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provides evidence supporting the existence of a successful drainage filter system. The Division should consider CTL/Thompson's opinion that "We believe the performance of Streeter Fill, which was conducted of similar materials in similar fashion to the proposed fills, clearly demonstrates spoil placed in this manner can satisfy criteria 4.09.2(3) (a,b,c,d) above". In the letter of January 28, 1992, the Division has incorrectly interpreted CTL/Thompson's Geotechnical Engineers to have "recommended the inclusion of inspection techniques to verify that the underdrawn is not contaminated by spoil". This is simply not CTL/Thompson's intention. In their letter of December 16, 1991, CTL/Thompson has recommended "contingency planning should observations during construction indicate additional measures are appropriate. For example, the thickness of the first lift over the drain could be established at 50 feet and adjusted if necessary". CTL/Thompson acknowledges the importance of maintaining a sufficient lift thickness of spoil over the drain to provide for gravity sorting of spoil material. CTL/Thompson asserts that the integrity of the rock underdrawn will be provided as long as gravity sorting is maintained. It has always been Colowyo's intention to maintain sufficient dump height to ensure adequate gravity sorting of spoil material. To address CTL/Thompson's recommendation, the inspection plan has been modified to incorporate the Division's concerns. To clear up any uncertainty by the regulating community regarding the issue of subdrain contamination, Colowyo will also conduct a gravity segregation demonstration as suggested by the Division. Colowyo has discussed this demonstration with the Division and it was agreed that we would construct a small demonstration "subdrain" within the current pit backfill area then spoil over the top with pit run spoil material. We will then excavate and expose the subdrain to verify the viability of our proposed method of subdrain/spoil placement. CTL/Thompson will subsequently analyze the demonstration, and submit a report to the Division. It was further agreed that successful completion of the demonstration "subdrain" should result in the resolution of the Division's remaining geotechnical issues on the proposed fills.