U.S. Water News Online
BATON ROUGE, La. --The Capital Area Groundwater Conservation Commission has been awarded a grant to develop strategies to control saltwater encroachment in the "1,500-foot" sand, a major water supply aquifer of the Baton Rouge area.
The grant, administered by the Louisiana Department of Environmental Quality, includes 60 percent federal funding.
At present, a plume of salt water north of the Baton Rouge fault is approaching the Government Street pumping station in Baton Rouge where two public water supply wells are screened in the "1,500-foot" sand. Although groundwater moves slowly, with its velocity measured in feet per year, the saltwater encroachment is continuing to be a problem and the need for corrective action is immediate, according to groundwater commission officials.
A recently published report by the U.S. Geological Survey and the Louisiana Department of Transportation and Development (Water Resources Technical Report No. 59) predicts the salt water will reach the public supply wells in a few years.
The saltwater remediation project will be conducted in two phases, including test drilling, and the construction and development of wells to connect the "800-foot" and "1,500-foot" sands.
The first phase of the project will include the installation of an observation well in the "800-foot" sand to determine its water quality and aquifer characteristics. If the water qualities of the "800-foot" and "1,500-foot" sands are compatible, the "800-foot" sand will be used as the source of recharge for the "1,500 foot" sand.
This phase of the project is critical because the source water must have a quality that would not adversely affect the quality of water in the "1,500-foot" sand, according to local officials.
The second phase will involve the construction of connector wells between the two sands. The hydraulic head difference (about 100 feet) between the sands will allow groundwater to flow directly from the "800-foot" to the "1,500-foot" sand. The hydraulic head buildup imposed on the "1,500-foot" sand would extend outward concentrically and act as a barrier against the movement of salt water toward the pumping wells.
The strategy calls for the connector wells to divert groundwater flow around the public supply wells, thus extending the length of time they can be pumped.
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