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<br />the underdrain fill to 8 inches as currently required in the Technical Specifications. This is <br />primarily due to the joint spacing of the granodiorite. The majority of the granodiorite <br />material comes out of the borrow area with a 12 inch maximum size with occasional oversize <br />pieces. Flow carrying capacity of the underdrain was discussed and it was noted that the 12 <br />inch maximum size would increase the flow capacity of the underdrain and would not be <br />structurally detrimental to the structural support necessary for the leaching facility. Golder <br />has advised CC&V that the grain size distribution of the underdrain fill as stated in the <br />Technical Specifications should be modified to include a maximum particle size of 12 inches <br />while maintaining a maximum 6 percent passing the No. 200 sieve. We therefore request <br />that change in specifications, and, once again, would appreciate receiving confirmation of <br />acceptance at your earliest convenience. <br />As mentioned above, the results of MWMP testing submitted by CC&V to the OMLR on <br />June 19 indicated that some water-quality parameters were present in the MWMP rinsate at <br />concentrations higher than surface water standards (using, as a surrogate, standards for <br />Cripple Creek). During a meeting with the OMLR and Golder on June 30 it was agreed, I <br />believe, that the aggressive ~1WMP testing performed on sand size sample specimens <br />obtained from drill cuttings would likely not be representative of potential contaminant <br />liberation from the larger grain size of the underdrain fill but would instead overstate the <br />concentrations resulting from normal infiltration. The consensus gained during the meeting <br />was that the MWMP may be an indicator of the constituents but the actual concentration of <br />constituents would be more of a function the surface area of the particle size. <br />Therefore, at the recommendation of those in attendance at the meeting, a "scale factor" was <br />developed by Golder by comparing the Dso of the underdrain fill (6 inch) to the Dso of a <br />medium sand (lmm or 0.04 inches). The particle shape was assumed spherical for <br />calculation purposes. The surface areas of a 6 inch and 0.04 inch diameter sphere are 113.1 <br />in2 and 0.005 ins, respectively, a difference of five orders of magnitude. Also, the volumes <br />of a 6 inch and 0.04 inch diameter spheres are 113.1 in' and 3.35 x 10-5 in;, respectively. <br />Assuming a typical value of 0.4 for porosity of sand, it can be shown that 2,025,671 <br />(precisely) grains of the medii~.m sand will occupy the 113.1 in' of the 6 inch sphere. Tlie <br />total surface area of the 2,025,671 grains of sand (spheres) is 10,128 inZ or approximately 2 <br />orders of magnitude higher than the 6 inch sphere which would occupy the same volume. <br />Based on these computations, a "scale factor" that relates MWMP rinsate to "real world" <br />conditions in the underdrain should be on the order of 0.01. <br />it was also noted during the meeting that certain of the additional analyses that were <br />requested appear inapplicable to Arequa Gulch because of the fact that the nearest classified <br />stream is Cripple Creek and even if it were classified, Arequa Gulch does not provide for <br />certain of the potentially designated uses, such as drinking water supply, because of natural <br />limitations. A few of the parameters were measured for a different, but more encompassing <br />form, that makes evaluation provided by CC&V more stringent. With the acknowledgement <br />of the conservative nature of the MWMP, and the safety factor thus imposed, we believe that <br />there is no longer a question about the chemical quality of the water and its lack of potential <br />3 <br />