2012-11-06_REVISION - C1982057 (6)

Home Browse Search

TR -79 POND 016 SLIDE AREA CONSTRUCTION SUMMARY The Pond 016 Slide Area remediation activities were conducted during the 2011 and 2012 construction seasons and were based on the proposed design package. The actual locations of some components were field fit, but the overall design criteria were adhered to. In 2012 it was decided to wait until 2013 to place topsoil and seed the area to ensure that the area was stabile. There were a number of factors involved with stabilizing the area: • A portion of permanent Road J/K was relocated • Pond 016 slide material was removed and the cut slope stabilized • Shrub Plot slump was regraded and material excavated to increase stabilization • Pond 016A was backfilled with the material removed from the unstable areas • Permanent Channel PM -2 was relocated and extended through the Pond 016A area REMEDIATION ACTIVITIES Relocation of Roads J/K A portion of the J and K roads was relocated through the slide areas once the remediation trench and the permanent channels were constructed. The roads do not exactly match the proposed design locations but were field fit to take advantage of the surface topography. The road location is shown on Exhibit 20 -2, Postmining Topography and Drainage. These construction criteria that SCC adhered to included: • Materials placed in approximate 12 inch lifts • Moisture/Density ( "Proctor ") curves for each separate type of fill material were developed prior to commencement of placement and compaction, and the information was available on site at all times • Compaction achieved a minimum of 95% MDD (See attached field reports in the Construction Documentation) • A sheepsfoot roller was used to achieved the required level of compaction On the approved design, there were three (3) culverts associated with Roads J/K. The final configuration resulted in Culvert J -2 one (1) 60" culvert installed even though only a 30" culvert is required (see attached Culvert J2A Design l0yr /24hr); Culvert J -7 (24" installed) being moved to take advantage of the underdrain ditch; Culvert K1 was eliminated due to final topography configuration. Pond 016 Slide Stabilization The slope was excavated back into competent material. A trench was excavated at the toe of the slope to collect the water and convey it along the trench to a ditch that will discharge to Pond 016. The trench bottom will be approximately ten (10) feet wide with a six (6) inch perforated pipe placed along the bottom and covered with a minimum of one (1) foot of 4" minus gravel and covered with material excavated from the slide area. The surface above the covered trench was configured to provide drainage from the area above the road and is conveyed through Culvert J -7 (24" installed) under the road and discharging into the same 20 -D.1 10/12