Abstract
This thesis outlines an ambitious research endeavor involving extensive geochemical analysis of two continuous cores, L63N and C38S, from the Lake Okeechobee Watershed Restoration Project Aquifer Storage and Recovery (ASR) wellfield area. The primary objective is to identify optimal flow zones for ASR storage by assessing metal concentrations within the cores. The research is significant for its potential to enhance ASR well design, construction, and operation, by addressing concerns related to metal mobilization during water storage. The thesis emphasizes the utilization of portable X-ray fluorescence (pXRF) technology for accurate measurements, ensuring data reliability through rigorous calibration. The central research question focuses on identifying suitable flow zones in continuous cores L63N and C38S for ASR storage, considering geochemical analysis data to minimizing the risk of metals enrichment in recovered water.
Aquifer storage and recovery (ASR) wells north of Lake Okeechobee have been proposed as part of the Comprehensive Everglades Restoration Plan. However, researchers have found elevated concentrations of As, Mo, Hg, and other transition metals in recovered groundwater because of ASR operation in carbonate rocks. The metals were mobilized during the water storage phase of ASR. Approximately 1500 feet of continuous core (L63N) and 909 feet of continuous core (C38S) were recovered along the Kissimmee River north of Lake Okeechobee. The recovered core L63N begins at a depth of 500 feet below surface in the intermediate confining unit, transects the Upper Floridan aquifer, the Avon Park permeable zones, and ends at 2000 feet below the surface. C38S begins at a depth of 500 feet and ends at 1410 feet below the surface. A pXRF unit was used to analyze L63N and C38S at approximately every foot to determine the concentrations of metals and other elements.
Within the continuous core L63N four flow zones are identified, one flow zone in the Upper Floridan aquifer from 700 feet to 800 feet (UFA), two flow zones in the Avon Park permeable zone from 1300 feet to 1450 feet and 1520 feet to 1645 feet., referred to in this thesis as Avon Park permeable zone 1 (APPZ1) and Avon Park permeable zone 2 (APPZ2). The fourth flow zone of L63N is in the Lower flow zone from 1900 to 2000 feet (LFZ). The study's importance lies in guiding the design of future ASR wells to avoid aquifer zones with high metal concentrations prone to mobilization during water storage. This research contributes to advancing sustainable water resource management and environmental stewardship by providing insights into the geological complexities of ASR storage and design. In core C38S three flow zones are identified. Two flow zones are located in the Upper Floridan aquifer from 570 feet to 590 feet and 1020 feet to 1170 feet referred to in this thesis as Upper Floridan aquifer flow zone 1 (UFAFZ1) & Upper Floridan aquifer flow zone 2 (UFAFZ2). The third flow zone of C38S is located from 1290 feet to 1410 feet in the Avon Park permeable zone (APPZ).
