Analysis of a Contaminated Bedrock Aquifer by Means of a Packer and Attempts at Remediation Using a Packer

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AbstractA dolomite bedrock aquifer in the Northeast has been contaminated with volatile organic compounds. These compounds have made their way into our pumping well, which contains total volatile organic concentrations averaging 2 to 4 ppm. The source of these organics has not been positively identified. Television video logs show considerable vertical fractures in the upper 20 feet of the bedrock aquifer. Below this, where bedrock is more consolidated, there are a few areas of caverns and large crevices, some of which are 10 feet thick. It was first thought that perhaps the organics were entering the well through a few of the crevices that could be grouted off from the remainder of the aquifer. We fabricated an inflatable packer so that isolated sections of the well could be sampled. Using the video logs as guides, the vertical sections of the well was sampled and the centerline of the plume was determined.The packer was comprised of two steel rim supports that supported innertubes. The two packers were separated with 4 feet of steel rod. Placed on top of the lower section was a standard submersible well pump that could pump a flow rate of 10 gpm. The packer assembly was lowered into the well with a winch and then at selected locations the packer was inflated with air to 50 psig. The submersible pump was turned on and allowed to pump the section for 30 minutes to adequately purge the area and obtain a representative sample.The results of the sampling showed the maximum concentration to be at 95 feet below the surface. The entire aquifer is 125 feet thick. This means the lower third contains the organics. To determine what vertical section supplies the most water, we divided the well into thirds, and ran a material balance using three different compounds. From the analysis, we determined that a packer placed at the 70‐foot level and only pumping from that section will reduce organics concentration by a factor of 10 and reduce flow only by 20 percent.A commercial packer has been installed at the 70‐foot level in the well and the pump was raised above this level in hopes to reduce organics concentration in the well water. The packer is still under testing, but after four months of operation, there has been no dramatic decrease in contaminant levels. This may be the result of leakage around the packer or due to the high permeability of the dolomite aquifer.