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Altamonte
Springs, Central Florida
Source Number: 2.2.1 Source
Description Key Words Executive Summary A recent estimate is that recharge to the Upper Floridan aquifer from these wells is approximately 30 to 50 million gallons per day (MGD). Continued increase in groundwater production is expected to adversely impact springflows, levels and flows of surface water features as well as wetlands to an unacceptable degree. One of the several alternatives for meeting projected future needs is to supplement local aquifer recharge with storm runoff that would otherwise flow from the area; however, a concern exists that current drainage well practices may be adversely impacting groundwater quality. To address this concern, the St. Johns River Water Management District (SJRWMD) has initiated a project to investigate the fate of microbiota and other constituents found in water entering representative drainage wells in the Central Florida area, and to determine what additional pretreatment measures, if any, would be needed to protect groundwater quality. Two initial sites, Lake Orienta and Lake Sherwood, were selected for baseline sampling, to be followed by monitoring during a series of events when the wells function for lake-level control during wet periods. Baseline sampling was conducted in August 2001, following an extended dry period when no recharge to the aquifer occurred through the selected drainage wells for several months. However, the two drainage wells at Lake Orienta and the single drainage well at Lake Sherwood are believed to have been operational for a period of approximately 40 years. As such, the baseline sampling also may be interpreted as the water quality response of the Floridan aquifer at these sites, resulting from long-term drainage well operation. It is planned to construct monitoring wells near each of these sites to monitor changes in water quality with both time and distance from the drainage well during recharge events. Baseline sampling at the two sites was conducted for a variety of chemicals (e.g., general chemistry, nutrients, metals, volatile organic compounds, semi-volatile organic chemicals, organochlorine pesticides, PCBs, chlorinated herbicides) and microbiota (total and fecal coliform, Esherichia coli; enterococci, C. perfringens, Cryptosporidium, Giardia and Coliphage). A summary of the detected chemicals is provided in Table 1; Table 2 provides a summary of the microbiota results; Table 3 provides water quality data comparison to criteria. Temperatures of groundwater samples ranged between 72 and 75 degrees F. These two sites provide the most extensive data set of any in Florida at this time, pertaining to the fate of microbiota and other constituents from recharge of surface water into a fresh water aquifer. Background sampling has been conducted for numerous constituents. In future years, additional samples will be collected at these and other sites to investigate the natural ability of aquifers to attenuate recharge water concentrations for a broad variety of constituents. This SJRWMD project reflects a risk-based approach to the issue and considers presence, pathway, and dose (concentration and time) that lead to increased risk. Without all three characteristics, there is no increased risk. The focus is on constituents for which the scientific community has documented health-related or environmentally related impacts and those same constituents that are found in the source water at unacceptable concentrations. For an increased risk through a completed exposure pathway from the water resources, sustained threshold doses need to occur. Graphics and
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