Dames & Moore, 1999 - USDA Forest Service

mountain peaks in excess of 9,000 feet ASL. The Site is remote, with access limited to boat or float plane to
a boat landing at Lucerne, and to the Site via an unpaved road generally along Railroad Creek. Vegetation
consists primarily of coniferous with some deciduous forest with under story. The climate in the region is
characterized by warm to hot, dry summers and mild to severe winters. Mean annual precipitation at
Holden is 35 inches. Approximately 77 percent of the precipitation falls in the form of snow between the
months of November and March.
The geology can be summarized as a glacial, u-shaped valley carved into bedrock. The valley bottom and
lower sidewalls have been covered with soil of glacial origin and deposits reworked by Railroad Creek. The
mine tailings and primary waste rock piles were placed directly atop the glacial soil and/or alluvium. The
general area contains a number of zones of economic mineralization, some of which were mined at the turn
of the century.
The Holden Mine ore body was discovered in the late 1800s. The mine property was purchased by Howe
Sound Company in the late 1920s. At the time of purchase, the mine consisted of a series of underground
workings that were accessed by six portals which were developed in the area of the Site known as
Honeymoon Heights. Howe Sound Company constructed two additional tunnels to access the ore body
from lower on the slope. The two tunnels were constructed at the same general mine elevation (1500-level)
and consisted of one used for ore haul-out and a second used for mine ventilation. Waste rock removed
fiom the development of the 1500-level main and ventilator tunnels, which were advanced through
approximately.one mile of non-mineralized bedrock, exists in two piles located near the 1500-level main
portal.
Approximately 60 miles of underground mine workings were developed during the period of operation.
The ore removed from the mine was processed in the onsite mill to produce concentrate of principally
copper and lesser amounts of zinc, gold, and silver which was shipped offsite for smelting. During the
period of operation, nearly 10 million tons of tailings materials were generated. Approximately 8 million ,
tons of tail'ings were placed in three piles (from west to east, tailings piles 1,2,.and 3) which coveran area of
approximately 90 acres. The remainder of the tailings was backfilled into the mine during the period of
mine operation. A majority of the mine openings below the lowermost mine portal near the mill building
(1 500-level) were backfilled.
The mine closed in 1957 and the mill building was partially salvaged. The patented mining claims were
deeded to the Lutheran Bible Institute which became Holden Village, Inc., .in 1961 and started an
interdenominational retreat that operates to this day. The remainder of the Site outside of the patented
mining claims was returned to the Forest Service when the mine closed.
After the mine closed, the lower mine workings eventually filled with groundwater and started flowing out
of the lowest mine opening, the 1500-level main portal. Studies were completed by the Forest Service,
starting as early as 1964, to characterize potential environmental concerns which became apparent after the
mine closed. The studies included the characterization of surface water hydrology and tailings pile
chemistry for revegetation, the sampling and analysis of various media, and the development of plans to
address the concerns identified.
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17693-005-019Uuly 28. 1999;12:16 PM;DRAFT FINAL RI REPORT ES-2