2017-05-04_REVISION - C1981010 (2)

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Page 4 of 8 PR8 Letter to Robin Reilley May 3, 2017 surface water, and groundwater. Once the overburden materials are mixed via mining and further mixed via regrading and reclamation operations, they will be at least of an equal, if not better, physical and chemical quality than the topsoil currently found on this site. d) Surface water information in the hydrology description with water quality data from surface waters in, discharging into, or which will receive flows from surface or ground water from affected areas within the proposed permit area in accordance with Rule 2.04.7(2) (b) (ii). As described in Section 2.7.4.1, on updated Page 2-4141 previously provided as part of adequacy response to PR -7, no perennial or intermittent flows have been recorded in the Deacon Gulch and Jeffway Gulch drainages within the expansion area. That discussion has been updated to provide additional information for this submittal and a revised Page 2-4141 is included with this letter. As part of the additional information, Table 2.7-12c is being added to the permit document as page 2- 414m to show the dates when flows have been observed for both gulches. Figure 2.7-15f as page 2-414n is being added to the permit document to show the location of observation points for flows in both Deacon Gulch and Jeffway Gulch. Further downstream from the PR -7 permit boundary the Deacon Gulch drainage becomes more incised and some ground water is exposed. Larger flows in Deacon Gulch are limited to springtime melts and precipitation events in the lower reaches outside of the permit boundary. Jeffway Gulch is dry for the majority of the length within the PR -7 permit boundary (as also shown in the added Table 2.7-12c, page 2-414m and added Figure 2.7-15f, page 2-414n). As described in replacement page 2-1411, at the southern edge of the expansion area a large un- named tributary to Jeffway Gulch joins the main channel. A series of seeps are present within the PR -7 expansion area, as is intermittent flows from a large seep complex within the tributary from the east. The area becomes very wet at this junction and a defined channel leaves the expansion area at County Road 33. This riparian area is not expected to be disturbed as it is beyond the extent of the coal reserves in this area. The seeps appear to originate from the base of the Twenty Mile Sandstone and shale layers below the sandstone. TMI has sampled Jeffway Gulch at the location of the seeps at the southern edge of the permit area at a site labeled as Jeffway Spring @ County Road 33. Replacement page 2-451s has been updated to reflect the addition of water quality sampling. Figure 2.7-15f, page 2-414n, shows the visual flow observations for Deacon Gulch and Jeffway Gulch and the water quality sampling for Jeffway Gulch. Water quality results are shown on Table 2.7-18b, pages 2-451v through 2-451 x. The water quality shows the dominant cations as magnesium and calcium, and the dominant anions as sulfate and bicarbonate. The samples can generally be characterized as magnesium - calcium -sulfate -bicarbonate type waters. Little variance is seen in the water quality over the time period of sampling. The pH is slightly alkaline at 8.0 to 8.2. All water quality values are below the primary drinking water standards and the surface water quality standards for the lower Yampa River (Colorado Water Quality Control Commission Regulation #37, Stream Classifications and Water Quality Standards for the Lower Yampa/Green River.