Geophysical test surveys with FDEM methods, Ewa Marina, Oahu, Hawaii

Abstract

This report contains the results of a geophysical test survey conducted on May 22, 1990, for Haseko (Hawaii) Inc. near Ewa Marina on the Island of Oahu, Hawaii. The test data were acquired on two lines. The objective of the survey was to determine the lateral boundary between saline saturated and fresh/brackish water saturated limestones. Due to the large change in electrical resistivity between saline saturated and fresh/brackish water saturated limestones, a method which is sensitive to the ground resistivity (or its inverse, conductivity) was chosen for the test. The geophysical method utilized was frequency domain electromagnetic (FDEM) measurements with the Geonics EM-34. The EM-34 is a rapid and inexpensive method which is highly sensitive to lateral changes in resistivity. Data coverage in the study area was somewhat limited to existing roads, due to the thick vegetation, and time constraints.