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• <br />APPERDIX II <br />A, Storm Runoff Predictions <br />In general, water does not fail to infiltrate the undisturbed <br />• <br />forest floor, but there are exceptions. Regardless, there are two <br />factors associated with storm flow production that can be altered by <br />mining activities: (a) alteration of the infiltration characteristics <br />of the surface, and (b) alteration by disturbance of the storage <br />c~acity in the soil. Leaf (1977) has discussed in detail the effect - <br />of tree removal on the distribution and melt rate of winter snowpack, <br />potentially a third factor. Because of changes in both the amount and <br />melt rate of the pack, either the infiltration rate or storage capacity <br />could be exceeded causing higher peak flow rates; but we are not treating <br />this runoff in the content of storm flow. <br />Most mining activities, excluding site preparation, do not signifi- <br />i• <br />cantly disturb the soil surface except for the access and related systems. <br />These access systems have the potential for changing the hill slope <br />hydrology. Subsurface soil water is intercepted by road cuts and benches, <br />for example, and routed over the surface as is the rain falling directly <br />on them. There is a potential for altering the timing and delivery <br />route to the channel of perhaps 10 - 15 percent of the precipitation. <br />The impact of this potential on the storm hydrograph can be expepted <br />to be variable--the storm flow peak and volume may or may not be increased <br />by water from the access system and the effect depends on how the re- <br />routed water enters the system. The net effect can be to reduce the <br />peak or augment it depending on normal basin response. <br />