Laserfiche WebLink
Page 7 . • <br />vertical backwall and backfilled to a 3:1 slope, as required by the plan. It is easier to calculate the <br />amount of fill needed if one starts with a right triangle that assumes the entire thing needs to be <br />backfilled. Thus (27.5 x (3 x 27.5))/2 = 1134 square feet. That is the cross-sectional area IF the <br />backwall was vertical. However, the actual final condition will have the inner 27.5 feet of that <br />triangle as solid rock that will not need to be backfilled. To determine the cross-sectional area of <br />the backfilled portion of the entire triangle one must deduct the solid rock (1:1 highwall) from the <br />cross-sectional area of the initial triangle. That cross-sectional area is (27.5 x 27.5)/2 = 378 square <br />feet. If you subtract 378 from 1134 it leaves a 756 square foot cross sectional area that will need to <br />be backfilled to create a final slope of 3:1. <br />Thus the "1:1 highwall not needing backfill" refers to the fact that that portion of the total <br />slope does not need to be backfilled and does not need to be included in the backfill cost. It does <br />not mean that a 1:1 slope will be left unbackfilled. The plan requires that all final reclamation <br />slopes be created to no steeper than 3:1. <br />Put another way, after the mining is completed a 1:1 or equivalent slope will remain at the <br />edge of the quarry. That is then backfilled to create a 3:1 slope thereby burying the 1:1 slope in fill <br />and eliminating any stability concerns. The confusion came about because of the way the <br />backfilled cross-sectional area was calculated. <br />Again, sorry about the confusion. Next time I will include a diagram that will explain this <br />better. <br />Respectfully, <br />~~~~ <br />Mark A. Heffner <br />cc: Castle Concrete <br />Mark Davis, Colorado State Board of Land Commissioners <br />