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• The variation in subsurface flow and normal surface <br />infiltration was derived from large amounts of early spring <br />precipitation and snow melt runoff from this years above average <br />winter snow pack levels in the region. This abnormal amount of <br />runoff induced slope failures throughout the North Fork Valley, <br />varying in size and characteristics, on both natural and man-made <br />slopes. <br />IMPROVING STABILITY CONSIDERATIONS <br />Practical considerations can require that slopes susceptible <br />to sliding have their stability improved to make the area usable <br />and safe. Slope areas that have experienced sliding in the past <br />should be considered likely to undergo further movement if loading <br />conditions change. In the interest of economy, improvement and <br />protective methods such as slope flattening and drainage control <br />conventionally are preferred and generally receive first <br />• consideration. Soil stabilization methods and the use of piling or <br />retaining walls are expensive procedures which are practical <br />practices in areas where public buildings or highways are located <br />or planned, and where the health and safety of the public are <br />potentially endangered. <br />A variety of procedures have been considered for use to <br />stabilize this slope. Generally, corrective or preventive measures <br />that involve reducing the mass or loading that contributes toward <br />sliding, improving the shear strength of the earth in the failure <br />zone, and construction or installation of elements that would <br />provide resistance to movement where considered. The protective <br />procedure recommended and implemented on this slope took into <br />consideration: <br />1) The type of soil in the slope, <br />2) The thickness and depth of the materials involved in the <br />sliding, <br />3) The groundwater conditions, <br />4) The areal extent requiring stabilization, <br />21-7 <br />