County wells closed near Miami International Airport due to chemical concerns

Miami-Dade has closed three wells near Miami International Airport and is monitoring three others after water from them exceeded federal guidelines for chemicals tied to fire-fighting foam and other potential contaminants.

The drinking water produced by the county plants fed by the underground wells hasn’t triggered health concerns, with levels from the plants still well below standards set by the federal Environmental Protection Agency, said Doug Yoder, deputy director of Miami-Dade’s Water and Sewer Department.

The problem lies in a portion of the wells that supply the Hialeah and Preston water plants in the Hialeah area north of MIA, Yoder said, where the foam has been used for years in training and rescue operations.

“When the foam was used and then washed off, it went into the ground and into the storm drains and into the groundwater,” Yoder said. “It’s pretty apparent the airport is certainly one location where there has been a problem.”

Yoder said the county is considering installation of filters or other treatment options that could cost tens of millions of dollars to build. There’s also the option of treating the source of the problem at MIA and finding the contamination causing the chemical “plume” seeping into groundwater.

“It all really needs to get analyzed to see what is going to be the most cost-effective way for managing this problem,” he said.

The ongoing response to groundwater contamination has been under way since the summer, and revealed indirectly in legislation filed this month tied to a potential county lawsuit against the chemical companies that produce the substances.

Three of the 23 wells serving the Hialeah plant were closed in August after worrisome readings for perfluoroalkyl and polyfluoroalkyl substances, a family of chemicals best known as PFAS.

They’ve been a problem for water systems in Florida and across the country, as regulatory agencies address growing concerns about health risks tied to the chemicals.

Known as “forever chemicals,” PFAS are found in everyday items such as fast-food wrappers, Teflon cookware and stain repellents in upholstery.

Their highest concentrations come in more industrial uses, such as fire-fighting foam often used at airports and military facilities where large amounts of fuel are present. Extensive exposure to the substances has been linked to higher risks for cancer and birth defects, though the chemicals are common enough that most people have been exposed to them.

The EPA does not yet have a firm rule on how much PFAS can be in drinking water, but maintains a “health advisory level” of .070 parts per billion. Some health advocates and researchers see that threshold as too high, and 10 states have implemented or are preparing to implement their own standards.

Florida does not have its own standard, and Miami-Dade said it uses the EPA guideline for its yardstick on PFAS contamination.

The well problems have thrust Miami-Dade onto a growing list of governments managing PFAS contamination and considering lawsuits against chemical companies to pay for the cleanup. Law firms are hiring lobbyists to encourage local and state governments to sue Dupont, 3M and other manufacturers. Michigan filed its suit this month.

PFAS contamination in drinking water is widespread and detectable in all water supplies that use surface water in the U.S., according to clean water advocacy group Environmental Working Group. In a study last year, Environmental Working Group concluded that more than 610 drinking water sources in 43 states contained potentially dangerous levels of PFAS.

Two of the closed wells for the Hialeah plant registered about double that EPA standard in the most recent round of tests in November, according to county records. One recorded a reading .184 parts per billion, and one .182 parts per billion. A third measured .124 parts per billion.

The Hialeah regional plant has enough water coming from the remaining wells to continue supplying businesses and homes connected to the facility. It’s one of the county’s four main water plants, and is connected to pipes that serve customers in the northern portions of Miami-Dade.

While the wells showed problematic readings, drinking water from the Hialeah test was well below EPA levels, about .04 parts per billion, according to a county summary. The nearby Preston plant, also linked to some wells with higher chemical readings, tested even lower, at .026 parts per billion.

Along with the three wells, Miami-Dade is studying next steps for three wells that registered PFAS levels just above the EPA standards. Because of where those wells sit relative to other wells, engineers are concerned shutting them down could cause the chemical plume to follow the natural flow of underground water south and contaminate more wells, Yoder said.

He said the agency expects to complete groundwater modeling in about a month and then decide what to do for those three wells. One that serves the Hialeah plant registered .091 parts per billion in the latest tests, and two that serve the Preston plant measured .077 and .079, just on the edge of the .07 EPA threshold.

Once the results come in, Yoder said, “it may make sense to shut those wells down.”