THE LINK BETWEEN PHOSPHATE MINES IN FLORIDA AND SINKHOLES
Dr. Constance Dogood
Aquifers and Sinkholes
Sinkholes are not unique to Florida, but Florida certainly ranks highest in the nation. That’s because geologically speaking, Florida is very different (and hundreds of millions of years newer) than the rest of the US. Underneath a thin layer of dirt, sand, and clay, the entire Florida peninsula has a sub-surface that is essentially a porous plateau of carbonate rock (primarily sandstone and limestone) that was formed over many millions of years by marine fossils when the area was a warm, shallow sea.
Some 1,000 feet thick on average, this “porous plateau” is not solid, but rather, contains numerous caverns and watersheds that store and transmit groundwater, in what is referred to as the “Floridian aquifer system.” Encased in a body of saturated rock, these permeable aquifers contain enough drinking water for millions of Florida citizens. This landscape contains almost all of the fresh water resources for the population of north-central Florida.
However, the ground sediments that cover the aquifer systems are delicately balanced by ground-water fluid pressure. This back pressure from the water below ground actually helps to keep the surface soil in place. Sinkholes occur when slightly acidic groundwater dissolves the hollow carbonate rock beneath the soil, creating a large cavity. When the overlying ceiling can no longer support the weight of the soil (and whatever is on top of it), the earth collapses into the cavity. Even the saturation of the ground from excessive rainfall can make the sand layer heavier, and trigger a sinkhole.
Sinkholes can vary from a few feet to hundreds of acres. Examples include the 20-foot wide sinkhole that inhaled 37-year-old Jeff Bush as he slept (a sinkhole swallowed his entire bedroom in Seffner, Florida in 2013). Another sinkhole swallowed up an entire city block, including nearby streets and five Porsches at an auto body shop in Winter Park, Florida in 1981.
Although sinkholes are often regarded to as “natural” phenomena, they are exacerbated by alterations in the delicate balanced between ground-water and surface materials. Both changes to the land surface and groundwater pumping that lowers the water table (from activities like mining) are catalysts for sinkholes. According to the Florida Office of Insurance Regulation, the annual number of sinkhole claims has more than tripled in the past 10 years. The demand for water from Florida’s rapidly growing population of over 20 million people suggests that this trend will only continue.
The Phosphate Industry
Phosphate refers to rock that contains phosphate ions, and is mined to obtain phosphorus. An essential plant nutrient, phosphorus is never found as a free element but is present in fossilized mineral deposits and must be mined. China, Morocco and the United States account for about 70% of world production, the bulk of which is for use as an agricultural fertilizer. Florida contains the largest known deposits of phosphate in the US because of the marine fossils that make up its unique sub-surface, and phosphate based fertilizer is one of Florida’s leading export commodities.
Indeed, a blanket of phosphate deposits covers much of the Florida peninsula. In the areas that are considered economical to mine, the “matrix” layer (which consists of phosphate rock, clay, and sand), averages between 12 and 15 feet thick. However, this is buried well below the surface or “overburden” as it is referred to by the phosphate industry. The Unites States Geological Survey (USGS) believes that phosphate mining removes up to 100 feet of “overburden” despite the fact that it holds Florida’s real treasure, the aquifers that hold our water. Ironically, fresh water resources in Florida are much more valuable than the agricultural fertilizer that is being mined.
However, phosphate officials are “permitted” by the state of Florida to remove everything within this “overburden” (including freshwater resources), to get to the phosphate rock that they seek. This process is done in enormous tracts of land, turning the environment into something that resembles more of a lunar landscape. The strip mining process can create sinkholes simply by removing significant amounts of weight to get to the “matrix” layer that contains the phosphate rock.
Sinkholes not only occur near phosphate operations, but can occur miles from phosphate mining plants due to over-pumping from local aquifers. The local aquifer becomes starved for water, and in turn, water from other local aquifers now flow to the starved aquifer until the land above those aquifers becomes unstable, and sinkholes can occur at any time.
The Real Threat
Phosphate mines excavate raw pebble phosphate (the “matrix”) which contains a number of chemical impurities, including naturally occurring uranium at concentrations of approximately 100 ppm. This by-product (phospho-gypsum) has a far denser source of radioactive materials than would occur naturally, and its use is banned in most situations. In fact, the Department of Environmental Protection does not allow the phosphate mining industry to move this by-product off-site because it is so toxic. Accordingly, there are about 1 billion tons of phospho-gypsum stored in at least twenty “stacks” in central Florida, and an additional 30 million tons are currently being generated each year.
These gypsum stacks create environmental hazards in and around all phosphate mining facilities. The threat of radioactive by-product material comes from the uranium content being strip mined. Radium and radon exist in the decay chain of uranium and are known to cause various types of cancers. Radon is in the form of gas and in some cases the wind carries these toxins for miles. Even worse however, sinkholes are known to occur beneath the radioactive stacks due simply to their enormous weight.
The millions of tons of phospho-gypsum cause a much higher probability of sinkhole formation, and can allow billions of gallons of toxic waste to flow through the stacks and into the aquifers. These are not immediately detected, and thus can severely pollute Florida’s freshwater reserves. Only once they are seen from above the gypsum stack (by plane or helicopter) do they become obvious to the public. However, there are warning signs that the phosphate industry largely chooses to ignore.
For example, in August of 2016, WFLA News Channel 8 flew over and saw a massive sinkhole on top of a Mosaic Company gypsum stack in Polk County, just south of Lakeland. By then, over 200 million gallons of radioactive water had been dumped into the aquifer, with the threat of contamination kept hidden from neighbors. However, there were indications that the sinkhole was forming much earlier.
According to Don Rice, a retired hydrologist from the U.S. Geological Survey, data from local wells showed that the level of the aquifer had jumped 40 feet, something that would not happen naturally. Rather, it was a sign that solid material from the gypsum stack had dropped into the aquifer, boosting the water level like an ice cube dropped into a glass of water. The only explanation for such a phenomenon would have been a sinkhole starting to form, just like others that have happened before under gypsum stacks throughout central Florida.
“Mosaic should have seen the 2016 sinkhole coming,” Rice said, “when they saw those levels rising, they should have shut down that gypsum stack until they could see what was happening.” Moreover, Mosaic employees had noticed that the water level in the 78-acre pond of polluted water (on top of the gypsum stack) was dropping. However, they waited until weeks later to identify the problem as a sinkhole. By that time, all 215 million gallons of contaminated water had drained out. Even then, no one informed nearby residents whose drinking water comes from the same aquifer. Only after WFLA News Channel 8 broke the story did this become known to the general public.
Rice noted that if Mosaic had pumped the contaminated water from on top of the stack back then, the company could have prevented most of it from releasing into the aquifer. However, Mosaic did nothing and later referred to Rice’s comments as “wildly speculative.” When these toxic releases occur, phosphate officials either try to hide the spills or offer little in the way of mitigating collateral damage. Florida’s phosphate industry is the direct cause for severe environmental accidents that repeatedly occur, and yet they continue to deny any negligence.
At least six other gypsum stacks in central Florida have already failed with devastating environmental impacts, and Florida’s drinking water is continually at risk. While we would think that the phosphate industry is not intent on contaminating Florida’s freshwater reserves, this brings to mind a memorable quote from the 1987 movie Wall Street, “the main thing about money, is that it makes you do things you don’t want to do.” For the phosphate industry, money certainly seems to have become more important than human lives and the environment that sustains us all. We can see the enormous greed involved here, because Florida’s elected officials know about these practices and yet do absolutely nothing to stop them.
“Florida Sinkholes Created By Phosphate Mining,” Florida Mines
“Mosaic, state should have seen sinkhole forming, experts say,” Tampa Bay Times, February 10, 2017
“Mosaic begins work on massive Polk sinkhole,” WFLA News Channel 8, February 3, 2017