The Island of Oahu is comprised of the remnants of two late Tertiary shield volcanoes and their associated rift zones. Geologic materials present in the vicinity of the KVA include Waianae basalts to the west, Koolau basalts to the east and, directly underlying the KVA, the weathered remnants of basaltic
lavas. Near surface materials consist primarily of the weathered remnants of the original basaltic surface. In situ decomposition of basaltic bedrock has progressed to depths of approximately l00 to 200 feet bgs. Near surface soils consist of several feet of a deep-red lateritic soil lithosol having a loose, and generally porous structure. Underlying the surface soil is the
subsoil, which extends to depths of about l0 to 30 feet. The subsoil is similar to the surface soil in texture and mineralogy, but has larger and more distinct structural units. The subsoil
grades with depth to saprolite, which is a highly weathered basalt that retains some textural and structural features of the parent rock, such as vesicles, fractures and relict minerals.
Saprolite is a clay-rich thoroughly decomposed rock formed by m-situ weathering of the basalt. Beneath the saprolite lies basalt.
The most extensive bodies of freshwater on Oahu occur as basal groundwater. Basal groundwater occurs when fresh water percolates into the saturated zone and displaces the underlying
seawater. The permeability of the unweathered rock that makes up the basal aquifers is generally high.
Targeted Environmental Media:
 Fractured Bedrock
The lateral and vertical extent of the plume was not defined.
Major Contaminants and Maximum Concentrations:
- Ethylene dibromide (EDB) (0 µg/L)
- 1,2-Dibromo-3-chloropropane (1 µg/L)
- 1,2,3-Trichloropropane (1 µg/L)
- Pumping Tests
- Pump and Treat
Comments:
One deep extraction well is used for the basal aquifer. It has been operational since 2005. The pumping rate is approximately 500 gpm.
Cleanup goals for the basaltic basal aquifer are Hawaii MCLs.
The system continues to has designed. There have been no decreases in concentrations. It is speculated that the background values in the aquifer from pesticide use throughout the valley will not allow cleanup levels to be reached at the site. http://cfpub.epa.gov/supercpad/cursites/csitinfo.cfm?id=0902876
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