2010-252A (17) - Laserfiche WebLink

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Geology/Hydrology The geology and hydrology of Indian River County are closely related. Basically, the underground geologic formations contribute to the movement, availability, quantity and quality of surface and ground water in the county. Consisting of marine limestone, dolomite, shale, sand and anhydrite, these formations contain two aquifers. The aquifers are depicted in Figure 2.19. Extending from the surface to depths of about 150 feet, the shallow aquifer is confined to the Anastasia and Fort Thompson Formations. Ranging from depths of about 250 to 500 feet below sea level, the Floridan aquifer underlies the entire county. These aquifers are separated by confining beds consisting of clay and other materials of the Hawthorne and Tamiami Formations. Within Indian River County, the shallow aquifer is recharged mostly by direct infiltration of rainfall that does not return to the atmosphere by evapotranspiration and does not leave the area directly as overland flow. The principal area of recharge of the shallow aquifer is along the Atlantic Coastal Ridge, where coarse permeable sands are exposed at the surface. Water is also added to the shallow aquifer by artificial recharge of water withdrawn from Floridan aquifer wells for agricultural irrigation. Over the long term, all of the recharge to the shallow aquifer is discharged from the aquifer. Virtually all of the natural discharge occurs as subsurface flow into the Indian River Lagoon and the St. Johns Marsh. Little water moves downward from the shallow aquifer into the Floridan aquifer because of the confining beds. Generally, the quality of water from the shallow aquifer is acceptable for domestic consumption with limited treatment. Currently, the City of Vero Beach municipal water system uses the shallow aquifer as one of its sources for potable water. Unlike the shallow aquifer, the Floridan aquifer is recharged northwest of the county. In these areas, water entering the aquifer moves eastward, discharging into the Atlantic Ocean. Floridan aquifer water is also withdrawn through wells, tapped for irrigation, used for industrial and municipal purposes, and discharged through uncontrolled free flowing wells. Generally, the high chloride concentrations in the Floridan Aquifer water require treatment to render the water acceptable for potable use. In Indian River County, both the South County Water Treatment Plant on Oslo Road and the North County Water Treatment Plant on 58th Avenue use the reverse osmosis method to treat water from the Floridan aquifer to make the water acceptable for human consumption. A critical concern regarding the Floridan aquifer is the intrusion of salt water as both increasing volumes are withdrawn and natural recharge areas are developed. Community public water systems are depicted in Figure 2.20, and public well locations are depicted in Figure 2.21. A complete discussion of public water systems and community wells may be found in the Conservation and Infrastructure Elements. Future Land Use Element 50