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 Slide <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