ing, and is capable of being tied into statewide emergency and seismic monitoring systems as they emerge. After almost two years of service, DSOD monitoring requirements have been met with a more complete picture of overall performance. “EBMUD’s infrastructure is spread out over a vast area and cov- ers multiple counties,” said Baldwin. “In particular, the Pardee and Camanche sites are several hours away from main offices, and the semiannual surveys took over a week to complete. This new system provides more accurate data, more or less constantly, and of course reduces the time survey crews spend on this task. It’s a big improve- ment, and it is performing beyond expectations.” Baldwin said one important design goal was interconnectivity with existing and future monitoring systems. “For obvious reasons, Califor- nia, and especially the Bay Area, is really focused on being responsive to seismic events, and continuous monitoring and alerting is a big part of that,” he said. “This big network is exemplary when it comes to continuous, autonomous monitoring and alerting, and the software de- sign makes it easy to add in more sensors if needed. Down the line, the information can be directly tied into statewide systems. The potential to automate and improve emergency responses to seismic events is a major advantage of monitoring networks.” “While the goal is to eliminate the legacy manual-read monitoring sys- tems, inevitably issues with a power supply or other minor components will crop up and require some attention,” Martin said. “Sensemetrics provided support and training through the first two years to help resolve most issues, and Leica Geosystems updated firmware based on feed- back from the project. So while the labor of a manual-read system will go away, some more technical support and software skills are required in an automated system. The trade-off between having an automated monitoring system that gives you a survey every day (or every hour if you wish) versus a survey only twice a year is worth the investment. “Once a communications backbone is built out to support an automated survey system, other automated sensors such as seismic recorders or vibrating wire piezometers (measures water pressure inside the dam) can easily be added to the system,” he said. “Installation of this net- work was a proactive system improvement. EBMUD now has more survey information immediately at its fingertips regarding structure performance than at any previous moment in the district’s history. By being proactive and automating monitoring systems, EBMUD has greatly improved dam safety monitoring. “The GPS system at Pardee Dam now gives us a complete picture of the seasonal deformations due to thermal expansion and contraction of the concrete structure,” Martin said. “With the Camanche Reservoir portion of the GPS monitoring system, we are able to meet DSOD monitoring requirements without long trips out of town by the survey crew and to check for any possible deformations remotely in near real time.”
The new system provides more accurate information more rapidly, reduces staff time spent on monitoring, and is capable of being tied into statewide emergency and seismic monitoring systems as they emerge. Photo: © EBMUD, used with permission
Automated dammonitoring in action A recent example of the benefits of automating a survey monitoring scheme comes from another EBMUD automated dam monitoring project on San Pablo Dam. In 2008-2009, the dam underwent a seis- mic improvement to buttress the toe of the dam to bedrock using a cement deep soil mixing process. Increased monitoring requirements from the DSOD while working on an active dam were met via an automated motorized total station (AMTS) system, which has been running several times a day since that project was completed in 2009. EBMUD also has a program to visually inspect dams and reservoirs immediately after an earthquake to check for cracking or other visible damage as a quick ground truth. After a 4.4 magnitude earthquake in January 2018 on the Hayward fault centered in Berkeley, less than 5 miles from the San Pablo dam site, EBMUD geotechnical engineers were able to log in to theAMTS automated monitoring system to review whether there had been any movement or slumping on the dam, and they confirmed that there was no significant movement. This ability to have information immedi- ately and at their fingertips has proven to be a huge asset in managing dam safety at EBMUD.
ANGUS W. STOCKING, LS , has been writing about infrastructure since 2002. To learn more about monitoring solutions, visit www.leica-geosystems.com.
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april 2018
csengineermag.com
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