Project Title: A Retrospective and Critical Review of Aquifer Storage and Recovery Sites and Frameworks within the Upper Floridan Aquifer in South Florida

Project Start Date: October 1, 1999 Project End Date: September 30, 2005

Web Sites: sofia.usgs.gov

Location (Subregions, Counties, Park or Refuge): Southern Florida (including and south of Charlotte, Glades, Okeechobee, and St. Lucie Counties)

Funding Source: USGS's Greater Everglades Science Initiative (PBS)

Principal Investigator(s): Ronald S. Reese, rsreese@usgs.gov, 305.717.5821

Project Personnel: Student

Supporting Organizations: U.S. Army Corp of Engineers and South Florida Water Management District

Associated / Linked Projects: CERP ASR Regional "Preliminary Hydrogeologic Framework"; PBS/CERP ASR Coordination Activity; and CERP ASR Regional "Geochemistry Data and Literature Search and Review"

Overview & Objective(s): Aquifer storage and recovery (ASR) has been described as "the storage of water in a suitable aquifer through a well during times when water is available, and recovery of the water from the same well during times when it is needed". Water can be stored in aquifers with poor water quality. Precedence for ASR in southern Florida has been set by wells constructed at over 30 ASR sites, mostly by local municipalities or counties in coastal areas. The Upper Floridan aquifer is the aquifer of interest to the Comprehensive Everglades Restoration Plan (CERP) and is the aquifer being used at 22 out of 27 sites. This aquifer is brackish to saline in south Florida, which can have a large impact on the recovery of the fresh or potable water recharged and stored.

The objectives of this study are to: (1) inventory and assess the strengths and weaknesses of available hydrogeologic, hydraulic, hydrochemical, well construction, and cycle test information at existing ASR sites, (2) conduct a critical review of hydrogeology on a site-by-site basis and relate to existing regional hydrogeology frameworks, (3) identify hydrogeologic, design, and management factors which locally or regionally constrain the efficient storage and recovery of fresh water within the Upper Floridan aquifer, and (4) conduct a comparative analysis of the performance of all ASR sites having adequate data.

Status: This six-year study is divided into two phases, the first of which was two years long. The first phase laid the groundwork for data inventory, review, and analysis, and the second will allow for collection of additional data as it becomes available, expand the delineation of the hydrogeologic framework at each site, and perform a more complete comparative analysis of ASR sites. The study is in the second phase. Data collection and inventory is continuing.

Recent & Planned Products: The major products from this study will be two USGS Water-Resources Investigation Reports, one for each phase. The first of these, "Inventory and review of aquifer storage and recovery in southern Florida", WRIR 02-4036, was published in May 2002. The second report will be a WRIR to be published in FY05.

Relevance to Greater Everglades Restoration Information Needs: Aquifer storage and recovery (ASR) in south Florida is proposed on a large scale in CERP as a cost-effective water-supply alternative that can help meet needs of agri-cultural, municipal, and recreational users while providing the water critical for Everglades ecosystem restoration. In CERP plans have been made to utilize ASR on an unprecedented scale. Results of this study will help the managers of the CERP program in locating, designing, constructing, and cycle testing ASR wells. These results will help establish a standard cycle testing protocol that can be used to measure the performance of individual CERP wells or clusters of wells.

Key Findings:

• Seven out of 16 sites with cycle test data had a potable water recovery efficiency of less than 10 percent for the first cycle or two; however, at two of these sites low recharge volumes per cycle (less than 10 million gallons) could explain the poor recovery.
• Factors that can affect recovery of freshwater, such as thickness of the storage zone, transmissivity, and salinity, vary widely between sites.
• Recovery efficiency performance is maximized when the storage zone is thin and located at the top of the Upper Floridan aquifer, and transmissivity and ambient salinity of the storage zone are moderate (less than 30,000 feet squared per day and 3,000 milligrams per liter of chloride concentration, respectively). The structural setting at a site could also be important because of the potential for updip migration of a recharged freshwater bubble or compromised confinement.