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INTEROFFICE MEMORANDUM <br />TO: <br />BROCK BOWLES <br />FROM: <br />JANET BINNS <br />SUBJECT: <br />NEW HORIZON NORTH, C2010-089, TRU REVIEW <br />DATE: <br />DECEMBER 21, 2015 <br />CC: <br />I have reviewed Western Fuels -Colorado (WF -C) adequacy response, dated November <br />16, 2015, to the Division's adequacy letter, dated October 27, 2015. <br />I specifically reviewed responses to adequacy concern No. 2.05.4(2)(4) 45. <br />WF -C proposes to update the testing parameters for Bench 1 overburden/ sub soil <br />material. Bench 1 material has previously been approved to place over graded spoil and <br />then covered with the appropriate topsoil prior to seeding during the reclamation process. <br />Updates to Table 2.05.4(2)(4)-1 include; raising acceptable subsoil pH from <8.4 to <8.5, <br />defining acceptable limit to electrical conductivity values (EC), eliminating the saturation <br />percentage parameter and replacing it with neutralization potential ratio, defining <br />acceptable sodium adsorption ratio as </= 15, defining acceptable soil electrical <br />conductivity ,/= 6 mmhos/cm, and reducing acceptable calcium carbonate percentage <br />from <40% to <20%. WF -C has not proposed any changes to the acceptable selenium <br />value or the acceptable textural class. <br />pH: increasing the acceptable sub -soil pH by 0.01 is acceptable. <br />Defining acceptable electrical conductivity (EC) for subsoil as </= 6.0 is adequate. The <br />commonly accepted units for EC are usually mS/cm. However, there is a 1:1 relationship <br />between mmhos/cm and mS/cm, so the Division accepts WF -C's units of mmhos/cm. <br />Elimination of the saturation percentage test is acceptable. The Bench 1 material will be <br />used as subsoil, and though it will be considered rooting media, the soil parameters for <br />the topsoil placed over the Bench 1 material is more critical to vegetation establishment. <br />Use of neutralizing potential ratio is acceptable. This parameter is commonly used to <br />evaluate mine waste. It is useful in anticipating if waste material will produce acid rock <br />drainage (ARD). Values greater than 2 have a low probability of developing ARD. <br />Requiring the NPR >/= 2 should provide reasonable confidence that the subsoil will not <br />be acid forming. <br />WF -C proposes to raise the SAR value for acceptable subsoil to </=15. SAR provides <br />adequate indication of sodicity of the soil. Most dryland and pasture grasses have a <br />