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b) In developing the amended minesoil reconstruction plan, operator is requested to give consideration to <br />replacement of varying thicknesses of topsoil within specified portions of the South Mine reclamation <br />area. In addition to azeas in which the "standard" mean replacement thickness of 1.6 to 1.7 feet would <br />be employed, consideration should be given to planned replacement of both "thickei" and "thinner" <br />soils in designated locations (to be indicated on the amended Topsoil Replacement Map). Soil <br />replacement thicknesses in excess of 2.5 feet (similaz to Skyway andCoutis soils) might be appropriate <br />on selected north slopes, swales, along minor ephemeral drainages, and other locations conducive to <br />the establishment of aspen and associated tall shrub species. Consideration should also be given to <br />replacing reduced soil thickness (e.g. 6 inches) within specified locations, to potentially enhance the <br />establishment of a number of the shrub species inSeedmix 6 and Planting List 2, which are typically <br />associated with relatively shallow, rocky soils. Over-all vegetative diversity within the reclamation <br />area would be expected to be enhanced by such planned variation in topsoil replacement thickness. <br />c) Areas of relatively extensive rill erosion have been observed on recentlytopsoiled, long, steep slopes <br />at Seneca II mine, and similaz slope conditions will be encountered within the II-W South, PR-3 area. <br />Please amend the Seedbed Preparation section of the application to address measures that will be <br />employed to minimize erosion on steep reclamation slopes (e.g. 4:1 or steeper) during the initial years <br />of revegetation establishment. Possible approaches which have proven successful in similaz situations <br />at other Colorado minesites, include extensive surface roughening by track-hoe ordozer gouging or <br />contour dozer ripping, or a combination of these techniques, followed byhydroseeding or broadcast <br />seeding; or, for use with drill seeding, a combination of diversion ditches at intervals along the slope <br />along with contour chiseling and/or closely spaced, short length (e.g. ] 0'), off-set contour furrows. <br />d) In addition to the relatively small scale surface roughening treatments referenced in Item c, above, <br />consideration should be given to the intentional creation of larger scale topographic roughness during <br />spoil grading, to provide a wider variety of slope exposures and sites conducive to the establishment of <br />various plant community types. <br />e) Patches of noxious weeds were observed at various II-W reclaimed area and facility locations during <br />the recent site visit. The most prevalent species were Canada thistle, houndstongue, and various <br />biennial thistles. Scattered individual black henbane and dahnation toadflax plants were also observed. <br />A generalized weed control plan is discussed on page 22-12 and 22-13 of the II-W application, and it is <br />mentioned that "a herbicide application program is currently in place at ...Seneca II Mine and will <br />form the basis for a program at Seneca II-W." Please amend the section to specify the control program <br />for the II-W mine. The program should describe the management and monitoring of noxious species <br />infestations currently present, as well as measures employed to detect and control invasion of any new <br />noxious species. <br />