While a toxic heavy metal was found in groundwater near a Coconut Grove park, county officials said Thursday they need to test further to determine whether the amount poses a hazard.
In a 687-page study, consultants hired by the city of Miami to test Blanche Park reported that antimony, a chemical used in batteries, ceramics and paint, was found in two monitoring wells above target levels for groundwater cleanup. However, testing could not accurately determine the exact concentration of the chemical, said Miami-Dade County’s environmental chief, Wilbur Mayorga. That means, he said, water must be further tested to determine the exact amount of antimony, which can cause lung and heart disease, in the groundwater.
“The report says clearly that the antimony was detected, but we don’t know exactly, with accuracy, at what concentration,” he explained. “It cannot be ignored. But it needs to be resampled to confirm.”
In a letter that the county provided Thursday, Mayorga ordered the city to retest the well within 45 days.
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Groundwater and surface waters typically have concentrations of antimony at 0.2 parts per billion, said University of Florida associate professor Gurpal Toor. In contaminated areas, that number can soar to 10 to 20 or more (parts per billion), he said.
“It is naturally alarming to see that number,” he said. But it may be that the elevated level is isolated to the contaminated soil. And because South Florida’s drinking water comes from the aquifer hundreds of feet deep, it may not necessarily be a risk, he explained.
In addition to retesting the wells, Mayorga ordered the city to conduct additional sampling to the north, south and west of the playground to define the boundary of solid waste believed to be ash. And because high amounts of antimony, arsenic, barium, copper, iron and lead were found in a single exposed area at the southwest corner of the property during last month’s testing, the city must remove soil or cap it.
Mayorga also said dioxins found in three locations fall below what state health workers consider a threat.
While levels of arsenic found in the dog park are not considered dangerous, Mayorga asked the city to firmly map out boundaries where buried ash was found in the southwest corner.
Contamination at the park at 3045 Shipping Ave. was first discovered in August after the city widened testing triggered by tainted soil found at an old incinerator site, now fenced in, about a mile away. Blanche Park was first purchased by the city in 1943 to dump ash and converted to a park in 1962. No cleanup of the soil was ever done.
The park has remained open because artificial turf, which the city began installing in 2010 and completed this year, covers the park. Heavy metals generally have to be ingested to be toxic, so officials believe the turf provides a protective cap.
The city has already begun additional testing to plot the boundaries of the buried ash and plans to truck away dirt from the one exposed spot, said Assistant City Manager Alice Bravo.
“It’s a really small area right at the curb, on the corner,” she said. “There’s some drainage area, so we’ll probably remove and replace [soil] rather than try to pave over it.”
The city removed dirt from a larger area used for parking and paved over it in August, after initial tests. Both paving and artificial turf provide the necessary barrier to prevent exposure to the metals, which were found near ash underground.
The city now has 30 days to come up with a plan for addressing the contamination and 45 days to complete additional testing.
The city is also continuing to draft a testing plan for Merrie Christmas Park, where toxic metals have also been found. The much larger park, which covers more than five acres and is not covered with artificial turf, has been closed and fenced off since late September while the city comes up with a plan for testing.
Bravo said the city’s consultant sent an initial sampling plan to Mayorga’s office and is now revising it.
“We’re definitely tracking all these dates so we don’t fall behind,” she said.
In addition, the city has trucked away a 10-by-10 foot section of contaminated soil at the site of the old incinerator, now a fire training facility, and replaced it with clean dirt.