Dames & Moore, 1999 - USDA Forest Service

and sodium were not evaluated as these metals are considered nutrient metals and MTCA levels are not
established. MTCA also does not include a groundwater value for iron, aluminum, or barium. For those
constituents where MTCA criteria are not available, concentrations were compared to criteria designated
under WAC 173-200. The data collected from the well at Lucerne were compared to MTCA and federal
MCLs. If metal concentrations were above MTCA or the MCLs, the analyte was considered a PCOC.
The chemistry discussion for seeps focuses on the PCOCs identified for surface water in Section 5.3 as
the primary concern is due to the interaction of seeps with surface water. The PCOCs and other
compounds of interest identified for surface water include aluminum, cadmium, copper, iron, manganese,
and zinc. Seep data were compared to groundwater quality criteria to determine if exceedances were
apparent and if so, the locations where they occurred. The comparison and assessment of PCOCs was
identical to the process for data collected from the groundwater monitoring wells.
Individual metal concentfations are plotted on concentration maps by each metal designated as a PCOC in
Railroad Creek. These metals include aluminum, cadmium, copper, iron, manganese, and zinc. All
discussions refer to dissolved concentrations. Discussions of constituent variability between May 1997
and September 1997 focus on monitoring well results, as most seeps were not flowing during the
September 1997 sampling event. Samples collected from seeps in May 1998 are compared to the 1997
data where appropriate.
Regional and Site groundwater quality are described in the following sections. The FU groundwater data
discussion includes background groundwater quality, and water quality from Site wells, lysimeters, and
seeps. The groundwater discussion is organized and presented beginning with a discussion on the
assessment of regional groundwater quality followed by Site groundwater quality. The Site groundwater
quality discussion includes a historical summary of previous groundwater and seep data collected on the
Site and in the area. The historical data summary is followed by background water quality based on the
results of the RI. Following the background water quality section, individual sections address
groundwater quality based on monitoring wells, lysimeters, and seeps by geographic area; Honeymoon
Heights, waste rock piles, maintenance yard, tailings pile 1, tailings pile 2, and tailings pile 3. Historical
data were compared to the RI data where station locations are considered compatible. At the end of the
section is a summary that identifies the occurrence of PCOCs by geographic area. Human health and
.
ecological risks associated with groundwater and seeps in the area are further assessed in Section 7.0.
5.4.1 Regional Groundwater Quality
A water-quality assessment was completed historically by others in the Lake Chelan Basin; the
assessment included the installation of groundwater monitoring wells at 26 locations in the lower Lake
Chelan basin as part of a Lake Chelan water quality assessment (Patmont, 1989). Metals analyses were
not completed on samples collected. pH and specific conductance ranged from 6.8 to 7.5 SU and 99 to
490 CLmhos/cm2 in background wells completed in surficial materials. One well in the basin was
completed in bedrock; four samples were collected from the well with a mean pH of 7.0 SU and mean
specific conductance of 590 pmhoslcm2 (Patrnont, 1989).
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