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rado Consultants, Inc. Geotechnical !Environmental Engineering • Materials Testing May 7, 2003 East Fork Mutual Ditch Company c/o Kent Whitmer Box 38 Hot Sulphur Springs, CO 80451 Job Number: 03-5547 Subject: Slope Failure Evaluation and Stabilization Recommendations, East Fork Troublesome Ditch - Elk Fork Ranch, Grand County, Colorado. Gentlemen: As requested, NWCC, Inc. (Northwest Colorado Consultants, Inc.) has prepared this report to summarize our observations made at the subject site and provide recommendations for stabilizing the slope failure that has occurred beneath a section of the East Fork Troublesome Ditch that is located on a portion of the Elk Fork Ranch in Grand County, Colorado. Project History: Based on our discussions with several of the ditch owners and ditch riders, it is our understanding that the subject irrigation ditch was constructed approximately 20 years ago. The ditch originates approximately ]mile north-northeast of the subject site along the East Fork of Troublesome Creek. It appears that the ditch, in the vicinity of the subject slope failure was constructed as a cut and that a considerable amount of blasting and ripping had to be completed to construct this portion of the ditch. We have been advised that the ditch runs with 2'/z to 3 feet of water in it and at a flow rate of approximately 75 cfs (cubic feet per second) when the ditch is flowing with it's adjudicated flow. It is understanding that the subject slope failure originally occurred in 1998 after the ditch had been turned on and that the slide/failed area has increased in size over the last several years. We were told that they have observed seeps/springs in the azea of the failure, as well as to south of the failed azea and below the ditch every year since the original failure occurred. We also understand that the springs/seeps are observed to start flowing ~ approximately 2 to 3 weeks after the irrigation ditch is put into use and the seeps/springs run for another 2 to 3 weeks after the ditch has been shut off. We have been notified that the ditch was put in use/opened this year on March 24. It is also our understanding that the ditch owners attempted to line the ditch several years ago with a 6-mil, reinforced plastic visqueen sheeting. However, the plastic lining did not appear to stop the seeps/springs from flowing and it was removed. Site Observations: As requested, NWCC, Inc. has visited the site three times to evaluate the site conditions in and near the subject slope failure. At the time of our first site visit on April 7, 2003, we met with Allan Wheatley, ditch owner, and Randy Keck from Elk Fork Ranch. At the time of our visit, we observed that the subject irrigation ditch was flowing and we were advised that the dischazge in the ditch was approximately 30 cfs. We also observed that a slope failure/slide had occurred below the ditch and the roadway/berm that runs along the west side of the ditch. It appeared that the upper portion of the failed ~ (970) 879.7888 • Fax (970) 879-7891 • nwccl @mindsprtng.com 2580 Copper Ridge Drive • P.O. Box 775226 • Steamboat Springs, CO 80477