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Type ojMovement: Sliding with a downslope movement of soil occurring dominantly on <br />surfaces of rupture or on relatively thin zones of intense shear strain <br />between the upper and lower colluvium. <br />Mode ojsliding: Translational sliding mode with a mass of relatively shallow depth <br />displacing along a planaz surface, sliding over the original ground surface. <br />Material: Earthen with SO% of the material smaller than 2 mm. <br />lf~ater Content: Moist to Wet sometimes containing some water with no free water; the <br />material possibly behaving plastically to containing enough water to have <br />liquid flowing from it or supporting significant bodies of standing water. <br />Rate ojMovement: Very Slow (1 foot per year) to Extremely Slow (1 inch per year). Rates <br />in spring have increased over time until 1997 and decreased significantly <br />• in the Springs of 1998 and 1999. <br />Style ojActiviry: Singular primarily but with some complexity due to smaller elements <br />within. The main body of the slide appears to be moving as an unbroken <br />block. However, small translational, rotational failures within the head of <br />the slide such as at the upper access road between the material storage <br />bench and F-seam portal bench or lower access road north of the <br />maintenance shop have occured. <br />Distribution ojActiviry: Advancing primarily since the surface of rupture has been primarily <br />extending in the direction of movement. This is particularly noticeable at <br />the abandoned substation, where the legs of the 46kV Deadend Structure <br />straddle the main scarp with the base of the north leg dropped lower and <br />spread farther apart. A similar phenomena has occurred at Tower 11-12 <br />of C-1 Conveyor where the tower has dropped in elevation and been <br />separated from the uphill gallery. There is some possibility that the slide <br />Barr Engineering Company July 31, 7999 <br />PCDOCSL2g8220ICAK 5 Appendix H <br />7999 Addendum to <br />1997199 landslide Corrective Measures Report <br />