2010-12-27_PERMIT FILE - C1981012

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SUMMARY OF CONCLUSIONS AND RECOMMENDATIONS A geotechnical investigation was conducted at the New Elk Mine near Trinidad, Colorado. The project location is shown on Figure 1 — Site Location Map. The purpose of the investigation was to evaluate the surface and subsurface conditions at the site with respect to foundation design and earthwork for the proposed construction. This summary has been prepared to include the information required by civil engineers, structural engineers, and contractors involved in the project. Subsurface Conditions (n. 2) The subsurface investigation consisted of seven borings at the New Elk Mine and one boring at the Jansen Yard, drilled on August 5 and 6' 2010. The borings at the New Elk Mine generally encountered fill materials above native clay and silt soils extending to dense gravel soils. Groundwater was encountered at depths of between 8.5 and 17.0 feet. The native clay soils and fill materials were determined to be moderately plastic and may have a slight potential for expansion. At the Jansen Yard, the boring encountered clay and shale fill above native sand and gravel soils. Groundwater was not encountered at the Jansen Yard boring location. The clay and shale fill materials are moderately plastic and slightly expansive. The native sand soils are non- plastic and may have a slight potential for collapse. • Summary of Foundation Recommendations Water Tanks ■ Foundation Type — Spread Footings or Monolithic (Turndown) Structural Slab. (p. 4) ■ Structural Fill — None required for foundations on bedrock. Minimum of 24- inches below foundations or extending to native gravel soils, whichever is less. Where structures are not sensitive to slight movements, the existing fill materials may be reused as structural fill provided wood and other organic materials removed. Imported structural fill should consist of pit -run, crusher fines, CDOT Class 6 base course, or other granular material approved by the engineer. (p. 4) ■ JVavimum Allowable Bew-ing Capacity — 4,000 psf for foundations on rock. 1,500 psf for foundations above structural fill. (p. 4) ■ Subgrade Modulus — 150 pci for existing fill materials. 250 pci for pit -run, crusher fines, or CDOT Class 6 base course. (p. 4) Pinup Station • Foundation Type — Monolithic (Turndown) Structural Slab. (p. 5) • Structural Fill — Minimum of 36- inches below foundations. The existing fill materials are not suitable for reuse as structural fill. Imported structural fill should consist of pit-run, crusher fines, CDOT Class 6 base course, or other granular material approved by the engineer. (p. 5) • Alavinurm Allowable Bearing Capacity-1,500 psf. (P-5) • Subgrade Moduhus — 250 pci for pit -run, crusher fines, or CDOT Class 6 base course. (p• 5) •