Three residents of rural Southwest Miami-Dade and three leading environmental groups have sued the county to stop an expansion of rock mining on agricultural land outside the urban development boundary that the plaintiffs say was approved in violation of state law.

The suit, filed in December in Miami-Dade Circuit Court, is the latest sally in long-running conflicts among homeowners and environmentalists on one side and companies that use blasting to extract limestone rock used in construction from a vast network of open mines on the western end of the county.

Property owners have long contended that the blasting damages homes and swimming pools and scares farm animals, while environmentalists raise concerns about the mines' effects on water quality on farmlands and in the adjacent Everglades National Park.

In this case, say homeowners Andres Fernandez, Angel Santos and Charles Boyd in their complaint, the expansion would bring mining operations by Cemex Construction Materials, a Florida subsidiary of the giant Mexican cement company, either within a few hundred feet of or right up to their property line.

The planned mine would create a 172-lake excavation pit on a 400-acre property owned by developer Masoud Shojaee, principal in Shoma Homes.

The property sits west of Krome Avenue at about Southwest 90th Street and is within several hundred feet of the Everglades National Park boundary.

The homeowners allege the newer mine would only worsen longstanding problems from an existing Cemex mine nearby that include cracks in their homes and pools, bright lights illuminated around the clock that make sleep difficult, and blasts that have forced them to give up raising large animals frightened by the noise.

Water seeping into their property from the mine also clogs and damages irrigation equipment, they say.

The county commission approved the mine on a 10-3 vote in October, granting Cemex a special use permit so that the industrial operation could occur on land zoned for agriculture.

The suit, filed by attorney Robert Hartsell, contends that in doing so the commission violated the county's own comprehensive development plan, which has set aside that land exclusively for agriculture or compatible uses.

According to the suit, that means the county has violated state law, which requires localities to abide by their comprehensive plans.

A county spokeswoman said she had no information on the suit late last week. Kerri Barsh, an attorney representing Cemex, which is not a party in the lawsuit, declined to comment.

The special permit also amounts to an end run around restrictions on where rock mines can operate, Hartsell said in an interview. The county has delineated a large special district in the area for such mines, but this new operation would sit outside it. County planners, who opposed the expansion, said there is ample mining capacity inside the district for years to come."

Here they are permitting rock mining outside the special district, which makes no sense if they already set aside an area for it,'' Hartsell said.

The environmental groups Tropical Audubon, 1000 Friends of Florida and Clean Water Action, meanwhile, say the mining expansion threatens water quality in the area and would destroy valuable agricultural land. Audubon director Laura Reynolds said in an interview that such mines could suck water from the Everglades at a time when billions of dollars are being spent to retain more water inside the park boundaries.

"It's short-sighted,'' Reynolds said. "We want to keep this buffer in place for the park. Once you dig a hole, that's it. You can't use the land.''