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Chapter V <br /> Areas of severe erosion are common both along the <br /> roads and on mine benches. They may be caused by <br /> insufficient or poor surface drainage; long, uninterrupted <br /> fill or cut slopes may also contribute to severe erosion. <br /> It appears that drainage and erosion problems are the <br /> most important factors contributing to most instability <br /> features and causing sloughing, sliding, rilling, gullying, <br /> rockfall and mudslides. <br /> The actual slopes along the haul roads, says the study, are for the most part <br /> fairly stable: <br /> Potentially unstable slopes are very rare along the haul roads and absent on <br /> mine benches. They include areas that were unstable prior to any mining <br /> activity; excavations of cuts or placement of fills probably caused a further <br /> decrease of stability and increased instability of fills. <br /> In establishing vegetative cover along the steep slopes above and below the <br /> road, Mid-Continent believes that the narrowed roadway, which will serve as, in <br /> effect, a small bench, will be helpful. <br /> The vegetative study of steep slopes which has been completed by <br /> Intermountain Soils notes that: <br /> — The spoil material appears suitable as a plant growth <br /> medium. <br /> — By far the most limiting factor in successfully <br /> revegetating these sites is the steep slopes. <br /> — Berms, furrows or benches may provide enough <br /> temporary relief from surface instability to allow more <br /> uniform initial establishment from top to bottom. <br /> Because of the erosion of steep slopes traversed by the roads, stabilization and <br /> establishment of vegetative cover above and below the road cuts will be aided <br /> by interruption of surface runoff down the steep slopes, such as would be <br /> afforded by retention of the narrowed roadway, acting as a small bench. <br /> The post-mining use of the roads is to provide the U.S. Forest Service access <br /> for land management.* <br /> • A landslide area above the No. 3 Mine road, near the tunnel portal, will be <br /> monitored for stability. if such monitoring indicates the slide area has <br /> de-stabilized, Mid-Continent will initiate further discussion with the U.S. Forest <br /> Service as to maintaining access to the No. 3 road after mine closure and <br /> reclamation. <br /> 23 <br />