Environmental Enlightenment #71
By Ami Adini -
Reissued July 8, 2010

This is a SHORT, LIGHT and SIMPLE newsletter. Its purpose is to rekindle, in the initiated, terminology they have once learned and enlighten the uninitiated on terms they may have heard but never knew the meaning of.

How to Find Buried Objects.
Electrical Resistivity

(The material in this article has been provided by US EPA publications)

Electrical resistivity, also referred to as galvanic electrical methods, is occasionally useful at UST sites for determining shallow and deep geologic and hydrogeologic conditions. By measuring the electrical resistance to a direct current applied at the surface, this geophysical method can be used to locate groundwater/contaminant pathways, clay lenses and sand channels, perched water zones and depth to groundwater, and occasionally, large quantities of residual and floating product.

A variety of electrode configurations can be used depending on the application and the resolution desired. Typically, an electrical current is applied to the ground through a pair of electrodes. A second pair of electrodes is then used to measure the resulting voltage. The greater the distance between electrodes, the deeper the investigation. Because various subsurface materials have different resistivity values, measurements at the surface can be used to determine the vertical and lateral variation of underlying materials.

Electrical resistivity has a number of limitations:

Electrodes must be in direct contact with soil; if concrete or asphalt are present, holes must be drilled for inserting the electrodes and then refilled when the survey is complete.

The distance between outside electrodes must be 4 to 5 times the depth of investigation.

Measurements may be limited by both highly conductive or highly resistive surface soils. If shallow clays and extremely shallow groundwater are present, most of the current may concentrate at the surface. Although the condition is very rare, the presence of thick, dry, gravelly material (or massive dry material) at the surface may prevent the current from entering the ground.

You can find past issues of our "Environmental Enlightenment" at amiadini.com Wealth of information about environmental site assessments in the real estate transactions and issues concerning assessment and cleanup of contamination in the subsurface soil and groundwater.

Call me if you have any questions. There are no obligations.

Ami Adini Environmental Services, Inc.
Environmental Consultants & General Engineering Contractors
California Lic. #1009513 A B HAZ ASB
818-824-8102; mail@amiadini.com
www.amiadini.com

Ami Adini is a veteran environmental practitioner with over 40 years of experience. He carries a Bachelor of Science degree (B.Sc.) in Mechanical Engineering including academic credits in Nuclear and Chemical Engineering and postgraduate education in these fields. His career includes design and construction of nuclear plant facilities, chemical processing plants and hazardous wastewater treatment systems. He is a former California Registered Environmental Assessor Levels I & II in the 1988-2012 registry that certified environmental professionals in the assessment and remediation of environmentally impacted land, and a Registered Environmental Professional (REP) since 1989 with the National Registry of Environmental Professionals (NREP). He is a California Business & Professions Code Qualifying Responsible Managing Officer (RMO) in the General Engineering Contractor classification with Hazardous Substance Removal and Asbestos certifications, and president of AMI ADINI ENVIRONMENTAL SERVICES, INC. (AAES), a general engineering contractor and consulting firm specializing in environmental site assessments, rehabilitation of contaminated sites and removal of environmental risks from real-estate transactions. (Contact Ami for a complete resume.) AAES provides practical solutions to environmental concerns using the highest standards of ethics and integrity while providing its clients with maximum return on their investments.