What We Are Doing

The USGS California Water Science Center is working in partnership with state and federal agencies to answer the following questions about oil and gas development and groundwater resources:

  • Where are protected groundwater resources

    State water quality laws and regulations provide for the protection of groundwater resources that are or may be useable for purposes including drinking water, irrigation, and industrial supplies, and SWRCB policy currently targets 3,000 milligrams per liter (mg/L) Total Dissolved Solids (TDS) as a general threshold for protection (SWRCB, 1988). Federal laws target the protection of groundwater resources for drinking water supplies and define these as resources containing less than 10,000 mg/L TDS. The same laws provide for an exemption to regulations governing injection of waste into aquifers if a) the zone does not currently serve as a drinking water sources, b) the zone cannot serve as a source in the future because it produces hydrocarbons, is too deep to be economically or technically practical, it is so contaminated that treatment would be impractical, or c) the groundwater contains between 3,000 mg/L and 10,000 mg/L TDS and is not reasonably expected to serve a public water system (summarized from 40 CFR 144.7).

    Groundwater containing less than 10,000 milligrams per liter total dissolved solids is defined under federal law and regulation as a source of drinking water, except where such water is within an aquifer that has been formally exempted from protection. For more information see the U.S. Environmental Protection Agency's Underground Injection Control Program

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  • How close are oil and gas operations

    A term used to very broadly describe all classes of activities undertaken by oil and gas operators in order to produce crude oil and natural gas, including extraction by water and steam flooding, injection of waste into wells designated for that purpose, and disposal of waste in surface ponds.

    and protected groundwater, and what geologic materials separate them?
  • Where is there evidence of fluids from oil and gas sources in protected groundwater? Where does evidence indicate no connections?
  • When fluids from oil and gas sources are present in protected groundwater, what pathways or processes are responsible for observed transport?
  • Have oil and gas operations as a whole contributed to water-quality changes in groundwater basins?

The program's framework was developed and adopted by the California State Water Resources Control Board (State Water Board) in July 2015.

The USGS is the technical lead in implementing the State Water Boards' Oil and Gas Regional Groundwater Monitoring Program through the COGG program. The program receives funding from the California State Water Resources Control Board, the U.S. Bureau of Land Management, and USGS cooperative matching funds.

Cross-section showing resistivity in ohm-m

Mapping Salinity

screenshot of 3D geological model

Geological Context

conceptual illustration of regional sampling design

Regional Sampling Design

conceptual illustration of potential pathways for constituent mixing

Potential Pathways

illustration mapping constituents to tracers and sources

Geochemistry Library & End-Member Mixing Analyses