Dames & Moore, 1999 - USDA Forest Service

The dense glacial till overlying the majority of the bedrock has been mapped by others to be present slightly
above the 1100-level mine portal in the Honeymoon Heights area. Borings completed on the Site by others
indicate that the glacial till has a relatively low permeability.
The near-surface glacial soils within the valley have apparently been reworked by stream erosion processes
by meandering of Railroad Creek across the valley floor at the Site during and since the last glacial advance.
The finer grained silt and sand soil within the near-surface glacial till appear to have been generally
removed by the alluvial action, resulting in the surficial soils being more permeable than the glacial till soil
present at depth.
Railroad Creek has been documented to have been rerouted in 1937 to accommodate the use of the portions
of the mine support area near the creek for surface water retention, and to allow for the construction of the
tailings piles. The creek was apparently rerouted by constructing a dike consisting of gravel, cobbles,
boulders, and occasional wood timbers along the eastern and southern banks of the creek west of the tailing
piles. A segment of the previous Railroad Creek stream bed appears to be present beneath the lagoon, north
of the maintenance yard and abandoned mill building, and portions of tailings piles 1, 2, and 3. Due to the
presence of creek bed material that most likely has a higher permeability than near-surface glacial soils or
alluvial materials, the abandoned stream bed appears to act as a preferential pathway for near-surface
groundwater movement from the western portion of the Site to Railroad Creek near the confluence with
Copper Creek, and beneath tailings piles 2 and 3.
(3
Western Portion of S~te
Undermound Mine and Honemoon Heights
The mine levels were developed based on the elevation &w the exposure of the ore body above the mine
in the Honeymoon Heights area. The exposure of the ore body is considered the "0" level. The 300-level
portal is approximately 300 feet below this point, the 550-level is approximately 550 feet below, and so on
(Figure 8.2- 1).
The two 1500-level portals of the mine are the lowest elevation openings to the surface. The 1500-level
main and ventilator portals were apparently timbered through 65 feet and 300 feet of glacial soil,
respectively. The thickness of the glacial soil at the ventilator portal is likely less than noted on the
underground maps due to the tunnel not being oriented perpendicular to the valley sidewall. The remainder
of the mine portals at the 1100, 1000, 800, 700, 550, and 300 levels were either not timber supported or
supported only through less than 15 feet of glacial soil andlor weathered bedrock exposed near the surface.
The ore-bearing bedrock within the mine is reported by others to consist principally of copper, zinc, gold,
and silver-bearing sulfides within a country rock of primarily schistose rock. Based on a review of historic
mine maps, the ore body is approximately 80 feet in width, nearly vertical in orientation, strikes northwest to
southeast, and is exposed at the ground surface approximately coincident with the 300-level to 1,000-level
mine workings in Honeymoon Heights. Portions of the ore body were removed from within the mine to
form openings called "stopes." The stopes range in height from approximately 100 to 600 feet, and
approximately 80 feet in width. Select portions of two of the stopes above the 1500-level of the mine
appear to have been mapped as being completed to within approximately 50 feet of the ground surface. The
potential for subsidence exists in these isolated areas along the strike of the ore body. The areas are
generally found between the 300- to 550-level, and the 700- to 1100-level portals.
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