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~ ~ ~IIIIIIIIIIIIIIIIIII` Er~vir~r~rr~er~~, Ir~c. LARRY E. O'BRIAN 7985 VANCE DRIVE, SUITE 205A PRESIDENT ARVADA, COLORADO 80003 303.423-7297 July 2, 1996 Mr. Bob Oswald Environmental Protection Specialist Division of Minerals and Geology Miner..lg Section. - Snuth 1313 Sherman Street, Suite 215 Denver, CO 80203 o1=r.FIVtD ~ui• p5 196 Division of Minerals 8 Geology Dear Bob: RE: Delta Sand and Gravel, CO., Spring Creek Pit Amendment MLRB Permit N M-94-097 After reviewing your most recent bond calculations I have concerns with some of your analysis. I can agree with your unit costs, but some of the volumes and resulting costs are where we differ. I will try to address ease concerns by the TASx number used in your bond analysis printout. After reviewing your numbers I prepared a new bond cost analysis. It is attached for your review, as you go thru my comments on each Tasx. TASK #1 - HIGI-IWALL REDUCTION, my concern here deals with the swell factor you used when figuring the volume of dirt that wouid need to be moved. 1 do not believe a swell factor is necessary here because the slopes to be created have a finite volume. If you add a swell percentage factor to the amount being placed there would be an excess amount of material left after the cut/fill process is done. Since compaction of the material occurs as the slope is created and very seldom does this compaction approach 100'%, the cudfill process will actually produce an excess of material. To effectively calculate the amount of material needed, is to multiply the bank measure fill volume needed by a shrink factor of some sort, say 85%. This would mean to obtain the 12,950 cubic yards we would have to cut 11,008 cubic yards since the swell that occurs and the compaction that takes place do not totally offset each other. The 12,950 cubic yards are a bank fill number used to calculate a bond