Health & Environment
On this page:
What Are the Risks at the Site?
EPA and PRPs, working under EPA oversight, have completed many actions to stabilize the site and to control and manage contamination since the former disposal facility stopped operating in 1991. Many improvements have been made to control risks. Site-related contamination has been contained on the former facility property.
EPA conducted risk assessments as part of the remedial investigations and feasibility study (RI/FS) process, including a human health risk assessment (HHRA) and an ecological risk assessment (ERA).
Human Health Risk Assessment (HHRA)
The HHRA looked at the likelihood of someone getting cancer and developing non-cancer effects if they were to come into contact with site contamination. The HHRA studied:
- Sources of contamination in different areas
- Potentially impacted populations
- Ways in which population could be exposed including direct physical contact, ingestion, inhalation, and movement of contamination through air, soil, fractured rock, surface water, and groundwater.
Potentially impacted populations included site workers, potential trespassers, recreational users, and off-property residents such as neighbors and local ranchers. Residents in the town of Casmalia are not impacted since site contamination does not reach the town.
EPA also evaluated risks that may occur for reasonably anticipated future land and water use. The HHRA looked at risks to future on-site workers and potential trespassers and to off-site ranchers, recreational users, and hypothetical future residents.
Of the 300 chemicals of interest, the HHRA showed that the human health chemicals of concern (COCs) include the following:
- Soil - Tetrachloroethene (PCE), and trichloroethene (TCE), and 2-(2-chloro-4-methylphenoxyl) propionic acid (MCPP)
- Surface Water – arsenic
- Groundwater – PCE, TCE, and 90 other chemicals that exceed MCLs
- Soil Vapor – PCE, TCE, and 1,3-butadiene
Ecological Risk Assessment (ERA)
The ERA studied risks for a wide range of plant and wildlife species in accordance with EPA policies and practices. EPA evaluated onsite sources of contamination to examine exposure pathways and potential risks to receptor species.
The results of the ERA showed that shallow waste materials and contaminated soils in some areas of the site exceed ecological risk standards and pose risks to animal species. The primary ecological COCs in terrestrial (land) areas are chromium, copper, and zinc.
The five surface ponds in Area 4 exceed ecological risk levels and present open uncontrolled sources of contamination. EPA has determined it is critical to close all five ponds based on various combinations of human health risk, ecological risk, attractive nuisances to endangered species, and long-term site management considerations.
The site also contains several listed threatened and endangered species, including the California Red Legged Frog, the California Tiger Salamander, and the Western Spadefoot toad. EPA has been working with the U.S. Fish and Wildlife Service and the California Department of Fish and Wildlife to address habitat mitigation and protection of these species.
The site includes many former waste management units (WMUs), including landfills, surface impoundments, evaporation pads, waste spreading areas, injection wells, burial trenches, and other engineered environmental systems. The property contains hundreds of mixed contaminants and multiple impacted media, including soils, on-property groundwater, soil vapor, surface water and pond sediments, and non-aqueous phase liquids(NAPL). Chemicals of interest include a long list of volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), pesticides and herbicides, metals, PCBs, and other inorganic compounds.
Please see the technical documents attached to this web site for further details.
A number of site photographs are included on this web site.
EPA uses performance measures to track environmental results at Superfund sites. If you have any questions or concerns about the measures at this site, please contact the site team members listed under Site Contacts.
Read more about Superfund Remedial Performance Measures.
|Status at this
|What does this mean?|
|Human Exposure Under Control||Yes||Yes means assessments indicate that across the entire site:
No means an unsafe level of contamination has been detected at the site and a reasonable expectation exists that people could be exposed.Insufficient data means that, due to uncertainty regarding exposures, one cannot draw conclusions as to whether human exposures are controlled, typically because:
|Groundwater Migration Under Control||Yes||
Yes means EPA reviewed all information on known and reasonably expected groundwater contamination. EPA concluded the migration of contaminated groundwater is stabilized and there is no unacceptable discharge to surface water. EPA will conduct monitoring to confirm that affected groundwater remains in the original area of contamination.
No means EPA has reviewed all information on known and reasonably expected groundwater contamination, and the migration of contaminated groundwater is not stabilized.
Insufficient data means that due to uncertainty regarding contaminated groundwater migration, EPA cannot draw conclusions as to whether the migration of contaminated groundwater is stabilized.
Yes means the physical construction of the cleanup is complete for the entire site.
No means either physical construction is not complete or actions are still needed to address contamination.
|Sitewide Ready for Anticipated Use||No||Yes means:
No means that one or more of these three criteria have not been met. However, a site listed as no may still have redevelopment occurring on portions of the site and may be eligible for additional redevelopment.