RUSKIN - Outside William Casey's construction trailer, earthmovers and dump trucks rumble across a rocky desert that will someday be wetlands - he hopes.

Ten years in the making with three years to go, the 160-acre site is being bulldozed into Hillsborough County's first wetlands mitigation bank. When it's finished, developers that want to destroy wetlands will be able to compensate for the environmental damage by buying credits in the form of wetland acreage in Casey's Tampa Bay Mitigation Bank.

The bank's 111 credits would cost about $100,000 each.

Developers and government regulators see the bank as the future of mitigation in a county that is becoming increasingly urbanized and where developable land is getting more scarce. But environmentalists are uneasy about the concept, saying it will encourage developers to dredge and fill wetlands, rather than try to build around them.

Up to now, the county's wetlands division has pressured developers to avoid wetlands - whose benefits include flood control, water purification, groundwater recharge and wildlife habitat - unless they have no viable alternative. Next month, however, the county commission could vote to abolish the division, leaving wetlands protection to state and federal regulators. If that happens, environmentalists fear developers will have an easy path toward buying credits that enable them to fill wetlands on their developments.

"When you're destroying wetlands in one section, how do you fix that by creating wetlands three or four or five miles away?" said Lutz environmentalist Denise Layne. "This doesn't work."

A Big Investment

Casey, a fifth-generation Floridian, is fond of folksy adages such as "You can't sell something from an empty wagon." It's his way of saying he can't start making money on the mitigation bank until it's completed.

"We've been in the project for 10 years and haven't sold a nickel's worth," he said.

For most of his life, Casey made a good living mining shell to sell to road builders. The empty shell pits became lakes, and Casey developed lots to sell on the water. Then a family friend who works as an environmental engineer got him interested in wetlands mitigation banking.

He thought he had a good spot for a bank on former agricultural land near Cockroach Bay. The elevation of the site was too low for houses, and there were degraded wetlands on the property that could be restored. Casey could use his earthwork experience to sculpt the higher land into terraces so the freshwater wetlands would drain slowly down to estuarine wetlands and saltwater marshes near the bay.

He assembled a team that included an environmental scientist, a civil engineer and a man who had mitigation bank experience on Florida's east coast. Casey estimates the team has put $1 million in sweat equity into the project based on what they would make for their services in the marketplace. When completed, the project's cost will approach $2.5 million.

Casey's project embodies all the promise and potential pitfalls that have characterized the industry since federal guidelines for mitigation banks were published in 1995.

On one hand, the project has undergone intense scrutiny by federal and state agencies to make sure it successfully re-creates wetlands functions that are being destroyed elsewhere. Casey said the involvement of so many agencies delayed the issuance of a mitigation bank permit for eight years.

But Casey and his partners are taking a gamble because most of the site was never a wetland. Although they are taking care to get the bank's topography, vegetation and water flow right, similar "created wetlands" often have failed because of man's limited ability to mimic nature.

"The success of creating new wetlands and having them perform the same functions that the old ones do is quite spotty," said Peter Frederick, an ecology professor at the University of Florida. "I think there is a great deal of risk in doing that."

Beverly Birkitt, an ecologist and Casey's partner, said there are degraded wetlands and former salt marshes on the property that will be restored. Andrews Creek, now dammed, will be reconnected to Cockroach Bay. That fits the accepted blueprint for successful wetland mitigation.

The tricky part of the project, however, is the freshwater wetlands, which will be constructed where Casey's machines are harvesting shell. The plan is to use groundwater from the upper aquifer to keep the wetlands wet.

"There are stringent requirements for the freshwater portion of the site," Birkitt said. "We can't release any credits until we determine if the freshwater mitigation is successful."

Large-Scale Benefits

Federal and state agencies have endorsed mitigation banks as an appropriate way to replace lost wetlands, and they are proliferating. A study by the Environmental Law Institute found there were 46 banks operating nationwide in 1993. That number had risen to 330 active banks by the end of 2005, the most recent figure available.

In Florida, 47 banks have been permitted. Thirteen are in the Southwest Florida Water Management District's jurisdiction, which includes Hillsborough, Pasco, Pinellas and Polk counties. Only about 665 acres have been mitigated in banks in the district's jurisdiction.

That number is sure to grow, said Clark Hull, who oversees mitigation banks for the district. The reasons are that developers like the concept and regulators think the banks often provide a better ecological benefit than smaller, isolated mitigation projects.

"It can do away with what would be a junky little wetland in the corner of a shopping center that's not looked after as carefully as it should be," said Rick Garrity, executive director of the county's Environmental Protection Commission. Garrity has proposed working with state agencies to encourage mitigation banks in all of the county's watersheds.

Mitigation banks also give local and state governments a way of preserving environmentally sensitive lands without buying them. For instance, Casey's mitigation bank is on land targeted for conservation in the Tampa Bay Estuary Program's 1996 master plan.

Mitigation bank investors often seek out those areas because they are easier to get permitted. The bankers agree to put a permanent conservation easement on the property, so it can't be developed or sold for development. After all the credits are sold, the land can be turned over to a local government or a private conservation group.

Other benefits: The wetlands in the bank are functioning well before they are sold for credits so that other wetlands can be destroyed. That overlap is a net ecological gain for the watershed, Hull and others said.

"You have a higher assurance of success because it's already in the ground," Hull said. "The other thing is, until your impacts occur, you're already in the black. You're ahead of the game because you have the mitigation in place before the impacts ever come along."

Some Areas Will Suffer

But some environmentalists fear the banks will speed marsh destruction in Hillsborough County, where an estimated 40 percent to 50 percent of historical wetlands are gone. Developers will choose the easy route of buying the credits, skeptics say, rather than employing engineers and biologists in time-consuming wetlands mitigation projects.

The result will be a transfer of the benefits derived from the wetlands - from the area around the development to the rural areas surrounding the mitigation banks.

"There is no question that it's frustrating that we set up this institution where we agree to get rid of some wetlands and save others," Frederick said. "To me it always seems a little sleight of hand."

The water management district requires that mitigation banks sell credits only to projects that are in the same watershed. For instance, Casey's bank will service only areas that drain into Tampa Bay. The service area doesn't include rivers that flow into the Bay; they are separate watersheds.

Still, having a service area that surrounds Tampa Bay means a developer can destroy wetlands in northwest Hillsborough or eastern Pinellas County and mitigate the damage by buying credits in Ruskin. The distance between the two could be more than 20 miles.

"The neighborhood where the wetland is damaged suffers flooding and pollution of their lake or river," said Mariella Smith, a Sierra Club member from Ruskin. "But they don't get the benefit of the mitigation when the developer purchases part of a wetlands somewhere else."

Also lost when benefits are transferred is wildlife that depends on small, isolated wetlands. Tree frogs, for instance, breed in small wetlands, then spread to higher elevations, Frederick said.

A possible solution to the long-distance transfer of benefits is breaking up banks into multiple projects, said Mark Rains, a geologist and wetlands specialist at the University of South Florida.

"Somebody identifies what the problems are in the basin. They identify what to do about those problems. Then they identify what sites can be restored," Rains said.

'A Very Good Legacy'

Sporting a straw-weave hat, 62-year-old Casey rambles through thick brush and brambles like an Eagle Scout. He uses a long global positioning system device as a walking stick when he's not checking elevations on the mitigation bank land.

Although he has worked outdoors his whole life, Casey never paid much attention to wildlife. Now he knows an ibis from a snowy egret.

"I'd seen sand hill cranes before, but I never really noticed them until now," Casey said. "They are such a beautiful bird."

Casey knows there are people who disagree with the mitigation bank concept. He said he'll never change their minds. In his heart, though, he knows the project will benefit the environment.

"I feel this is going to leave a very good legacy," he said. "And I feel over the long run it's going to be a profitable venture. It's just going to be a slow profit."

Reporter Mike Salinero can be reached at (813) 259-8303 or msalinero@tampatrib.com.

WHAT'S NEXT

The Hillsborough County Commission will meet as the Environmental Protection Commission on Thursday to consider a plan to save the EPC wetlands division. The commission took a preliminary vote to eliminate the division last month.

Commissioners said the division performs the same functions as state and federal agencies and is an unneeded expense at a time when the county needs to cut budgets. But they have agreed to listen to a plan presented by EPC Executive Director Rick Garrity that promises to cut the division's annual budget by $375,000 and speed wetlands permitting.

A final vote on whether to keep the division is expected in August.

HOW BANKS WORK

• Investors with available land apply to the appropriate state and federal agencies for a permit to build a wetlands mitigation bank.

• After the permit is issued, the investors start work on the bank with oversight from government regulators. The regulators allow the investors to start selling credits only after they have shown they have met standards for water flow, soil types, drainage and vegetation.

• Government regulators allot credits to the bank based on acreage and the value of the ecological functions the wetlands perform.

• Developers that need to destroy wetlands for a project ask government regulators for permission to buy credits in the mitigation bank. The regulators decide how many credits are needed to make up for the lost wetlands functions.

• The developers pay for the credits and fill the wetlands.