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has the potential to store 0.1 Acre -feet of water on the uphill side of the island assuming <br />a 300 foot length and 1 feet depth of water. This is approximately the amount of water <br />that would runoff from the 1 acre that is above each island during a 2.6 inch event. This <br />is the approximate drainage area for each island. The estimated infiltration rate is 100- <br />500 gpm. This would allow the stored water to infiltrate in roughly 72 hour. Since this <br />amount of water stored is from an 100 year event, water rights issues are not expected <br />from this stored water. We are not aware of any similar reclamation techniques that use <br />this island method on dry areas with minimal topsoil. <br />4. Page E -4 should have said "All on site flows will end up in a sediment pond either in <br />Mining Area 1,3 or 4 not 1,2 or 4." The sediment pond sizes are shown on the <br />Stormwater Plan Map. The collection ditch design criteria is shown on the ditch detail <br />figure. <br />5. All 100 year event calculations have been revised from 2.2 inches to 2.6 inches as <br />requested. <br />6. All runoff calculations have been revised to us a CN of 88 instead of 85. <br />7. The sediment ponds are sized to collect and hold the runoff form a 100 year 24 hour <br />event. The ponds are oversized to account for sedimentation as well as equipment and <br />product stockpiles located within the ponds during operation of the site. Delineation and <br />capacity of the sediment ponds is shown on Map G - Stormwater Plan Map. The <br />western sediment pond captures flows from 119.56 acres and with a CN of 88, the <br />effective runoff is 1.46" which results in 14.62 acre -feet. The same calculation from the <br />eastern sediment pond with a drainage area of 40.26 acres results in 4.92 acre -feet. The <br />collection areas are shown on the Stormwater Plan Map. <br />8. The soil listed on Page I -1 was incorrectly labeled and the correct label is 45 for that <br />soil group. <br />9. A stormwater discharge permit will be required since the natural topography of the site <br />without man made controls would discharge runoff from disturbed areas. <br />10. The Stormwater Plan Map has the drainage areas delineated. The TC (using TR -55), <br />Peak Flow and channel calculations are attached. There are two peak flow calculations <br />that were used to categorize all the channels and the ditches on site and to size the <br />culverts crossing the BLM access road. The largest area that will flow through one <br />structure is SWB 6 and SWB 7 combined and has the largest peak flow of 96 cfs. This <br />is the flow that was used to design the Larger Channel that will be ripped into the <br />bedrock. The channels in SWB 2,3,4 and 5 were all designed using the largest of their <br />areas and have a resulting peak flow of 46 cfs. Some of these channels outlet into other <br />structures like the culverts and the collection ditches. These were also designed at 46 <br />cfs. <br />There is also a transition area where the flows from the BLM property to the south of <br />the site will need to transition from on top of gravel and overburden down to the <br />sandstone channel. These transition zones will be designed with the same cross section <br />