Aquifer Storage and Recovery (ASR) for Ecosystem Restoration: Kissimmee River ASR System, Florida

Aquifer storage and recovery (ASR) is a major water storage and management component in the Comprehensive Everglades Restoration Plan (CERP). In south Florida, the high permeabilities of Eocene and Oligocene marine limestones, with a thick overlying confining unit are a well-suited for ASR. The Kissimmee River ASR (KRASR) system, located at the confluence of the Kissimmee River and Lake Okeechobee, was a CERP "pilot system" to evaluate ASR feasibility at interior locations. Four recharge-storage-recovery cycles of increasing duration and volume were completed between 2009 and 2013. The largest and longest cycle resulted in 1 billion gallons recharged and recovered through a single well. The surface water pretreatment system at KRASR was unique compared to drinking water ASR systems. Surface water was pumped through a pressurized media filter then disinfected using flow-through UV chambers prior to recharge. No chemicals were added during pretreatment. Many studies were completed during the testing program. A geotechnical evaluation confirmed that microfracturing of the limestone could occur at pressures slightly greater than typical operating pressures (30 to 50 psi), but microfractures were unlikely to propagate upward into the confining unit. The changing redox environment of the Upper Floridan Aquifer showed that arsenic was mobilized during recharge but was attenuated during storage and recovery such that arsenic concentrations in recovered water were below the 10 μg/L criterion after cycle test 1. Frequent sampling of recharge water showed that the UV disinfection system was ineffective resulting in total coliform exceedances. The KRASR pretreatment system is being redesigned to improve regulatory compliance.