American Society of Civil Engineers


Geophysical and Remote Sensing Characterization to Mitigate McMicken Dam


by Michael L. Rucker, (Senior Engineer, AMEC Earth & Environmental, Inc., 1405 West Auto Drive, Tempe, AZ 85284 E-mail: michael.rucker@amec.com), Michael D. Greenslade, (Dam Safety Engineer, Flood Control District of Maricopa County, 2801 West Durango Street, Phoenix, AZ 85009 E-mail: mdg@mail.maricopa.gov), Ralph E. Weeks, (Senior Geologist, AMEC Earth & Environmental, Inc., 1405 West Auto Drive, Tempe, AZ 85284 E-mail: ralph.weeks@amec.com), Kenneth C. Fergason, (Project Geologist, AMEC Earth & Environmental, Inc., 1405 West Auto Drive, Tempe, AZ 85284 E-mail: ken.fergason@amec.com), and Bibhuti Panda, (Senior Engineer, AMEC Earth & Environmental, Inc., 1405 West Auto Drive, Tempe, AZ 85284 E-mail: bibhuti.panda@amec.com)
Section: Risk-Based Analysis and Design, pp. 207-214, (doi:  http://dx.doi.org/10.1061/40971(310)26)

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Document type: Conference Proceeding Paper
Part of: GeoCongress 2008: Geosustainability and Geohazard Mitigation
Abstract: By 2002, earth fissures, open ground cracks in the subsurface induced by groundwater withdrawal from basin alluvium, had visibly propagated close to McMicken Dam west of Phoenix, Arizona. Using surface seismic measurements, these fissures were traced to and beyond the dam. Initial test pits and trenches at seismic fissure interpretations confirmed this otherwise undetectable piping erosion hazard at the dam. An investigation to characterize the hazard extent, mechanisms and predict future behavior for risk assessment and mitigation design was then implemented. Deep alluvial basin geometry and material properties characterization across the site was accomplished using surface geophysical gravity, large array surface resistivity and s-wave refraction microtremor seismic methods. Earth fissure presence and absence was further assessed using seismic refraction and test trenches; the results also assisted geotechnical characterization. Newly developed satellite interferometry by synthetic aperture radar (InSAR) provided historic differential subsidence information for the area back to 1992 when data collection began. Finite element modeling developed and calibrated using these results provided predictions for risk assessment and mitigation design. A new dam section avoiding fissures was designed and constructed. The monitoring program includes InSAR and GPS survey, tape extensometers and Time Domain Reflectometry (TDR) at the dam toe.


ASCE Subject Headings:
Cracking
Dams
Groundwater
Remote sensing