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BN 111 LOADOUT <br /> <br />2.05.3 (4) PONDS, IMPOUNDMENTS, AND DIVERSIONS <br />The loadout site is a small flat area which produces very little <br />runoff. Runoff which does occur drains to the Northeast. Three <br />sets of Burlington Northern Railroad tracks prevent any runoff <br />from leaving the site on it's eastern boundary and flowing into <br />the Purgatory River, as they are higher in elevation than the <br />loading area. <br />A sump on the northern boundary of the loadout site is planned to <br />be used to contain the runoff from a 10 year - 24 hour storm with <br />a sediment storage volume for a 3 year period. A diversion ditch <br />on the western side of the loadout will be used to divert runoff <br />water from unaffected areas to the west. The diversion ditch <br />would flow in a northerly direction. Construction of the ditch <br />would consist of a grader cut 2 feet in depth and approximately <br />570' in length with an approximate 1% grade. The ditch would be <br />maintained as necessary to keep it clear. <br />Material excavated from the sump would be used in the construction <br />of 1 foot high berms where necessary to help control runoff and in <br />the truck ramps. <br />Existing Area Description AC Curve No. Land Use <br />Railroad Yard 3+ 87 Industrial <br />Sump Design <br />10 year - 24 hour precipitation event at the loadout site is 3.00 <br />inches. <br />10 year - 24 hour runoff is 1.74 inches. <br />Sump volume required to contain the 10 year - 24 hour storm runoff <br />at this site is: <br />1.74 in. X 1 ft. X 3 acres .44 acre-ft. or 18,949 ft' <br />12 inches <br />• <br />V <br />~- 654 <br /> <br />