2021-09-03_PERMIT FILE - C1981019A (8)

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R. LE PERMITS Water quality data are available for the valley-fill monitoring wells from 2004 through 2006. Additional data collected in 1996 and 1997 from wells MJ-95-01, MJ-95-02, and MJ-95-03 were reviewed. Results of the valley-fill well samples are summarized in Table 2.04.7-42. The complete dataset is provided in Appendix 5.K of the WMC (2005) report (Exhibit 7, Item 21), as are laboratory analysis sheets for samples collected in 1995-1996. Table 2.04.7-42 also lists the Federal MCLs and secondary drinking water quality criteria. All samples except from well MJ-95-02 exceeded the secondary drinking water MCL for TDS of 500 mg/L. Water quality in several wells also exceeded the secondary drinking water MCLs for iron(0.3 mg/L)and manganese(0.05 mg/L). Groundwater Use— Groundwater use in the Colowyo revised permit area is limited due to the depth to water, the generally poor quality, and its limited overall availability. Colowyo installed and developed two wells in the late 1970s to supply a portion of the domestic needs. The two deep wells, Taylor Creek Nos. 1 and 3, are located in Section 33, T4N, R93W, and in Section 4, T3N, R93W, respectively (Map 11C). Taylor Creek No. 1, completed to a depth of 850 ft in the Williams Fork Formation, produced 40 gpm. Taylor Creek No. 3, completed to a depth of 2,284 ft in the Iles Formation, produced 20 gpm. Neither well has been pumping since the early 1980s. Colowyo installed a new potable water supply well in 2004. That well was completed in the Trout Creek Sandstone and is located in the NW'/4 of Section 3, T3N, R93W. The production rate is less than four gpm. The information from Colowyo's existing operations indicates that groundwater is very limited, even to depths significantly below current mining activities. This conclusion is supported by the depths of the potable wells, Taylor Creek No. 1 and Taylor Creek No. 3, and the newer water well. Further evidence of lack of significant groundwater resources within and adjacent to the mine area is that most residents in the general area haul drinking water from the towns of Craig or Meeker. A search of the Colorado Office of the State Engineer's files revealed 116 permitted wells located inside or within one mile of the permit revision area (Table 2.04.7-44). Of the 23 wells with reported yields, only three have yields greater than 15 gpm. The maximum reported yield is 50 gpm, and the median reported yield is 8 gpm. Most (91) of the permitted wells are used for monitoring purposes; nine of the permitted wells support domestic or domestic and livestock uses, and 11 are used for livestock. The locations of the permitted wells are illustrated on Map 11C. Groundwater is not currently used for industrial or mining purposes such as watering haul roads or dust control, but potentially could be depending on availability and demand during the dewatering process. Water for these purposes is currently supplied by Wilson Reservoir located in Section 13, T4N,R93W. 2.04.7 (2) Surface Water Resource Information Both general and detailed information regarding surface water in the vicinity of the mining areas are presented in the following subsections. General Surface Water Resource Information Surface Water Characteristics—The Colowyo Coal Company's area of operation is located within the Lower Yampa River basin in northwestern Colorado. The physiography of the area consists of a montane region and an upland plateau. The montane region typifies the headwater reaches of most drainages, which are characterized by steep, narrow, bedrock-controlled channels. The channels are generally straight with limited sediment accumulation. Active erosion is limited to areas with erodible shale or friable sandstone(Camp Dresser&McKee(CDM), 1985b). Collom—Rule 2,Page 28 Revision Date: 12/20/19 Revision No.: TR-135