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~ ~- <br />~ ~ ' ~~ <br />`_. <br />2.05.6(3) PROTECTION OF HYDROLOGIC BALANCE <br />1.0 Surface Water <br />Runoff from Pryor Canyon is not currently used for domestic or livestock <br />consumption since flows are very infrequent. The stock watering pond in the <br />upper basin of the unnamed drainage xill not be disturbed by current mining <br />plans. If channels are restored to their original capacity and no <br />impoundments are created by roads or culverts xhen reclamation is complete, <br />the quantity of runoff in Pryor Canyon will not be affected. <br />The primary area of concern for protection of the surface xater system is <br />erosion during and after mining. The following discussion will outline useful <br />techniques in runoff control and describe indicators of high-potential erosion <br />zones. Design criteria for erosion control structures are presented in <br />section 4.05 HYDROLOGIC BALANCE. <br />1.1 Basic Goals of Runoff and Erosion Controls <br />Expose the smallest practical area of land for the shortest possible <br />time. <br />Loss of vegetative cover and creation of steep slopes greatly <br />increase soil loss. If these disturbances are reclaimed as soon as <br />possible, soil loss from the watershed and resultant clogging of the <br />downstream cha.nels can be minimized. Thus, efficient scheduling of <br />mir._~;g and reclamation activities can help protect the hydrologic <br />balance, <br />Keep detached sediment close to its source. <br />Minimal disturbance occurs if the sediment is redeposited near its <br />origin. This also avoids disposal of large, accumulated masses of soil <br />at some downstream point in the basin. Slowing the runoff permits the <br />sediment to drop out of the flow.. Berms around the base of the <br />stockpiles, small depressions on long or steep slopes, contour furrowing, <br />and terracing are examples of methods used to slaw runoff velocities, <br />~' - <br />Design stable channels diversions roads culverts and embankments <br />These structures can produce excessive erosion if not properly <br />designed. This is especially true if failure occurs. Specific examples <br />of design considerations pertinent to the Pryor mine site are discussed <br />1FSA-61 <br />~ ~~ ~~ <br />J. F SATO & IISSOCiATES. iNC. <br />