Dames & Moore, 1999 - USDA Forest Service

a The Copper Creek diversion accounted for approximately 5 percent or less of cadmium and
copper, and approximately 3 percent or less of zinc loading to Railroad Creek during the
spring and fall sampling events. The majority of the metals loading within this drainage
appears to be attributed to seepage from the east waste rock pile (seep SP-8 which flows to
become SP-19), and groundwater flow from the west portion of the site. The
concentrations of metals within Copper Creek below the drainage ditch confluence were
below surface water aquatic life criteria values.
a Two seeps (SP-1 and SP-2) appear to flow year round from near the base of the tailings
pile. The seeps appear to represent groundwater exiting from the tailings pile. Each of the
two seeps account for approximately 1 percent or less of dissolved cadmium, copper and
zinc loading to railroad Creek and approximately 10 to 11 percent of the dissolved iron
loading to Railroad Creek during the spring snow melt period. In contrast steeps SP- 1 and
Sp-2 each account for approximately 0 percent of dissolved cadmium and copper,
approximately 1 percent or less dissolved zinc, and approximately 2 percent or less of the
dissolved iron loading to Railroad Creek during the fall period.
Tailings Piles 2 and 3
a The surface water diversion ditches on the surface of tailings piles 2 and 3 do not appear to
contribute significant loading of dissolved metals to Railroad Creek. Concentration of
dissolved cadmium, copper and zinc are above surface water aquatic life criteria at seep SP-
21 year round. However, the majority of the metals loading at this location appears to be
groundwater in the form of seeps flowing from the east end of tailings pile 3.
a Two seeps (SP-3 and SP-4) appear to flow year round from near the base of tailings piles 2
and 3, respectfully. The seeps appear to represent groundwater exiting from the tailings
piles. Each of the two seeps account for approximately 3 percent or less of dissolved
cadmium, copper, and zinc loading to Railroad Creek, and 16 to 24 percent of the dissolved
iron during the spring snow melt period. In contract, seeps SP-3 and SP-4 account for
approximately 0 percent of dissolved cadmium, copper and zinc, and approximately 3
percent or less of the dissolved iron loading into Railroad Creek during the fall period.
a Ground water flow into Railroad Creek from beneath the tailings piles account for less than
15 percent of dissolved cadmium, copper and zinc loading and approximately 35 percent of
the dissolved iron loading to Railroad Creek during the spring snow melt period. In
contrast, ground water flow into Railroad Creek accounts for the majority of dissolved
metals loading to Railroad Creek during the fall period.
8.4.5 Railroad Creek
8.4.5.1 Surface Water
As noted above, the final point of discharge of affected groundwater which originates from both the
western and eastern portions of the Site is Railroad Creek.
Copper cadmium and zinc loads to Railroad Creek from measured point sources and other groundwater
(baseflow) sources are highest during the spring snowmelt and groundwater discharge period when
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17693-005-019Uuly 28. 1999;10:24 AM;DRAFT FINAL RI REPORT
8-37 DAMES & MOORE