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Three-dimensional time-domain induced polarization of a desert Aridisol for septic design


Septic leach field design in the arid southwestern US requires direct testing of soils to ensure adequate drainage. We propose that direct testing costs can be reduced if electrical geophysical methods are used to determine soil structure that facilitates proper drainage rates. We demonstrate this concept at a residential site where resistivity and induced polarization data were acquired within a desert soil with variable mixtures of clay (Argid) and calcareous (Orthid) components. Electrode arrays were tested to ensure high data quality and minimal workload during inversion modeling. The resulting resistivity structure identified a sharp boundary between the eastern and western halves of the property. The west was more conductive than the east, which could indicate the presence of higher moisture or higher clay content. Chargeability data gathered from the induced polarization survey showed similar stark patterns between east and west halves of the property. The western portion of the survey area was verified to have some clay based on high chargeability values and direct soil testing from pits. Test pits dug to 3.65 m showed transitions between Argid and Othid conditions; the test pits were in locations of moderate resistivity and low chargeability. From this study, we concluded that resistivity and IP were useful in septic design because they reduce the total amount of direct testing needed when testing locations are carefully chosen based on the geophysical results.

ISSN: 1083-1363
EISSN: 1943-2658
Serial Title: Journal of Environmental & Engineering Geophysics
Serial Volume: 26
Serial Issue: 2
Title: Three-dimensional time-domain induced polarization of a desert Aridisol for septic design
Affiliation: hydroGEOPHYSICS, Tucson, AZ, United States
Pages: 153-164
Published: 202106
Text Language: English
Publisher: Environmental and Engineering Geophysical Society, Englewood, CO, United States
References: 34
Accession Number: 2021-053124
Categories: Engineering geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables, geol. sketch maps
N31°23'60" - N32°30'00", W113°22'00" - W110°28'00"
Secondary Affiliation: W.K. Walker, P.E., Tucson, AZ, USA, United StatesAdvanced Geosciences, Austin, TX, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2021, American Geosciences Institute. Abstract, copyright, Environmental & Engineering Geophysical Society. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 2021
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