What Is Phosphogypsum and Why Is It Stacked?
PG is a normal byproduct of phosphate product manufacturing. The EPA requires that PG is stored in large structures called gypstacks due to low-levels of naturally occurring radionuclides present in the phosphate rock that PG comes from. Today, PG is approved by the EPA for limited use in agriculture and research. Already more than fifty-five beneficial uses for PG have been discovered by scientists world-wide. This short video explores PG and gypstack facts:
Gypstack systems are heavily regulated to ensure safety for the surrounding environment and personnel that work on them daily. The phosphate industry undergoes a rigorous permitting process overseen by the Florida Department of Environmental Protection (DEP) and county governments.
Innovative technologies and practices used to construct gypstacks and keep them safe include high-density polyethylene liners throughout the stack, an extensive network of monitoring equipment and water recovery systems that help producers meet their goal of recycling 95% of the water they use while also using 20% less water by 2025.
Water is essential to the phosphate product manufacturing process. Highly-trained technicians use water to move product throughout processing facilities where manufacturing takes place. Dubbed “process water” by scientists, it’s also used to transport PG to gypstacks. Process water does not leave the facility and is circulated in ponds on top of gypstacks to be sustainably reused in the manufacturing process, reducing the need to obtain more water from nature.
The amount of water in a gypstack changes depending on the season, rainfall and production. Ahead of hurricane season, engineers prepare gypstacks and process water to withstand the effects of strong winds and rain to ensure the stacks are safe. Only tested and treated water that meets the strictest quality standards can be discharged through permitted and monitored points.
Inspections / Maintenance
Highly trained technicians and engineers constantly monitor gypstack systems to ensure compliance with regulations and to protect the environment. Inspections occur twice a day and are documented for future verification. Shift supervisors complete their own weekly inspection, and operating supervisors complete another monthly review. Annually, a third-party inspects and verifies stack safety. When repairs are required, they are carried out with regulatory oversight and onsite inspection.
Innovative technologies and practices are used to monitor stacks for hidden, subsurface structural abnormalities. Vibrating piezometers and microseismic monitoring sensors monitor water levels and provide real-time data confirming a stack's structural integrity.
NORM - Naturally Occurring Radioactive Materials
Phosphate ore contains low levels of naturally occurring radioactive materials that scientists refer to as “NORM.” Like the name implies, it’s natural and virtually everything we come into contact with on a daily basis like granite countertops, ceramic dinnerware and even some types of fruits like bananas contain it.
NORM is, well… normal! Radiation is measured in doses and a dose unit is quantified in millirems per unit of time — typically per year. The EPA states that an average person in the U.S. is exposed to 600 millirems per year, split into two categories:
- Environmental exposure - like the sun or soil
- Common medical procedures, like dental x-rays and mammograms
NORM is found in the ground across the country. In fact, ambient NORM found in Florida’s soil is considered to be amongst the lowest in the nation. A typical Floridian is exposed to an average of 200 millirems per year because our soil contains less radium in comparison to the 300 millirem average in other parts of the county.
Process water and PG are part of the phosphate manufacturing process and contain these naturally occurring elements found in Florida’s soil. NORM from process water and PG is low and is considered to be well below the EPA’s risk threshold even for people working on or with it daily. PG has been extensively studied and reviewed by the EPA for innovative uses like road construction, and evaluation for suitability as a road base material is ongoing.