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could account for the shear zone preferring the base of the oxidized zone. <br />Two conditions are required for this theory to hold. If the colluvium was deposited by down slope <br />movement of detrital material from up slope, then there must be enough material in the up slope azea to <br />create the deposit; and, furthermore, the lower colluvium material must be deposited in an unoxidized <br />condition. <br />if either condition cannot be proven, then the Lower colluvium, and perhaps some of the Upper <br />colluvium, may not be colluvium but rather an alluvial deposit. In any case, a more detailed examination <br />of the physical chazacteristics of the Upper and Lower colluvium, particularly near the contact, may be <br />needed to verify these theories. Figure H3 shows a cross section of the landslide neaz the abandoned <br />substation area that illustrates the geological stratigraphy. The present estimated boundary of the landslide <br />is also shown on Figure H 1, based upon a combination of information taken from survey mirrors and <br />visual observations. <br />• In any case, downslope from the estimated location of the buried rock bluff, the base of the slide (shear <br />zone) generally coincides with the contact of upper and lower colluvium. This landslide is termed the <br />"Main Landslide". Up slope from the buried rock bluff, the base of further shallow slides appears to be at, <br />or near, the bedrock surface (Rao, 1983) (HLA Cross Sections, 1998). These landslide areas are termed <br />"Secondary Landslides". Fundamentally, the secondary slides are not part of the main slide, but are related <br />and can be effected by activity at the main landslide. <br />In the "main landslide' area, downslope of the rock bluff, the landslide can be chazacterized as follows: <br />Overall Dimensions: Present Maximum Width of 1400 to 1500 feet. <br />Present Maximum Length of 1200 to 1300 feet. <br />Maximum Depth of 60 feet. <br />Surface Area of 30 to 40 acres. <br />Maximum Volume of 2 to 3 million cubic yards. <br />Maximum Ratio of Depth to Length of 0.05 <br />• Barr Engineering Company July 31, 7999 <br />PCDOCS1208220/CAK 4 Appendix H <br />1999 Addendum to <br />1997198 Landslide Corrective Measures Report <br />