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<br />drawing of 6-foot post-operations berm above Mine Highwalls (Extract from financial warranty <br />worksheet")). The overburden will be obtained from the area immediately in front of the berms. <br />Other means of warning trespassers of mine highwalls will be subject to OMLR approval. <br />Diversion Channel Stability: The channel flow velocities for design storms and the criterion for <br />erosion requiring riprap was established in the application for Amendment No. 7 as 7 fps (feet <br />per second) based on documentation provided with the application. In responses dated October <br />25, 1998 and November 11, 1998, CC&V explained that the design flow velocity cited by the <br />OMLR is based on the 10-year, 24-hour precipitation event rather than the 100-year, 24-hour <br />event that is used to size the Flow capacity of the diversion system. CC&V understands from <br />the OMLR that the design storm is not considered in the OMLR's determination of whether the <br />channel velocity exceeds the erosive value for the channel substrate. Therefore, CC&V is <br />required to provide properly sized riprap or otherwise demonstrate that the channel sections with <br />design velocities exceeding 5 fps are adequately protected. CC&V will continue to pursue <br />consideration of the proper design storm for channel velocities outside of Amendment No. 7. <br />Soil Amendment for Interim Reclamation: The OMLR requested CC&V to reassess the <br />previously-adjusted financial warranty to provide for the possibility that reclamation might, at <br />some intermediate stage of the operations, require lime amendment of the subsoil. In response, <br />CC&V is providing information to the OMLR regarding the rooting depths for grass species and <br />plant communities representative of rangeland conditions in this area (Attachment 2). <br />Attachment 2 identifies the rooting zone for certain grasses including western wheatgrass, <br />characteristic of the species used for the Cresson Project reclamation. Sixty five percent of the <br />wheatgrass root mass is in the first 12 inches and 79 percent is within the first 24 inches. The <br />biomass, or root system, for most grasses CC&V uses have similar distributions of root mass <br />with depth. Given that 6 inches of soil are applied over the subsoil, the amendment of lime to <br />one foot provides an 18 inch-deep amended area. The other table in Attachment 2 states that <br />from 94 to 98 percent of the root mass of grasslands that are grazed, that is the "below ground <br />biomass," is located in the zone from 0 to 18 inches. Thus, the proposal in our November 11, <br />1998 letter to add lime to the upper foot of the subsoil would neutralize, if neutralization were <br />required, the layers that were most important to the grassland growth. Further, the proposal was <br />for the application of lime to the entire surface of the overburden storage areas, 581.30 acres, <br />which would not be the case in the field because some, and possibly much, of the area would <br />not require lime. <br />Notwithstanding CC&V's belief that the application of lime to one foot of overburden over the <br />entire acreage of overburden storage areas was adequate, CC&V is increasing the computed <br />financial warranty an additional amount that will provide 10 tons of lime per acre and place the <br />lime in the upper two feet of subsoil. The total increase in financial warranty for this <br />hypothetical case of liming is $596,280. This is a two-fold increase in comparison to the <br />computations submitted on November 11, 1998. The revised computations follow. <br />3 <br />