GRU discharges treated effluent from its Main Street Wastewater Treatment Plant into Sweetwater Branch. Flow from this point continues to its terminus at Alachua Sink in Paynes Prairie Preserve State Park, where it drains into the Floridan Aquifer system. This situation required GRU to obtain a NPDES permit from the U.S. EPA.
Additionally, the high levels of nitrates in the effluent discharge have in the past been a problem in the flora management of Paynes Prairie Preserve State Park. The elevated level of nutrients in Sweetwater Branch has caused an increase of plant communities not native to the preserve. There are several smaller, private wastewater facilities that also discharge treated effluent to surface water systems and have the potential to create similar water quality problems.
The groundwater tends to move downgradient (i.e., from higher to lower elevations). Flow is generally from the Eastern part of the County toward the Northwest, and most discharge from the aquifer occurs beyond the boundaries of Alachua County.
Local pumpage from wells, sinkholes, fractures in the limestones, rainfall and other factors may influence the flow regime. For example, the circular low of 40 feet near Gainesville is caused by pumping at the Murphree Wellfield for Gainesville's water supply. Drawdown in this manner may increase the amount of recharge that occurs in the vicinity of this pumping. Recent sampling activities have confirmed these elevated levels of nitrates in western and northwestern Alachua County. As part of the FDEP Ambient Monitoring Program, Status Network sampling was conducted in the Suwannee River Basin during 2001 (FDEP, 2002). During this time period, 20 groundwater sites in western Alachua County were sampled. The nitrates concentrations for samples from these sites ranged from <0.004 milligrams per liter (mg/L) to 4 mg/L. In June 2001, ACEPD sampled selected monitor and residential supply wells southwest of the City of Alachua in an area that had been used historically for agricultural activities. Concentrations in the samples obtained from these wells ranged from 1.6 to 30.3 mg/L (ACEPD, 2001).
Current wellfield protection regulations are as follows:
1) The Murphree Wellfield Protection Code (Chapter 355 of the Alachua County Code) was developed to protect the primary water supply for the Gainesville Urban Area. This is a deep well system operated by the City of Gainesville that penetrates the Floridan Aquifer.The code regulates hazardous material transport and storage, well construction, and related activities in three protection zones around the Murphree Well Field.
2) The Hazardous Materials Management Code (Chapter 353 of the Alachua County Code) contains siting prohibitions for certain hazardous materials storage facilities within specified distances from public and private water supply wells.3) Conservation Policy 4.5.2 in the Alachua County Comprehensive Plan provides for interim wellfield protection areas around public potable water supply wells serving at least 15 service connections or regularly serving at least 25 individuals daily at least 60 days out of the year and permitted to pump more than 100,000 gpd. These areas consist of a 200©foot exclusionary zone and a 200©400 foot restricted zone. These restrictions are to be replaced by permanent regulations once better data is available through modeling.
4) Conservation Policy 4.5.2 in the Alachua County Comprehensive Plan also provides for permanent wellfield protection areas around public potable water supply wells serving at least 15 service connections or regularly serving at least 25 individuals daily at least 60 days out of the year and permitted to pump less than 100,000 gpd. These areas also consist of a 200©foot exclusionary zone and a 200©400 foot restricted zone.
GRU