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-20- <br /> <br />Facilities Area (cont'd) <br />In addition, this exempted area includes alI the area disturbed by the proposed <br />operation. <br />Alluvial Vallee Floor - Findi <br />Those portions of the permit area within Sections 26, 27, 28, 33 and 39 are exempt from <br />the requirements that prevent an operation from interrupting, discontinuing, or <br />precluding farming, and from effecting the quantity and quality of water supplying <br />the alluvial valley floor. This area will not be discussed in the following findings. <br />Xowever, this area is not exempt from the requirements for restoring the essential <br />hydrologic functions of the alluvial valley floor which will be discussed below. <br />AZ1 of the non-exempt alluvial valley floor is located outside the permit area <br />within Section 26 and 27. <br />1. No portion of the non-exempt alluvial valley floor is presently disturbed by <br />the mining operation. A small portion of this area is indicated as being historically <br />flood irrigated on Exhibit 33. There are no plans to disturb any additional land <br />on the alluvial valley floor. Therefore, the proposed coal mining operation will <br />not interrupt, discontinue, or preclude farming on the alluvial valley floor. <br />2. As previously discussed, a portion of the non-exempt alluvial valley floor was <br />historically flood irrigated. In addition, a portion iS subirrigated. The remaining <br />area is potentially flood irrigable. Surface waters which could be and were used <br />to irrigate the non-exempted alluvial valley floor would be diverted from the Highline <br />Canal. Water in the Highline Canal is diverted from the Colorado River approximately <br />one mile upstream of fhe disturbance. The Highline Canal will not be affected by <br />subsidence or by mine discharges: Therefore, the quantity and quality of surface <br />water which.aupplies the AVF would not be affected by the proposed operations. <br />Discharge-from the Roadside and Cameo mines will have a minor salt Loading effect <br />on the Colorado River. The affect on the water quality from this discharge will <br />be to increase the specific conductance and total dissolved solids about 0.1 e. This, <br />in turn, would have a minor effect on the water which supplies the subirrigated <br />portion of~the AVF, since recharge water from the adjacent Colorado River is the <br />source of alluvial ground water which subirrigates the AVF. <br />During mining, the sediment control system will temporarily reduce surface flows and <br />will remove'sediment Loads. Sediment ponds will not remove dissolved solids. Thus, <br />the mine operation wi3.E increase salt loads. Reduction in flow will only occur <br />during significant precipitation events and possibly during spring snowmelt. During <br />these events, flows will be redud~d for only a period of 24 hours. Even then, the <br />amount of wa"ter stored in..the sediment ponds is minor compared to the average flow <br />of the Colorado River. (3549 cfs): Salt loading effects of the sediment pond discharges <br />are unquantifiable at present because none of the ponds have discharged. However, <br />the comparatively:minor,quantity of discharge from the ponds would result in a <br />negligible effect on~water quality of the Colorado River following dilution. <br />AZ1 effects from the mining operation will be short-termed. With reclamation and <br />removal of the sediment control system, these effects would be mitigated. <br />Y. ~. ~~ <br />