2016-10-21_REPORT - M1980244 (27)

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Technical Memorandum Solution Collection Piping Modifications NewFields Job No. 475.0106.006 August 22, 2016 Page 3 Containment Berm Plan and Profile, and Figure 5, the geomembrane was anchored on the top of the containment berm at an approximate elevation of 9889’ around the mill platform. During the 2016 construction season, the contractor will install 80 mil LLDPE geomembrane between the crest of the Process Solution Storage Area (PSSA) Pond and the Mill Site Earthwork containment berm. Once the geomembrane is installed, the area will be completely lined and the pipe bench will be constructed below the containment berm as depicted in Section A on Figure 2. If the barren pipe should fail along the mill platform, the barren solution would be contained within the limits of the Squaw VLF or within the sump of the Mill Platform. It is NewFields professional opinion that the Barren pipe can be installed along the 9880 construction bench, near the toe of the containment berm within the limits of the mill platform as shown in Section A in Figure 2 because this area is completely lined with geomembrane, posing no risk of barren solution migrating off the lined surface in the event of a failure. There is sufficient surge capacity within the lined area to ensure containment of any flows that might result from a failure. 3.0 REMOVING THE PERIMETER 12” DIAMETER PERIMETER DRAIN ALONG THE MILL PLATFORM NewFields was requested to review the removal of the 12” diameter perimeter drain along the mill platform, as illustrated in Figure 2. The perimeter drain is shown below in Figure 3 and in Detail J on Drawing A230 of the Squaw Gulch Valley Leach Facility drawing set. The perimeter drain is to be installed within the pipe bench around the perimeter of the facility and its purpose is to aid in the collection of barren solution in the event of a barren pipe failure and reduce the chance of solution flowing off the lined area.