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Phosphate companies mine phosphate ore through strip mining. However, they have to remove a great deal of sandy overburden prior to getting to the phosphate-rich layers underground. The strip mining creates big gashes in the earth that require considerable restoration. The phosphate ore is transported to processing plants (often using water transport in pipes) where acids and other chemicals treat the ore to pull the phosphate from the slurry. Some of the leftover liquids, some of which are highly acidic and often full of nutrients and some radon (an accessory material associated with the ore) are stored in ponds.
Over the years there have been several notable leaks of these ponds. One occurred during a hurricane when heavy rains caused a pond to leak into a local river. The leak caused a massive fish kill and led to significant pollution of Tampa Bay. Another leak was caused by the collapse of a sinkhole. The entire pond leaked into underground aquifers.
This latest leak into Tampa Bay highlights the dangers of toxic ponds associated with mining to the environment and to the public at large. They often linger for years after mining companies leave an area and cause great challenges for long term management leaving them a burden to tax payers for decades.