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• delineated on the basis of vegetation growth as established by use <br />of low altitude color IR photographs. Most vegetation on the <br />terraces receives moisture by either flood irrigation or precipita- <br />tion. <br />5.1.4 Alkali Creek <br />5.1.9.1 Unconsolidated Sediments <br />Sediments along Alkali Creek were mapped entirely as alluvium. <br />Colluvial material is present, but because of intensive reworking <br />of the area by a local rancher, Barton Porter, it is not always <br />possible to distinguish one sediment group from another. The main <br />stream system has also been significantly changed in certain areas <br />by the addition of reservoirs, ditches, and other diversions. <br />The unconsolidated material is about 35 feet thick in the area of <br />• the two monitoring holes OW-2 and OW-3 (Figure 3.3-6). The <br />alluvium consists of clays, silts, and silty and clayey sands. <br />Further downstream west of Section 12, the valley narrows and the <br />alluvium is quite thin. The valley remains narrow until its <br />confluence with the Colorado River. A relatively large fan has <br />developed at the confluence, but data is not available as to its <br />thickness. <br />5.1.4.2 Monitoring <br />Monitoring holes OW-2 and Ow-3 were designed as up and downgradient <br />AVF groundwater monitoring sites when the mine plan called for <br />disturbances on the south side of the hogback. However, the mine <br />plan has been changed and does not include any disturbances in this <br />drainage, other than vent holes. A two-year record from these <br />wells is included in Appendices 3.3-6 and 3.3-7. The records from <br />the two surface water sites (ALK-1 and ALK-2) can be found in <br />. Appendices 3.3-10 and 3.3-11. <br />NC&C - Coal Ridge #1 5-5 118C/1145/900301 <br />