_INSPECTION - C1982057 (50) - Laserfiche WebLink

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September 21,2010 C-1 982-057/Seneca II-W Mine JRS c� BACKFILL and GRADING—Rule 4.14 Contemporaneous Reclamation 4.14.1; Approximate Original Contour 4.14.2; Highwall Elimination 4.14.1(2)(f); Steep Slopes 4.14.2,4.27; Stabilization of Rills and Gullies 4.14.6 -Prior to the inspection,the Division created three cross-sections on Exhibit 20-2 in the reclaimed Seneca II-W South area to assess the post-mining topography.A random starting and ending point in each of the three drainage areas(PM-1,PM-2 and PM-3)were created in the office using ArcMap. A line was then created by connecting these random points. The resulting line became the Division's cross-sections. These lines were then uploaded to the Trimble GeoXT for use in the field. The Division created cross-sections are shown on Inspection Map 1 and numerous,random elevation points were taken along each cross-section during the inspection.Field data was compared with the approved post-mining topography at those points from Exhibit 20-2. The cross-section profiles comparing the Division's point data to the approved topography and the Division's raw point data are attached to the end of this report. Observations were made in the field regarding the erosional stability of the landscape as post-mining topography elevation data points were collected. -Cross-section A-A' runs along the north side of permanent,post-mining drainage channel PM-3 and is approximately 3,700 feet in length. The field data shows that the majority of the backfilled area along cross- section A-A' varies from the approved post-mining topography from+1.6 feet to-5.4 feet(with one point showing a-9.4 foot difference. The cross-section A-A' area was stable, with no settling or cracking observed in the backfill at the time of the inspection. There was some minor rilling in some areas but it did not appear to be a problem at this time. -Cross-section B-B' runs along permanent,post-mining drainage channel PM-2A and bisects channels PM-1B, PM-lA and PM-3. It is approximately 4,700 feet in length. The attached data show that the backfilled area along cross-section B-B' varies from the approved post-mining topography from+3.9 feet to-3.7 feet(with one point showing a-7.0 foot difference). The south portion of the cross-section B-B' area was stable in the PM-1 drainage area,with no signs of settling or cracking in the backfill. There was some minor rilling in the area but it did not appear to be a problem at this point. The backfilled area along the north end of cross-section B-B', in the PM-3 drainage area,was also stable,with no signs of settling or cracking in the backfill. There were,however some erosional problems in the PM-2A drainage area. Seneca was actively repairing rills and gullies and repairing permanent,post-mining drainage channels and stock tanks in this area at the time of the inspection. The Division reviewed aerial photographs from August 20,2010 after work had been completed. Additional rill and gully repairs may be necessary but this is normal maintenance included in the approved rill and gully plan and the Division's reclamation cost estimate(task 118). -Cross-section C-C' runs along permanent,post-mining drainage channel PM-1/1A and is approximately 4,600 feet in length. The data shows that the backfilled area along cross-section C-C' varies from the approved post- mining topography from+6.9 feet to-7.2 feet(with one point showing a-10.9 foot difference). The cross-section C-C' area appeared to be stable. There was no visible cracking or settling observed in the backfilled and regraded area. There was some minor rilling in the area but it does not appear to be a problem at this time. -Besides taking data points along the Division's cross-sections,the Division also walked all of the permanent drainage channels in the Seneca II-W South area(see"Hydrologic Balance"below for more detailed information regarding these drainage channels). This allowed the Division to cover the vast majority of the backfilled and regraded areas in the Seneca Il-W South extension area. Number of Partial Inspection this Fiscal Year: 3 Number of Complete Inspections this Fiscal Year: 2 Page 3 of 18