2008-05-15_REVISION - C1981008 (2)

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35% by volume. The proposed standard would allow for coarse fragment content of up to 50% in individual locations, with anover-all average coarse fragment content of 25%. Notation 5 to the table indicates that, for prime farmland Lift A at least, the suitability levels for total coarse fragments and fragments greater than 3" diameter, would be based on weight. Coarse fragment suitability limits are typically presented as percent by volume (initial calculation may be by weight, then converted to volume). Email correspondence from David Dearstyne of NRCS to Edward Baltzer of Walsh Environmental, included in Attachment 2.04.9-11, recommends sampling of percent rock fragment sizes and amount by volume. In a letter of March 20, 2008 to Ross Gubka, Mr. Baltzer states that percent coarse fraction and other information was recorded into a field notebook and transferred to Table 2 of Attachment 2.04.9-11. Presumably, the coarse fraction estimates included in Table 2 of the attachment, for the replaced Bench 1 subsoil substitute material, are percent by volume, but this is not specified. Please revise Table. 2.04.9-2 to specify that proposed coarse fraction limits are based on by volume, or, if applicable, provide documentation to support use of limits based on by weight. Also, please specify in footnote to Table 2 of Appendix 2.04.9-11, whether reported coarse fragment % values are based on weight or volume, and provide detail regarding the procedure used. Finally, please specify a Lift B upper limit of 35% by volume for individual sample locations, or provide rationale/documentation to support the 50% individual / 25% average limits proposed. The methodology associated with the proposed limits should be consistent with that used to obtain the values reported in Table 2 of Attachment 2.04.9-11. 5. The suitability level for selenium (2 ppm) appears to be relict from original permitting activities. Current guidelines available from other western states indicate more stringent marginal levels or suspect levels for selenium (e.g. 0.1 ppm suspect level in Montana, 0.4- 0.8 marginal levels in Wyoming). Colorado does not have aSoils/Overburden guideline document, but typically we accept suitability levels established based on Wyoming or Montana guidelines, or independent documentation based on relevant current literature. As such, the suitability level for selenium may need to be amended. Conversely, if previous soil sampling and sampling of Bench 1 overburden that could potentially be placed in the root zone has documented the absence of elevated levels of selenium, continued analysis of selenium within replaced topsoil, subsoil, or rootzone overburden may not be warranted. Please address this concern, provide appropriate documentation, and amend the table as appropriate. 6. The statement in the first paragraph under Prime Farmland Determination - 2008, that there are 107.96 acres of 98E Map Unit in the permit boundary is somewhat misleading. The 107.96 acres would appear to be the entire acreage of the Morgan property in the permit area, southwest of the intersection of BB Road and 2700 Road. This property is dominated by the 98E map unit, and the entire property will be treated as prime farmland. Limited areas of the 98E map unit located to the east of 2700 road in the permit area are also depicted on Map 2.04.9-1, but these areas have been previously reclaimed under the permitted assumption that the units were not prime farmland. Please clarify that the 2008 2