Todd Engineers

In recent years, the Mother Lode gold-mining region of the Sierra Nevada has experienced substantial residential development. Much of this development has been focused around small towns such as Sutter Creek with a historical mining legacy expressed in nineteenth century architecture and historical sites. In some cases, new residential developments have been constructed on mining tailings. Such construction has the potential for exposing residents to a problematic legacy of gold mining: elevated concentrations of arsenic.

Several properties near Sutter Creek were the site of the Central Eureka gold mining operation through the 1930s.

Key Issues
Presence and bio-availability of arsenic in tailings Responsibility for remediation costs

The site included not only the underground gold mine and head works, but also a stamp mill, cyanide plant, trestles for tailings flumes, and waste rock and tailings piles. Subsequently, the mine was closed, the properties sold, and the land use shifted to cattle grazing and residential development.

The presence of tailings with elevated arsenic resulted in designation of a Superfund Site and soil remediation efforts mandated by the United States EPA. Subsequently, EPA sought allocation of the costs that had been incurred in the remediation effort. Todd Engineers was retained by a subsequent property owner to provide expert technical support in litigation over the equitable allocation of the remediation costs.

Our investigations included documentation of the background geochemistry, arsenic concentrations and occurrence, and potential environmental impacts.

Services Provided
Documentation of arsenic in soils and mine tailings Technical support to cost allocation Preparation of expert reports

The cost allocation analysis required substantial investigation of historical land uses and the remediation efforts, some of which involved translocation of soils from the remediation activities. This included collection and examination of archived documents, review of historical aerial photographs, inspections of the mining sites, review of EPA files, and interviews with key civil and geotechnical engineers involved in the remediation. Todd Engineers designed the cost allocation model that eventually was utilized for settlement proceedings.