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levels above the threshold value at which crop yield decrease; 2) potential increases in the average depth to water <br />that would reduce the amount of sub-irrigated land; 3) potential decrease in surface flows that would reduce the <br />• amount of Flood-irrigated land; 4) potential changes in the surface or ground water systems that reduce the area <br />available to agriculture as a result of flooding or increased saturation of the root zone; and 5) loss of irrigated area <br />due to retention of facilities upon completion of mining and reclamation activities. <br />The first and second subject areas, the Foidel-Middle Creek Floodplain, are flood irrigated. The applicable criteria <br />for determining material damage are potential TDS concentration as compared with crop salt tolerance, potential <br />surface water availability measured against irrigation requirements, and potential Flooding as it impacts <br />agricultural land use. From Table 29, Surface Water Quality Data, the average and maximum TDS concentrations <br />for affected water at sample site 29 in 1983 are 888.2 mg/I and 2,450 mg/I, respectively. The TDS concentrations <br />of affected water are well within the recommended salt tolerance level (5,000 mg/I) for stock water in the Foidel- <br />Middle Creek floodplain. <br />Although impoundments will detain runoff from the proposed permit area, there will not be a corresponding <br />reduction in water supply for irrigation because the ponds will fill during early spring before the annual imgation <br />season begins and because the headgates for the irrigation ditches are located either upstream from the proposed <br />permit area or in other unaffected watersheds. Furthermore, as pointed out under Rule 2.05.6(3), the total amount <br />of water impounded in impoundments is small as compared with total streamflow in the Foidel-Middle Creek <br />floodplain. Thus, the impoundment of surface water in impoundments is not expected to have an adverse impact <br />on the supply of irrigation water to the Foidel-Middle Creek floodplain. The sedimentation ponds will also <br />function as flood protection facilities, thus insuring against the loss of agriculturally useful lands by Flooding. The <br />retention of the Middle Creek office/shop building and surrounding parking area is not deemed to significantly <br />impact the fimctioning of the valley floor. The facility and parking area are approximately 2 acres in size, which is•/ <br />less than 2% of the valley floor immediately upstream of the Foidel Creek/Middle Creek confluence area. In <br />summary, no material damage to [he Foidel-Middle Creek floodplain is anticipated considering the sediment <br />control and reclamation plans in [his application. <br />Tlie third subject area, the Fish Creek floodplain, is flood-irrigated by diversion ditches. The applicable criteria for <br />determining material damage area potential TDS concentration as compared with crop salt tolerance, potential <br />surface water availability measured against irrigation requirements, and potential flooding as it impacts ~ <br />agricultural land use. All the effects of future mining and mitigative factors discussed above for the Foidel-Middle i -• <br />Creek Floodplain apply to Fish Creek. That is, salt loading from the effluent released by sedimentation ponds will"` <br />not result in TDS levels in excess of recommended standards. Tltus, mining will not have adverse effects on the <br />quantity or quality of the water used to irrigate Fish Creek. Therefore, no material damage to the Fish Creek <br />floodplain in anticipated from mining and reclamation operations at Energy Mine No. 3. <br />i ~~ ~ <br />C~ Se~~~-ces w~iz~ aMe.. wt ~~(~c~cf~j . ~S a~ s~~Zy <br />w~, d~iV S?>,t,,..~G,,,~ ~ S ~2v ~ /~ 7b ~ w 1711 -+~~aa7/~~ r N?~. ~7';n, <br />APPROt~EU JAL 1 8 199 <br />TR 97-OS 2.06-37 Revised 5/02/97 <br />