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March 1998 Slump Investigation and Mitigation Report ~ Page 11 <br />6.0 FOLLOW-UP SITE INSPECTION <br />On October 30, 1997, MWA conducted an additional site inspection, including water level <br />monitoring, analysis of available data, and development of a recommended slump stabilization <br />plan. The results are presented in the following sections. <br />6.1 SITE INSPECTION <br />The site inspection included general observations of the slump area and collection of water level <br />data from the piezometers. Z'he following observations and conditions were noted: <br />• The general area was covered by a two-inch snow layer, but with approximately 50 <br />percent of the ground surface still visible. <br />• Water was observed in 5 of 6 piezometers, as indicated in Table 1. <br />• The outfall pipe from the existing French drain and the soil around the outfall pipe <br />were dry. <br />• The upper quarter of the slump surface was approximately level to slightly sloped <br />back towards the head scarp. This surface was also very irregular and would not <br />allow positive drainage of incidental surface water or snowpack that could <br />accumulate in that area. <br />• Observations indicated that the temporary movement markers previously placed in <br />aline across the center of the slump mass appeared to be in the same alignment as <br />the last site visit on September 8, 1997. The two eastern-most posts appear to be <br />outside of the eastern slump limit. <br />• A shallow drainage ditch perpendicular to the slope that previously bisected the <br />slump area was blocked by the offset resulting from the slump. <br />• There appeared to be no noticeable movement of the slump since the September <br />1997 investigation. <br />6.2 DATA ANALYSIS <br />6.2.1 Subsurface Soils <br />As discussed in Section 4.1, the strike of the bedrock is N90W, with a dip of 8 degrees to the <br />north. This is generally consistent with the orientation of the ground surface in the area of the <br />slump. Piezometer borehole logs, which are included in Appendix A, indicate that the top of <br />weathered bedrock was observed between 3 and 10 feet bgs, with very dense material occurring <br />just below the soil/bedrock contact. The blow count data indicated that competent material is <br />shallower on the west side of the slump in the vicinity of PZ-S, which may help account for the <br />slight eastward or cross-slope trend of the slump mass. <br />Motttgon:ery Watson Americas ' P.O. Box 774018 `Steamboat Springs, Colorado " 80477 (97D) 879-616G <br />m: ~v~~sr.mp.M,np.m~~9.mp x~,., <br />J~:)/+l d6 <br />