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9/30/93 <br />Responses to Comments <br />San Luis Reclamation Evaluation Report <br />Page 22 <br />represent the natural precipitation cycle and second <br />because the recycling might cause surface coatings <br />on the tailings prohibiting further reaction. The <br />use of fresh water for each flushing is believed to <br />represent a "worse case" for the acid generation <br />during the humidity cell testing. <br />Comment: <br />BMRI should explain why the EPA Method 1312 was chosen, and <br />describe more fully why this method was chosen over accelerated <br />weathering tests that are available. <br />Response: As discussed in Section 4 of the Preamble, the EPA <br />1312 test method was chosen for several reasons. <br />This test method was developed and is recoggnnized by <br />the EPA as an acceptable test method for det!ermininq <br />the leachability of mine waste materials. The <br />second reason that this method was used was to <br />provide data for comparison to the original tailings <br />materials as required by Abatement Requireanent #8. <br />EPA 1312 leachability tests were conducted on the <br />original tailings material as discussed in the <br />approved permit and changing methods at this point <br />would not allow for the required comparison. <br />Comment: <br />BMRI should also describe the results of the accelerated <br />weathering test in terms of the Battle Mountain tailings <br />system. What is likely to happen to the leachates under the <br />physiographic and climatic conditions at the site once the <br />system is closed? <br />Response: In respect to the chemistry and leaching of the San <br />Luis tailings, the EPA Method 1312 test pXotocols <br />will result in enhanced levels of dissolved species <br />in the test leachates, with respect to leaching that <br />will be seen on site and once the system is closed. <br />This is due to the relatively aggressive nature of <br />the test protocol. <br />However, once the physiographic and climatic <br />conditions are factored in, very minimal, if any, <br />water movement is expected through the tailings and <br />leachate is expected to be virtually non-existent. <br />As discussed in the report, the tailings have <br />compacted to a permeability of l0~ cm/sec and will <br />