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001039 GEOLOGIC SITE WORK James Soule, a senior CGS geologist, provided technical services and oversight in the drilling and instrumentation program. In addition detailed field observations were made and noted as snow cover decreased. A summary of this work is included as a subsequent section of this report. CONCLUSIONS AND RECOMMENDATIONS ( A monitoring system very close to the initial design is now in place at Dowds Junction and observations should be continued for at least two years or until prevailing high soil moisture conditions have returned to normal. Our initial evaluation from field and instrumental observations is that there continues to be a very real threat especially to the transportation corridors. Larger than historical but not catastrophic events accompanied by higher maintenance costs and lengthy highway closures seem probable unless feasible engineering mitigation measures can be devised and put in place. At least minor blockage of tile adjacent streams is also possible. Tile upper regions of all four slides do not appear to currently be actively moving. This seems to preclude imminent major catastrophic slides, and continued surveillance of instruments in place from approximately March. through July of each year will allow any major changes in stability to be observed. It should be noted that significant enlargement of currently active parts of any of the four slides (the most probable scenario) is to be expected and should be the sUbject of continuing planning. ~ The landslide alert and surveillance has in our opinion been a very valuable experience~.~a11 concerned. For the technical people from CGS and CDOH it demonstrated that even with an urgent mission considerable time is required to get a monitoring system in place and operational. This was primarily owing to the fact that it was done in difficult terrain and at a time when access was most difficult -- while a heavy snow pack was melting and running off. Our preliminary recommendations .for minimizing the damage from existing slides and decreasing the potential for future much ,larger slides includes: 1) A reasoned program to improve surface water management should be undertaken especially in the lower half of the Meadow Mountain slide. Some initial efforts with this have been made by CDOH near U.S. Highway 24 and some additional recommendations are contained in our attached preliminary geologic report. More comprehensive recommendations can be made based on our forthcoming detailed geologic report for CDOH that includes new and accurate topographic mapping. 2) Based on water level observations in the spring of 1986, methods for dewatering of active slide areas on Dowds No.1, Dowds No.2 and the east lobe of the Whiskey Creek slide should be devised. Stabilization of the currently active lower parts of all four slides is a critical factor in preventing future larger and much more serious slide activity. - 3A -