2010-12-09_REVISION - C1982057 - Laserfiche WebLink

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SCC projects impacts from all spoil springs will increase TDS in Dry Creek from 1,048 mg/l to 2,451 mg/l. The TDS increase extends from Hubberson Gulch to the Dry Creek reach monitored by Station WSD5 (upstream of the fields irrigated from Temple Reservoir #1). At this point, the baseline TDS level in Dry Creek begins to increase downstream. At a downstream location in Dry Creek, the TDS concentrations are elevated enough (TDS = 3,567 mg/1) that the cumulative spoil discharge influences from both mining areas (Seneca H-W and Seneca II-W South) will be minimal. The source of the salt loading to Dry Creek is principally seepage from dry land farming that extends from the hillslopes at the base of the mountains to Hayden. Dry Creek water is mixed with water from the J.C. Temple Reservoir #1 for irrigation in fields below this reservoir. The Division finds that there will be no material damage to water in Dry Creek since the background TDS levels are higher than the projected TDS levels from Hubberson Gulch. IV. Topsoil Soil resource information is provided in Tab 9, Volume 5 of the permit application. Information on topsoil handling, maintenance and testing is contained in Tab 21, Volume 13. The PR-1 submittal extensively reorganized the soils sections of the application and updated the soil baseline information to reflect 1990 survey of portions of the north mine area which had not previously been surveyed. Baseline data had been collected for the South Extension Area covered in PR-2, and in 1997 SCC conducted a topsoil depth verification survey to confirm the topsoil resource information collected previously. This information is also included in Tab 9. The referenced permit sections were further amended to address the expanded disturbance area associated with PR-3. In PR-5, the Soil Survey Map (Exhibit 9-3) was updated to reflect disturbance boundary modifications in the southern Wolf Creek/Sage Creek block in the south extension area. Cessation of mining operations earlier than originally anticipated resulted in a reduced area of disturbance in the deep "70D" soil map unit. Associated updates were made to the Soil Replacement Map (Exhibit 21-1) and topsoil balance narrative and tables in Tab 21. The permit area is occupied by three soil orders; Mollisols, Entisols, and Aridisols. The presence of these three orders is characteristic of the soils found in steep, semi-arid regions of Northwestern Colorado. These orders represent soils that grade from recently developed soils with minimum horizon development to more developed soils with well developed diagnostic horizons. Specific soil types within these orders occur on predominantly three types of parent material-land form combinations, namely: 1) upper side slopes, ridges, and swales of sandstone residuum; 2) toe slopes, side slopes, rounded ridge tops of shale residuum and colluvium; and 3) toe slopes, side slopes, ridges, and escarpments of sandstone and shale. Among the 22 soil types occurring within the permit area, major topsoil salvage limitations include clay textures, high coarse fragment content, steep slopes, shallow bedrock, salinity, and alkalinity. Seneca II-W Findings Document 43 C1982057 Permit Renewal No. 5 December 9, 2010