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Elk Creek Mine TR-60 <br />2nd Adequacy Review <br />16 Dec 2008 <br />Page 4 of 9 <br />pond routine for straw bale sediment control modeling, please explain. <br />Otherwise, please see comment number 7D below. <br />C. In the Sedcad designs, Oxbow used the pond routine to model the silt <br />fence sediment trap. Please explain why Oxbow used the Sedcad pond <br />routine for the silt fence when a silt fence routine is available in Sedcad. <br />D. It does not appear that there is a satisfactory way of directly modeling <br />straw bales for sediment control in Sedcad. Previous attempts by other <br />operators involved either modeling the straw bales as silt fence or as grass <br />filters, with the assumption that the straw bales act similarly. If Oxbow <br />would like to use another approach to Sedcad modeling for straw bales <br />besides the pond routine, the Division suggests that the silt fence routine <br />be used in Sedcad with a permissivity rate of 5.6 gpm/ftz, similar to that of <br />straw bales. A note should be added that the designs assume that the straw <br />bales will filter sediment similar to silt fence. <br />8. None of the Sedcad designs for the small area exemptions that use silt fence or <br />straw bales for sediment control show the construction requirements, such as <br />length, height and tie back distance. Only the required surface area is given. <br />Since the silt fence and straw bales are part of a designed structure, please revise <br />the Sedcad designs to show the construction requirements for the silt fence and <br />straw bales. <br />The Division has no further concerns. In the submittal dated November 26, 2008, <br />Oxbow provided the dimensions for the straw bale sediment control structures. <br />9. Please add a notation in the legend for Map 2.05-El-BCA2 that explains the use <br />of yellow color to designate small area exemption areas. <br />The small area exemptions on Map 2.05-E1-BCA2 have been labeled. However, <br />as noted in item number 3 above, the Division is requesting that all disturbed <br />areas be designed as SAES, including the inlet and outlet disturbed areas for Bear <br />Creek culvert BCC-1 and the cut slope just east of the fan pad. <br />10. No entry road is designated on Map 2.05-El-BCA2. Please explain how the fan <br />site will be accessed from the Bear Creek ranch road and whether or not a road <br />culvert will be needed. <br />The Division has no further concerns. The November 26, 2008 submittal <br />contained a revised facilities plan in which a light use road will be used for access <br />to the fan site.