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<br />• <br />• <br />bodies of standing water. <br />Rate ojMovemenr: At the time of movement, Slow (5 ft/yr) to Moderate (<5 ft per month). <br />At present little or no movement. <br />Style ojActiviry: Singular. <br />Distribution ojActiviry: Advancing primarily since the surface of rupture has been extending in <br />the direction of movement. <br />State of Activity: Reactivitated at the time of failure because the area had previously been <br />activated when the F-Seam Portals were constructed, but at present <br />Suspended. <br />In summary the "secondary landslide" above the buried rock bluff and the F-Seam portals can be classified <br />to be a[ [he time of failure as a reactivated, advancing, singular, moderate, moist to wet, lronsiationa! <br />earthen slide. However, at present the slide is suspended and dry. The rate of landslide movement is <br />triggered by wet conditions. <br />The observations between deep wells and shallow wells indicate that a downward vertical gradient <br />(decreasing water levels with depth) exists throughout the site. The majority of the shallow wells seem to <br />indicate that the rate of groundwater recharge exceeds the rate of discharge causing some seasonal, or <br />longer term, groundwater mounding. A strong downward vertical gradient is chazacteristic of a <br />groundwater recharge area. Seasonal or continued groundwater mounding is characteristic of local <br />recharge [o a system with well developed shallow inlets but inefficient outlets. In other terms, the primary <br />groundwater source comes from surface snow melt or rainfall on areas above and within the landslide. In <br />the past, the slide could not remove this water effectively. Water levels in piezometers at the head of the <br />slide rise about twice as much as water levels in piezometers in the body and toe of the slide, suggesting <br />that the primary source of water entering the landslide is land above the landslide. Approximately 126 <br />acres of land surface or watershed azea, lying above the head of the slide, drains into the landslide area. <br />The landslide is part of approximately 86 acres of watershed azea that drains to the North Fork. These <br />Barr Engineering Company <br />PCDOCS1208220/CAK <br />July 37,1999 <br />Appendix H <br />1999 Addendum to <br />1997/98 Landslide Corrective Measures Report <br />