Dames & Moore, 1999 - USDA Forest Service

Organics
TPH and PCBs were analyzed only at RC-2 and were not detected. PCBs were not included in the list of
analytes for the September 1997 and later sampling events based on the results from the previous 1997
sampling rounds.
5.3.3.4 Downstream of Tailings Piles
Surface water sampling locations downstream of the tailings piles included RC-5 and RC-5A. RC-10, RC-8
and RC-3 (Figure 5.3-1). RC-5 was sampled approximately 500 feet downstream of RC-2 during the April
1997 sampling round. RC-5A was established in May 1997 just above the confluence of ~enmile~reek, the
next downstream tributary to Railroad Creek. Station RC-10 was established as an aquatic habitat station
downstream of Tenmile Creek, and was sampled for water quality only once in September 1997. Stations
RC-8 and RC-3 are both near Lucerne. RC-8 was located near the old USGS gauging station at Lucerne
upstream of RC-3 (Figure 5.3-1). Samples were collected at stations RC-5(A) and RC-3 during all four
sampling events in 1997 (April, MayJJune, July, September) and one sampling event in May 1998. Station
RC-10 was sampled in September 1997 and May 1998. Station RC-8 was established as a comparison to
RC-3, and was sampled during April and September 1997 only because high stream flows created
accessibility and safety issues at this location during the MayJJune and July events.
Laboratory analytical results and field data are summarized in Table 5.3-29 and the dam are compared to the
AWQCJCWQC for each sampling event in Tables 5.3-23 through 5.3-27.
Inorganics
The metals data associated with RC-5, RC- 10, RC-8, and RC-3 are described below.
The comparison of RC-5 data collected during the RI to area background concentrations indicate that
dissolved aluminum was above background (37.4 p a) on May 20, 1997 at RC-5 (70 pgiL) and at RC-
5A in September 1997 (50 pg/L) and May 1998 (90 pg/L). Manganese was detected above background
(2.42 p a) during each sampling event and ranged from 7.04 pg/L to 26 pgL. The concentrations of
aluminum and manganese at RC-5 and RC-5A are similar to concentrations of these metals detected at
stations RC-7 and RC-2. Metal concentrations were not above MTCA Method B cleanup levels for those
metals without WQC. Comparison of RC-5 data to WQC is discussed in the following paragraphs.
Cadmium, copper, and zinc were the only metals that were above WQC in one or more sampling events.
Silver was not detected at RC-5 on May 20, 1997, however, the detection limit (0.14 p a) was just above
the AWQC (0.13 p a). Silver was not detected at RC-5A on May 22, 1997. The detection limit (0.04
pg/L) was well below the AWQC (0.18 pg/L). In April 1997, cadmium (0.4 pgL) was above the CWQC
(0.38 p a). On May 20, 1997, cadmium (0.5 pa) was above the CWQC (0.25 pg/L) and slightly
above the AWQC (0.47 p&). The RC-5 station was relocated further downstream (RC-SA) and
resampled on May 22, 1997. The cadmium concentration (0.4 pg/L) at RC-5A was also above the
CWQC (0.29 p a) and below the AWQC (0.58 pg/L). A sample was collected from this station in May
a 1998. The cadmium concentration (0.58 pg/L) was above CWQC (0.25 I&) and AWQC (0.47 pg/L).
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28, 1999;11:09 AM;DRAFT FINAL RI REPORT