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R.J. Gordon Construction LLSI Project 2211 <br />October 30, 2015 Page 5 of 5 <br />The current is monitored using an electronic detector that converts the increase in the <br />current to an audible tone indication. This method does not require the liner to be flooded with <br />water. However, the liner under test must be in contact with the supporting sub -grade. Therefore, <br />the surveys are usually conducted at night or early morning when wrinkles are minimized. <br />C. Soil -Covered Survey <br />A high voltage isolated DC power supply was used to impress a voltage across the <br />geomembrane using one electrode placed in the operations layer located on top of the geomembrane <br />and a second electrode in contact with earth ground. Therefore, the geomembrane liner provides an <br />electrical barrier between the electrodes except where there are holes in the geomembrane liner. <br />Electrical current flowing through the holes in the geomembrane liner produces localized anomalous <br />areas of high current density near the holes. This electrical current path is provided by electrically <br />conducting material such as water, sand, or soil. <br />The survey of Area 2A, was conducted by making potential gradient measurements <br />on the moist soil with measurement electrodes spaced approximately three feet apart. These <br />measurements were made approximately every three feet along numbered survey lines that were <br />spaced approximately five feet apart. A portable digital data logger was used to collect the data. The <br />data was then downloaded into a portable computer for display, plotting, and analysis. <br />When a leak signal is detected, manual measurements are made to locate the position <br />of the leak between the survey lines. The leaks are excavated by others and the leak is isolated from <br />the materials covering the geomembrane. Additional measurements are made to make sure there are <br />no additional leaks in the area. <br />If there are any questions regarding the electrical survey or this report, please contact us at <br />(210) 408-1241. We appreciate the opportunity to have been of service to you. <br />Respectfully, <br />'�'4 <br />John Ortiz <br />Senior Project Manager <br />Approved <br />I, / d•� <br />Daren L. Laine <br />President <br />