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through into the ground so that the water is returned to the natural drainage. The dam will be less than <br />10 feet high and will have 2.SH:1 V sideslopes. The pond azea as shown on Map C-2 is 0.25 acres, <br />therefore the average depth is 3.6 feet. Much of the volume will be attained by excavation within the <br />pond azea. <br />Collection Ditches #2 and #3 will be v-ditches of 1.5 feet depth and 2:1 sideslopes cut out of the <br />natural gravel and shale below the gravel deposit. The slopes of the collection ditches will be less than <br />4%. No lining is needed. A 12" CMP will be used where Collection Ditch #3 crosses under the access <br />road. <br />B) Collection Ditch #1 and Sediment Trap to contain runoff from the western portion of Strips 1 and <br />2 that drain to the West Drainage arroyo. As seen on Map C-2, much of the slope below Strips 1 and 2 <br />will not be disturbed but some minor overburden/gravel may move down the slope during gravel <br />mining. For this reason, a sediment trap and collection ditch are installed to provide sediment control. <br />The trap will detain the flows from the 100 yeaz 24 event for at least 24 hours and the water will seep <br />through the gravel back into the ground. <br />Design Volume Calculations Sediment <br />Trap <br />Area (acres) 3.73 <br />Design Event 100 yr. storm <br />Design Precipitation 2.2 Calculated S <br />Average CN 86 1.62790697674 <br />Description Exposed Porous Gravel and Part <br />Undisturbed Pinon Juniper <br />Calculated Runoff Volume (Q) 1.00317489731 <br />Calculated Runoff Volume (acre-ft.) 0.31182019725 <br />Ponding Percentage 4 <br />Actual Runoff Volume (acre/ft.) 0.29934738936 <br />Bellgazdt Pit 1/06 12 <br />