Vadose zone transport field study: Detailed test plan for simulated leak tests

Ward, Anderson L.; Gee, Glendon W.

doi:10.2172/756986

Cited by 8 publications

(1 citation statement)

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“…When applied over time intervals, the methods allow depiction of transient features, such as developing and migrating contaminant plumes. The characteristics of these advanced methods are described in Barnett et al (2001) and in the individual reports of Appendixes A through D. Ward and Gee (2000) described the process of selecting and eliminating geophysical monitoring technologies that have application to problems at Hanford. Despite the logistical/operational difficulties involved, the simultaneous deployment of multiple methods during the testing at the Mock Tank does allow comparisons of methods to provide verification of results.…”

Section: Summary Of Geophysical Methodsmentioning

confidence: 99%

Results of Tank-Leak Detection Demonstration Using Geophysical Techniques at the Hanford Mock Tank Site-Fiscal Year 2001

Barnett¹,

Gee²,

Sweeney³

2002

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Under the Tri-party Agreement with federal and Washington State regulators, the U.S. Department of Energy will remove wastes from single-shell tanks (SSTs) and other miscellaneous underground tanks for storage in the double-shell tank system. Waste retrieval methods are being considered that use minimal amounts of liquid to dislodge, mobilize, and remove the wastes. As additional assurance of protection of the vadose zone beneath the SSTs, tank wastes and tank conditions will be monitored aggressively during retrieval operations, possibly by methods that are deployed outside the SSTs in the vadose zone.The FY 2001 TLDD was conducted at the Mock Tank Site in the 200 East Area of the Hanford Site. The 15.24-m (50-ft)-diameter Mock Tank structure was constructed in 1994-1995 for testing the applicability and effectiveness of ERT imaging of simulated fluid leaks beneath a steel-lined tank. A 36-wt% solution of sodium thiosulfate pentahydrate (benign waste surrogate) was released to a central leak point in the Mock Tank at different discharge rates during five leak periods. A total of ~15,100 L (~4,000 gal) of solution was released during the two-week test period. All geophysical methods required the monitoring of background and noise conditions before the solution (leak) detection portions of the test. Two of the five solution releases were "blind" in that none of the operators knew the solution release volumes/flowrates. ERT and HRR-SCRT were the only geophysical methods of the five tested that produced estimates of volumes leaked during these releases. The XBR method was able to detect a leak after ~378 L (~100 gal) were released but did not produce leak-volume estimates.Qualitative estimates based on the FY 2001 results of the ERT method indicate that the minimum detectable leak for the most robust configuration of the method (16 vertical electrode arrays around the tank with tomographic imaging) is in the range of hundreds of gallons. The three-dimensional (3-D) tomographic method also allowed approximations of leak location, size, and movement.Results of CEMI deployment were only marginally successful in identifying a developing leak beneath the tank. Changes in soil resistivity between background conditions and post-solution release periods of August 13-15 suggest that leaks were detected, but other conditions (such as unplanned leaks in peripheral wells) distorted the data. The large inductive influence of the metal tank significantly degraded the effectiveness of the method, as did the minimal separation (~21 m [~70 ft] of the transmitter and receiver boreholes. It was concluded that CEMI would not be effective in the steel-cased wells that iv surround SSTs at the Hanford Site because of the combination of low frequencies needed to penetrate the casings and the high soil resistivities of the tank settings.Four electrode configurations (central-leak-point electrode to surface electrodes, steel well casing to surface electrodes, tank to pseudo-casings ["short-circuited" ERT arrays], and surface electrode to ps...

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Section: Summary Of Geophysical Methodsmentioning

confidence: 99%