Preserving Instrumentation at New Waddell Dam

Abstract Only - New Waddell Dam is one of the newest dams in Reclamation’s inventory. Completed in 1992, New Waddell Dam was the first large embankment dam that Reclamation constructed after the Teton Dam failure. As such, it was designed and constructed using the most modern zoned embankment dam techniques with a central impervious core, internal filter and drainage zones and cobblefill shells. New Waddell Dam has a hydraulic height of 300 feet and a crest length of 4,900 feet. The total embankment volume is approximately 16,000,000 yd3.
In addition to using a modern zoned embankment design, New Waddell Dam was heavily instrumented during the initial filling. The total initial monitoring system included the following:
• 78 embankment surface measurement points
• 26 structural measurement points
• 7 inclinometer casings for both deflections and settlements
• 8 extensometer anchors
• 3 shear indicators
• 5 tiltmeters
• 24 porous tube piezometers
• 69 vibrating-wire piezometers
• 33 observation wells
• 16 seepage and drainage flows
After more than a decade of monitoring with excellent performance, many of the instruments were placed on standby as a result of Reclamation’s 2005 Comprehensive Facility Review of New Waddell Dam. Actively monitored instruments afterwards fell to the following:
• 78 embankment surface measurement points
• 2 porous tube piezometers
• 9 vibrating-wire piezometers
• 16 seepage and drainage flows
• On-going Visual Inspections Checklist
Over the years, the active and standby instruments fell into disarray due to minimal and/or no maintenance. In the 2011 CFR, Reclamation recommended that Central Arizona Water Conservation District (CAWCD): 1) improve the degrading condition of the active instruments to preserve the monthly monitoring requirements; 2) investigate the operability status of all standby instruments; and 3) make repairs to standby instruments to preserve the standby instruments’ functionality if needed in the future.
CAWCD initiated a study in 2013 which included a field reconnaissance of the operability status of all instruments. CAWCD assessed several alternatives ranging from doing nothing to upgrading instruments to preserve current monthly manual monitoring functionality while being ready for automated monitoring if needed. The decision was made to just preserve the current manual monitoring functionality and make repairs to the operable standby instruments to preserve their ability to also me read manually. CAWCD completed the design in 2016 and made the repairs/improvements to the instruments in the spring of 2017. These repairs have improved data collection from the actively monitored instruments and identified which instruments are still operable if needed.