2011-10-31_REVISION - M1976009HR (7)

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Menzer Quarry Corrective Action Amendment Exhibit D October 2011 Page 2 Mining Plan As can be seen, the original slope was sparsely vegetated and very rocky. As the ground level photograph (Photo 2) shows, the slope was also very steep with overhanging rocks at the top. The slope also has a slightly concave shape that looks as if the slope might have failed at some time in the distant past and some rock had slid down in a landslide. In these young, steep canyons, such features are very common above the main stream that eroded the canyon. This feature was recognized about 15 years ago, but the slope failure theory had a problem. There was no clearly identifiable evidence of where the material that came down the slope went. The stream channel at that time contained some large rocks, but not nearly enough to replace what appeared to be missing from the hillside. Looking at the ground level photograph, the overhang at the top of the slope appears to have been broken off. It was thought that was the source of rocks in the stream channel. Although we now know that was probably true, it still did not explain where the rest of the rock went if there had been a landslide. It was therefore concluded that the scree was a thin veneer on top of a steep slope of bedrock and that no actual landslide had ever occurred; just occasional rockfalls. Basically, very slow mass wasting at a rate about equal to what Turkey Creek could remove explained the shape of the slope. Besides the channel downstream from the toe of that slope was full of medium sized rock that could have arrived by that very process. Those rocks are still there and were not removed in the corrective action as they are not spill rock. As mining proceeded down the slope shown in Photo 2, care was taken to avoid rock falls down the hillside. There was some rock that came down, but it was minor in volume and always stopped before reaching the toe of the slope. The mining was conducted from the quarry side of the hillside and blasting was done to avoid blowouts on the stream side of the slope. Removal of shot rock was done by pulling the rock back into the quarry. This all went very well until the bottom of the slope was reached and the spill over the side occurred. In the course of mining this slope it was found that the bedrock was usually very hard and stable. PLAN FOR CORRECTIVE ACTION: At the time of the spill, the height of the slope above the stream was approximately 60 feet. When the permit was issued, the total height of the slope was about 175 feet. Thus, about 115 feet of rock had been removed with minimal spillage and that spillage was onto slope that was already a scree slope and would be mined in the future. The mining limit in the permit was identified to be about half way down that 60 foot slope where the spill rock was located. The approved permit plan required that at least a 25 foot barrier of native rock be left between the stream and the quarry to keep the stream from breaking through the quarry edge and establishing a new course through the quarry. That is a requirement for all quarry edge areas along the two major drainages that flow through the permit area. The only exception is at the end of Phase 1 when the smaller and most ephemeral of the major drainages is allowed to flow through a cut in the wall south of the channel. That water would then be diverted through the quarry in a controlled fashion. It is conceivable that action might not be needed, but it is included just in case it turns out it is needed. In that case, the union of Turkey Creek and the large but ephemeral tributary that flows between Phase 1 and Phase 2 would remain as it is today.