Slightly elevated chloride levels in quarry water prompted FDEP to order owner to determine if mining in this coastal setting was causing deep, salty groundwater to up-cone beneath the property, placing nearby potable water wells at risk. FDEP believed that the freshwater/saltwater interface was very shallow because of the proximity of the quarry to the coast, and that the 80-foot-deep mining activity was breaching this interface. To investigate, deep core holes (500 feet or more) were advanced and groundwater samples were collected at discrete intervals which proved that the base of the upper Floridan aquifer was at 500 feet (well below the base of mining). Approximately 90 monitor wells were installed along transects perpendicular the Gulf shoreline and to the Cross-Florida Barge Canal, including shallow and deep well pairs. Water quality and water level data (recorded with electronic data loggers) proved the chlorides were introduced to the quarry by storm surge and not through saltwater intrusion or up-coning. Groundwater modeling proved expansion of the mine would not significantly increase chloride levels in the quarry and that area wells would not be affected.