After years of staying mostly quiet about a cancer-linked chemical in county drinking water wells, Seminole officials have launched an aggressive effort to get the polluters to clean up what they say is rapidly expanding contamination.

Lawyers hired by the county say the concentration of 1,4-dioxane in the underground water supply —while currently posing no threat to residents — will grow to dangerously high levels in coming years as a toxic plume originating from a defunct telecommunications plant continues its spread west of I-4 into the northwest side of the county. This will come as Seminole’s population and demands for water will grow.

That’s according to a legal petition filed this month in the wake of a state Department of Environmental Protection report in February that for the first time definitively laid the blame for the contamination on General Dynamics, Siemens and MONI Holdings, owners and former operators of the factory site off Rinehart Road.

Seminole agrees with the DEP’s general findings, which are based on extensive chemical fingerprinting of wells tapping the Floridan Aquifer.  However, the county says the state report — done in coordination with the Florida Geological Survey — does not go far enough in mandating that the global companies pay to clean up the mess on Seminole’s side.

Meaningful cleanup could cost tens of millions of dollars, and might involve construction of a new water treatment plant for west county residents.

The contamination of the region’s groundwater was the subject of a 2023 series by the Orlando Sentinel, Toxic Secret, which unveiled little-known tests that had found the plume of 1,4-dioxane underground near wells in Sanford, Lake Mary and unincorporated Seminole County. Earlier this year, the Sentinel revealed that state officials had finally laid the blame on the plant, long suspected as the culprit.

In Seminole’s new legal filing, its powerhouse attorneys from the Florida-based firm GrayRobinson say 1,4-dioxane in the future will reach concentrations of 50 parts per billion in the most heavily affected wells – nearly 143 times greater than the EPA’s recommended safe levels — if it is not cleaned up. It’s the first time any government has stated what officials anticipate the level of contamination of 1,4-dioxane will be in the future, although the county cited no source for the estimate in the filing and would not respond to questions.

The contamination “presents health concerns and threatens the public health and welfare of the county’s residents and water customers,” according to the county’s April 4 petition for an administrative hearing sent to the DEP. “To date, remediation efforts have fallen woefully short of removing the contaminants and preventing the spread of the plume. … The spread and intensity of plumes will only get worse.”

Such a hearing is similar to a court proceeding where evidence and testimony are presented in front of an administrative law judge, who later delivers a decision.

1,4-dioxane is a synthetic chemical — commonly referred to as a forever chemical — that was long used in solvents in a variety of industrial and manufacturing facilities. Once it’s released into the environment — such as poured into the ground — 1,4-dioxane is difficult to separate from water and remove it from aquifers.

The chemical is considered by the U.S. Environmental Protection Agency as likely to cause cancer. But it is unregulated, and there is no legal limit of how much can be in drinking water.

Even so, state and federal health agencies advise public utilities to limit 1,4-dioxane to 0.35 ppb.

Beginning in the late 1960s, General Dynamics, Siemens and its subsidiaries used solvents with 1,4-dioxane along assembly lines at the factory tucked between Rinehart Road and Interstate 4. MONI Holding LLC held the financial assets of the factory.

Dozens of former workers — many sick with cancers — described in lawsuits and to the Sentinel that heavily rusted storage drums filled with used solvents were left outside and leaked.

In 2013, the U.S. Environmental Protection Agency directed utilities nationwide to test for 1,4-dioxane and other unregulated contaminants. In Seminole County, the tests showed varying levels of the chemical in the tap water of Sanford, Lake Mary and the county’s northwest quadrant, including along Markham Woods and Heathrow.

The three governments then significantly reduced levels of the chemical by decreasing the amount of water pumped out of the ground in that area of the county by capping wells or reducing withdrawals. Lake Mary — whose water wells are closest to the factory and showed the highest levels of contamination — quietly made a deal with the three companies for the construction of a new advanced treatment plant that went online in 2021 and rids its water of nearly all 1,4-dioxane.

However, there was no clear warning to the public until the Sentinel’s 2023 stories.

Last year, Sanford filed a lawsuit against the companies after spending the past decade calling for state intervention. Even then, Seminole remained mostly quiet, although it finally set up an information page on its county web site that shows monthly levels of 1,4-dioxane at five water treatment plants, long after that information was first promised.

In March 2024, tests showed 0.16 ppb, according to the web site. In June 2024, the levels crept up to 0.23 ppb. But last month, the levels decreased to 0.15.

Commissioner Lee Constantine said this week that County Attorney Kate Latorre, working with GrayRobinson lawyers, decided to file the petition for the administrative hearing after consulting with commissioners.

“I believe it is our responsibility to protect the citizens of Seminole County,” Constantine said Thursday. “All of the commissioners have been very supportive of making sure that we minimize the threat to our citizens and go after those who created the problem.”

County attorneys said Friday, in response to detailed questions from the Sentinel about their legal filing, that they could not comment on “pending litigation.”

Jake Varn, a former director of the state’s DEP and an attorney now assisting the city of Sanford, said with Seminole, Sanford, Lake Mary and the state joining forces against the polluters, there will be an eventual cleanup.

“It will happen, and it’s just a question of when,” he said Thursday.

Staff writer Kevin Spear contributed to this report.