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Tropico - Abandoned Mine Lands Project

Project Description:

The historic Tropico Hill Mill Tailings site was the result of a historic mining and milling activity in the  Rosamond Mining District, which was mined for its rich gold lode deposits,  during the early 1900’s to 1950’s time period. The historic Tropico Mill was constructed during the 1920s’ with a rotary ball mill circuit. The mill tailings were produced by the rotary ball milling operations.

Approximately +50,000 tons of mill tailings were generated by mining and associated milling operations. These mill tailings have discharged from the mill site and formed an elongate, southerly directed tailings deposit over a last +50-year period downslope onto the alluvial fan surface adjacent to a residential subdivision area and thence into the adjacent floodplain areas within the Rosamond Basin drainage. The Tropico Mill tailings contain elevated levels of arsenic.

Previous/Existing Assessments:

Significant potential human health risks to the community and regional environmental impacts may have resulted from release of arsenic-bearing tailings into the waters of the state and airborne sources. The Tropico Mill tailings have been designated as an AML CERCLA site.

Sediments sample results indicate that elevated arsenic levels exist in the hillslope below the mill and steam and floodplain sediments.

A preliminary site inspection was undertaken during November 2007, when elevated concentrations of arsenic were detected in the mill tailings material. This survey was followed up by a detailed investigation during January 2008 by the USGS technical team. The results of this latter investigation will be incorporated into a multi-faceted environmental study of arsenic contamination in the region. 


  • The CERCLA remediation plan by BLM staff is awaiting CERCLA site study coordination with the U.S. Environmental Protection Agency (EPA).
  • EPA has Compiled a Preliminary Site Investigation (PSA document).
  • No recommendations for remediation have been made to date, due to the early phase of site investigation. 

Risks:   Water quality, Arsenic contamination

Location:   Section 4, T9N, R13W,SBBM,  Kern County, CA

Field Office:   Barstow

Congressional District:   25

Tropico Mill Tailings
Tropico Mill Tailings

Tropico Mill Tailings in wash with Tropico Mill in background
Tropico Mill Tailings in wash with Tropico Mill in background