Cleaning Up the Mother Lode, the Closure of the Jamestown Mine

The Jamestown Mine Reclamation Project was awarded as a guaranteed fixed price contract to Shaw Environmental in July 2006 by the Jamestown Trust (Trustee for the California Attorney General’s Office).  The presentation will describe the work completed to date, which includes:

·       Dewatering of the 80-acre supernatant pond on the tailings impoundment and transferring over 300 million gallons of tailings supernatant and subdrain water to the Harvard Mine Pit,

·       Closure and capping of the 130-acre tailings impoundment with onsite soil to meet California and federal RCRA final cover standards, which required a 2-foot minimum thickness including a 1-foot layer of low permeability soil (1x10^-6 cm/sec),

·       Crushing and screening over 420,000 cubic yards of onsite shale to produce low-permeability soil for the tailings impoundment cap

·       Evaluation of the 100-acre rock waste dump cover and characterization of the waste rock,

·       A site investigation to determine the extent of  impacts to groundwater, and

·       Evaluation of water treatment technologies for groundwater and mine pit water impacted by arsenic and salts.

Under the terms of the contract, Shaw assumes environmental responsibility for operation and maintenance of the mine site for a 10-year period.  The key technical issues that faced Shaw were the following:

·       Was there enough stockpiled weathered rock to cap tailings impoundment?  There was.

·       Could we turn the shale back to clay for the low permeability cover layer?  We did.

·       What potential changes in environmental regulation could occur over a 10-year period?  We do not know.

Most unknown regulatory issues are covered by cost cap environmental insurance obtained from AIG, which will safeguard us, the State, and the Trust from unforeseen cost over runs.