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Water samples were taken from test wells drilled near an inactive phosphatic clayey waste storage settling pond, from the settling pond and its perimeter ditch, and from an active settling pond near White Springs, Hamilton County, in north-central Florida. The purpose was to document the seepage of chemical constituents from the inactive settling pond and ditch into the adjacent surficial groundwater system, and to assess the potential for movement of these constituents into the deeper Floridan aquifer system which is the major source of public supply in the area. The study area is underlain by at least a 2,500-foot-thick sequence of Coastal Plain sediments of Early Cretaceous to Holocene age. The rocks of Tertiary and Quaternary age that underlie the test site area can be grouped into three major hydrogeologic units. In descending order, these units are: surficial aquifer, Hawthorn confining unit, and Floridan aquifer system. Phosphate deposits occur in the upper part of the surficial aquifer. Water in the active settling pond is a calcium magnesium sulfate type with a dissolved-solids concentration of 250 milligrams per liter and contains greater amounts of phosphorus, iron, aluminum, barium, zinc, and chromium than the other surface waters. Water in the perimeter ditch is a calcium sulfate type with a dissolved-solids concentration of 360 to 390 milligrams per liter and contains greater amounts of calcium, sulfate, nitrogen, and fluoride than other surface waters. Water from the inactive settling pond is a calcium magnesium bicarbonate type with a dissolved-solids concentration of 140 milligrams per liter and contains more bicarbonate than the other surface waters. Large amounts of the chemical constituents in the phosphate wastedisposal slurry are apparently trapped in the sediments of the settling ponds. The quality of water in the upper part of the surficial aquifer from wells within 200 to 400 feet of the inactive settling pond shows no signs of chemical contamination from phosphate industry operations. The horizontal groundwater velocity calculated for this aquifer between, the ditch surrounding the settling pond and the test wells is between 100 to 2,000 feet per year, which is enough time for water to have reached the test wells in the 6 years the pond has been operating. The groundwater velocity beyond the test wells to a distance of 1 mile is much less. The water in the lower part of the surficial aquifer is almost identical in quality to the water in a distant background uncontaminated well.

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1009 ____ . _____ ____ ___ _. . ____ ___________________________ 97 J_ .7 O ^ ___________________________ __ 4* *J 1 UP! 1 JL VT W .^ .1.2. Data-collection frequency range and analytical procedures for chemical constituents 14 IVTemperature units are converted from degrees Fahrenheit (°F) to degrees Celsius (°C) by the formula °C = 5/9 (°F -32); from degrees Celsius to degrees Fahrenheit by the formula °F = 9/5 (°C + 32). ABSTRACTAn 1,840-acre agricultural field southeast of Tallahassee, Florida, which has been used for land application of wastewater by spray irrigation, is the site of a long-term, ground-water monitoring study. The purpose of the study is to determine effects of wastewater application on water-table elevations and ground-water quality. The study was conducted in cooperation with the City of Tallahassee. This report summarizes the findings for the period 1980-82.Wastewater used for spray irrigation has high concentrations, relative to those in ground water, of chloride, nitrogen, phosphorus, organic carbon, coliform bacteria, sodium, and potassium. At most locations, percolation through the soil has been quite effective in attenuation of these substances before they can impact the ground water. However, increases in chloride and nitrate-nitrogen were evident in ground water in some of the monitoring wells during the study, especially those wells which are within the sprayed areas. Chloride concentrations, for example, increased from approximately 3 milligrams per liter to 15 to 20 milligrams per liter in some wells and nitratenitrogen concentrations increased from less than 0.5 milligrams per liter to 4 milligrams per liter or more.Ground-water levels in the area of the spray field fluctuated over a range of several feet. These fluctuations were affected somewhat by spray irrigation, but the primary control on water levels was rainfall.As of December 1982, constituents introduced to the system by spray irrigation of effluent had not exceeded drinking water standards in the ground water. The system has not yet stabilized, however, and more changes in ground-water quality may be expected.

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