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Page 4, Item 5(A) — Packer Testing <br />Table 8 -11 reports packer test results. Does the borehole number indicate the mine level at <br />which the test was conducted, i.e., borehole 19D -53 indicates a borehole drilled from the 19 <br />level? If that is correct, then it appears that all packer tests were conducted at the 15 level or <br />deeper. Statements are made in various sections of the EPP that the bulk hydraulic conductivity <br />of the bedrock is on the order of 1.0E -07 to 2.8E -07 cm /sec. Is this estimate of the bulk hydraulic <br />conductivity based on the packer test results from mine level 15 and deeper? If so, it excludes the <br />hydraulic properties of the upper two thirds of the mine workings. Independent assessments <br />suggest that fractures in deeper workings of the mine are less transmissive to ground water flow <br />relative to fractures in shallower workings, and therefore the packer tests at depth may <br />significantly underestimate overall mine hydraulic conductivity. Please provide an assessment of <br />the validity of bulk hydraulic conductivity estimates that are biased toward only the lower one - <br />third of the mine workings. <br />RESPONSE: <br />Cotter Corporation (N.S.L.)'s Response to December 14, 2010 Adequacy Review, <br />Comments 5(A) and 11(D) <br />May 5, 2011 <br />Yes, the name of each packer test indicates the drill hole or drill station from which the test was <br />conducted. The length of each drill hole (up to 742 feet), angle ( -71 to +8 degrees), and test <br />interval indicated which zone of the bedrock was being tested. The selection of test locations <br />was intended to provide hydraulic conductivity data for the individual rock types (mica schist <br />(MS), lime - silicate hornblende - gneiss (LSHG), garnet biotite gneiss (GBN), and pegmatites. <br />The 19 Level drill station was selected for most of the packer testing because the holes had been <br />drilled relatively recently, at the time, and were expected to have remained open for testing. <br />The overall hydraulic conductivity of the mine is known from the 40 -year pumping test of inflow <br />to the mine workings, and is presented in Section 8 of the EPP. The overall hydraulic <br />conductivity of the mine can also be calculated from seven years of water level recovery (refill) <br />data. All of these evaluations of mine rock hydraulic conductivity are presented in the EPP. <br />Future revisions to this section of the EPP will include a footnote explaining how the drill holes <br />were named and the purpose of the packer testing in identifying variations in hydraulic <br />conductivity of different rock types such as the GBN (Schwartz Trend rocks). However, since <br />the over - arching focus of the EPP is the protection of Ralston Creek from near surface impacts, <br />the bulk hydraulic conductivity of the bedrock is not discussed in the revised EPP Section 15. <br />Page 6, 11(D) — Tests <br />Section 15 (b)(iii) Source Removal, page 15 -7. The operator proposes accelerated weathering <br />tests. As previously discussed in the review process for TR -14, EPA method 1312 (synthetic <br />precipitation leaching procedure, or SPLP) is more appropriate for this type of characterization <br />than method 1311. However, these tests are only 18 hours in duration and do not provide a <br />complete assessment of long -term leaching behavior. For that reason, the operator must select <br />one sample among the suite to be submitted for SPLP analysis that will also be subjected to a <br />long -term accelerated weathering test. The Division recommends the humidity cell test, ASTM <br />1 <br />