Dames & Moore, 1999 - USDA Forest Service

In May 1997, copper (21.5 pg5) in the sample collected at RC-5 was above CWQC (2.2 pgL) and
AWQC (2.8 p a). Copper concentration (7 p a) at the RC-5A location sampled on May 22, 1997 was
above CWQC (2.6 p a) and AWQC (3.4 pa). Copper (2.4 pg5) was detected in July 1997 above the
CWQC (1.7 p a) and AWQC (2.1 p a). Copper was below WQC in the sample collected in September
1997. A sample was collected at this location in May 1998. The concentration of copper (26.9 p@) was
above CWQC (2.2 p a) and AWQC (2.8 p a).
Zinc ranged from 24 to 98 p a, which was above AWQC and CWQC during all sampling events (Tables
5.3-23 through 5.3-27). The July 1997 zinc result may be due to the introduction of zinc during field
filtration. In general, station RC-5 and RC-5A data indicated similar water quality as RC-2.
Iron (1,290 p a) was above WQC (1000 p a) at RC-5 Sampled in April 1997 and at RC-5A sampled in
September 1997 (1,250 pg/L). Field pH measurements ranged from 6.1 to 7.6 SU, similar to upstream
measurements.
- RC- I 0
RC-10 data collected during the RI was compared to area background concentrations. Dissolved
aluminum and manganese concentrations are above background. Aluminum ranged from 40 to 80 pa. Manganese ranged from 9.29 to 13.5 pfl. Area background concentrations for aluminum and
manganese are 37.4 pg/L and 2.42 pa, respectively. The concentration of aluminum at RC- 10 is similar
to the concentration detected at station RC-5. In the spring, the data indicates a decrease in concentration
of cadmium, copper, iron, manganese and zinc from RC-5A to RC-10. In the fall, iron significantly
decreases from RC-5A to RC- 10.
Metal concentrations detected at RC-I0 in September 1997 were below WQC. Cadmium, copper, and
zinc concentrations detected in the sample collected in May 1998 were above WQC. Cadmium (0.4
pa) was above CWQC (0.27 p a) but below the AWQC ( 0.5 1 p a). Copper (I 8.5 pg/L) was above
CWQC and AWQC (2.4 and 3.0 pg5, respectively). Zinc (69 pg5) was above CWQC and AWQC (22
and 24 p a, respectively).
- RC-8
RC-8 data collected during the RI was compared to area background. Dissolved aluminum and
manganese concentrations are above background. Aluminum (50 pgL) was just above background (37.4
pa). Manganese (9.97 to 15 p a) was above background (2.42 p a). Generally, the concentration of
metals at this station did not indicate seasonal fluctuation with thk possible exceptions of manganese and
zinc which decreased from the spring to the fall. Additionally, the fall data for RC-8 compared to the RC-
10 data collected during the same timeframe are similar with the exceptions of iron and manganese which
decrease.
The RC-8 data was compared to WQC. Dissolved cadmium (0.72 p a) at RC-8 was above the AWQC
(0.65 p a) and CWQC (0.3 1 CLgn) in September 1997; however this result appears to be an anomaly. The
dissolved result (0.72 p a) is higher than the total result (0.10 pa) and locations sampled upstream of
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5-28
17693-005-01Wuly 28.1999;11:09 AMDRAFT FINAL RI REPORT
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