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Design Precipitation 2.8 Calculated S <br />Average CN 67 4.9253 73 1 343 3 <br />Description Porous Gravel Topsoil <br />Piles <br />Calculated Runoff Volume (Q) 0.4886955832 <br />Calculated Runoff Volume (acre-ft.) 0.25249271799 <br />Ponding Percentage 5 <br />Actual Runoff Volume (acre/ft.) 0.23986808209 <br />A CN of 67 is assigned to the gravel since it is neazly void of fines and almost all runoff penetrates <br />into the ground. This pond has a surface azea of 0.19 acres therefore, its required depth is 1.26 feet. It <br />will be dug 2.0 feet deep with 2H:1 V sideslopes. <br />Willits Ponds #4, #5, and #6 have collection ditches which feed them at the toe of the disturbed az- <br />eas. These ditches will be dug in gravel so they need no lining and they will be dug to 1.5' depth with <br />2H:1 V sideslopes. <br />Since the runoff from the 100 year event is contained in all parts of the site, no discharge permit or <br />stormwater permit is needed for the site with the CDPHE. SPCC plans will be maintained for the <br />entire operation. <br />2.3 Access Roads <br />All access roads are described in Section 1.3 of this mine plan. All trucks that leave the site for the <br />gravel operation will use Accesses 1, 4 or 6. All traffic supplying product demand to the south of <br />Alma will enter Highway 9 using Access 1 or 4 so that the traffic does not go through the town. Ev- <br />ery effort will be made to minimize the truck traffic through the town for all demand that exists to <br />the north. As described in Section 1.3, the roads will either be watered or sprayed with magnesium <br />chloride to keep dust down. These measures will be done on an as needed basis to ensure that dust is <br />Alma Placer 7/03 29 <br />