Safety in numbers16 June 2000
Monitoring of over 250 geotechnical instruments was automated at the Diamond Valley Lake in the US
Diamond Valley Lake (formerly known as Eastside reservoir) is the newest reservoir in California and one of the largest emergency storage projects in the US. It was built by the Metropolitan Water District of Southern California (MWDSC), and is located about 145km southeast of Los Angeles. When full, Diamond Valley will contain approximately 800,000 acre-feet of water, or enough to provide about six months of storage for MWDSC's customers.
Initial filling started in late 1999 and is expected to be completed in 2002. Water for the reservoir is provided by the Colorado river aqueduct and the state water project. The project consists of three dams: the West dam, (2774m crest length; 87m high), East dam (3200m crest length; 56m high) and the Saddle dam (701m crest length; 40m high). The dams are zoned earth and rockfill dams with a sandy clay central core supported by rockfill outer shells.
Monitoring of the approximately 250 geotechnical instruments installed to measure dam safety and performance parameters has been automated using the Geomation System 2300, provided by Geomation of Colorado, US. The instruments include vibrating wire piezometers, vibrating wire settlement sensors, ultrasonic level sensors and turbidimeters, load cells and tiltmeters in the inlet/outlet tower, and a barometer. Alarms from strong motion accelerographs are also sent through the Geomation system.
Measurement and control units (MCUs) were installed at 90 locations along the crest, on sections on the downstream faces, and along the toe of the dams. The MCUs are solar powered, with battery backup, and communicate locally via UHF radio. The individual sensors are connected to the MCUs and the measurements are sent via radio from each MCU to a central location at the dam site. From there, the information goes directly to MWDSC's main office in Los Angeles via a T-1 line.
Each geotechnical instrument is user configured with the relevant calibration data, reading frequencies and alarm limits through the Geomation software GEONET suite. This user programming is stored at each MCU location and can be altered as needed from the MWDSC's main office, from the dam site local office, or at each MCU location. All of the data is stored in a SQL data base where is can be accessed to provide the relevant reports and graphs as needed by MWDSC.