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These culverts are designed to pass drainage flow intercepted by the roadway <br />ditches, and flow originating on the roadway under the roadway to natural drainage <br />channels. As the roads are intended to remain in service for the duration of the mining <br />activity, the culverts have been sized by criteria for permanent culverts and have been <br />checked by the Board's regulations. These regulations require that permanent culverts <br />35 square feet or less in area be designed to pass flow from a 10-year precipitation event, <br />culverts with areas over 35 square feet be designed to pass flow from a 20-year precipita- <br />tion event, and that bridges with spans over 30 feet 6e designed to pass flow from a 100- <br />year precipitation event. All the culverts, except the Taylor Creek culvert, have less <br />than 35 square feet in ores and were thus checked for passing the flow from a 10-year <br />precipitation event. The Taylor Creek culvert is a 10-foot diameter culvert which placed <br />this culvert in the class required to pass flow from a 20-year precipitation event. <br />The results of the capacity checks are given in Tables 3 thru 6. The 24 culverts <br />ranging in size from 18" to 48" were all found to be of adequate size to pass the 10-year <br />flow event, and similarly the 10-foot Taylor Creek culvert was found adequate to pass a <br />20-year flow event. In these checks, the culverts were assumed to be flowing full which <br />• requires minor heeding up at the culvert entrances. The amount of this heading up above <br />the top of the culvert is approximately equal to the sum of the entrance loss and the velocity <br />head of flow through the pipes. For the culverts checked, the required heading up to obtain <br />full pipe flow ranges from about one. to two feet, which amount is provided by the height of <br />the road embankment above the top of the culvert entrances. <br />DRAINAGE OF MINE AND FILL AREAS <br />The initial excavation from the mined area was placed in the Streeter Gulch mine <br />fill, and subsequent excavation is being placed in the area where mining has been completed. <br />Similarly as mining proceeds into the Section 11 area, mine fill will be placed in Gulch A <br />initially, followed by placing of fill in the area where the mining has been completed. <br />Later, as the mining proceeds into the area adjacent to a tributary of Taylor Creek, the <br />area will be progressively mined and then filled by successive mine waste. The final <br />• <br />4 <br />