Project Description:
The historic Calico Mill Tailings site was the result of a historic mining and milling activity in the famous Calico District, which was mined for its rich silver lodes, during the 1890’s – early 1900’s time period. The historic Calico Mill was constructed during the 1880’-1890’s and consisted of a large stamp milling circuit that is now in ruins. Roughly $20 Million dollars of silver bullion was produced by the +500 mines in the Calico Mountains District during the peak +25-year life of the mines. The mill tailings are the only obvious evidence of the size and magnitude of the mining operations.
Approximately +100,000 tons of mill tailings were generated by milling and mining operations, respectively. These mill tailings have discharged from the mill site and formed an elongate, southerly directed tailings deposit over a last +115-year period downslope on the alluvial fan surface adjacent to both a residential subdivision area and San Bernardino County – Calico Historical Park thence into the Calico Lake Basin and adjacent floodplain areas within the Mohave River drainage. The Calico 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 Calico Mine has been designated as an AML CERCLA site. Sediments sample results indicate that elevated arsenic levels exist in the steam and floodplain sediments.
A preliminary site inspection was undertaken during April 2007, when elevated concentrations of arsenic were detected in the mill tailings material. This survey was followed up by a detailed investigation during May 2007 by the USGS technical team. The results of this latter investigation will be incorporated into a multi-faceted environmental study of arsenic contamination at the site.
Reclamation/Recommendations:
The CERCLA remediation plan by BLM staff is awaiting site study coordination with San Bernardino County.
Compilation of the Removal Site Investigation (RSI) Engineering Evaluation/Cost Analysis (EE/CA) is pending.
The latter document will likely recommend a several remediation options including and capping excavation, consolidation, of mill tailing wastes.
A mill tailings capping proposal would minimize runoff onto adjacent lands during storm events as well as minimize air-borne transport of arsenic particulate material into adjacent inhabited areas.
The capped mill tailings would be recontoured with native soil and then reseeded with native plants.
A post-remediation monitoring and sampling program would be implemented to determine effectiveness of remediation efforts.
Risks: Water quality, Arsenic contamination
Location: Section 22,27,34, T10N, R01E,SBBM, San Bernardino County CA
Field Office: Barstow
Congressional District: 25
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