Dames & Moore, 1999 - USDA Forest Service

RC-4 is located downstream of the portal drainage inflow to Railroad Creek, as shown in Figure 5.3-2.
The comparison of RC-4 data to area background concentrations indicates that dissolved aluminum was
above background in May 1998 (60 pg/L vs. 37.4 pg/L). Dissolved manganese was detected above
background (2.42 pg/L) in April 1997 (3 to 4 pg/L), May 1997 (2.94 pg/L), and May 1998 (4.83 pg/L).
Metal concentrations for those metals without WQC were also compared to MTCA Method B cleanup
levels. Concentrations were not above cleanup levels. Comparison of RC-4 data to WQC is discussed in
the following paragraphs.
Dissolved copper concentrations during April through July 1997 ranged from 3.4 to 26.4 pg/L which were
above hardness corrected AWQC (1.8 to 4.3 pgL) and CWQC (1.5 to 3.2 p&). Dissolved zinc
concentrations ranged from 17 to 73 pg/L during the first three sampling rounds (April, May, July 1997)
and were above AWQC (15 to 33 pg/L) and CWQC (14 to 30 pgL). Cadmium and lead were the only
other metals that contained levels above AWQC and/or CWQC, but were not consistently above the criteria.
Hardness, alkalinity, pH, and specific conductivity were similar to upstream locations. The measured pH at
RC-4 was 5.5 to 7.8, within the range noted for the upstream stations, but in some cases below the criteria
specified in WAC 173-201A (6.5 to 8.5 SU). Concentrations of copper, zinc, cadmium, and lead were
highest during the May sampling event that corresponds to the highest flow observed in Railroad Creek in
1997. Data collected at RC-4 in May 1998 generally supports the data collected in May 1997; however,
dissolved concentrations of aluminum, cadmium, copper, manganese, and zinc were 1.5 to 2 times higher
in 1998 than 1997. The use of the low level lead techn'ique in 1998 indicates that lead concentrations do
not exceed CWQC as previously indicated during 1997.
Bank samples collected on the south side of Railroad Creek at RC-4 in 1997 were compared to WQC and
to the results from samples collected across the creek. Dissolved copper concentrations during all three
sampling events ranged from 58.5 pg1L in May 1997 to 3.9 pg/L in September 1997, which were above
hardness corrected AWQC (1.8 to 2.8 pg/L) and CWQC (1.5 to 2.2 p a). Dissolved zinc concentrations
ranged from 191 pg/L in May 1997 to 20 pg/L in September 1997, which were above AWQC (15 to 23
pg/L) and CWQC (14 to 21 pg/L). Cadmium detected at the south bank only in May (1.1 pg/L) was
above the AWQC (0.47 pg/L) and the CWQC (0.25 pa). Dissolved lead concentrations in May 1997
(0.6 pa) were above'the CWQC (0.3 pa) but below AWQC (7.8 pg/L). The south bank data was
compared to samples collected across the width of the creek. During May, July, and September 1997,
copper concentrations were approximately two times greater on the south bank. Cadmium and zinc were
approximately two times greater on the south bank in May, but were similar to the creek width results in
July and September. Field parameters collected from the bank and across the creek width were
comparable. All other metals were below established AWQC and CWQC. Metals that do not have
established water quality criteria were compared to background and MTCA Method B cleanup levels.
Results were below area background and MTCA levels with the exception of manganese in May 1997
(7.46 pg/L vs. 2.42 pg/L) which was above background.
RC-7 is located downstream of the inflow from Copper Creek to Railroad Creek and is adjacent to tailings
pile 2 (Figure 5.3-2). Dissolved metal concentrations measured at RC-7 were similar to concentrations
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17693-005-019Uuly 28. 1999;11:09 Ah4;DRAFT FINAL RI REPORT