PLANT CITY – Part of the Coronet Industries site might be so contaminated that it might not be safe for future use, the county’s top environmental regulator said.

Testing will determine whether the holding ponds and the phosphate processing factory can be cleaned up enough, said Rick Garrity, director of Hillsborough County’s Environmental Protection Commission.

During a speech Thursday to a Plant City group, Garrity said he doubts that some of the property could be salvaged. He said he could make that call only after more testing.

The future of the site has become a top concern since Coronet announced it plans to cease operations March 31, Garrity said Thursday. Pollutants found in large concentrations on the site include arsenic, fluoride and boron.

Coronet covers about 750 acres, not including a 200-acre golf course on its property.

Garrity said he is encouraged that the new management of Coronet is going to “do the right thing” and work to ensure that pollution doesn’t contaminate the area. He said he spoke with new Coronet Chief Executive Officer David Denner and was impressed with his pledge to cooperate with regulators.

The options for polluted sites include cleaning up the contamination or putting an impervious cap over it to make sure rain can’t reach it and wash it into groundwater, he said. Old garbage dumps, for example, are sometimes capped and never used for other purposes, he said.

After the plant shuts down, a crew will remain to maintain the site. Coronet spokesman Tom Stewart said the future of the site is unclear.

The company is working with government regulators to decide what’s best, to either clean up the site or to cap it.

“It’s a point and it’s obviously something that everybody is thinking about, including us,” Stewart said.

At Coronet, a partial solution may be to build a clay and earthen barrier between a large holding pond and some nearby houses. Many wells serving those houses along Cason and Gentry roads are polluted, and the state suspects Coronet is to blame.

The barrier would keep contaminated water from flowing from the pond into shallow wells in the neighborhood, he said.

State Department of Environmental Protection spokeswoman Merritt Mitchell said her agency isn’t sure what remediation will be required.

Garrity said the federal Environmental Protection Agency will play a major role in the future of the plant. EPA was brought in partially because it has the legal clout to take action against the two Japanese companies that are the major shareholders in Coronet Industries Inc., he said.

An EPA spokesman couldn’t be reached for comment. EPA and state officials have made surprise inspections in recent months at Coronet to take water and soil samples and review company records.

Garrity made his comments in a speech to members of the Plant City Downtown Luncheon Club. He gave a similar talk earlier in the day to the Brandon Kiwanis Club.

Garrity’s other major points included:

* Coronet, founded in 1908 as a phosphate mining company, is old and poorly maintained. During one visit, inspectors found that some of the air pollution control equipment was held together with roofing material and ropes, he said. Air pollution will cease when the plant shuts down.

* A number of law firms are pursuing civil suits against Coronet. One Miami firm, for example, has set up its equipment in the Environmental Protection Commission office in Tampa and is scanning in every document with the name “Coronet” on it.

* Many of the wells around the plant at 4082 Coronet Road are shallow, 25 to 30 feet deep, and are vulnerable to pollution. The best solution is to supply homes around the plant with public water. The county, city of Plant City and other agencies are working to extend city water lines to the neighborhood.

Reporter Dave Nicholson can be reached at (813) 754-3765.