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the roadside ditch from entering the disturbed area. To that <br />end, EFCI must provide documentation that the berm is <br />adequately sized to perform both jobs, and that velocities <br />will not result in erosive conditions. A berm is a structure <br />which results in the funneling of water in the same way that <br />a ditch focuses water, and from that perspective, designs in <br />accordance with 4.05.3(1)(e) and 4.03.1(4) should be <br />submitted. In contrast to the argument in the submittal, this <br />berm is not a voluntary, supplemental control feature. <br />9. Please demarcate the west loadout topsoil pile and its <br />topography on Map 13, Loadout Area Surface and Groundwater <br />Hydrology Map. While the staff can appreciate that the map is <br />a hydrology map, the function of the perimeter berm is to <br />prevent water from flowing west, offsite, opposite the general <br />slope direction, simply because there is a topsoil pile there. <br />10. The light use road associated with the rock dust tank does <br />not need to be included in the small area exemption section <br />per the definition of disturbed area found in Rule 4.05.2(4). <br />Please make two other changes. One, document the size of the <br />berm at this site and make an estimate of the amount of water <br />that this berm is supposed to route around the Rock Dust Tank <br />pad, to verify that it is adequately sized. Two, prepare an <br />estimate of the discharge and sediment concentration of any <br />discharge from this site. <br />11. Page 12R was modified to drop references to ditches CD-2 <br />and CD-3. However, staff noticed that the second paragraph <br />still contains references to an emergency open channel <br />spillway. TR-11 resulted in a demonstration that Pond 1 could <br />contain runoff from a 25-year 24-hour event. <br />12. Please revise page 93R to indicate that the 10-year 24- <br />hour peak flow for CD-1 is 4.51 cfs. Also, please reinstate <br />the notations on Map 17 to distinguish between the three <br />reaches of CD-1. <br />13. The April 28, 1992, submittal in response to Stipulation <br />19 modifies rip-rap thickness and commits to a rock filter <br />blanket of 6"-9". The Division uses OSM's Surface Minincr <br />Water Diversion Design Manual, OSM-74 (OSM/TR-82-2), for <br />guidance on rip-rap design and recommends the following <br />criteria to EFCI: <br />a. Dm,,, = Dso x 1.25 (slopes > 10%) <br />b. D~ = Dso x 2 (slopes < 10%) <br />c . Dio = Dso / 3 <br />d. Rip-rap thickness = D,o,,, but no less than 9" <br />The filter blanket maximum sizes should be less <br />than the Dio of rip-rap and the blanket should be <br />composed of a distributed size range of rock. <br />3 <br />