2024-06-07_PERMIT FILE - M2024026 (29)

Home Browse Search

Geotechnical Stability Report — Kersey Mine May 24, 2024 Kersey, Colorado Page 2 The borings were drilled to depths ranging from approximately 15 to 25 ft bgs using 4-inch diameter continuous flight augers. The soil samples were obtained by driving a Modified California-type Sampler (2.5-inch O.D.) 12 inches into the subsurface. The number of blows required for each 6 inches of penetration was recorded separately. The blow counts were summed for each sampling interval and were correlated to N-values determined by the Standard Penetration Test (SPT)ASTM D1586 by applying a correlation factor. When using a sampler size of 2.5-inch O.D. a conversion factor of 0.85 for clay type soils and 0.63 for sand type soils is typically used. The SPT N-value serves as an indicator of relative consistency for cohesive soils and relative density of granular soils. The blow counts are shown on the attached boring logs prepared by CTL. (Attachment B), at the respective sample depths. Boring (TH-1, TH-5, TH-6, and TH-7)were drilled to a depth of 25 bgs, while borings (TH-2,TH-4,and TH-8)were terminated at 20 feet bgs. Lastly, boring TH-3 was drilled to a depth of 15 feet bgs. Upon completion, all test borings were backfilled to the approximate existing ground surface with the auger cuttings. Table 1 summarizes the coordinates, existing ground surface elevations, and boring termination depth. Table 1: Summary of Borings Boring Coordinates1 Elevation of Depth to Termination Existing Auger Boring Latitude Longitude Ground Depth 2 Refusal Surface1 (ft. bgs) (ft. bgs) TH-1 40.439167 -104.425000 4754 25 23.5 TH-2 40.435278 -104.400556 4710 20 12.0 TH-3 40.417324 -104.406412 4680 15 8.0 • TH-4 40.407166 -104.412785 4663 20 20.0 TH-5 40.400045 -104.400439 4631 25 22.5 TH-6 40.399007 -104.427685 4667 25 23.0 TH 7 40.411876 -104.422103 4679 25 23.0 TH-8 40.427222 -104.419444 4708 20 14.5 1. Coordinates and elevations of existing ground surface atthe boring locations are approximate and are based on a handheld GPS unit and Google Earth,respectively. 2. bgs=below existing ground surface Laboratory Work Upon completion of the borings, the soil samples were delivered to CTL Thompson, Inc. laboratory for subsequent geotechnical laboratory testing. Representative soil samples were selected for laboratory testing by TRC. Laboratory testing was performed on selected samples in order to determine soil index properties (moisture contents, particle gradations, and plasticity) and direct shear testing. The laboratory-testing program was conducted in accordance with applicable ASTM specification. The laboratory test results are provided in Attachment B. Table 2 below summarize the quantities of laboratory testing performed. TiRc