the waterline has been replaced by built-up silt. Nearly four feet of sediment has been deposited near the outflow of the Arroyo Simi since it was built not quite five years ago.

“That’s significant,” Caron said, “though the rate of silt buildup will slow with time.” Still, he said, in 20 years or less, the area will convert to a different type of habitat not suitable to songbirds or waterfowl.

“It has a lot of biological resources, but the focus was to create a wetlands, and that eventually will not be the case,” he said.

Regardless of whether the area stays wetlands or becomes a habitat known as uplands, which supports plants and animals that need less water and shade, ecologist Muthena Naseri is happy to have it.

Naseri, a professor of environmental science at Moorpark College, uses the parcel for student field trips.

“It’s a wonderful outdoor lab for us,” he said. “I call it a nature center because a wetlands by definition has water year-round. But if someone gives you a limo and calls it a compact, who cares?”

The parcel will eventually be handed over to the college to manage and maintain. The area is also a favorite spot for some local bird-watchers and nature lovers.

“I’ve seen warblers, a hawk’s nest, a deer and a few coyotes and bobcats,” said Marc Bolinger, an amateur birder from Simi Valley. “I went looking for the bobcats the next morning and I found some baby coyotes.” Bolinger also sighted herons, woodpeckers, owls and a black-shouldered kite.

“There are road runners everywhere and all kinds of cool stuff,” he said. Back out at the site last week, Caron said he believes it is possible to create working wetlands with enough money and the right design. But for now, questions persist over how to create wetlands.

“The answer is still a long ways down the line,” Caron said.