Groundwater and Hydrogeology
Over the past 25 years, a tremendous amount of data have been collected and analyzed with respect to the groundwater and hydrogeologic conditions at the Kettleman Hills Facility (KHF). These data provide a detailed and clear understanding of subsurface conditions beneath the site and support a common conclusion: the Kettleman Hills Facility is not impacting groundwater for the residents of Kettleman City or in the Kettleman Plain.
Intensive Data Collection History and Analyses
- Since the mid-1980s, approximately 200 soil borings, some to more than 500 feet below ground surface, have been drilled at the KHF to characterize subsurface conditions. The surface and subsurface geology has been examined and recorded by scientists from the U.S. Geological Survey, the California Regional Water Quality Control Board, the California Department of Toxic Substances Control, and the U.S. Environmental Protection Agency.
- Groundwater data have been collected for more than 25 years from nearly 100 on‐site groundwater monitoring wells. Water levels are measured at least four times per year in 48 monitoring wells to verify continually groundwater flow conditions.
- The geology of the area has been investigated since the late 1800’s, with the most definitive geologic work on the area done in 1940. As a result, a definitive characterization of the subsurface geology is available for study.
Stagnant Groundwater Conditions
- Groundwater occurs beneath the KHF in individual sandstone layers at depths of approximately 350 to 520 feet below ground surface. These sandstone layers are steeply inclined, dipping sharply towards the southwest, away from Kettleman City.
- Individual sandstone layers are separated from each other by claystone and siltstone beds that significantly restrict the movement of groundwater. Movement of groundwater in the sandstone layers is very slow to essentially stagnant, with a maximum velocity of approximately four feet per year, or 400 feet per century.
- Groundwater has been calculated to move at a rate 10,000 times slower through the claystone and siltstone beds, than it would through individual sandstone layers.
- Groundwater that was present when the site first opened in the early 1970’s has not moved more than 200 feet, and would require more than 1,800 years to travel across the site, and more than 17,000 years to move to the nearest plausible discharge outlet.
- Age-dating indicates the groundwater beneath KHF is 16,000 to 30,000 years old. Typical of extremely old and stagnant water, it is very salty (also known as “brackish”), to the point that in 1989 the state of California resolved that groundwater within one‐half mile of the area permitted for waste disposal would not be useable for as a municipal or domestic water supply.
KHF Groundwater is Isolated from Other Water Sources
- There is no plausible pathway for groundwater to migrate from below the site to drinking water resources of the Kettleman Plain or the San Joaquin Valley. Siltstone and claystone barriers isolate groundwater below the site from other geologic formations and from drinking water supplies.
- The sandstone beds beneath KHF dip toward the southwest, away from water supply wells in the vicinity of Kettleman City. Groundwater cannot move eastward from the site toward the San Joaquin Valley.
- Although studies have confirmed that groundwater movement does not occur down deep in the sandstone beds, even if this were to occur, the San Joaquin Formation plunges to a depth of several thousand feet below the drinking water resources of the Kettleman Plain.