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Vidler Water Company (VWC), a privately held corporation, has developed the Vidler Recharge Facility (VRF) in the Harquahala Valley, approximately 90 miles west of the Phoenix, Arizona metropolitan area to be used as a groundwater storage facility of excess Central Arizona Project (CAP) water supply. This facility has been designed and permitted to store 100,000 acre-feet of water annually for 20 years. Associated with the recharge project, a recovery facility, consisting of high capacity production wells, will be developed in the near future to recover 40,000 acre-feet of stored water annually. The VRF uses a combination of methods to store the CAP water including basins and vadose zone recharge wells. This is the first article in a three part series that discusses the development of the recharge facility from the pilot recharge facility construction to full scale operation. This article will focus on the development of the pilot recharge facility. In 1998 VWC initiated the design and construction of a pilot recharge facility at the MBT Ranch properties in La Paz County, Arizona. This was done under a “constructed” underground storage facility permit issued by the Arizona Department of Water Resources (ADWR). The pilot recharge facility was used to evaluate state-of-the-art recharge methods by coupling shallow basins and vadose zone recharge wells. Figure 1 shows the three identical four-acre basins and headworks that were constructed as part of the facility. The areal photograph presented in Figure 1 is oriented to the northwest and shows the intersection of Interstate 10 and the CAP delivery canal. CAP source water was pumped from the canal and piped to a distribution box located at the top of the “T” in between the three recharge basins. Water was pumped at a rate between 3,000 and 3,500 gallons per minute (gpm) from the CAP aqueduct to the pilot recharge site through a 15-inch PVC pipeline approximately 6,000 feet in length. Hourly performance data, including water level and flow rate for each basin were collected by a programmable controller and transmitted via satellite back to the office of HydroSystems, Inc., for analysis. Soil resistivity and neutron logging data as well as groundwater level and water quality data were used in evaluating the efficiency of the water migrating to the aquifer. Initial pilot studies were performed on the basins during a 90 day test period. Two of the three basins had no form of infiltration rate enhancement and yielded an infiltration rate of 0.8 to 0.9 feet per day. The third basin (Basin B) incorporated the use of two vadose zone recahrge wells within the basin itself. Utilizing the vadose zone wells allowed the source water to bypass upper fine grained soils and access coarser grained sediments approximately 80 feet below the basin. This allowed the recharge of the source water directly into a coarser grained zone. Incorporating the use of one vadose zone recharge well yielded an increase in the recharge rate to 1.05 feet per day over the same time period. This was an increase of between 15 to 24 percent depending on which control basins used for comparison. Figure 2 shows the results of the pilot recharge facility testing and includes the addition of operating vadose zone recharge well number 2 only. Vadose zone recharge well number 1 was not operated during this test. More vadose zone recharge wells would only increase the infiltration capacity of the recharge facility. |
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Figure 1. Recharge basins and headworks of the Vidler Recharge Facility. Photo is oriented to the northwest; intersection of I-10 and the CAP delivery canal can be seen. |
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Development of a Large Scale Groundwater Storage Facility in Western Arizona by Dorothy Timian-Palmer , P.E., Greg L. Bushner , R.G., and Gary G. Small , P.G.
Part 1 of 3 / Volume 1, Issue 1 |
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Date: May/June 2002 |
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