_INSPECTION - C1982057 (50) - Laserfiche WebLink

Home Browse Search

September 21,2010 C-1982-057/Seneca II-W Mine JR&C� Bacldilling and Grading Summary Based on data collected in the field during this inspection, and observations from previous inspections,the reclaimed areas have been restored to approximate original contour of the pre-mining landscape and as approved in the permit. The present surface configuration achieved by the backfill and grading of the mined areas closely resembles the general surface configuration of the land prior to mining. Reclaimed areas blend in well with the existing undisturbed landscape. Comparison of the data collected in the field is consistent with the approved Post Mining Topography in Exhibit 20-2 and achieves the approximate original contour. Reclaimed slopes in the south area are stable. Some areas of rills and gullies are present as discussed above. During and subsequent to this inspection, SCC was repairing the area of highest concern adjacent to the PM-2A and PM=2D drainages. SCC conducts an annual rill and gully survey and makes repairs as necessary. See Tab 22, Revegetation Plan for a more details. The area will be included in the Phase I bond release, and the Division will continue to monitor in future years. Dan Mathews and Christy Hulsman walked the PM-4 drainage channel reclamation. The backfilled slopes were all well vegetated and stable and no erosional problems were noted. No problems with cracking or settling in the backfill were noted. There was a 12.1 acre area in the north portion of the mine that was excluded from the Partial Phase I Bond Release Inspection SL-02 due to a slump. The area is immediately north of an undisturbed area in the 006 Gulch drainage area. The area was graded to blend into the undisturbed area to the south and will be included in the Phase I Bond Release SL-03. HYDROLOGIC BALANCE -Rule 4.05 Drainage Control 4.05.1, 4.05.2,4.05.3; Siltation Structures 4.05.5, 4.05.6; Discharge Structures 4.05.7,4.05.10; Diversions 4.05.4; Effluent Limits 4.05.2; Ground Water Monitoring 4.05.13; Surface Water Monitoring 4.05.13; Drainage—Acid and Toxic Materials 4.05.8; Impoundments 4.05.6,4.05.9; Stream Buffer Zones 4.05.18: Certified designs were approved for all post-mine drainage channels prior to this inspection and are provided in the permit in Tab 20, Attachment 20-1. The permanent channels are designed to safely convey the peak discharge from the 10-year, 24-hour storm event in accordance with 4.05.3. Post-mine drainage channels PM-1, PM-lA, PM-1B,PM-IC,PM-2,PM-2A,PM-2B,PM-2C,PM-2D,PM-2E, PM-3, PM- 3A,PM-4, PM-4A,PM-4B,PM-4C, PM-4D and PM-6 are within this bond release request area and are shown on Exhibit 20-2—Post-Mining Topography and Drainage and the channel profiles are shown on Drawing 20.5-9. The channels are also shown on the Division's Inspection Map 2. These channels were inspected for function with regard to knick points,blending at disturbance boundaries and channel erosion. In addition to the certified designs, as-built drainage profiles (Exhibit D of the bond release application package) were also reviewed and evaluated in the field. The entire length of each drainage channel was walked for comparison with design and as-built information. The Division took elevation measurements with the Trimble GeoXT and channel bottom width, depth and lining observations at random points along each channel(with the exception of the PM-4 series of channels). The corrected elevation points were used to construct a drainage channel profile for each channel,which was compared with both the as-built channel profile(SL-03 Exhibit D)and the approved design profile(Exhibit 20-5.9, sheets 1 and 2). The results of the field measurements are provided in the table below and the channel profiles and data are attached at the end of this inspection report. Number of Partial Inspection this Fiscal Year: 3 Number of Complete Inspections this Fiscal Year: 2 Page 4 of 18