Geophysical survey with FDEM methods, Ewa Marina, Campbell Industrial Park and Barbers Point Harbor, Oahu, Hawaii

Abstract

A geophysical survey was conducted in three areas in the vicinity of the Barbers Point Naval Air Station on Oahu, Hawaii. The areas are designated as Ewa Marina, Campbell Industrial Park, and Barbers Point Harbor. The objective of the survey was to infer from the geophysical data information about the thickness of a brackish water lens floating on saline water in the limestone aquifer of this region. A geophysical method was employed that allows relatively quick areal coverage for determining lateral variation in the thickness of the brackish water lens. To also derive from the survey information about the thickness of the brackish water lens, the geophysical data was correlated to salinity observations in boreholes placed in the three survey areas. The results of the survey are given as profiles of the thickness of the brackish water lens along lines generally perpendicular to the shore. The profiles are mainly characterized by a rapid increase in the thickness of the brackish water lens in the first 150 ft from the shore. The thickness of the brackish water lens varies from about 100 ft in the Ewa Marina area to less than 50 ft in the Barbers Point Harbor area.