CHEVRON QUESTA MINE
Health & Environment
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What Are the Risks at the Site?
The Human Health Risk Assessment (HHRA) and Baseline Ecological Risk Assessment (BERA) evaluated potential human health and ecological risks that may result from current and future exposure to mining-related contamination present at the Site if no remediation is performed.
Mill Area: The HHRA found a potential risk to future workers exposed to polychlorinated biphenyl (PCB)-contaminated soil in the Mill Area. This potential risk has been alleviated by the excavation of PCB-contaminated soil at the Mill Area.
Mine Site Area: The HHRA found a potential risk to future recreational visitors exposed to seepage in mine site catchment basins and to drainage (i.e., seeps/seepage) from the waste rock piles. This potential risk will be addressed by the remediation of the Mine Site Area waste rock piles and through groundwater protection.
The HHRA found a potential risk to future residents exposed to groundwater as a drinking water source. This potential risk will be addressed by the remediation of the waste rock piles.
Tailing Facility: The HHRA found a potential risk to future residents exposed to groundwater as a drinking water source and to future recreational visitors exposed to sediment at the Tailing Facility. These potential risks will be addressed during the remediation of the Tailing Facility.
The BERA found a potential risk to grazers (i.e., elk and deer) at the Tailing Facility from consumption of terrestrial plants (e.g., grasses) that have accumulated molybdenum from the tailings. These potential risks will be addressed during the remediation of the Tailing Facility.
Red River, Riparian and South of Tailing Facility Area: The BERA identified an unacceptable risk to aquatic life (e.g., fish) in the Red River from groundwater discharge into the river. This risk will be addressed by the additions to extraction systems to capture groundwater before it reaches the Red River at Springs 13 and 39.
The BERA found a potential risk to soil dwelling organisms and terrestrial birds (e.g., birds that eat insects) from tailing spills. This potential risk has been alleviated by the excavation of tailing spills.
The BERA found a potential risk to wildlife (e.g., deer and elk) and livestock in the South of Tailing Facility Area from terrestrial plants (e.g., grasses) that have accumulated molybdenum from the soil.
Eagle Rock Lake: The BERA found a potential risk to aquatic life (e.g., aquatic insects) from sediments in Eagle Rock Lake. This potential risk has been eliminated by the removal of sediment in Eagle Rock Lake and the installation of inlet stormwater controls.
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||No||
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.