Project Description:

The Sonoma Mercury Mine is situated in the West Mayacmas Mining District near the headwaters of Anna Belcher Creek.  According to historical records the mine was located about 1870 and was intermittently active up to 1956.  The mine workings which are mostly caved consists of a series pf shafts, adits and underground mine workings. Production through 1942 is estimated in excess of 1000 flasks of mercury.  This site and the upstream Contact Mercury Mine may be contributing mercury-laden sediments to the drainage system which flows into the Russian River.

Previous/Existing Assessments:

The locations and condition of mine features were collected by the USGS technical team in April, 2001 where high flow water sampling and retort tails were sampled.

Reclamation/Recommendations:

• Future remediation plans will entail capping excavation and consolidation of mercury calcine mill wastes.
• A Removal Site Investigation (RSI) document has been compiled by an environmental contractor and has documented the release of mercury into the environment.
• A pending Engineering Evaluation/Cost Analysis (EE/CA) document will likely propose several remediation alternatives or options, including capping and transport of a minor amount of tailings material.
• The tailings capping proposal would minimize runoff into the adjacent wash during storm events as well as minimize air-borne transport of mercury into the adjacent soils and watershed.
• 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.

Estimated Costs:

Sampling costs of sample water and sediments downstream of the mine site were incurred as the result of the USGS technical team activities during 2002 and 2003.

Risks:   Water Quality, Mercury

Location:    N38 45 31, W122 45 47

Field Office:   Ukiah

Congressional District:   01