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Memo to Larry Oehler 2 October 24, 1993 embankment are less saturated than was anticipated during the original design analyses. in fact, during the original design review, the design engineer indicated that there would be no saturated tailings in the vicinity of the dam, yet the 1993 cone penetrometer testing identified two potentially saturated zones, including one layer that is quite pervasive. Also, drawings included in the 1989 amendment indicate that Raise 1 will be constructed from type 1 material with an outer shell of type 2 material, whereas drawings included in the 1993 design report depict Raise 1 constructed out of type 1 material in its entirety. Finally, it is disturbing to me that a specification change that represents a 350 percent increase in the fines content of the material, is referred to in the construction status report as a "material with slightly greater fines content". Liner Cover / Drainage Blanket The operator has agreed with the Division that the maximum allowable amount of fines in the drainage blanket material will be 35 percent, and has modified the contractor's borrow and placement procedures to allow conformance testing of the drainage blanket materials prior to placement. The operator has initiated a conformance testing program which will consist of gradation analysis of one sample from each 1/2 acre of drainage blanket that has been placed. One sample per 1/2 acre may be sufficient frequency, unless a large percentage of failing samples are identified, in which case the sampling frequency may have to be increased. Conformance testing for gradation of drainage blanket material that has yet to be placed should be condmcted at a frequency of one test (ASTM D422) for each 1500 yards of material borrowed if the material is shown to be consistent, or one test for each 500 yards of material if the material is variable. Also, the operator should provide details as to how out of specification materials identified by conformance testing of drainage blanket already in place will be amended or removed without damaging the VLDPE liner. The Division is concerned not only with the gradation of the drainage blanket materials, but also with the hydraulic conductivity. The operator has stated that there is no specification in the permit for hydraulic conductivity; the Division does not agree with that statement. The calculations included in the 1989 amendment for performance of the drainage blanket rely on a certain minimum hydraulic conductivity, and in the June 3, 1993 memorandum from Rob Dorey (SRK) to Andre Douchane (BMG) that was provided to the Division in response to concerns regarding seepage from the facility, it was stated that the calculations "conservatively assumes a drainage layer permeability of 5 x SO_q cm/sec". The Division has no alternative ]but to look at such wording as an assessment of the worst case scenazio; recent in situ permeability testing of drainage blanket material shows