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excavation refusal, approximately 4 to 7 feet deep Test pit locations were surveyed by <br />Mountain Man Surveying of Durango, Colorado. The field engineer, David McLay, logged the <br />pits and obtained bulk samples of the materials encountered. Logs of test pits are presented in <br />Appendix A. <br />Bulk samples collected from the test pits were placed in sealable 5- gallon buckets. They <br />were observed to confirm field classifications; selected samples were transported to Terracon <br />Materials Testing Laboratory in Farmington, New Mexico for laboratory testing. Laboratory <br />tests performed included the following: <br />• Moisture Content (ASTM D2216 -10) <br />• Atterberg Limits (ASTM D4318 — 10) <br />• Compaction (ASTM D1557 — 09) <br />The laboratory results are presented in Appendix B. <br />3.0 Site Conditions <br />3.1 Geology <br />The geology in the portal area generally consists of 5 to 7 feet of Holocene or Late <br />Pleistocene age colluvium, ranging from unsorted, clast- supported, pebble to boulder gravel in a <br />sandy or silty matrix to matrix - supported gravelly sand or clayey silt (CGS, 2000). Underlying <br />the colluvium is bedrock consisting of brecciated Entrada Sandstone and Pony Express <br />Limestone. Although there are numerous fractures in the bedrock, they are generally sealed by <br />calcite and quartz. The fractures tend to be random and thus do not have a preferred orientation <br />(Gonzales, 2012). <br />3.2 Surface Conditions <br />As shown on Figure 3, surface conditions on the slope above the portal consists primarily <br />of colluvium. During the 2009 portal reconstruction, material was removed directly above the <br />portal, causing some of the colluvial material to fall down the slope. The slope above the portal <br />is approximately 50 feet high and has an approximate slope of 1:1 (horizontal:vertical). The <br />portal is partially covered with rock and fill. There is an approximate 1,200 square -foot bench <br />south of the portal. The access road to the portal from the Incas Access Road is approximately <br />10 to 12 feet wide, and is at an approximate 3:1 downward slope. <br />1 Test borings were planned but not installed during the Chief Portal investigation. Attempts to access to the portal <br />location by the drilling rig were not successful. <br />Rule 6.5 Geotechnical Stability Technical Revision <br />Chief Portal <br />March 16, 2013 <br />Page 2 <br />