Although Aquifer Storage and Recovery (ASR) technology has been used successfully in Florida since the 1980s, some concerns have been raised about using ASR in large scale projects in the Comprehensive Everglades Restoration Plan (CERP), explained Jennifer Reynolds of the South Florida Water Management District (SFWMD) in a Zoom workshop on Dec. 8.

SFWMD and the U. S. Army Corps of Engineers developed an ASR Science Plan to identify areas that need to be studied in order to implement ASRs in a phased plan, she explained. The studies will be conducted in areas identified for ASRs in the Lake Okeechobee watershed where ASRs are planned.

SFWMD Principal Hydrogeologist Robert Verrastro said the 1999 “yellow book” included 333 ASR wells that were envisioned to work with other CERP projects. The “yellow book” was a printed compilation of the CERP project plans. He said 200 ASR wells were envisioned in the Lake Okeechobee watershed; 44 in the Caloosahatchee Basin and 89 on the lower east coast.

The “yellow book” included pilot projects to study the feasibility of ASR use on this scale, he continued. One pilot project was completed on the Kissimmee River near Lake Okeechobee and one on the Hillsboro Canal.

The Kissimmee River ASR intakes water from a canal. The water is disinfected to drinking water standards and pumped into the upper Floridian Aquifer. After a period of storage the water is pumped back out. “It turned out to be a very successful ASR,” Verrastro explained. Not only did they report nearly 100% recovery of the water stored, the recovered water was lower in phosphorus than it had been when it was pumped in.

Verrastro said they completed several monitor wells in the same zone, which enabled the scientists to “look at where the water went when it was pushed underground,” he explained.

They conducted four cycles with successively larger volumes, and longer storage intervals.

The last, largest study pumped a billion gallons of water into the ASR well and they were able to recover 100% of that water, he said. The study showed ASR wells can be pumped at 5 million gallons a day.

Since the wells were first proposed, geological research and computer simulations found some areas of Florida are not suitable for ASR. He said they narrowed down the list and found 140 ASRs would be “doable in South Florida.” Of those 140 total wells, “80 could be operated safely in the area of Lake Okeechobee,” he explained.

The plans were reviewed by the National Research Council (NRC) which found there were “no fatal flaws” uncovered that would limit the use of ASR and that large capacity ASR wells can be built, however it is prudent to do exploratory wells first.

The study recommended ASR work proceed in a phased approach.

The Lake Okeechobee Watershed Restoration Plan (LOWRP) is the CERP component to store water north of the lake. LOWRP includes a wetlands attenuation feature (WAF), restoration of some wetlands along the Kissimmee River and 80 ASR wells. The 80 ASR wells in the Lake Okeechobee Watershed Restoration Plan could provide 448,000 acre feet of storage a year.

With water storage projects already under construction south, east and west of the lake, the state appropriated $50 million in Fiscal Year 2019-20 and $50 million in Fiscal Year 2020-21 to allow SFWMD to accelerate LOWRP. The funds were to be targeted for the greatest amount of storage.

“We have focused on the ASR clusters located north of Lake Okeechobee,” said Verrastro. Two of the cluster areas have existing ASRs. One is the Kissimmee River ASR. The other is referred to as the Taylor Creek ASR. It was built in the 1980s by SFWMD.

“We have been working to reactivate those ASR systems, trying to repair and reactivate them so they can become functional in the next year,” said Verrastro. SFWMD is also developing a project to extract and construct continuous cores from 500 to 2,000 feet below land surface in areas proposed for wells “to make sure we do have the hydrogeology that is conducive to ASR.”

Along with extracting the cores for geological study, water samples will be taken every 30 feet.

The options for the water treatment component are also under study. Water must be treated to drinking water standards before it can be pumped into an ASR. “There are an entire universe of water treatment methods available for us to evaluate,” he said.

SFWMD also created an independent ASR peer panel to come up with recommendations for how to implement the additional study encouraged by the National Research Council. That panel includes Dr. John Arthur of the Florida Geological Survey, Dr. Tom Missimer of Florida Gulf Coast University, Dr. Rene Price of Florida International University, Reid Hyde of the Florida Fish and Wildlife Conservation Commission Research Institute, and Dr. Sam Upchurch, retired, University of South Florida.

Verrastro said they are also studying the aquifers. The Taylor Creek ASR is in the Avon Park Permeable Zone. “We are looking to reactivate that system and resume testing on that system in order to have more information on the Avon Park Permeable Zone,” he explained. Preliminary tests show that ASR can be pumped at almost 10 million gallons a day.

SFWMD is also planning on constructing test exploratory wells in two areas along the C-38 canal. These wells will be nested with monitoring wells. A food-based dye will be used as a tracer to find out where the water goes in the aquifer and how much is spreads outs. They will also be able follow the tracer vertically to find out if there is fracture flow within the rock, where the water might be moving up or down within the aquifer.

This additional research and testing will help SFWMD make good design choices for well field locations.

“CERP doesn’t work without ASR,” said Nyla Pipes of One Florida Foundation in the comment period. She complimented SFWMD on their very scientific, well vetted, slow implementation process.

“This is a really attainable, affordable way to provide a significant amount of storage north of the lake,” said Ernie Barnett of the Florida Land Council.

ASRs will not provide an alternative to coastal releases after a hurricane or tropical storm, pointed out representatives of the Everglades Foundation. An ASR that can pump 5 million gallons per day is only 7.7 cubic feet per second so the 80 ASRs planned for LOWRP would only pump 616 cfs. Currently the U.S. Army Corps of Engineers is sending 3,000 cfs from Lake Okeechobee to the Caloosahatchee River alone.

Newton Cook of United Waterfowlers Florida, said while he supports ASRs for water storage, Deep Injection Wells (DIW) could be used to protect the estuaries. DIW sends water into the Boulder Zone that eventually flows to the ocean. He said the water that is being sent to tide through the estuaries today could instead be sent to tide without damaging the estuaries.

ASRs can store water in wet years so that it is available for use in dry years. The 80 ASRs planned for LOWRP would have an annual storage capacity of 448,000 acre feet – the equivalent of about one foot on Lake Okeechobee. ASRs can continue to store water below ground when above ground reservoirs are already full. During droughts, the water stored in the LOWRP ASRs could be used for the lake, for the Caloosahatchee or sent through the lake south.

Storing water in the ASRs year round would slow the flow into the lake, leaving more capacity in the lake for high rain events. A slower rise would also benefit the lake’s ecology. Before flood control, according to the U.S. Geological Survey, water that fell in the upper Kissimmee River Basin took six months to slowly sheetflow into Lake Okeechobee. Along the way, some of that rainfall evaporated into the air or percolated into the earth. Due to the channelization of the Kissimmee River, that hydrological journey now takes just two to four weeks, as evidenced by the rapid rise of the lake after a storm.

SFWMD will post the completed ASR plan on their website for public review in January.