Dames & Moore, 1999 - USDA Forest Service

detected at RC-4 with the exception of manganese and iron which increased significantly from RC-4 to
RC-7. The comparison of RC17 data collected during the RI to area background concentrations indicate
that aluminum was above background (37.4 p a) in May 1997 (60 p a), September 1997 (40 pgL).
and May 1998 (90 p a). Manganese was detected above background (2.42 p a) during each sampling
event and ranged from 5.48 pg/L to 27 pg/L. Data for metals without WQC were also compared to
MTCA Method B levels. Metal concentrations were below MTCA levels. Comparison of RC-7 data to
WQC is discussed in the following paragraphs.
Metal concentrations measured at RC-7 were similar to those observed at RC-4. Dissolved cadmium
concentrations during April 1997 (0.5 p&) and May 1997 (0.58 pgk) were above the CWQC only in
April (0.39 p a) and the AWQC and CWQC in May (0.44 pg/L and 0.24 p&, respectively) (Tables 5:3-
23 and 5.3-24). Dissolved cadmium was below the criteria in subsequent rounds collected in July and
September 1997. Cadmium results at RC-7 collected in May 1998 were similar to May 1997. The
concentration of dissolved cadmium (0.67 pg/L) was above both the AWQC (0.40 p a) and the CWQC
(0.23 pg/L).
In May and July 1997, dissolved copper (23 pg/L and 2.6 p a, respectively) concentrations were above the
AWQC (2.7 and 1.9 p a, respectively) and the CWQC (2.1 pg/L and 1.6 p a, respectively), but were
below the criteria in April and SeptemberlOctober 1997 (Tables 5.3-23 through 5.3-27). The copper result
(37.5 pg/L) from the May 1998 sampling event was above AWQC (2.5 pa) and CWQC (2.0 pg/L).
The concentration was also above the May 1997 result (23 p a).
Dissolved zinc concentrations during the first three rounds in 1997 ranged from 20 to 90 pg/L which were
above the AWQC (16 to 38 p a) and the CWQC (15 to'34 p a). The July zinc level (20 pg/L) may be
related to the artificial introduction of zinc during field filtration. Zinc was below both criteria in
SeptemberIOctober 1997. The zinc concentration measured in May 1998 was 1 15 p a, above the May
1997 concentration (85 pg/L). The 1998 result was also above the AWQC (20 p a) and the CWQC (19
clgn).
In May, July, and September 1997, dissolved lead (0.5 pg/L, 0.5 pgL, and 0.4 pa, respectively) was
above the CWQC (0.28 pa, 0.19 pg/L, and 0.28 pa, respectively), but below the AWQC (7.2 pa, 4.9
pa, 7.2 pa, respectively). The May 1998 lead data (performed by low level lead technique) indicates
that lead (0.126 pa) is below the CWQC (0.26 pa). Iron was above WQC (1000 pg/L) in April and
September 1997 (1,680 p a and 1,150 pa, respectively). Other metal concentrations were below
AWQC and CWQC.
Silver detected in May 1997 at RC-7 was 0.54 pg/L. The result was qualified as not detected during data
validation due to method blank contamination. The AWQC (0.12 pa) is below the revised detection
limit. Silver was not above AWQC at RC-7 during any other sampling event including May 1998.
Dissolved iron during 1997 was highest in April, decreased in May and July, and increased in September,
indicating an inverse relationship with flow. Specific conductivity, pH, hardness, and alkalinity were
similar to the upstream locations. Field measured pH at RC-7 in 1997 ranged from 5.8 to 7.6 SU, similar
to upstream measurements.
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17693-005-019Uuly 28,1999;11:09 AM;DRAFT FINAL R1 REPORT