Solute Transport Modeling Studies for Aquifer Storage and Recovery System Perfomance Predictions and Design

Client: Marco Island Utilities

Location: Florida

Summary: Cardno ENTRIX was contracted to develop an aquifer storage and recovery (ASR) system for Marco Island Utilities, operated by Florida Water Services in Colllier County, Florida. Early in the project it was determined that selection of the storage interval would require choosing among several alternative storage zones persent between depths of about 300 feet and 1,200 feet below land surface. Also, because the ASR project was to store non-potable water, it was expected that substantial regulatory demonstrations of no adverse impacts would be necessary. Cardno ENTRIX had determined that computer modeling would be necessary to make intellegent planning choices and to provide reasonable assurance of no adverse impacts to regulatory agencies.

Cardno ENTRIX selected the SWIFT solute transport model code for demonstrating fluid migration and recovery efficiency. The storage interval would contain water having relatively high TDS values, in excess of 6000 mg/l.

Extensive drilling and testing was conducted to acquire site specific data, modeling was first undertaken to aid in the selection of the storage interval. Among the several alternative storage intervals available, one interval demonstrated a predicted recovery performance that was substantially better than all other options. On this basis a 50 foot thick storage zone was selected between the depths of 750 and 800 feet.

In the next phase of the project the same model was used in permitting, to demonstrate the extent of vertical and horizontal movement of the storage plume. Later, the ASR system was constructed and the model was calibrated to the first and second operational cycles and future recovery performance was predicted for cycles. The actual performance matched very closely with the predictions. The ASR system has now been expanded to include 8 storage wells that allow seasonal recovery of more than one billion gallons.