LOWP offers options for water storage north of lake

OKEECHOBEE — Can water storage north of Lake Okeechobee significantly reduce releases to the coastal estuaries?

At the Water Resources Advisory Commission (WRAC) meeting Feb. 2, engineers and hydrologists at the South Florida Water Management District (SFWMD) presented a report outlining a combination of water storage technologies north of Lake Okeechobee. The results were generated by the collaborative work of state and federal scientists and engineers during the ongoing Lake Okeechobee Watershed Planning Project (LOWP).

“Aquifer Storage and Recovery (ASR) is the idea that we can use wells that are drilled into the Floridan aquifer, about 1,000 feet underground,” said Robert Verrastro, lead hydrologist.

An Aquifer Storage and Recovery (ASR) pilot project on the Kissimmee River has stored 3,000 acre feet of water, and is shown to be 100 percent efficient with water recovery, according to information provided at the Feb. 2, 2017, Water Resources Advisory. Source: USACOE

He said they can pump fresh water about 1,000 feet underground into the upper Floridan aquifer.

The water in the aquifer is slightly brackish, and the freshwater creates a bubble around the well.

“In dry times, we can recover the water from that same well, he explained.

He said they have successfully operated a Kissimmee River ASR system.

The Comprehensive Everglades Restoration Plan (CERP) concept in 1999 was to use up to 333 ASR wells, pumping up to 5 million gallons a day. He said 200 of these ASR wells were proposed in the Lake Okeechobee system.

These wells would be integrated with above-ground reservoirs, with water from the reservoir pumped into or out of the ASR as needed.

Advantages of ASR wells include the ability to store large amounts of water for multiple years, he explained. ASR requires only a small amount of land, and generally can use land the SFWMD already owns. Stored water can be recovered when needed, which can help optimize the function of reservoirs and stormwater treatment areas (STAs), he explained.

For example, the Kissimmee River ASR stores 3,000 acre feet of water under 2 acres of land.

ASR also eliminates the loss of water through evaporation.

“ASR can act as a safety valve,” he said. “If a reservoir is filled up, water can be pumped down the ASR well and the reservoir volume can be filled up again.

“It actually increases the storage capacity of reservoirs,” Mr. Verrastro said.

For the ASR pilot project, researchers went to those sites where the yellow book (the 2000 CERP plan) indicated the ASRs would be used.

Exploratory wells were constructed in the Caloosahatchee basin as well as north, east and west of Lake Okeechobee, the Kissimmee River and near the Hillsborough Canal, he continued.

Regional studies reviewed the effects of the ASR on the aquifer in regard to potential for rock fracturing, upcoming of water into higher levels of the aquifer, lateral salt water intrusion, effects on the ASRs to existing wells in the area and maintaining artesian conditions.

With these constraints, they found they could construct 130 ASR in the system with about 80 in areas adjacent to Lake Okeechobee, less than half of the number originally proposed.

Mr. Verrastro said they also limited sites to land the SFWMD already owns.

He said if they expanded the site search to land the SFWMD does not own, they could probably add about 20 more.

He said they took the 200 well sites they couldn’t use as ASR wells and ran computer simulations to find out if those sites could be used as deep wells to recharged the Boulder Zone.

“We figured out that we could inject roughly a billion gallons a day into the Boulder Zone without affecting the ASR wells,” he explained.

The Boulder zone is around 3,000 feet underground.

Water pumped into deep injection wells cannot be recovered, he explained. The water in that zone is salt water. The freshwater pumped into the well pushes out the saltwater.

“The Boulder Zone is filled with seawater and connects with the ocean many, many miles offshore,” he said.

Boulder Zone injection wells have a simple design, would require no additional land acquisition and can hold relatively high capacities relative to ASR wells. The deep wells could be built in advance of large reservoirs, and could assist in estuary and dike protection.

Boulder Zone wells can inject 30 cubic feet of water per second, compared to about 8 cfs for ASR.

“The whole idea is they can assist in controlling the lake level and the estuaries discharges,” he said.

The disadvantage is that the water is lost.

“It’s as if the water were discharged to tide,” he said.

These wells could be used to discharge excess water to tide before the water gets to Lake Okeechobee, he explained.

This technology is not new, he said. There are 180 deep injection wells in operation in the State of Florida today, he said. Most of these wells are used for wastewater disposal. There are over half a dozen deep injection wells that have been operating around Lake Okeechobee for the past decade. They have all been operating effectively.

He said they looked at the possibility of using wells constructed at the edge of the system before the water reaches the estuaries. For the St. Lucie estuary, 60 deep injection wells could capture almost 90 percent of the damaging discharges. On the west side, 90 wells could reduce damaging discharges by 40 percent.

Their models found that 30-60 deep injection wells adjacent to Lake Okeechobee could control the lake by half a foot to one foot in one year.

Graphic courtesy South Florida Water Management District.

He said people always want to know how efficient ASR wells will be, since freshwater is pumped into the brackish water of the aquifer. The Kissimmee ASR pilot project had 100 percent recovery, Mr. Verrastro said. He said the Floridan aquifer water is fairly fresh, so they did not have a problem with the freshwater mixing with brackish water found in some ASR projects in other areas.

“Those same conditions pretty much apply throughout the Lake Okeechobee area,” he said.

“The water we pump into an ASR well has to go through a filtration and treatment process,” he said. “It has to meet drinking water standards, which we were able to do.”

“At the Kissimmee ASR system, we found that we are using very lightly treated surface water, it is very stable water,” he said.

“Both ASR technology and deep water injection look very promising in our planning process to reduce discharges to the northern estuaries,” said Matt Morrison, federal policy chief.

“We’re getting one management measure, and that is above ground storage.

If we are really going to reduce the damaging discharges to the Calooshatchee and St. Lucie estuaries, we need storage,” said Mr. Morrison.

“We know we need storage north of the lake. We need storage south of the lake. We know we need storage east and west of the lake.

“The good news is we have construction of storage currently taking place on both the Caloosahatchee and the St. Lucie and the Central Everglades Planning Project, which includes storage south of the lake, was recently approved by Congress for upcoming implementation.

He said about 700,000 acre feet of storage is needed north of the lake.

LOWP project performance measures include:
• Increase water storage capacity in the watershed increasing improved Lake Okeechobee water levels, and reducing the damaging high water levels;
• Improving the quantity and timing of discharges to the St. Lucie and the Caloosahatchee estuaries which adversely affect salinity;
• Creating habitat to increase extent and functionality of freshwater wetlands; and,
• Improve water supply for existing legal users.

Components of LOWP includes above ground reservoirs, ASR, deep well injection and wetland and flood plain restoration. Areas currently under evaluation for reservoirs are west of the Kissimmee River.

Options considered are reservoirs to provide 150,000 acre feet to 300,000 acre feet of above ground storage.

He presented documentation which showed a combination of 250,000 acre foot reservoir and 80 ASRs and 150 deep injection wells could reduce the estuary flows by 82 percent. Total cost for that option is estimated at $3.7 billion.

“We’re going to continue to move forward and develop a project plan north of the lake that is going to really help minimize those damaging discharges from Lake Okeechobee that contribute to undesirable conditions in both the St. Lucie and the Caloosahatchee.”

“I appreciate this presentation today, as well as the outstanding research of our engineers and hydrologists,” said WRAC Chairman Jim Moran. “Multi-faceted storage north of Lake Okeechobee provides a cost-effective, flexible strategy to meet environmental and water supply goals in South Florida.”

Search for the truth about Lake Okeechobee

The Feb. 2, WRAC meeting was the first presentation of LOWP findings that detailed storage and cost information north of Lake Okeechobee. The WRAC is an advisory body to the SFWMD Governing Board and the South Florida Ecosystem Restoration Task Force. It is a forum for improving public participation and decision-making about water resource issues in the District.

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