Dames & Moore, 1999 - USDA Forest Service

RC-2 is'located immediately downstream of tailings pile 3 (Figure 5.3-2). The comparison of RC-2 data
collected during the RI to area background concentrations indicate that dissolved aluminum was above
background (37.4 pg/L) in May 1997 (90 p a), September 1997 (40 pg/L), and May 1998 (100 p@).
Manganese was detected above background (2.42 p@) during each sampling event and ranged from
5.52 pgL to 26 pg/L. For metals without WQC, data were below MTCA Method B cleanup levels.
Comparison of RC-2 data to WQC is discussed in the following paragraphs.
Cadmium at station RC-2 was above the CWQC in April 1997 (0.40 pg/L vs. 0.38 p@) and the CWQC
and AWQC (0.25 pg/L, and 0.47 pa, respectively) in May 1997. In May and July, copper (23.6 and 2.3.
p@, respectively) was above. AWQC (2.8 and 1.9, respectively) and CWQC (2.2 and 1.6 pa,
respectively). In April, May and July 1997, zinc concentrations (77, 84, and 24, respectively) were above
AWQC (37,23, and 16, respectively) and CWQC.(33,21, and 15 pg/L, respectively). The concentration in
September 1997 was 23 pa, just above CWQC (21 pa) and equal to AWQC (23 pg/L). The result in
July is a potential anomaly related to zinc introduction during field filtration of the sample. Data collected
in May 1998 show concentrations similar to those detected in May 1997. Iron was above WQC (1000
pgL) in April (1,430 pg/L) and September (1,080 pa). Other metals were below the AWQC and
CWQC.
Near bank samples were collected on the south side of Railroad Creek at RC-2. Metal concentrations near
the south bank at RC-2 were comparable to concentrations detected in samples collected across the creek
width. Cadmium, copper, .and zinc concentrations exceeded AWQC in May 1997. Copper and zinc
exceeded AWQC in July 1997. In September 1997, zinc (23 pg/L) was above the CWQC (2 1 pg/L) and
equal to the AWQC (23 pg/L). Iron (1,150 pg/L) was above WQC (1,000 p a) in September. Field
parameters (pH and specific conductivity) were comparable between bank and creek width samples as well.
The measured pH at RC-2 ranged from 5.7 to 8.2 SU. Measurements collected at the south bank ranged
from 6.2 to 7.7 SU. The measurements are within the range of the upstream stations (5 to 8 SU).
In summary, the water quality at stations RC-7 and RC-2 were higher in iron and zinc relative to upstream
locations. Iron concentrations at RC-7 and RC-2 were also higher than RC-4 concentrations. RC-7 showed
higher iron than RC-2 during all of the sampling events in 1997. RC-2 showed higher aluminum than RC-7
during the May 1997 event. The pH at RC-4, RC-7 and RC-2 were all similar to upstream measurements.
Samples collected at RC-4, RC-7, and RC-2 in May 1998 generally confirm the trends indicated in the 1997
data.
Seasonal variability in metals concentrations at RC-7 and RC-2 are similar to RC-4. Zinc, copper, lead and
cadmium in 1997 were all highest during the MayIJune sampling event followed by April, July and
September. Aluminum, however, was lowest in April, highest in MayIJune and decreased in July and
September indicating that this metal may be directly correlated with Railroad Creek flow. Iron, along with
specific conductance, alkalinity and hardness exhibited the opposite relationship, and was inversely
correlated with streamflow. Hardness and concentrations of aluminum, cadmium, copper, iron, manganese,
and zinc at RC-2 are plotted against stream flow measured at RC-4 on Figures 5.3-5 to 5.3-9.
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28. 1999;11:09 AM;DRAFT FINAL RI REPORT