Assessing Brownfields Throughout California’s North State

Sierra Institute’s North State Rural Brownfields Program works to perform brownfields assessments, cleanups, and training throughout California’s North State. A brownfield is a site where redevelopment is complicated or hindered by the presence of hazardous substances, pollutants, or contaminants. To perform assessments of brownfields in the North State, Sierra Institute received a Community-Wide Assessment Grant from the United States Environmental Protection Agency (US EPA) Brownfield Program.

Mohawk Mine

What Does Assessment Look Like?

Assessing a brownfield is a multi-step process, including site investigation, sampling for hazardous substances, and planning for cleanup. Performing a comprehensive site assessment involves the following steps:

• Phase I Environmental Site Assessment (ESA): Dig into historical records, review past site activities and the physical setting of the site, interview individuals with site knowledge, and perform a site visit. This process determines if there is any indication of contamination on the site.

• Sampling & Analysis Plan (SAP): If the Phase I ESA indicates that there may be contamination on the site, a SAP is developed to prepare for a Phase II ESA. SAPs outline the sampling design for collection of environmental samples, project action levels for potential contaminants, and quality control parameters to ensure accurate sampling and analysis.

• Phase II ESA: If the Phase I ESA indicates the possibility of contamination on the site, a Phase II ESA will be performed to better classify and confirm the presence of that contamination. During the Phase II ESA, sampling and lab analyses are performed according to the SAP, and results are analyzed to determine contaminant levels and risk.

• Analysis of Brownfields Cleanup Alternatives (ABCA): If the Phase II ESA indicates that hazardous substances are present on the site above acceptable levels, an ABCA will be prepared. ABCAs explore and compare different pathways that could be taken for cleanup. Examples of cleanup alternatives include hauling material off-site, consolidating and capping material, or leaving the material as is.

• Cleanup Planning: If cleanup is necessary, a Removal or Remedial Action Workplan will be prepared, selecting and outlining a cleanup alternative discussed in the ABCA.

Dawn Institute Greenhouse

Our Brownfield Assessments

Under the Community-Wide Assessment Grant, we are conducting assessments, planning for cleanup, and assisting with the redevelopment of six brownfields in Plumas, Lassen, and Humboldt Counties.

• Bracut Marsh, Eureka, Humboldt County: A former sawmill in Eureka, CA, that has been restored to a tidal marsh. Contaminant concerns include metals and dioxins in soil. We are currently developing a SAP for further contaminant characterization at the site.

• Dawn Institute Greenhouse, Indian Falls, Plumas County: Dawn Institute intends to restore an old greenhouse on their property, but it may have been painted with lead paint. Our SAP is currently under review before we can conduct soil sampling and analysis for soil lead content.

• Former Indian Valley Hospital, Greenville, Plumas County: Plumas District Hospital plans to restore the former Indian Valley Hospital for additional medical care and/or housing capacity. Sierra Institute developed a Phase I ESA in 2025 and identified a potential for total petroleum hydrocarbons (TPH) soil contamination. We are awaiting SAP approval prior to sampling.

• Sierra Army Depot, Herlong, Lassen County: A former barracks and cafeteria located in Herlong, CA, now owned by the Susanville Indian Rancheria. Sierra Institute performed a Phase I ESA in 2025, identifying several hazardous substances of potential concern, including asbestos, lead paint, abandoned electrical equipment, and groundwater PFAS (persistent, long lasting chemicals) contamination.

• Johnstonville Road Site, Susanville, Lassen County: The Local Area Revitalization Project (LARP) Cooperative intends to develop a small farm incubator and compost facility on this site, which has historically been used for agriculture. Sierra Institute completed a Phase I ESA in 2025, finding that the historic agricultural use does not pose a high risk for contaminants remaining on-site.

• Mohawk Mine, Chilcoot, Plumas County: A former copper mine on the Feather River Land Trust’s (FRLT) Spring Creek Ranch property. FRLT intends to transfer the property to the U.S. Forest Service for recreational use following remediation. We are currently finalizing a SAP to better characterize acid mine drainage potential and heavy metal content in the mine waste piles and Spring Creek.