The relatively flat Schofield Plateau was formed as basaltic lava flowed from the adjacent Koolau and Waianae volcanoes to the east and west, respectively. The upper 100 to 200 feet of the basaltic bedrock within the Schofield Plateau is weathered saprolite. The saprolite consists of soil (primarily fine-grained materials including silt and clay) formed by in situ decomposition of the basaltic bedrock. The saprolite is underlain by relatively unweathered basaltic bedrock consisting of interbedded pahoehoe and a'a lava flows. The lava flows are
highly fractured with cinder and clinker zone.

Three types of groundwater systems have been identified in central Oahu: (1) the Schofield High-level Water Body, (2) basal groundwater, and (3) dike-impounded groundwater. The Schofield High-level Water Body is located beneath the Schofield Plateau, and subsequently, the site. This water body is bound to the east and west by dike-impounded groundwater and to the north and south by basal groundwater. Lower permeability rocks (possibly
volcanic dikes and/or buried ridges) structurally separate these groundwater systems from one another. The Schofield high-level aquifer has a high transmis- sivity and hydraulic conductivity.
The depth to groundwater at the site is approximately 600 feet below ground surface (bgs) (approximately 270 feet above mean sea level [msl]).

• Fractured Bedrock

Vertical contamination is greater than 800 feet bgs.

• Trichloroethene (63 µg/L)
• Carbon tetrachloride (Not given)

• Pump and Treat

MCLs for TCE and carbon tetrachloride (CCl4).

The treatment at the production well heads continues. Between 2002 and 2007 TCE and CCl4 concentration remained stable.

http://cfpub.epa.gov/supercpad/cursites/csitinfo.cfm?id=0902923