Rehabilitation of Embankment Dam
Hope Valley Reservoir, Southern Australia: This 12,700 megaliter reservoir has serviced the city of Adelaide for more than 120 years. Now, the earthen embankment dam that forms the reservoir is being rehabilitated to extend its useful life.
The remedial work involves excavating the downstream toe of the embankment to a depth of about six meters and the reconstruction of the embankment with collapsible filters and an engineered rock fill. To avoid compromising the safety of the dam, this work is being carried out one section at a time, each section being ten meters wide.
An intensive instrumentation program has been installed to allow the contractor, Bardavcol, to maintain "real time " monitoring of the embankment as construction proceeds. Some instruments are read manually every other day. These include six inclinometers and twelve standpipe piezometers.
Other instruments have been connected to an automatic data acquisition system so that site engineers have near real-time readings. These instruments include three In-Place Inclinometers and six VW piezometers. The piezometers monitor the piezometric pressure in the embankment upstream of the construction zone.
The in-place inclinometers and VW piezometers are connected to a Campbell Scientific CR10X data logger which is located on the embankment. A computer at the site office, about 300 meters away, retrieves data via a shorthaul modem. Slope Indicator's MultiMon software (now Atlas Web-Based Monitoring) then processes and updates a graphic display of the site every 15 minutes.
The monitoring program updated its display every 15 minutes. In the screen shot at right, you can see green data boxes superimposed on a plan view of the site. Each data box holds the current reading of a sensor. Clicking on any data box pops up a five day trend chart for that sensor.
The program has three color-coded alarm levels. Green indicates normal data, but if any reading exceeds a particular alarm threshold, its data box turns yellow or red. In addition, an auto-dialer is activated to deliver a preprogrammed message to Bardavcol personnel, advising them of the alarm status and the location of the sensor that triggered the alarm. An emergency response procedure is in place so that actions can be taken, depending on the severity of the alarm condition.
Thanks to Mike Matthews of Bardavcol for this story and the site photographs.