2008-02-04_PERMIT FILE - C1982056A

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Soil Core Locations: Twelve continuous soil cores were located and excavated with a Giddings drill rig and with a manual soil bucket auger along the proposed vent shaft access road corridors and withinthe footprints of the two proposed vent • shaft pads (Map 1 S 18 Right Bleeder Shaft and Map 2S Future Intake Shaft). Two soil cores (#2 and #9) were placed within the previously delineated Fish Creek AVF at locations that best represent the variable conditions within the AVF. Soil cores #2 and #9 were excavated to the groundwater table. The remaining upland soil cores were excavated to a lithic contact or pazent material and did not encounter any groundwater. Cm completion of soil sampling activities, all sample holes were completely backfilled with soil material and backfilled soil materials•were tamped down and leveled at the.r~atural ground surface. Soil Descriptions: ~ , Each soil core was described by horizon following accepted United States Department of Agricultwe Natural Resource Conservation Service (NAGS) soil survey procedures for the following parameters: horizon depth; field texture; Munsell color (matrix and mottles); root presence and depth; soil structure; and depth of ground water table. Additional soil descriptions were recorded as needed. Photographs were taken of each soil core after chazacterization. Major soil horizons aze marked with orange markers along a tape in each photograph. Field soil descriptions 'for each soil core aze contained in Exhibit 16C, Appendix 1. Photogaphs of the soil cores aze contained in Exhibit 16C, Appendix 2. NRCS soil series descriptions of the potentially affected soils aze contained in Exhibit i 6C, Appendix 3. Soil Mapping & Taxonomy Preliminary soil maps from the unpublished NRCS Soil Survey 'for Routt County were reviewed prior to locating soil mapping unit boundaries for the study area. Field descriptions from each of the 12 soil cores and additional non-chazacterized cores were used to detem>ine soil map unit boundaries (Maps 1S and 2S of the soils report) and soil taxonomy to the soil series or family level. Preliminary NRCS map unit descriptions of the • Slocum loam, Winevad-Splitro Complex, Clayburn loam, Aaberg clay and Binco silty clay loam and their known inclusions were used,to determine the affected soil series (Exhibit 16C, Appendix 3). As with all floodplains in this azea, flooding and the deposition and erosion off' material may be a frequent occurrence (100 yeaz precipitation event). Frequent flooding, channel movement, erosion and deposition have resulted in highly variable soil profiles within the previously mapped AVF. Results The soil description field forms and photographs for each characterized soil core aze contained in Exhibit 16C, Appendix 1 and Appendix 2 respectively. The primary soil pazameters including bottom depth of rooting, depth to the top of mottling and depth to surface of the groundwater table aze summarized in Table 2.04-1. NRCS soil series descriptions are contained in Exhibit 16C, Appendix 3. Soil core #1 was characterized as a Winevada and soil cores # 3 and #4 as Splitro series within the Winevada- Splitro complex, 3-25 percent slopes, map unit X8D. Soil core #2 was chazacterized as a Cumulic Cryaquoll and soil core #9 was chazacterized as a Menbaz series and both were mapped as inclusions within the Slocum loam variant, 0-5 percent slopes, map unit 56A. Soil cores #5 and 6 were characterized as within the Clayburtt series, 3-25 percent slopes, map units 68C and 68D. Soil cores #7 and 8 were mapped as Aaberg silty clay, 25- 65% slopes, map unit 35F. In Section 17, soil cores #10, 11 and 12 were located within the Binco silty clay loam, 3-25 percent slopes, map units C10 and D10. A narrow inclusion of Cumulic Cryaquoll soil was observed in the small drainage channel bisecting the ventilation pad area in Section 17 (Map 2S). • PR06-07 2.04-50.1 11/07/06