Pyrite Canyon is underlain by three geologic units: (1) fill/alluvium, (2) weathered/decomposed granitic bedrock, and (3) unweathered, fractured granitic bedrock. In general, the alluvium and fill material is found at the surface and beneath lies the weathered and unweathered bedrock. The depth of each geologic unit varies within the canyon. The fill/alluvium unit extends to its greatest depth (100 feet) along the eastern side of the canyon in the area south of Highway 60, which is believed to be a former channel. The weathered bedrock is also the deepest, and thickest, under the former channel and forms a trough shape. Weathered bedrock varies in fragment and particle size due to the amount of weathering. The top of the weathered bedrock is at or near the surface in the sidewalls of the canyon (Environ, 2000). Unweathered bedrock beneath the weathered bedrock also forms a trough shape along the eastern side of the canyon. Depth to the unweathered bedrock in the trough is 150 feet and greater. Downgradient, the structure of the underlying geologic units is approximately the same, with varying depths to each unit.

Groundwater originates from groundwater upstream of the site and canyon sidewalls. Surface water from the northwest face of the canyon and Mount Jurupa also contribute to the groundwater beneath the site. Contribution due to infiltration is negligible in years with little rainfall due to the high evapotranspiration rate. Depth to groundwater varies within the canyon. Groundwater is found in all three underlying hydrostratigraphic units (alluvium, weathered bedrock, and unweathered bedrock). These units are capable of storing and transmitting varying amounts of groundwater. In the unweathered bedrock, groundwater flow occurs only in the fractures. As groundwater flows south out of the canyon, it enters the regional groundwater system under the Glen Avon community, and then continues to the southwest.

• Fractured Bedrock

Groundwater contamination from the site extends from Zone 1 to the Santa
Ana River in Zone 4. The vertical extent of contaminated groundwater in Zone 1 includes the alluvium, weathered bedrock, and the fractures in the unweathered bedrock. Contamination in Zones 2, 3, and 4 may be limited to the alluvium and weathered bedrock, but could potentially migrate to the unweathered bedrock.

The plume is approximately 4 miles long.

• 1,2-Dichlorobenzene (Not given)
• 1,4-Dichlorobenzene (Not given)
• 1,2-Dichloroethene (Not given)
• 4,4'-DDE (Not given)
• 4,4'-DDT (Not given)
• 4-Methyl-2-pentanone (MIBK) (Not given)
• 1,1,2,2-Tetrachloroethane (Not given)
• Tetrachloroethene (Not given)
• Trichloroethene (Not given)
• Chloroform (Not given)

• Pumping Tests

• Pump and Treat

Background or MCLs. 5 ug/L for TCE and 6 ug/L chloroform (health based).

Chlorobenzenesulfonic acid, a byproduct in DDT production was found at 2,000 mg/L.

There is indication that concentrations of the key parameters (excluding perchlorate) are stable or trending downward in many wells within all four zones.

The final remedy for the site has not been selected.