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1 `. Memo to Cathy Begej - 3 - March 13, 1990 The following comments apply: 1. Colorado Mined Land Reclamation Division does not have guidelines for overburden suitability determinations at this time. We believe that ESP is a better determination of sodium hazard in materials, such as overburden, that are not presently in equilibrium with their environment. SAR tnen may be a more accurate determination of sodium hazard in materials, such as topsoil, that are more or less in equilibrium with their environment. It is also obvious, from side by side comparison of ESP and SAR values of the samples, that the ESP values were somehow calculated from other numbers than the SAR values. Please provide the raw sodium milliequivalent per 100 grams of soil values that must have been used to calculate the ESP value on the Overburden Analysis Tables so the Division can check their accuracy. These would most likely be from ammonium acetate extraction methods used in the lab. Alternatively, please provide ESP test values run on alternate overburden samples from the Pit 2 area. 2. The Division assumes that the units used for the Cation Exchange Capacity (C.E.C.) column were milliequivalents per 100 grams of material. Is this correct? Documentation of Overburden Mixing KCC is probably correct in its assumption that the truck and loader operation they use will suostantially mix the overburden. The report they cite does seen to prove this point with standard deviations of highly variable parameters decreasing substantially with mixing. However, the one thing that the repori did mention is that with organic carbon, mixing made a substantially greater portion of overburden unsuitable as opposed to ameliorating this problem. Thus, ii would seem that the best strategy still is to carefully identify unsuitable overburden material and selectively handle thai material. With this in mind, the following comment applies: 1. The Carter Mining Company (CMC) study (Lindsey, 1987) that KCC cites to back up its contention that truck and shovel operations mix overburden has been reviewed by the Division. We agree that substantial mixing of overburden will occur with the mining methods used by KCC. We do not agree that this mixing will necessarily alleviate all the problems identified in the overburden. Review of the CMC study revealed the conclusion that mixing does not always alleviate problems associated with the overburden (see the conclusion that relates to organic carbon). KCC may want to institute a study similar to the CMC one which will demonstrate that the problems identified by more intensive overburden sampling will indeed be eliminated by mixing. In any case, the CMC study conclusions increase the belief of Division personnel that KCC should immediately institute an overburden sampling program in the Pit 1 and 720 Pit areas to ensure that high sodium materials are not placed in the groundwater or plant rooting zones. Please respond to this concern.