Precipitation, Pore-pressure, and Extensometer Measurements from area above the 1997 Woodway landslide, Snohomish County, Washington

On January 15, 1997, a landslide of approximately 100,000-m 3 from a coastal bluff swept five cars of a freight train into Puget Sound at Woodway, Washington, USA, 25 km north of downtown Seattle. The landslide resulted from failure of a sequence of dense sands and hard silts of glacial and non-glacial origin, including hard, jointed clayey silt that rarely fails in natural slopes. Joints controlled ground- water seepage through the silt and break-up of the landslide mass. During September of 1997, the U.S. Geological Survey began measuring rainfall, ground-water pressures, and ground movement at the bluff where the landslide occurred. The original sensor array comprised a tipping-bucket rain gauge, four extensometers (cable-extension transducers) to measure movement near the edge of the bluff, and ten pressure transducers, nine of which were buried directly in four boreholes to measure subsurface pore-water pressures at various depths. The sensors were connected to a Campbell Scientific CR10x data logger. Data were retrieved by telephone modem and saved to a personal computer at USGS offices for further processing. The datalogger was housed in a shed and the battery connected to an AC charger. Five strain-gauge- type pressure transducers were installed in two boreholes, B1 and B5, and four sealed, temperature- compensated vibrating-wire pressure transducers were installed in two boreholes, B2 and B3. The tenth pressure transducer (of vibrating wire type) was kept at the surface (in the shed with the data logger) to record changes in surface temperature and atmospheric pressure. In November 1998, one more vibrating wire pressure transducer was installed in an open-tube piezometer at B1. Data were collected every 15 minutes and are saved as comma-delimited text files. The raw measurements were processed to convert them to engineering units and remove any values that were out of range. The data set consists of time-series of precipitation, temperature, pressure, and extension measurements. The data collection ended in October 2006. Although we have made an effort to provide a complete data set, the data contain many null (no-data) records resulting from various causes: The signal cable of one of the pressure transducers broke during downhole installation, two others quit working soon after installation, faulty cable and ground potential errors caused by built-in signal conditioning of the strain-gauge pressure transducers hampered accurate measurements until the cables and ground potential errors were fixed in December 1997. The strain-gauge transducers quit working within a year of installation.