Laserfiche WebLink
Technical Memorandum ' <br /> Liner Integrity Engineering Support ■ <br /> Leak Detection Recommendations <br /> NewFields Job No.475.0106.023 <br /> March 27,2018 <br /> In March,2018, NewFields completed a second site visit to assess the area after removal of some <br /> of the ore and discuss the path forward with CC&V. At this time,the majority of the ore had been <br /> removed, to an average thickness of 10-12' above the geomembrane, and it appeared that an <br /> isolating strip of geomembrane could be exposed to facilitate the leak detection survey. <br /> 2.0 RECOMMENDATIONS AND PATH FORWARD <br /> At this time, NewFields recommends performing a leak detection survey in the area of concern <br /> to determine the integrity of the existing geomembrane. Prior to the arrival of the leak location <br /> survey company,TRI-Environmental (TRI), the following steps need to be completed. <br /> Isolate the area of concern by exposing geomembrane around the entire perimeter of the <br /> area. During this work, NewFields will continuously observe and document the removal of <br /> remaining ore and drain cover material to create the isolation strip of geomembrane liner. <br /> Any potential tears or punctures of the geomembrane will be documented with coordinates <br /> and photos for future repair; as necessary. <br /> Test in in-situ resistivity of the ore along the perimeter of the survey area following the ASTM <br /> G57-Standard Test Method for Field Measurement of Soil Resistivity Using the Wenner Four <br /> Electrode Method. The results will be used to create a baseline for the leak location survey <br /> results. <br /> Moisture condition the area to be surveyed. This is needed to ensure that any leaks in the <br /> survey area are adequately wetted. This can be accomplished by first adding fresh water <br /> along the top of the slope, making sure that the water reports to the toe of the slope so that <br /> the surface of the geomembrane under the survey area is completely wetted. Then, the <br /> surface of the entire survey area can be wetted by sprinklers or with a water hose in order to <br /> decrease overall resistivity in the survey area. At this time, we anticipate this will take three <br /> days to accomplish, and should be completed several days before the arrival of TRI. The <br /> perimeter isolation trench must be dry before beginning the leak detection survey. <br /> After these steps are completed, TRI will perform the leak detection survey utilizing industry <br /> standard procedures from ASTM D7007-Standard Practices for Electrical Methods for Locating <br /> Leaks in Geomembrane Covered with Water or Earthen Materials. This procedure will <br /> determine: <br /> y If the ore movements observed in December resulted in a defect in the geomembrane liner <br /> and; <br /> y The location of the hole, if present. <br /> The above standard also outlines procedures to simulate a hole in the geomembrane to add <br /> confidence in the survey results. <br /> Page 2 <br />