Dames & Moore, 1999 - USDA Forest Service

The abandoned Railroad Creek stream bed appears to exist beneath the northern portions of all three tailings
piles. However, the majority of the segment of Railroad Creek adjacent to tailings piles 1 and 2 appeared to
be in a gaining condition between the April to October period. Therefore, the water in Railroad Creek did
not appear to be flowing frorn the creek and into the tailings materials.
In contrast, the portion of Railroad Creek adjacent to the eastern portion of tailings pile 2 and all of tailings
pile 3 may be in a losing condition during the September to April period. During this period of time, water
appears to flow frorn Railroad Creek to beneath the respective portions of the tailings piles, and eventually
into the wetland area to the east of tailings pile, and then to drainage noted as seep SP-21 before flowing
back into Railroad Creek.
Upslope surface water runon in the form of snowrnelt and precipitation flows into the three tailings piles.
Surface water is generally collected and diverted into a series of drainage ditches on the surfaces of the piles
which were constructed as part of the tailings pile rehabilitation project completed by the USFS. The
ditches on tailings pile 1 drain to the northwest to the Copper Creek diversion and to the east to Copper
Creek. In addition, one of the ditches is situated immediately adjacent to an apparently abandoned decant
tower which was open and receiving surface water; the water entering the decant tower is assumed to flow
eventually into Railroad Creek as groundwater.
The ditches constructed across tailings piles 2 and 3 generally flow to the east to Railroad Creek: the surface
water flows into the wetland area east of tailings pile 3 before flowing into Railroad Creek by way of the
ditch at seep SP-21. A relatively small portion of the water collecting on top of tailings pile 2 also flows
directly into Copper Creek. A ditch constructed in a primitive road above tailings pile 3 also diverts some of
the upslope surface water around the eastern end of tailings pile 3 to SP-21. The presence of bedrock
exposed in the south bank of Railroad Creek near the confluence of seep SP-21 and Railroad Creek suggests
that the near-surface ground water occurrence within the glacial deposits becomes surface water at this
point. This assumption is based on the absence of the glacial materials at this location and since water flow
into the bedrock is anticipated to be negligible.
The drainage ditches do not fully prevent ponding of water on the tailings. Ponded water on the southern
border of all three piles results in surface water infiltration into the tailings from spring melt until mid to late
summer. Some of the water flowing in the ditches constructed across the piles likely infiltrates into the
tailings. However, the permeability of the tailings materials appears to be relatively low.
Based on the transport pathways discussed herein the sources of dissolved metals leading into Railroad
Creek from the tailings piles consist of overland flow seeps, andfor diffuse ground water flow into the
bottom of the stream bed. The sources of loading for each tailings pile are as follows:
Tailing Pile 1
Surface water diversion ditches on the surface of tailings pile 1 flow into the Copper Creek
diversion and Copper Creek. However, the flow of water on the surface of the tailings pile
does not appear to contribute significant loading of dissolved metals to Railroad Creek.
Concentrations of cadmium, copper and zinc in the Copper Creek diversion were detected
above surface water aquatic life criteria during the spring period only.
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