Geophysical surveys for assisting in determining the ground water resources, North Kohala site, Island of Hawaii

The main objective of the geophysical survey was to assist in characterizing the hydrologic regime in the North Kohala study area for a proposed ground water well. Ground water resources can occur on the Island of Hawaii basically in two modes: • In a basal mode, where a lens-shaped body of fresh water floats on saline water, and • In a high-level mode, where the ground water occurrence is controlled by subsurface damming structures. The surficial volcanic rocks are generally highly permeable and this allows rainwater to infiltrate directly downward through the island mass. In the Hawi area, ground water was expected to occur as both a deep basal fresh-brackish water lens and possible high-level water occurrences at locations above subsurface damming structures (i.e, dikes; rift zones). Previous TDEM surveys on the Hawaiian Islands have reliably mapped the boundary between fresh water in the basal mode and high-level water occurrences. Geophysical surveys, combined with other hydrogeologic information, are used to provide optimum locations for well placement and completion depths."Chalon International of Hawaii, Inc