The Bone Valley: Where Lakeland’s Water Story Begins
Lakeland, Florida — population roughly 115,000 — sits in Polk County, right in the middle of Florida’s Bone Valley. This region earned its name from the enormous deposits of phosphate rock mixed with fossils that lie just beneath the surface. Since the 1880s, companies have been strip-mining this phosphate to produce fertilizer, and today the Bone Valley supplies the majority of U.S. phosphate production.
Mining made this region economically. But it also created one of the most complex water quality situations in the southeastern United States.
Phosphate Mining and Water Quality
Phosphate mining is a massive surface operation. Companies strip away topsoil and overburden, excavate the phosphate matrix, then process it through washing plants and chemical beneficiation. This process generates several major water quality concerns:
Phosphogypsum Stacks
For every ton of phosphoric acid produced, the phosphate industry generates about five tons of phosphogypsum — a slightly radioactive byproduct containing radium-226, uranium, and other radionuclides. This waste is piled into enormous stacks (called “gypstacks”) that can rise 200 feet or more above the flat Florida landscape.
Polk County has some of the largest phosphogypsum stacks in the world. These stacks contain acidic process water that can — and does — leak into groundwater. The most dramatic failure was the 2016 Mosaic sinkhole, where a 45-foot-wide sinkhole opened beneath a gypstack at the New Wales facility in Polk County, sending 215 million gallons of contaminated water into the Floridan Aquifer.
Radionuclides
Phosphate rock naturally contains elevated levels of uranium and its decay products, including radium-226 and radon. Mining disturbs these materials and concentrates them in waste products. Groundwater near phosphate operations and gypstacks can show elevated levels of:
- Radium-226 and radium-228 — radioactive metals that accumulate in bones
- Gross alpha radiation — a measure of total radioactive particle emissions
- Uranium — both naturally occurring and concentrated through mining processes
- Radon — a radioactive gas that can dissolve in groundwater and be released at the tap
Other Contaminants
Beyond radioactivity, phosphate mining operations introduce:
- Fluoride — phosphate rock contains significant fluoride, which enters process water and can migrate to groundwater
- Heavy metals — arsenic, cadmium, chromium, and lead are associated with phosphate deposits and mining waste
- Sulfate — from the sulfuric acid used to process phosphate rock into phosphoric acid
- Nitrate and ammonia — from fertilizer production facilities co-located with mining operations
Sinkholes: The Hidden Connection
Central Florida’s limestone geology makes it prone to sinkholes — and phosphate mining makes them worse. Mining removes material that supports the limestone surface, alters drainage patterns, and changes groundwater levels. All of these increase sinkhole risk.
Sinkholes matter for water quality because they create direct conduits between surface contamination and the Floridan Aquifer — Florida’s primary drinking water source. When a sinkhole opens beneath a gypstack or settling pond, contaminated water bypasses the natural filtration that soil and rock normally provide.
The 2016 Mosaic sinkhole was the most publicized example, but smaller sinkholes and subsidence events occur regularly in the mining district. Each one is a potential pathway for contamination to reach drinking water.
Lakeland’s Drinking Water
The City of Lakeland draws its drinking water from deep wells tapping the Floridan Aquifer. The water receives treatment including aeration (to remove hydrogen sulfide and radon), disinfection, and pH adjustment. The city’s water has generally met federal drinking water standards.
However, Polk County’s unique geology creates some persistent water quality characteristics:
- Hardness — Floridan Aquifer water in this region is very hard, with high calcium and magnesium levels from the limestone
- Hydrogen sulfide — the “rotten egg” smell common in Florida well water
- Naturally elevated radioactivity — radium and gross alpha levels in source water can approach regulatory limits, requiring careful well selection and blending
The concern isn’t that the treated tap water is unsafe today. It’s that the cumulative impact of over a century of phosphate mining continues to degrade the aquifer that serves this region, and the timeline for contamination migration from gypstacks and mine sites extends decades into the future.
What Lakeland Residents Can Do
If you’re on city water, check the annual Consumer Confidence Report from Lakeland’s water utility. Pay particular attention to radionuclide results (radium-226/228, gross alpha) — these are the contaminants most specifically associated with the phosphate district.
If you’re on a private well in Polk County, testing is especially important. The Florida Department of Health recommends testing private wells for bacteria, nitrates, and — in the phosphate district — radionuclides. The Florida Department of Environmental Protection can provide guidance on testing near mining operations.
For residents concerned about radionuclides, fluoride, or heavy metals, a certified water treatment professional can test your water and recommend treatment. Reverse osmosis is effective against most of these contaminants. Whole-house systems may be appropriate for wells with elevated radioactivity.
Sources: Florida Department of Environmental Protection phosphate program; EPA radionuclide monitoring data; Polk County Environmental Lands Program; Florida Geological Survey sinkhole database; USGS circular reports on phosphate mining and water quality; Mosaic Company environmental monitoring reports; City of Lakeland Utilities.