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to interpret. Please provide a revised Attachment page 2.04.9-7-11, with <br />columns correctly aligned beneath appropriate headings. <br />4. The suitability levels for coarse fragment content for Prime Farmland Lift B and <br />Single-Lift Soils in Table 2.04.9-2 will need to be further explained and <br />documented. Typical upper limit recommendations for root zone coarse fragment <br />content are in the range of 30% to 35% by volume. The proposed standard would <br />allow for coarse fragment content of up to 50% in individual locations, with an <br />over-all average coarse fragment content of 25%. Notation 5 to the table indicates <br />that, for prime farmland Lift A at least, the suitability levels for total coarse <br />fragments and fragments greater than 3" diameter, would be based on weight. <br />Coarse fragment suitability limits are typically presented as percent by volume <br />(initial calculation may be by weight, then converted to volume). Email <br />correspondence from David Dearstyne of NRCS to Edward Baltzer of Walsh <br />Environmental, included in Attachment 2.04.9-11, recommends sampling of <br />percent rock fragment sizes and amount by volume. In a letter of March 20, 2008 <br />to Ross Gubka, Mr. Baltzer states that percent coarse fraction and other <br />information was recorded into a field notebook and transferred to Table 2 of <br />Attachment 2.04.9-11. Presumably, the coarse fraction estimates included in <br />Table 2 of the attachment, for the replaced Bench 1 subsoil substitute material, are <br />percent by volume, but this is not specified. <br />Please revise Table 2.04.9-2 to specify that proposed coarse fraction limits <br />are based on % by volume, or, if applicable, provide documentation to <br />support use of limits based on % by weight. Also, please specify in footnote <br />to Table 2 of Appendix 2.04.9-11, whether reported coarse fragment % <br />values are based on weight or volume, and provide detail regarding the <br />procedure used. Finally, please specify a Lift B upper limit of 35% by <br />volume for individual sample locations, or provide rationale/documentation <br />to support the 50% individual / 25% average limits proposed. The <br />methodology associated with the proposed limits should be consistent with <br />that used to obtain the values reported in Table 2 of Attachment 2.04.9-11. <br />The suitability level for selenium (2 ppm) appears to be relict from original <br />permitting activities. Current guidelines available from other western states <br />indicate more stringent marginal levels or suspect levels for selenium (e.g. 0.1 <br />ppm suspect level in Montana, 0.4-0.8 marginal levels in Wyoming). Colorado <br />does not have a Soils/Overburden guideline document, but typically we accept <br />suitability levels established based on Wyoming or Montana guidelines, or <br />independent documentation based on relevant current literature. As such, the <br />suitability level for selenium may need to be amended. <br />Conversely, if previous soil sampling and sampling of Bench 1 overburden that <br />could potentially be placed in the root zone has documented the absence of <br />elevated levels of selenium, continued analysis of selenium within replaced <br />topsoil, subsoil, or rootzone overburden may not be warranted. Please address <br />2