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Preliminary Results of Subsurface Exploration and Monitoring at the Johnson Creek Landslide, Lincoln County, Oregon

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Preliminary Results of Subsurface Exploration and Monitoring at the Johnson Creek Landslide, Lincoln County, Oregon Preliminary Results of Subsurface Exploration and Monitoring at the Johnson Creek Landslide, Lincoln County, Oregon Open-File Report 2007-1127 U.S. Department of the Interior U.S. Geological Survey Preliminary Results of Subsurface Exploration and Monitoring at the Johnson Creek Landslide, Lincoln County, Oregon By William H. Schulz and William L. Ellis Open-File Report 2007-1127 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior DIRK KEMPTHORNE, Secretary U.S. Geological Survey Mark D. Myers, Director U.S. Geological Survey, Reston, Virginia: 2007 For product and ordering information: World Wide Web: http://www.usgs.gov/pubprod Telephone: 1-888-ASK-USGS For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment: World Wide Web: http://www.usgs.gov Telephone: 1-888-ASK-USGS Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Suggested citation: Schulz, W.H., and Ellis, W.L., 2007, Preliminary results of subsurface exploration and monitoring at the Johnson Creek landslide, Lincoln County, Oregon: U.S. Geological Survey Open-File Report 2007-1127, 11 p., 1 appendix. iii Contents Abstract ...........................................................................................................................................................1 Introduction.....................................................................................................................................................1 Previously Installed Monitoring Equipment .....................................................................................3 USGS Upgrades of Monitoring Equipment ................................................................................................3 USGS Installation of Subsurface Monitoring Equipment ...............................................................4 Vibrating-Wire Piezometers .......................................................................................................4 Water-Content Sensors ..............................................................................................................9 Monitoring Data .............................................................................................................................................9 References Cited..........................................................................................................................................10 Appendix A. Preliminary Monitoring Data ..............................................................................................11 Figures 1. Index map showing the location of the Johnson Creek landslide .......................................1 2. Map showing landslide boundaries and the locations of monitoring equipment .............2 3. Map showing the locations of monitoring equipment ............................................................5 4. Log of borehole B-4 ......................................................................................................................7 5. Log of borehole B-5, 2 sheets .....................................................................................................8 Tables 1. Depths of grouted piezometers ..................................................................................................4 2. Details of well construction ........................................................................................................4 3. Estimates of landslide basal shear zone depth .......................................................................9 4. Depths of water-content sensors ..............................................................................................9 iv Conversion Factors Inch/Pound to SI Multiply By To obtain Length inch (in.) 2.54 centimeter (cm) foot (ft) 0.3048 meter (m) mile (mi) 1.609 kilometer (km) Pressure atmosphere, standard (atm) 101.3 kilopascal (kPa) m of water at 15.5° C (m H2O) 9.798 kilopascal (kPa) inch of mercury at 60ºF (in Hg) 3.377 kilopascal (kPa) pound per square foot (lb/ft2) 0.04788 kilopascal (kPa) pound per square inch (lb/in2) 6.895 kilopascal (kPa) Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: °F=(1.8×°C)+32 Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows: °C=(°F-32)/1.8 SI to Inch/Pound Multiply By To obtain Length centimeter (cm) 0.3937 inch (in.) meter (m) 3.281 foot (ft) kilometer (km) 0.6214 mile (mi) Pressure kilopascal (kPa) 0.009869 atmosphere, standard (atm) kilopascal (kPa) 0.10206 m water at 15.5° C (m H2O) kilopascal (kPa) 0.2961 inch of mercury at 60°F (in Hg) kilopascal (kPa) 20.88 pound per square foot (lb/ft2) kilopascal (kPa) 0.1450 pound per square inch (lb/ft2) Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: °F=(1.8×°C)+32 Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows: °C=(°F-32)/1.8 Preliminary Results of Subsurface Exploration and Monitoring at the Johnson Creek Landslide, Lincoln County, Oregon By William H. Schulz and William L. Ellis displacement and occurred January 27 - February 3, 2003. Abstract Recent movements in response to heavy rainfall have only been on the order of a few centimeters. The Johnson Creek landslide is a translational, primarily The Oregon Department of Transportation (ODOT) per- bedrock landslide located along the Oregon coast about 5 km formed an investigation of the landslide during the 1970s. A north of Newport. The landslide has damaged U.S. Highway more comprehensive investigation and evaluation of possible 101 many times since construction of the highway and at least mitigation measures was initiated in late 2002 as a collabora- two geological and geotechnical investigations of the landslide tive effort between ODOT and the Oregon Department of have been performed by Oregon State agencies. In cooperation Geology and Mineral Industries (DOGAMI). As part of that with the Oregon Department of Geology and Mineral Indus- study, six boreholes were completed along a longitudinal sec- tries and the Oregon Department of Transportation, the U.S. tion of the landslide. Piezometers were installed just above the Geological Survey upgraded landslide monitoring systems and landslide basal shear zone in three of the boreholes, and incli- installed additional monitoring devices at the landslide begin- nometer casing was installed in the other three boreholes (LT- ning in 2004. Monitoring devices at the landslide measured 1P, LT-2P, and LT-3P are piezometer-equipped boreholes and landslide displacement, rainfall, air temperature, shallow boreholes LT-1, LT-2, and LT-3 are equipped with inclinometer soil-water content, and ground-water temperature and pres- casing, fig. 2). Later, manual extensometers were installed in sure. The devices were connected to automatic dataloggers the inclinometer boreholes when landslide movement made it and read at one-hour and, more recently, 15-minute intervals. Monitoring results were periodically downloaded from the dataloggers using cellular telemetry. The purposes of this report are to describe and present preliminary monitoring data from November 19, 2004, to March 31, 2007. 123°35' 119°20' Introduction 45°56' The Johnson Creek landslide is located near the com- Johnson Creek munity of Otter Rock, Oregon, approximately 5 km north Newport Landslide of Newport (fig. 1). The landslide occurs on a nearly flat marine terrace within marine terrace deposits and seaward- N dipping sedimentary rock (Landslide Technology, 2004), and it displaces through a coastal bluff. The landslide is as 42°58' much as 26 m thick, 200 m long, and 360 m wide (fig. 2) and exhibits primarily translational movement. The landslide is visible on 1939 aerial photos and has affected the alignment 0 100 200 Kilometers of the Old Coastal Highway and, more recently, U.S. Highway 101 (Priest and others, 2006). Total landslide movement as 0 100 200 Miles estimated from a balanced geologic cross section is about 28 m horizontal and 6 m vertical (Priest and others, 2006). The largest recorded movement episode involved about 25 cm of Figure 1. Index map showing the location of the Johnson horizontal displacement and several centimeters of vertical Creek landslide. PACIFIC OCEAN Preliminary Results of Subsurface Exploration and Monitoring at the Johnson Creek Landslide, Oregon Landslide, Creek Johnson the at Monitoring and Exploration Subsurface of Results Preliminary WC-1S, WC-1D LT-1 LT-1P LT-1A LT-2A LT-2P LT-2 B-4 B-5 WC-3S, WC-3D LT-3 LT-3P Explanation LT-2 - Location and name of borehole WC-1S - Location and name of water-content sensor Location of rain gauge Landslide scarp mapped by DOGAMI N (Landslide Technology, 2004) Base map modified from Landslide Technology (2004) 0 25 50 m Contour interval is 0.5 m. Elevations are relative to a local datum. Figure 2. Map showing landslide boundaries and the locations of monitoring equipment. USGS Upgrades of Monitoring Equipment 3 impossible to conduct inclinometer surveys through the basal using a battery-powered datalogger located at each borehole. shear zone. The manual extensometers consisted of wire rope A tipping-bucket
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