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exception oFthat portion in Section 26. However, that portion of Section 26 within the permit area <br />as noted in Exhibit 33 was disturbed as part of construction of the unit train loadout prior to August <br />3, 1977, and therefore is eligible for the "grandfathering" exemption. <br />Alluvial Vallev Floor- Findines (Facilities Area) <br />Those portions of [he permit area within Sections 26, 27. 28, 33 and 34 are exempt from the <br />requirements that prevent an operation from interrupting, discontinuing, or precluding farming, and <br />from affecting the quantity and quality of water supplying the alluvial valley floor (4.24.3(4)). <br />However, this area is not exempt from the requirements for restoring the essential hydrologic functions <br />of the alluvial valley floor, which will be discussed below, in Item 3. <br />All of the non-exempt alluvial valley floor is located outride the permit area within Section 26 and Z7 <br />No portion of the non-exempt alluvial valley Floor is presently disturbed by the mining operation. <br />A small portion of this area is indicated as being historically flood irrigated on Exhibit 33. <br />There are no plans to disturb any additional land on the alluvial valley Floor. Therefore, the <br />proposed coal mining operation will not interrupt, discontinue, or preclude farming on the <br />alluvial valley floor (4.24.3(1)). <br />2. As previously discussed, a portion of the non-exempt alluvial valley floor was historically flood <br />irrigated. In addition, a portion is subirtigated. The remaining area is potentially flood irrigable. <br />Surface waters which could be and were used to irrigate the non-exempted alluvial valley floor <br />would be diverted from the Highline Canal. Water in the Highline Canal is diverted from the <br />Colorado River approximately one mile upstream of the disturbance. The Highline Canal will <br />not be affected by subsidence or by mine discharges. Therefore, the quantity and quality of <br />surface water which supplies the AVF would not be affected by the proposed operations <br />(4.24.3(3)). <br />Discharge from the Roadside and Cameo Mines will have a minor salt loading effect on the <br />Colorado River. The affect on the water quality from this discharge will be to increase the <br />specific conductance and total dissolved solids about 0.2 percent. This, in tum, would have a <br />minor effect on the water which supplies the subirrigated portion of the AVF, since recharge <br />water from the adjacent Colorado River is the source of alluvial groundwater which subirrigates <br />the AVF. <br />During mining, the sediment control system will temporarily reduce surface Flows and will <br />remove sediment loads. Sediment ponds will not remove dissolved solids. Thus, the mine <br />operation will increase salt loads. Reduction in flow will only occur during significant <br />precipitation events and possibly during spring snowmelt. During these events, flows will be <br />reduced for only a period of 24 hours. Even then, the amount of water stored in the sediment <br />ponds is minor compared to the average flow of the Colorado River (3549 cfs). <br />All effects from the mining operation will be short-termed. With reclamation and removal of <br />[he sediment control system, these effects would be mitigated. Based on the above discussion, <br />the Division finds that the proposed operations will not materially damage the quantity and <br />quality of water in the surface and underground water systems that supply the alluvial valley <br />floor or portions of the alluvial valley floor (4.24.3(3). <br />48 <br />