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3. In the Letter, Tri-State cites the Banta guidance document in regards to salt tolerant ranges and <br />uses a 2-4 mmhos/cm range for moderately salt tolerant species. It appears to the Division that <br />Tri -State's tolerant range and the guidance document contradict each other in terms of an <br />acceptable range for moderate salt tolerance. <br />a. The guidance document states that "For a given mining region, the material damage <br />suspect level would be equivalent to the threshold irrigation water conductivity for the <br />most salt sensitive species grown in the region..." and "...the following salinity suspect <br />levels for material damage are proposed... ...Yampa River Basin and North Park: 1.0 <br />millimhos/cm". <br />b. Table 1 includes four grasses: Smooth Brome, Orchardgrass, Timothy (all Moderately <br />Sensitive) and Mountain Brome (Moderately Tolerant). Per the guidance document, <br />"...yield reductions for moderately sensitive crops could be expected to result from <br />irrigation water having conductivities between .75 and 2.0 mmhos/em". <br />For these reasons the 2-4 mmhos/em range cited by Tri-State does not appear appropriate <br />without further justification. Please provide Tri -State's additional rational for the use of <br />2-4 mmhos/cm range for moderately salt tolerant species. <br />4. During the discussions between Colowyo and the Division, Tri-State committed to performing a <br />salinity study to address the salt tolerance of vegetation species present at and adjacent to <br />Colowyo. Based on correspondence from Tony Tennyson of Tri-State, due to unusually dry <br />conditions and other uncontrolled outside factors, the field portion of this study would need to be <br />postponed. Understanding this, the Division respectfully requests Tri-State to provide other <br />available documentation of the crops grown with irrigation water from Wilson Creek, Milk <br />Creek, Good Spring Creek and Taylor Creek until the salinity study can be completed. <br />5. Referring to the Letter, it states that "[t]he fields being irrigated with water from Good Spring <br />Creek are comprised of grass hay, which Tri-State believes could be more tolerant to higher TDS <br />than an alfalfa, as production yields obtain from annual harvests are indicating." Although this <br />statement may be accurate for the irrigated fields, the Division must ensure that these statements <br />are defensible. As such, please provide any literature or production ,yield data and <br />additional discussion which would support the above referenced statement. <br />6. It is the Division's opinion that the proposed salinity study would be a useful addition to the <br />Colowyo PAP and may help to inform any potential future revision of the Probable Hydrologic <br />Consequences section if deemed necessary. The Division would like to request that the salinity <br />study be included into the Colowyo PAP once conducted. <br />7. To better characterize the impacts of the Colowyo Mine on surface water quality, the Division <br />suggests additional downstream monitoring. Suggested monitoring point locations are in <br />Section 35, approximately one mile downstream of LGSC, and in Section 23 within the permit <br />boundary (a short distance north of the mine entrance road) for the Good Spring Creek. <br />Taylor Creek <br />S. In the Letter, Tri-State states that, ..... the Division does not have any regulatory authority <br />