_GENERAL DOCUMENTS - C1981017 (200)

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diversion. The inner channel will meander within the larger outer channel. Approximately twenty (20) meanders will be created during construction of the inner channel. Placement and curvature of the constructed meanders of both the inner and outer channels is critical, and must be accomplished as depicted on the maps and cross sections provided. It is estimated that twenty seven thousand cubic yards (27,000 yd3) of material will be excavated during construction of the diversion. Environment The diversion will be constructed through the former location of the Coal Basin Mines facilities area. Structures which were formerly located within the foot print of the diversion include the District Office Building, asphalt covered parking area, and an equipment maintenance shop. Most, if not all, of the concrete foundations and footers which were associated with these and other structures has been demolished and removed through a different contract. A minor amount of buried concrete containing rebar, possibly including an abandoned septic system, may be encountered during excavation of the diversion. The exact geomorphologic nature of the Project Area prior to mining is unknown. However, it is surmised that Dutch Creek flowed into Coal Creek within the vicinity of the Project Area as a series of migrating stream channels. Due to the elevation differences between the current Dutch Creek and Coal Creek channels, the probability of channel migration over time, and the occurrence of large scale debris flows, it is likely that, at depth, the foot print of the channel is underlain by alluvial materials washed down the Dutch Creek channel. Photographs taken during the early to mid 1960's indicated that coal refuse, generated from the wash plant formerly located to the west of the Project Area, was used as fill over the alluvial materials to create the relatively flat land form which now exists in the northern half of the Project Area. Limited drill data from the northern most half of the channel tends to confirm the presence of these materials. The drill data suggests that, in the northern half of the Project Area, coal refuse may be encountered for the upper three feet (3) to fifteen feet (15'). The thickness of the refuse appears to increase toward the north. Alluvial materials consisting of slightly metamorphosed Mesaverde Formation and Mancos Shale were encountered immediately underlying the refuse to a depth of twenty five feet (25') to thirty one feet (31') below ground surface. The depth of this material also increases to the north. Mancos Shale was encountered below the alluvial materials. In late October, 1997, ground water was encountered at twenty seven feet (27') below ground surface at the north side of the Project Area. At the time, depth to water in the central portion of the Project Area was measured at twenty one feet (21') to twenty five feet (25) below ground surface. It should be noted, however, that the ground water levels may fluctuate given the time of year and the surface elevations of Coal and Dutch Creeks in the vicinity of the Project Area. From the central portion of the Project Area south toward Dutch Creek, it is assumed that the depth of coal refuse fill decreases to zero and that the thickness of the alluvial material increases. While the thickness of the alluvial material in this area is not known, it is not anticipated that in situ Mancos shale will be encountered in this portion of the Project Area.