Dames & Moore, 1999 - USDA Forest Service

5.4.4 Groundwater Summary
Groundwater samples were collected from monitoring wells located in Holden Village. west of Holden
Village near the baseball field, on the Site downgradient of the maintenance yard, in tailings piles 1, 2,
and 3, east of tailings pile 3, and from a single well located at Lucerne. Samples were also collected from
lysimeters completed within tailings piles 1 and 3. Seep samples were included as part of the
groundwater quality assessment based on the apparent relationship to underground water sources.
Samples were collected from seeps located on the Site and on the banks of Railroad Creek upgradient,
adjacent to, and downgradient of the Holden Mine.
Samples were collected during sampling events in the spring, summer, and fall of 1997. The samples
were analyzed for dissolved metals, conventional parameters, and field parameters as outlined in the
SAPS and QAPPs. Select groundwater and seep samples were analyzed for organic constituents (PCBs '
and TPH).
The data collected from monitoring wells and seeps were compared to MTCA cleanup levels and WAC
173-200 to assess PCOCs. The sample collected at Lucerne was also compared to federal MCLs as the
water from this well is a current drinking water source for the Lucerne community. PCOCs were
identified if metal concentrations were above MTCA cleanup levels, outside of WAC 173-200 criteria, or
above MCLs. Data collected at SP-21 were compared to surface water quality criteria rather than
groundwater criteria as this location is available to support aquatic life. Arsenic, beryllium, cadmium,
copper, iron, lead, manganese, and zinc were identified as PCOCs at one or more monitoring well
locations. Arsenic, beryllium, cadmium, copper, iron, manganese, and zinc were above groundwater
criteria at various seeps in the west and east portions of the site. Additionally, pH, sulfate, and total
dissolved solids were commonly assessed as PCOCs at both monitoring well and seep locations. The
PCOCs at seeps were generally similar to PCOCs identified in monitoring wells in the same geographic
areas. Cadmium, copper, and zinc were identified as PCOCs at SP-21. A summary of PCOCs by
individual sample location is provided at the end of each subsection in Section 5.4.2. A general summary
of PCOCs is tabulated in Table 5.4-7.
The primary potential concern regarding seeps at the Site and in the Site area is the relation to surface
water quality in Railroad Creek. Aluminum, cadmium, copper,'iron, manganese, and zinc concentrations
were evaluated at each seep location. Additionally, the relationship of seeps within each geographical
area as designated in Section 4.0 were discussed based on metal results. The relationship of the seeps to
surface water quality is discussed in Section 6.0 as part of the fate and transport discussion.
Lysimeter data were compared to monitoring well data at each location sampled. These data were not
used to assess PCOCs. .
5.5 SEDIMENT
5.5.1 Railroad Creek
Sediment in Railroad Creek consists primarily of large grain size, including boulder, cobble and large
gravel. Previous evaluations of sediment grain size completed by PNL (1 992) upstream and adjacent to the
Site indicate that the cobble and boulder fraction of streambed sediment is on the order of 90%. PNL (1992)
further reports that the boulderlcobble fraction diminishes to 70% downstream of the Site (and upstream of
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17693-005-019Uuly 28,1999;11:09 AM;DRAFT FINAL RI REPORT