Underground Injection Control at Riverview

A Proven, Highly Regulated Technology

Underground Injection Control (UIC) is a proven, highly regulated technology that adds resiliency to Mosaic’s comprehensive water management strategy. Used safely in Florida for decades, UIC allows treated, non-hazardous water to be managed in deep underground formations that are separated from drinking water sources by impermeable rock and clay. At Riverview, Mosaic is pursuing a Class V Exploratory Well Permit as part of the state’s rigorous permitting process, which includes extensive testing, monitoring, reporting, and regulatory oversight.

UIC would complement existing water management practices by providing an additional option during periods of heavy rainfall, storm events, or other conditions that can limit surface water discharge, while supporting Mosaic’s ongoing commitment to environmental protection and operational reliability.

About UIC

Underground Injection Control is a proven technology. It adds resiliency to Mosaic’s overall water management strategy. In other words, another resource in our already comprehensive operations. It’s also not new. UIC has been successfully demonstrated across the state since the 1960s, including in the Tampa Bay area. Florida’s UIC program is rigorous, allowing the injection of only treated, non-hazardous wastewater. Today, there are more than 200 UIC systems in place in Florida.

Mosaic has engaged stakeholders and neighbors across Hillsborough and Polk Counties in the conversation around the use of UIC, how it works, and its successful track record. UICs allow us another effective approach to manage treated, nonhazardous wastewater, complementing existing strategies with an option other than surface water discharge. In 2023, Mosaic applied for a Class V Exploratory Underground Injection Well Permit to the state. These permits require extensive reporting and are subject to renewal every 5 years in addition to ongoing financial assurance.

Placeholder for a Riverview site map showing the proposed Class V UIC wells — Placeholder for the Riverview facility and proposed Class V UIC well locations.

Learn More About the UIC Process

Watch the video below to learn more about the UIC process, including an interview with well-known hydrologist and Professor Emeritus Dr. Tom Missimer, PhD, PG.

Frequently Asked Questions

What type of well is being permitted?

This is a Class V Exploratory Well Permit. This type of permit only allows “construction and testing” of the injection well to make sure it can safely inject treated water deep underground without affecting drinking water sources closer to the surface. After construction and testing are completed, which is estimated to take 18 to 21 months, Mosaic will need to apply for a Class I UIC permit to use the UIC well. This permit only allows non-hazardous fluids to be injected. Injection of hazardous waste is not permitted in the State of Florida.

What fluids will be injected in the exploratory well?

Only freshwater will be used to test the exploratory well, and only after the well is confirmed to be properly constructed and approved for testing by the Florida Department of Environmental Protection (FDEP). The water source must also receive prior approval.

Will the injected water mix with drinking water?

Extensive testing is performed during well construction to prove injected waters introduced into the well will not mix, or adversely influence, drinking water supplies. Injected water will be pumped more than 4,000 feet underground, well beneath any drinking water aquifers and is vertically separated by thick layers of impermeable rocks. In addition, the Florida Department of Environmental Protection (FDEP) requires a dual-zone monitoring well to be constructed for the sole purpose of confirming drinking water supplies are safeguarded.

What if the well stops working?

To prevent such an issue, Mosaic intends to perform extensive integrity testing during construction, which is reviewed and approved by the FDEP, to certify the well is operationally sound and protective of underground drinking water sources.

Can the treated water come back up?

If and when the exploratory well is permitted as a Class I well, it will be continuously monitored to confirm it is operating safely. The nearby dual-zone monitoring well will provide constant oversight to detect any potential movement of treated water outside of the permitted injection zone. If a failure were to occur, any vertical migration of treated water would be detected, allowing for immediate corrective actions. Additionally, Mosaic will provide financial assurance to the FDEP to safely plug the well, if needed.

How often do you check the overall health of the well?

Well performance is continuously monitored using real-time data collection systems. If the well is converted to a Class I well, detailed Mechanical Integrity Tests (MITs) would be performed every five years and FDEP would conduct a thorough review of all operational and water quality data prior to any permit renewal. Other inspections may be required periodically under regulatory guidelines to confirm the well remains safe and operational.

If I want to review well reports, where do I find those? Are they public record?

During well drilling and testing, weekly reports will be provided to FDEP. All the submitted reports and test results will be available to the public through FDEP’s online portal.

Is the drilling of the well loud?

The drilling and testing of the well will produce some noise, but it is significantly reduced compared to traditional methods. The project uses a highly advanced electric drill rig, known as an “E-Rig,” which is quieter than conventional drill rigs.

Once complete, is the above ground portion of the well unsightly, or overly large?

Once complete, the above-ground portion of the well is minimal. The overall footprint of the well and related infrastructure is relatively small and not visually intrusive. In fact, many Class I UIC wells that have been in use for years are located near residential areas and are virtually unnoticeable.

Will the well disrupt Florida geology? Could it cause a void?

No. The targeted injection zone consists of deep, stable rock formations well below any drinking water aquifers. Extensive testing during well construction will verify the integrity of the impermeable rock layers to confirm that injected water remains insolated below the overlying geologic units. In addition, FDEP requires that the water’s chemistry be compatible with the surrounding rock formations to prevent void or cavity formation.

Why spend millions of dollars drilling a well when you can just treat and release the water through designated outfalls?

Surface discharge of treated water will continue to be used where conditions allow, but a deep well will provide an additional water management tool in the event of hurricanes, flooding or downstream capacity limitations which make surface water discharges impractical. UIC is a proven, regulated method that provides safe, long-term management of treated water without impacting drinking water supplies. This investment adds operational resilience to our water management strategy.