Completion Date: 2004
- Hydrogeologic modeling
- Evaluate alternative supplies
- Aquifer storage and recovery
- Dam and reservoir
- Wastewater reuse
- River supply
- 65-MGD river intake
- Industrial pretreatment facility
- Ground storage and booster pump
- 23 miles of 12- to 48-inch pipeline
- Financial planning
In April 1999, the Arkansas legislature passed Act No. 1050 authorizing the creation of groundwater conservation boards in counties designated as 'critical groundwater areas.' The first county to form such a board was Union County, which borders Louisiana in south central Arkansas. A U.S. Geological Survey (USGS) monitoring well near the center of the county recorded a static water level in 1942 of 60 feet above sea level. By 1999, the static level in the same well had dropped to 180 feet below sea level. This represents an average depletion of 4.2 feet per year over the 57 years of records.
Burns & McDonnell refined a two-state USGS groundwater model of the Sparta Aquifer to represent the information collected in Union County, which covers more than 1,000 square miles. All water supplies in Union County come from the Sparta Aquifer. There are seven cities, 22 rural water associations and 11 major industries using Sparta water. Many major supply wells were metered as a part of this project, as the legislation allowed the county to charge 24 cents per 1,000 gallons for all water pumped from the Sparta. This revenue source allowed the conservation board to retain Burns & McDonnell to prepare a master plan to “Save the Sparta.”
Hydrogeologic modeling approximated that the groundwater usage must be reduced from a peak of 25 million gallons per day (MGD) to an average of 7 MGD to recover the aquifer to original levels in 30 years. In addition, a new merchant power plant was planned for the county that would have an average daily demand of around 20 MGD. Well location data and pumping information were used to model the aquifer for several alternatives. Those alternatives considered for supplemental supply included the Ouachita River that forms the northern border of Union County; aquifer storage and recovery; five dams and surface water reservoirs; wastewater reuse; and water conservation.
The selected alternative was to provide non-potable water to the major industries and new power plant in the county by constructing a 65-MGD intake on the Ouachita River. Water treatment was thus limited to coagulation and sedimentation. The settled water will be pumped to the power plant and on to a storage tank/booster pump station near El Dorado, where it will be boosted to serve the largest industries. The master plan suggested methods for the board to finance the improvements.
Groundwater levels will be monitored for two or three years to determine the rate of recovery of the aquifer from the first phase of the project. If the rate of recovery is not acceptable, then a second phase is recommended converting more industrial users from groundwater to the non-potable surface supply. The third phase, if needed, will be to provide a membrane water treatment plant that takes non-potable water from the storage tank to provide potable water for a portion of the county.
Burns & McDonnell opened an office in El Dorado to enhance the planning and design effort and ensure that the client’s interests were clearly of utmost importance. A full-time representative of the firm provided continuous interaction with the board. Project development was handled under the direction of the project manager, who made frequent presentations at biweekly meetings with the Union County Water Conservation Board. A rate study established the recommended base rate of cost for the raw water supply to the industries. Several grants were received, and Union County citizens voted a sales tax to pay the balance of the project.