Floridan aquifer

The maximum salinities in the Tertiary section of the Gulf of Mexico basin (the most extensively used strata for deep-well injection) reach almost four times that of seawater. The Michigan basin has the highest salinity, reaching 400,000 mg/L TDS, more than 11 times that of seawater. In Florida, however, where seawater circulates through the Floridan aquifer, maximum salinities tend to be controlled by the salinity of the seawater.79... 

A primary injection well and a standby well are situated about 460 m (1500 ft) apart. A shallow monitoring well is located near the primary injection well in the upper limestone Floridan aquifer that overlies the confining Bucatunna clay. Two deep monitoring wells in the injection zone are located 300 m (1000 ft) southwest and 2492 m (8170 ft) northeast of the primary injection well. 

At the time injection began, a shallow monitoring well was placed 23 m (75 ft) south of the injection well in the upper part of the Floridan aquifer above the confining layer. A downgradient, deep monitoring well was placed in the injection zone 300 m (1000 ft) southeast of the injection well. Another shallow well, located 3.2 km (2 miles) southeast of the injection site at the University of Florida s Everglades Experiment Station, has also been monitored for near-surface effects. 

The wastes are injected into the lower part of the carbonate Floridan aquifer, which is extremely permeable and cavernous. The natural direction of groundwater flow is to the southeast. The confining layer is 45 m (150 ft) of dense carbonate rocks. The chloride concentration in the upper part of the injection zone is 1650 mg/L, increasing to 15,800 mg/L near the bottom of the formation.172 The sources used for this case study did not provide any data on the current injection zone. The native fluid was basically a sodium-chloride solution but also included significant quantities of sulfate (1500 mg/L), magnesium (625 mg/L), and calcium (477 mg/L). 

Kaufman, M.I. and McKenzie, D.J., Upward migration of deep-well waste injection fluids in Floridan aquifer, South Florida, J. Res. U. S. Geol. Surv., 3, 261-271, 1975. 

Osmond, J. K., Kaufman, M. I., Cowart, J. B., Mixing volume calculations, sources and aging trends of Floridan aquifer water by uranium isotopic methods, Geochim. et Cosmochim. Acta, 38, 1083-1100 (1974). 

Arthur, J.D., Cowart, J.B. and Dabous, A.A. (2000) Arsenic and uranium mobilization during aquifer storage and recovery in the Floridan aquifer system. Abstracts with Programs. The Geological Society of America, 32(7), 356. 

Figure 7.43. Predicted reaction path for the meteoric diagenetic system of the Floridan aquifer. These reaction path calculations agree reasonably well with observations, as shown by variousl symbols. Reaction path calculations of this nature can be applied to other modern meteoric diagenetic systems, and perhaps, with modifications to ancient systems now removed from original meteoric water. (After Plummer et al., 1983.)...

Plummer L.N. (1977) Defining reactions and mass transfer in part of the Floridan Aquifer. Water Resources Res. 13, 801-812. 

The Floridan aquifer system consists of the Upper and Lower aquifers, which are separated by... 

Figure 4 Map showing the prepumping potentiometric surface of the Floridan aquifer and locations of wells shown...

Figure 5 Cross-section showing location of wells and concentrations of dissolved solids in the Floridan aquifer...

Table 4 Water chemistry of the Upper Floridan aquifer.

Similar solutions of these mass-balance equations can be used to explain water chemistry changes from Polk City and Ft. Meade, and from Ft. Meade to Wauchula (Plummer, 1977), as well as other parts of the Floridan aquifer (Sprinkle, 1989). 

Table 5 Results of mass-balance calculations for the Floridan aquifer assuming a system closed to CO2.

Miller J. A. (1986) Hydrogeologic framework of the Floridan aquifer system in Florida and in parts of Georgia, South Carolina, and Alabama. US Geol. Surv. Prof. Pap. 1403-B, 91pp. 

In the Floridan aquifer, traces of gypsum are present in the carbonate rock. The high calcium concentration from gypsum dissolution exceeds its value at saturation with calcite, leading to precipitation of the carbonate and the production of additional CO2 (reaction 8). Concurrently, anaerobic decay of buried organic matter (reaction 3) and sulfate reduction (reaction 6) take place. The combination of these processes has caused an increase in the CO2 pressure of the groundwater from 10" bar in the recharge zone to 10" bar downdip as the pH decreases from 8.0 to 7.4 over a map distance of 115 km (Fig. 5.3) (cf. Back and Hanshaw 1970 Plummer et al. 1983). 

There are a variety of potential explanations for carbonate mineral supersalurations that exceed uncertainties in the saturation indices of the pure, well-crystallized carbonates (about 0.1 SI units for calcite). As discussed earlier in this chapter, calcite supersaturation in surface-waters may result from a temperature increase, evaporation, and/or a loss in CO2 to photosynthesis or by exsolution to the atmosphere. Mixing of surface-waters or groundwaters can also produce a supersaturated mixture. The dissolution of more soluble gypsum causes calcite supersaturation in some groundwaters of the Floridan aquifer. 

The primary hydrologic units of interest in this study are, in descending vertical order (1) the residuum which forms the water-table aquifer and acts as an upper confining unit, (2) the Upper Floridan aquifer (formerly the principal artesian aquifer), which consists of the Ocala Limestone, the Clinchfield Sand, and the upper part of the Lisbon Formation, and (3) the basal part of the Lisbon... 

Formation which hydraulically separates the Upper Floridan aquifer from underlying sediments and serves as the lower confining unit (Figure 3). 

The decreased infiltration of water into the residuum caused a decrease in the vertical leakage through the base of the residuum, and so recharge to the Upper Floridan aquifer decreased. Water levels continued to decline in both the water-table aquifer and the... 

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