ENFORCE34541 - Laserfiche WebLink

Home Browse Search

Memo to Boulay Jumbo Mountain Landsliding page 4 North Fork Valley on slopes of varying gradient and aspect. The largest and most notorious active landslide in the area is the Muddy Creek Landslide, east of Paonia Reservoir. The immediate area of the rejuvenated landslide movement is grossly headed by the large (up to 50' vertical relief) headscarp mapped by Dames and Moore in their 1993 report. The active landslide mass appears to be approximately 1,600 in length between approximately the 7450-foot and 7150-foot elevation contours. While numerous extensional cracks were examined, I did not discern a major compressional zone, but our logistics did not allow me to examine the lower third of the landslide where I would expect compressional features to predominate. Norm Every of MCC, who has examined this area recently, did not recollect a significant compressional or overrun area. Translation of the sliding debris can be accommodated in general bulging of the landslide mass, which is normally evidenced by cracking parallel to the fall line. Many such cracks do exist on the active landslide mass. Commonly, the specific translocation of landslide material can only be determined by the comparison of precision pre-failure versus post-failure surveys of the landslide mass. In my opinion, the cracking and disruption which we examined in the SW1/4 of Section 24 on Jumbo Mountain is indicative of a 30 to 50 acre landslide mass. This landslide exhibits characteristics common to modern landslides throughout the North Fork valley. As such I would expect this landslide to undergo several years of active creep, after which it may become more stable. The cracks and troughs affecting roads and trails will require grading to render them passable. Cracks in the off-road areas will close by in-filling and features will become more subdued with erosion. I recommend road repair be more extensive than just filling the crack. If a four or five foot pad of ripped and recompacted material is placed across the major features it will increase the capability of accommodating the continued creep movements which will normally occur for the next several years. Some larger cracks and troughs will undoubtedly require repeated treatment to maintain trafficability. These repairs should restore safe access to the affected area, which may be important for emergency situations on the Mautz's Chipeta Guest Ranch. Continued monitoring should be periodically conducted to determine if additional repairs are required. Signage should be erected to inform users of possible hazards. Aerial Photographic reconnaissance of Muffler Rock landslide In an attempt to examine the coincidence of the current landsliding