2007-02-16_REVISION - M2005045 - Laserfiche WebLink

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PN: 50663GE November 20, 2006 3.2 Site Description The proposed roadway crosses a sloped azea below the terrace soil deposits located to the east and above the Florida River Valley to the west. The slope inclination is down to the west/northwest with inclinations of about three to one (3:1, horizontal to vertical) and locally steeper. We observed evidence of slope movement or existing instability along portions of the roadway where some springs were observed. Generally the unstable azeas appeazed to be associated with very moist to wet soil conditions as influenced by the springs. We did not observe evidence of large scale slope movement, or global instability, at the time of our field work. Vegetation along the slope azea consists of Pinon Pine and Juniper trees. 3.3 Subsurface Soil and Water Conditions We advanced six (6) test borings in azeas near the sloped portion of the proposed access roadway. Vegetation and slope inclinations influenced our choices for test boring locations. The locations of the test borings aze shown on Plate 1. The logs of the soils encountered in our test borings aze presented in Appendix A. We encountered clay with a variable amount of gravel and cobbles in our test borings from the ground surface to depths ranging from about five (5) to thirteen (13) feet below the ground surface. We encountered claystone beds of the Animas Formation in our test borings below the soil materials at the depths noted above. The Animas Formation is an assemblage of claystone, shale, sandstone and conglomerates. We encountered claystone and fine-grained sandstone in our test borings. We observed seeps along portions of the hillside and we encountered subsurface water in Test Borings One, Two and Three at depths of 12, 11'h, and 13'/z feet below the ground surface at the time of our field work. After returning to the site 24 hours after drilling the water level in Test Boring One was at a depth of about 9 feet below the ground surface. We suspect that some of the subsurface water is associated with local irrigation. It appeazs that the subsurface water may accumulate and migrate along the soil/formational material interface. The proposed roadway construction and retaining structure design should include provisions for subsurface and surface drainage. We did not encounter subsurface water in Test Borings Four, Five and Six at the time of our field work. 4.0 LABORATORY STUDY The laboratory study included tests to evaluate the general soil chazacteristics and to estimate the strength potential of the soils tested. We performed the following tests on select samples obtained from the test borings. 6 TRAUTNER ~ A DIVISION OF TRIGONN~~J