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the relatively small component of moderately sensitive species, material damage <br /> would not occur unless flood irrigation water conductivity were to exceed 2.0 <br /> mmhos/cm (which is assumed to correspond to a root zone conductivity of 3.0 <br /> mmhos/cm). <br /> A 1.5:1 relationship between soil salinity and irrigation water salinity is considered <br /> to be a conservative assumption (the actual relationship may be less than 1.5:1). <br /> Data collected by the Division on August 15, 1986, showed root zone soil <br /> conductivity to be slightly lower than Fish Creek surface water conductivity. <br /> The major portion of the Fish Creek Alluvial Valley Floor is not flood irrigated but <br /> is assumed to be subirrigated based on vegetation types, alluvial water depths and <br /> late growing season color infrared photography. Material damage to subirrigated <br /> vegetation would not occur because the majority of discharge to the aquifer occurs <br /> during spring and early summer when mine discharge is diluted by high runoff <br /> volumes. <br /> Predicted alluvial water salinity on Fish Creek is approximately 1 mmhos/cm. <br /> Well 008-AU-3 on Fish Creek corresponds more closely with surface water quality <br /> and is thought to be a more representative site than 006-AW-2. Based on 008-AU- <br /> 3, a measurable increase in salinity of alluvial aquifers is projected, but the <br /> predicted conductivity would be well below the 3 mmhos/cm material damage <br /> suspect level for sub-irrigation. Water quality measured in well 006-AW-2 <br /> exceeds the suspect level in both the existing and predicted case, but mine <br /> discharge water would actually dilute the salinity of 006-AW-2 water, resulting in <br /> an improvement in water quality due to mining. <br /> Following mining and reclamation, the mine workings would fill with ground <br /> water, and water passing through the mine workings would again discharge to the <br /> stream/alluvial aquifer system. This water would be expected to have a degraded <br /> water quality (3200 mg/l TDS at the source), but concentrations would decrease as <br /> the affected water flows to the discharge area. The ground water discharge would <br /> be further diluted by flow in the stream/alluvial aquifer system. Because of the <br /> low flows involved (0.02 cfs), water quality degradation in the stream/alluvial <br /> aquifer system would not be sufficient to cause material damage to the waters <br /> which supply the Fish Creek Alluvial Valley Floor. <br /> 3. The proposed operation will preserve, throughout the mining operation, the <br /> essential hydrologic functions of the Alluvial Valley Floor. <br /> The essential hydrologic functions of the Fish Creek Alluvial Valley Floor have <br /> been identified as having the capacity to support subirrigated and flood irrigated <br /> agricultural activities. <br /> Mining beneath the Fish Creek AVF has been limited to panels 5, 6 and 7 of the <br /> Southwest Mining District and did not result in dewatering of the stream/alluvial <br /> system. Also, as discussed previously, no material damage would result from <br /> Foidel Creek Mine 41 August 4,2023 <br />