HR: 14:15h
AN: H13C-04    [Abstracts]
TI: Movement of Saltwater in the "2,000-Foot" Sand of the Baton Rouge Area, Louisiana
AU: * Tomaszewski, D J
EM: djtomasz@usgs.gov
AF: United States Geological Survey, 3535 S. Sherwood Forest Blvd, Suite 120, Baton Rouge, La 70816 United States
AB: Ground-water withdrawals in southeastern Louisiana have caused saltwater to encroach into some freshwater aquifers. The most heavily pumped area, East Baton Rouge Parish, includes the city of Baton Rouge and surrounding areas. The Baton Rouge aquifer system includes 10 extensive aquifers that were pumped about 150 Mgal/d (million gallons per day) in 2003. Ground-water investigations in the 1960's delineated a freshwater-saltwater interface located at the Baton Rouge fault. Test drilling and water well data collected near the fault indicate that the fault is associated with major discontinuities in water levels and water quality. Generally, aquifers south of the fault contain saltwater and aquifers north of the fault contain freshwater with chloride concentrations less than 10 mg/L (milligrams per liter). Saltwater encroachment into freshwater areas north of the fault has been monitored and delineated with well networks in several aquifers. Saltwater was initially detected as early as the 1960's; by the 1990's saltwater had been detected in six of the aquifers north of the fault, including the "2,000-ft" sand. Northward encroachment of saltwater across the fault in the "2,000-ft" sand in East Baton Rouge Parish is in response to large water withdrawals from the aquifer totaling about 22.7 Mgal/d in the Parish in 2002. Encroachment of saltwater has been monitored by a system of wells. The approximate location of the freshwater-saltwater interface north of the fault was delineated for the years 1966, 1977, and 1992. At present, wells in the "2,000-ft" sand at two public-supply well fields located north of the fault are producing water with chloride concentrations approaching 200 mg/L. Wells at these fields may help protect the aquifer from northward advancement of saltwater by intercepting and discharging saltwater. In 2002, about 0.8 Mgal/d from the aquifer was withdrawn by the impacted wells. If withdrawals from the impacted wells were discontinued, saltwater could advance more rapidly toward the industrial district, unless remediation steps were taken to reduce northward encroachment. The resulting saltwater contamination in wells underlying the industrial district, located about 3 miles north of the fault, could affect approximately 70 percent of the withdrawals from the "2,000-ft" sand in East Baton Rouge Parish.
DE: 1800 HYDROLOGY
DE: 1803 Anthropogenic effects
DE: 1831 Groundwater quality
DE: 1884 Water supply
SC: Hydrology [H]
MN: 2005 Joint Assembly