Dames & Moore, 1999 - USDA Forest Service

submerged at high water levels. Flow in SP-5 (near the northeast comer of tailings pile 3) varies in direct
response to flow in Railroad Creek because the discharge point for this seep is below the water surface
elevation in the adjacent Railroad Creek. Thus, head in the creek influences flow rates in SP-5.
Referring to Figure 4.3-8, surface water runon from offsite sources onto the tailings,and mine workings, and
subsequent direct surface runoff fiom the tailings and mine-related features was evaluated by observations
made during the MayIJune, July and September 1997 field programs.
During MayJJune 1997, water was flowing in drainage ditches on the upslope side of tailings pile 1 (SP-20)
which was routed directly into Copper Creek. The water in this ditch appeared to be rneltwater from upslope
wooded areas, and to a lesser degree meltwater generated on the access road to the tailings piles. Although
the majority of this water was routed into Copper Creek, an unknown amount of surface water was observed
infiltrating into an apparent open decant tower at the upstream end of tailings pile 1 (near the northeast
comer of the base of the eastem waste rock pile), thus potentially contributing to groundwater stored within
this pile.
During MayIJune, flow in the SP-18 drainage channel, which discharges to SP-21 and then into.Railroad
Creek downstream of tailings pile 3, also appeared to include snowmelt from areas upslope of tailings piles
2 and 3.
Seepage water was also observed in May emanating from the base of the eastern waste rock pile (SP-8).
The water was observed flowing into a culvert and then across tailings pile 1 in a drainage ditch constructed
by the USFS in 1991 (SP-19). The water eventually flowed into the Copper Creek diversion below the
sauna pool. The potential exists that water infiltrates into tailings pile 1 for the brief period of seepage flow.
Direct meltwater runoff from the abandoned mill area and waste rock piles collected in seeps SP-6, SP-7
and SP-15 and was routed into the lagoon (SP-16), with limited discharge into Railroad Creek. Meltwater
runoff also appeared to comprise a component of SP- 12, SP-23, and the Honeymoon Heights intermittent
drainage (SP-14). Flow from SP-12 and SP-23 discharges directly into Railroad Creek. Flow in SP-14 has
no direct surface outlet into Railroad Creek; however, the drainage feature appears to be coincident with an
apparent avalanche chute which terminates near both SP-12 and SP-23. A seep was observed flowing from
the base of the 800-level waste rock pile and into the intermittent drainage (SP-14) during June 1998
(personal communication with Rick Roeder, Ecology, and Norm Day, Forest Service, 1998); however, the
seep was not observed later during a visit in July 1998.
During sampling events in July and September 1997, surface water runoff was not observed on the tailings
piles. During relatively high rainfall in mid-September, runoff was observed pooling in the drainage ditches
at the southern end of tailings pile 1 and flowing in road ditches along the access road to the museum and
portal area. Additionally, SP-14, SP-1 5E and SP-23, which were all dry before the precipitation events,
began to flow again within several days, indicating a relatively rapid response to rainfall runoff. Surface
water runoff also accumulated in meltwater ponds on tailings pile 1, in the wetland area east of tailings pile
3, and in the SP-2 area.
Based on these observations, it is concluded that drainages associated with SP- 12, SP- 14, SP- 17, SP- 18,
SP- 19, and SP-23, carry runoff from rneltwater and heavy rainfall. SP-6, SP-7, and SP- 15 also transport
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