Rectangular Schlumberger resistivity arrays for delineating vadose zone clay-lined fractures in shallow tuff

Conference · Wed May 01 04:00:00 EDT 1996

OSTI ID:224261

Miele, M ^[1]; Laymon, D ^[2]; Gilkeson, R ^[3]; Michelotti, R ^[4]

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1. ICF Kaiser, Rancho Cordova, CA (United States)
2. ICF Kaiser, Chicago, IL (United States)
3. ERM PMC Inc., Los Alamos, New Mexico (United States)
4. Los Alamos National Lab., NM (United States)

Rectangular Schlumberger arrays can be used for 2-dimensional lateral profiling of apparent resistivity at a unique current electrode separation, hence single depth of penetration. Numerous apparent resistivity measurements are collected moving the potential electrodes (fixed MN spacing) within a rectangle of defined dimensions. The method provides a fast, cost-effective means for the collection of dense resistivity data to provide high-resolution information on subsurface hydrogeologic conditions. Several rectangular Schlumberger resistivity arrays were employed at Los Alamos National Laboratory (LANL) from 1989 through 1995 in an area adjacent to and downhill from an outfall pipe, septic tank, septic drainfield, and sump. Six rectangular arrays with 2 AB spacings were used to delineate lateral low resistivity anomalies that may be related to fractures that contain clay and/or vadose zone water. Duplicate arrays collected over a three year time period exhibited very good data repeatability. The properties of tritium make it an excellent groundwater tracer. Because tritium was present in discharged water from all of the anthropogenic sources in the vicinity it was used for this purpose. One major low resistivity anomaly correlates with relatively high tritium concentrations in the tuff. This was determined from borehole samples collected within and outside of the anomalous zone. The anomaly is interpreted to be due to fractures that contain clay from the soil profile. The clay was deposited in the fractures by aeolian processes and by surface water infiltration. The fractures likely served as a shallow vadose zone groundwater pathway.

• Research Organization: Los Alamos National Lab., NM (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 224261
• Report Number(s): LA-UR--96-512; CONF-960477--2; ON: DE96008703
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
FLUID FLOW
GEOLOGIC FRACTURES
GROUND WATER
LANL
RESISTIVITY SURVEYS
SITE CHARACTERIZATION
TRACER TECHNIQUES
TRITIUM