2007 Ground Water Summit

Wednesday, May 2, 2007 : 9:20 a.m.

Geophysical Detection and Characterization of Earth Fissures Crossing the Central Arizona Project (Cap) Canal: What Works and What Doesn't in Arizona

Robert McGill, PG, EIT, C.A. Baldyga, MS, J.B. Fink, PhD, PE, J.B. Fleming, PhD and W.J. Greenwood, MS, hydroGEOPHYSICS Inc.

Since its inception, the CAP canal network and the Central Arizona Water Conservation District that governs it (CAWCD) has had to contend with differential land subsidence issues that are caused by historical agriculture ground water pumping overdrafts.  In some instances, CAWCD personnel have needed to increase the canal freeboard because of substantial amounts of ground subsidence, such as the Pool 23 and 24 areas located west of the McDowell Mountains.

 

Because ground subsidence and fissure development cannot be directly controlled, the CAWCD must investigate how best to deploy localized engineering controls in order to mitigate the risks of localized canal failure or overtopping caused by these subsurface processes.

 

HGI deployed seismic refraction, High Resolution Resistivity, electromagnetics, and ground penetrating radar (GPR) techniques within areas where new fissure cracks were occurring along the canal by-ways.  HGI also deployed marine capacitively coupled resistivity and GPR techniques along the canal water surface for sediment thickness estimations.

 

This paper discusses the results of each method, and ranks them according to data acquisition efficiency and cost per metric.

Robert McGill, PG, EIT, hydroGEOPHYSICS Inc. Rob is Sr Proj Engineer and Principal of HydroGEOPHYSICS (HGI. Rob has a Geol. Eng. degree from U AZ 1997 and a Bus. Degree from WTSU (now part of A&M). Rob has 10 years experience with environmental geophysical applications.


The 2007 Ground Water Summit