Laserfiche WebLink
9/30/93 <br />Responses to Comments <br />San Luis Reclamation Evaluation Report <br />Page 12 <br />investigation for the embankment raise (10~ cm/sec) <br />are sufficient to characterize this material as a <br />soil liner effectively tens of feet thick. <br />However given the discussion above, BMRI recognizes <br />that the limits of the augering equipment did not <br />allow for sampling at depth in the lower tailings <br />disposal area. During the week of September 20th, <br />BMRI collected additional samples utilizing a vibra <br />core drill. Information on the vibra core drill is <br />included as Attachment 1. Two holes were <br />successfully completed to within 10 to 15 feet of <br />the liner. Ten feet above the liner was sHt as the <br />maximum depth based on the requirements approved by <br />the Division for the geotechnical investigation that <br />holes completed using mechanical drilling equipment <br />not go within ten feet of the liner. The third hole <br />was completed to a depth of 25 feet before meeting <br />with refusal due to the dense nature of the <br />tailings. BMRI will collect a water sample from <br />these tailings as well as complete initial <br />geochemical testing of the tailings solids to <br />determine if geochemical changes warrant completion <br />of the full geochemical test program. <br />Comment: <br />The report contains an explanation of the history of tailings <br />deposition within the Upper and Lower Tailings Ponds from the <br />April 1991 facility start up through March of 1993 when the <br />final fluid sample was collected. Briefly summarized, at the <br />time of sampling on November 10th through 13th, 1992 the Upper <br />Pond contained only pre-violation tails (April '91 - January <br />'92). However, these tails had been exposed to hydrogen <br />peroxide which was added to the standing pool of fluid in the <br />summer of 1992. Six shallow holes (Holes ~1 - #'6) were augered <br />(six feet or less in depth) in the Upper Pond tails aid no in- <br />situ fluid samples were collected. These shallow hails may <br />have been invaded by the hydrogen peroxide treated' fluids, <br />which may have modified their chemical constituency. No <br />information was collected regarding the migration of high-WAD <br />fluids through these tails, or the affects of subsequent <br />exposure to hydrogen peroxide treated fluids. <br />Response: As discussed in Section 2 of the Preamble, the <br />tailings samples collected from the Upper Disposal <br />Area were not influenced by the addition of hydrogen <br />