News.bytes News.bytes Extra, issue 236

Rinconada Mine cleanup

This former mercury mine produced an estimated 3,000 flasks of mercury since 1872, and operated intermittently until about 1961. The site includes lands managed by BLM and the U.S. Forest Service, plus private land.

Mill Retort cleanup (below) :
EPA contractors undertook a CERCLA ("Superfund") cleanup of the highly toxic mercury retort (equipment used in distilling), condenser soot waste material, plus calcine waste product materials that had been discharged from the mill. The long, metal cylinder represents a rotary furnace, which roasted cinnabar ore and transformed the mercury ore into a vapor. The mercury vapors were condensed into elemental mercury using a sophisticated retort design.
The millsite was effectively cleaned, so that it was not necessary to remove the rotary furnace and other important historical features of the mill site.

Scott Furnace (below):
The upper photo depicts a historic Scott mercury furnace that was widely used in California during the latter 19th century. It was built of brick and usually contained a single metal cylinder chamber. The chamber was filled with mercury ore and heated to the required temperature with local wood, in order to retort the cinnabar ore and convert it to elemental or liquid mercury. The Scott Furnace was dismantled as part of the CERCLA cleanup on BLM-administered lands, since it contained highly-elevated mercury concentrations around its base.

Mill Tailings - Creekbed cleanup:
The "before cleanup" photo (at right, below) shows the creekbed choked with mercury mill tailings. The surface of the tailings has formed a hard crust, creating an effective erosion barrier and inhibiting streambed restoration processes.

The "after cleanup" photo (below, at left) shows the restored creekbed with all mercury mill tailing materials removed. The tailings were excavated using heavy equipment and then trucked off site to a designated hazardous waste repository. The creek bed restoration project involved collaboration of both EPA and BLM technical staff, in order to create a streambed that was sufficiently durable to heavy storm events that would easily erode the stream banks, but allow development of a series of step-pools, approximating natural streambed restoration processes.

David Lawler
BLM - California - Energy and Minerals Division
Abandoned Mine Lands Program

June, 2006

BLM California News.bytes, issue 236