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(Exhibit 42)that demonstrate that moderately sensitive species comprise a very <br /> small portion of the total vegetative production on those areas irrigated <br /> downstream of the Foidel Creek mine. The applicant also points out that irrigation <br /> water is applied in excess of what is necessary for the species grown, and this <br /> excess leaches the soil profile, thus making the assumed relationship between soil <br /> salinity and irrigation water salinity a worst case assumption. The applicant <br /> proposes that no decrease in production of any of the species currently grown on <br /> the Trout Creek AVF would be expected unless the conductivity of the irrigation <br /> water were to exceed 1 mmhos/cm. Based on species composition data submitted, <br /> the applicant predicts that significant production decreases (>3%for a farm unit) <br /> would not occur unless irrigation water salinity were to exceed 2.0 mmhos/cm. <br /> Given the factors involved, the Division finds it is appropriate to propose an <br /> irrigation water material damage suspect level of 1.5 mmhos/cm for Trout Creek, <br /> from the confluence of Middle Creek to the Yampa River. Establishing the <br /> suspect level at 1.5 mmhos/cm acknowledges the evidence submitted by the <br /> applicant while maintaining a reasonable suspect level established through <br /> research and application. <br /> As a result of TR-32, the applicant has proposed a plan to discharge mine water <br /> only when the stream has the dilution capacity to maintain waters at or below the <br /> discharge points on Fish Creek and Trout Creek to 1.5 mmhos/cm. In summary, <br /> projected flood irrigation water quality is 1.230 mmhos/cm and material damage in <br /> terms of productivity declines would not be expected unless water salinity were to <br /> exceed 1.5 mmhos/cm. <br /> Given the minor effect of mine discharge on Trout Creek surface water quality, a <br /> specific projection of alluvial groundwater impact was not made. Since alluvial <br /> recharge would occur in late spring and early summer when dilution due to <br /> snowmelt runoff is at its peak, it follows that alluvial waters (and thus <br /> subirrigation) would be less affected by mine discharge than Trout Creek surface <br /> water(and flood irrigation). <br /> 3. The proposed operation will preserve the essential hydrologic functions of the <br /> alluvial valley floor. <br /> The essential hydrologic functions of the Trout Creek alluvial valley floor have <br /> been identified as the capacity to support subirrigated and flood irrigated <br /> agricultural activities. <br /> The proposed plan would not result in any surface disturbance or undermining of <br /> the Trout Creek AVF. Also, as discussed previously, no material damage would <br /> result from changes in the quality of surface and ground water that supply the <br /> alluvial valley floor. Thus, the essential hydrologic functions of the alluvial valley <br /> floor would not be affected by the proposed operation. <br /> Foidel Creek/Middle Creek Confluence Area <br /> Foidel Creek Mine 44 August 4,2023 <br />