Summary Data
Notes about data in summary file
Determination of daily values
The data are collected on a 15-minute interval. Total daily rainfall values, in inches, have been determined by summing the 15-minute rainfall amounts for each 24-hour period ending at 12:00 a.m. (midnight). Days for which the number of values is less than 96 (see tabulated data file) are incomplete, and may have had greater rainfall than our total indicates.
Representative daily values for pore pressure and movement have been determined by computing the median value of all measurements collected during the 24-hour period ending at 12:00 a.m. The original measurements have been rounded to a number of digits appropriate for the accuracy of the data.
Notes about specific sensors
We have included measurements only for sensors believed to be operating correctly and reliably. No data are included for sensors that consistently have signals out of the manufacturer's specified range.
Pore pressure sensors
Pore pressures are reported as pressure head, in feet of water. Small negative pressure indicates partially saturated or unsaturated conditions, the porous tip on the sensors has a relatively low air-entry pressure, so negative pressures measured may not be accurate.
Range and Resolution – The pore pressure sensors in borings 2 and 3 are temperature-compensated vibrating-wire transducers that have a range of 50 p.s.i. ( 115 ft of water), resolution of .05 p.s.i. (0.11 ft of water) and accuracy of 0.25 p.s.i. The sensors in borings 1 and 5 are strain-gauge type pressure transducers that have ranges of 30 p.s.i. (69 ft) or 100 p.s.i. (231 ft). These sensors have resolution of ± 0.05% of full scale and accuracy of ±0.4% of full scale.
Pressure sensors in B-5 at 70 ft and 220 ft show evidence of a warm-up period of a few days following hook-up to the data logger. Therefore, summary data for these sensors are not reported before September 8 (70 ft) and September 10 (220 ft).
Extensometers
Extensometer output is reported in centimeters. Constant output indicates no movement. Steady change from a constant trend indicates movement.
Range and resolution – Extensometers E-1 and E-2 use displacement transducers that have a range of 80 inches (200 cm), resolution of ±0.03 in. (±0.08 cm) and accuracy of ±0.1% of full scale. Extensometers E-3 and E-4 use continuous-turn potentiometers that have a range of about 9.1 in. (23 cm) per turn, resolution of ±0.01 in. (±0.03 cm) and accuracy of about ±1% of full scale.
No data are reported for extensometer E-1 for the first few days of record due to data-logger programming error. E-1 has a noisy signal, no actual movement has occurred.
Extensometer E-2 recorded movement when a block broke off the face of the bluff on January 10, 1998, between 11:00 a.m. and 11:15 a.m.
Extensometer E-3 was repaired on 15 September 1999. Movement occurred at E-3 when a block of soil fell off the landslide head scarp sometime between 11 June and 30 June 1999. The exact date is unknown because we lost data between those dates becasue the telephone line was out of service for several weeks. The head scarp has raveled significantly since the January 15, 1997 Woodway landslide.
Extensometer E-4 has a noisy (15-minute) signal; however, the median daily value appears to remove most of the noise. E-4 was repaired 25 August 1999 to move its downhill end away from the sagging rootmat of a tree at the edge of the bluff.
