2010-05-07_PERMIT FILE - C1994082A

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test pit/trench, was excavated in August 2009. It should be noted that due to the excessive caving of the saturated fill materials and overburden soils in the sidewalls of the west test pit/trench the underlying bedrock depths and conditions could not be determined. Subsurface/Groundwater Conditions: The subsurface conditions encountered in test holes /monitor wells (TH -11 through TH -14) were highly variable and generally consisted of variable layers of fill materials, ranging from 0 to 35 feet in thickness, overlying either weathered claystone material or sandstone bedrock that was underlain by claystone -shale bedrock materials that generally extended to the maximum depths investigated. It should be noted that coal seams were encountered within the claystone -shale bedrock materials in two of the test holes (TH -13 and TH -14). The subsurface/bedrock conditions encountered in TH -11 and TH -12, which were located to the north and upslope of the subject slide area, were fairly consistent and generally consisted of sandstone bedrock overlying the claystone shale bedrock. A thin veneer of topsoil fill materials, approximately 1 foot thick, was encountered at the ground surface in TH -11; whereas, a layer of weathered claystone materials, approximately 2 feet thick, was encountered at the ground surface in TH -12. Sandstone bedrock was encountered beneath the fill and weathered claystone bedrock materials and the sandstone bedrock materials extended to depths ranging from 40 to 50 feet beneath the existing ground surface. The sandstone bedrock materials were slightly silty to silty with interbedded claystone lenses, fine to medium grained, low to non- plastic, hard to very hard, dry to slightly moist and light brown to gray in color. A sample of the sandstone bedrock materials classified as an SM -SC soil in accordance with the Unified Soil Classification system. Claystone -shale bedrock was encountered below the sandstone materials and extended to the maximum depth investigated in these two test holes, 180 and 120 feet respectively. The claystone -shale bedrock materials were nil to slightly sandy, low to moderately plastic, hard to very hard, slightly moist to moist and gray in color. Sample of the claystone -shale bedrock materials classified as CL soils in accordance with the Unified Soil Classification system. The laboratory test results completed on the bedrock materials are summarized in the attached Table 1. Groundwater was not encountered in either TH -11 or TH -12 at the time of drilling. However, groundwater was encountered in these two test holes, when measured 1 day after the drilling was completed, at depths ranging from 80 to 115 feet bgs. The groundwater levels were encountered at depths of 68 and 79 feet bgs when measured 74 days after the drilling was completed. The depths at which the groundwater levels were encountered, along with the number of days after the drilling that the measurements were completed are shown on the logs (Figure #1). The subsurface/bedrock conditions encountered in T14-13 and TH -14, which were located to the east and upslope of the subject slide area, were variable and generally consisted of man-made fill materials overlying weathered claystone materials that were underlain by claystone shale bedrock. Coal layers were also encountered above and below the claystone -shale materials in these test holes. The thickness of the man- made fill materials was highly variable and generally ranged from 5 to 35 feet. The fill materials generally consisted of clays that were slightly sandy to sandy with bedrock fragments ranging from gravel to boulder in size, low to highly plastic, soft to stiff, moist to wet and light brown to gray in color. The fill materials were underlain by weathered claystone materials that extended to depths ranging from 57 to 55 feet bgs. Job Number: 07.7600 NWCC, Inc. Page 2