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Mining Plan By trimming, the next lower bench is created. The process is then repeated on that • bench. This process will be repeated over and over until the bottom of the total slope is reached. The result should tie a series of benches containing sufficient backfill to allow for good growth and an average slope (the line drawn from the top of the hillside to the bottom of the hillside through the benches) closely approximating the reclamation slope shown on the Reclamation Plan Map. As discussed previously, the formation itself imparts some degree of instability in the benches that are created. This instability results from the bedding planes in the limestone and the dip of the rock. This instability is graphically illustrated in Figure MP-5. Most sedimentary rocks exhibit bedding planes that represent changes in the conditions that control sedimentation. Limestone is usually a marine formation created by a combination of various organisms that produce calcium carbonate shells, either bottom dwelling creatures like clams or planktonic organisms. Changes in the marine environment causes changes in the populations of these organisms and that results in variations in the kind of limestone produced. Cataclysmic events ranging from massive floods on nearby land masses, mountain building, submarine landslides and turbidity flows, and even collisions with extraterrestrial bodies can also contribute to producing changes in the nature of the bedding planes. • When the Rocky Mountains were created during the Laramide Revolution and the subsequent uplift in the Miocene, most of the limestone mined on this site was uplifted at an angle of about 30 to 35 degrees. Before uplift, of course, the bedding was level. Because of other tectonic processes, the limestone th Area MS on the south end of the site lazgely escaped this severe deformation. There the dip of the rock is no more than about 5 degrees, or, for all practical purposes, essentially level. When the limestone is mined, a bench is produced. This bench cuts across the bedding planes of the limestone. Unfortunately, the normal tendency of the limestone is to break along the bedding planes tilted at 30 to 35 degrees. Level steps cut into the limestone remain level until weathering processes begin to weaken the joint along the bedding planes. As the weathering proceeds pieces of an exposed bench exfoliate and this eventually creates a sloping step out of what was originally a level step. Usually, the resulting slope is about 5 to 15 degrees but local areas can fail so severely a step slope of 25 to 30 degrees results. About 1980, after realizing the difficulty that was occurring with the benches and the difficulty of reclaiming benches, an experiment was tried on old benches located in the northern portions of the quarry (Area RB). Essentially, the top of the mountain was blasted away including all the er:isting soil and vegetation. This material was allowed to spill over the benches • further down the slope. Although rapid backfilling of the lower benches was accomplished, the Page 16 Pikeview Quarry Amendment Exhibit D