Laserfiche WebLink
INTRODUCTION <br />During the heavy spring runoff of 2011, the Seneca II -W reclaimed areas experienced numerous <br />new and reactivated landslides, slumps and mudflows. A site visit and meeting was held on July <br />6 and 7, 2011 with Jill Carlson (Colorado Geological Survey), Sandy Brown (DRMS), Susan <br />Burgmaier (DRMS), Brian Len (NWCC) and SCC personnel to discuss and identify areas of <br />instability. SCC has prepared the following documentation to: 1) indentify unstable areas within <br />the disturbance boundary; 2) document present conditions of each area; and 3) present a <br />remediation plan/approach for each area. This proposed plan is based on a report prepared by <br />Jill Carlson (CGS); the report is attached for reference. <br />AREAS TO BE REPAIRED /STABILIZED <br />® Oil Well Access Road Slump <br />— Problem: This was a small slump that encroached upon the road ditch and disrupted <br />surface drainage on upper side of the road. <br />— Remediation: The slump area was regarded; the ditch reopened; a drain was installed to <br />allow unrestricted water flow out of the slump area; and, a rock toe buttress /retaining <br />wall was install to add additional stability. <br />— Status: Work has been completed <br />• Pump house Slade <br />— Problem: This was a small slide area that had water flowing out of the toe and that <br />encroached into the road ditch. <br />— Remediation: The slide area was regarded; the ditch reopened; a drain was installed to <br />allow unrestricted water flow from the toe of the slide area; a road above the slide area <br />was reclaimed to eliminate channelized flow into the slide area; and, the area was <br />revegetated. <br />— Status: Work has been completed <br />® Pit Ramp Slide <br />— Problem: The slide is situated on or near a final pit highwall and access road ramp. This <br />area has been "remediated" numerous times using recommendations from Division <br />specialists and from accredited geotechnical engineers to no avail. These measures <br />included reducing the slope grade above the slide, regrading the scarp and reducing the <br />loading in the upper portions of the slide block. <br />During the latest inspection, SCC learned that the area was historically mapped as <br />containing a mud flow, landslide deposits and generally unstable slopes (Madole, Colton, <br />and Miller). So it appears that the backfill in this area is resting on unstable native <br />materials causing continuing instability and "sliding ". <br />Remediation: <br />1. Excavate two trench drains <br />2. As recommended by CGS, one trench is proposed along the existing gullies near the <br />horizontal midpoint of the slide mass, and another in the wet area near the western toe <br />bulge above the road ditch. The trenches should extend through the slide mass and <br />TR -76 20 -E -1 11/11 <br />