Dames & Moore, 1999 - USDA Forest Service

Seep samples were collected at SP-5, SP-17, SP-18, and SP-21 east of tailings pile 3 in May and July
1997. Additionally, a sample was collected at SP-21 in September and after a rain event in October 1997.
Metal concentrations (aluminum, cadmium, copper, iron, manganese, and zinc) decreased significantly
from May to July. At seep locations SP-17, and SP-18, concentrations of aluminum, cadmium, copper.
iron, manganese, and zinc tended to be similar in May and July. At SP-2 1, concentrations were similar or
decreased slightly from May to July. July and September concentrations were similar at SP-21 with the
exception of iron and manganese, which increased approximately 2 times. The data collected at SP-21
after the rain event in October was similar to the September sampling with the exception of slight
increases in aluminum and iron.
The concentrations of metals at SP-17 were significantly below the concentrations at SP-5, SP-18 and SP-
21. Concentrations at SP-5 were similar to those detected at SP-18 in May. In July, SP-5 was
significantly below SP-18. The concentrations of metals at SP-21 were an order of magnitude below SP-
5 and SP-18 in May. The pH measured at SP-17 ranged from 6.4 to 7.4 SU. The pH at locations SP-5,
SP- 1 8, and SP-2 1 ranged from 3.4 to 5.4 SU with the lowest pH readings occurring at SP- 1 8 and SP-5.
Seep samples SP-5, SP-17 and SP-18 were compared to MTCA groundwater levels and groundwater
quality criteria designated in WAC 173-200. Seep SP-21 was compared to surface water quality criteria
instead of groundwater criteria as this seep is more indicative of surface water and available for aquatic
habitat. The following PCOCs are identified in monitoring wells and seeps associated with the east side
of tailings pile 3.
5.4.2.7 Holden Village
A sample was collected from seep SP-13, which originates as drainage from beneath two of the buildings
in the southern portion of Holden Village and was noted to flow only during the snowmelt runoff period.
Analytical data are summarized in Table 5.4-2. Aluminum and copper were not detected. Concentrations
of cadmium, iron, manganese, and zinc were 0.31 pa, 330 pg/L, 74 p/L, and 71 pg/L, respectively.
Field pH was 6 SU. The data were compared to groundwater quality criteria. Iron (330 pg/L) and pH
were outside of water quality criteria (300 pg/L and 6.5 SU, respectively).
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5 -5 3 . DAMES & MOORE
17693-005-019Uuly 28,1999;11:09 AMDRAFT FINAL RI REPORT