Will water spoil undeveloped Florida Keys?

At the beginning of the chain of islands that make up the Florida Keys lies an undeveloped area known as North Key Largo that is the home of several endangered and threatened species and is adjacent to America's largest living coral reef.

The area has remained in nearly pristine condition because it has lacked a large reliable drinking water supply. For years, only enough water has been piped to the area or produced through desalinization to support a population of no more than 3,000.

But recently the Florida Keys Aqueduct Authority, using a loan from the Farmers Home Administration, extended a pipeline along North Key Largo that can supply enough water to support more than 36,000 people.

Developers have flocked to the island with plans to build thousands of homes, which environmentalists say will destroy the habitat for such endangered creatures as the American crocodile and the Key Largo cotton mouse. And, they say, sewage and storm water runoff from an urbanized North Key Largo could upset the fragile balance that maintains Pennekamp Reef, America's only underwater park.

To counter that threat, the Florida Audubon Society filed suit in Miami's United States District Court Oct. 7 against the Aqueduct Authority, the Farmers Home Administration, and 11 developers, charging that the pipeline had been built without regard to environmental laws and asking that all development be halted until environmental impact studies could be completed.

Audubon president Peter Rhoades Mott says the Aqueduct Authority and the Farmers Home Administration showed ''a cavalier attitude'' toward environmental protection by building a water line onto North Key Largo without assessing its effect on the environment.

''The potential development that will use that water line will have an impact on the John Pennekamp Coral Reef State Park and on the endangered species that live in the area,'' Mott says. ''The Farmers Home Administration and the Aqueduct Authority did not take that into account. If development is to proceed, they must take into account the damage it can do to these unique resources.''

Jack Harper, director of the Aqueduct Authority, says his agency had complied with all requirements set by the Farmers Home Administration (FmHA) for getting a loan to build the pipeline. He says the pipeline was built with development in mind.

''You don't build things for today; you build them for the future,'' Harper says, explaining why the authority built a pipeline capable of supplying 3 million gallons a day for 3,000 people. ''The numbers we had at the time said we would need a pipeline of this size to meet the water demand in the near future.''

Charles Shuman, Farmers Home Administration administrator, declined to comment on the suit.

The Aqueduct Authority used a $63 million FmHA loan to build a pipeline, stretching all the way to the outermost island of Key West, to increase the amount of water available for all of the populated Florida Keys. What irritated the Audubon Society, however, was the construction of a spur pipeline as part of that project which greatly increased the amount of water available to the sparsely populated North Key Largo.

''The (Aqueduct Authority's) loan application did not disclose the limited extent of the then-existing water demand in North Key Largo, nor that the actual capacity of the proposed spurline would greatly exceed 3 million gallons a day of water supply,'' the suit read. ''The (Authority) knew or should have known that the proposed spurline would be a catalyst for substantial development in North Key Largo.''

Yet the FmHA did not comply with the National Environmental Protection act by completing an environmental impact statement on what effect the pipeline would have on North Key Largo's natural resources before it made the loan, the suit charged.

''North Key Largo is physically and biologically unique, and is one of the most environmentally sensitive areas in Florida and the nation,'' the suit read.

''In the ocean waters off the eastern coast of North Key Largo exists the most extensive living coral reef system in the continental United States. The coral reefs are able to live and thrive because of the pristine water quality of this protected Atlantic Ocean location, which provides a delicate balance of the various natural conditions required for living coral.''

Those reefs are part of the 23-mile-long Pennekamp State Park and National Marine Sanctuary, a magnificent ''forest'' of coral reefs which attracts scuba divers and boaters, and which parallels Key Largo. Mott says about 100,000 boats with divers and fishermen visited the Pennekamp Reef last year.

''It appears to me they are going to make a trade,'' Mott says. ''Those 36, 000 residents are going to be allowed to live there at the risk of destroying the reef which was visited by 100,000 boats.''