Dames & Moore, 1999 - USDA Forest Service

sampling rounds, the field filter blank results suggested that barium and zinc were artificially introduced
during the filtration process. Other metals (aluminum, calcium, copper, manganese, silver, and sodium)
were also detected at levels near the detection limits; however, these detections did not impact data usability.
Concentrations detected in the filter blank for barium (1 8.7 pg/L) and zinc (6 to 16 pg/L) were considered
during the data evaluation as these potential introductions did impact the assessment of the data when
compared to water quality criteria.
As previously described in Section 5.1.2, Site surface water data was initially compared to the federal and
state acute (AWQC) and chronic (CWQC) aquatic life criteria established. Where WQC were not
established, Site data were conipared to area surface water background concentrations and MTCA
Method B cleanup levels for surface water. AWQC and CWQC is established for dissolved '
concentrations of arsenic, cadmium, chromium, copper, lead, nickel, and zinc. Only an AWQC is
available for dissolved silver concentrations. AWQC and CWQC for selenium are based on total
concentrations. The AWQC for mercury is based on dissolved concentrations; however, the CWQC is
based on the total recoverable concentration. Criteria for cadmium, chromium, copper, lead, nickel,
silver, and zinc are corrected based on water hardness. The federal AWQC and CWQC specifies the use
of a 25 ppm hardness value for metals requiring hardness correction when measured hardness is less than
25 ppm. The State of Washington specifies the use of actual hardness measurements. The data tables
provide both the use of 25 ppm hardness and measured hardness corrected criteria. For discussion
purposes, the measured hardness corrected criteria is discussed.
Criteria for the protection of aquatic life is provided for beryllium and iron by reference to the EPA
document "Quality Criteria for Water, 1986" in the Washington State regulatory guidance WAC 173-
20 1 A. These criteria are shown in Table 5.1 - 1 and are assumed to be based on dissolved analysis.
The analytical methods used to measure surface water metal concentrations were selected to provide the
lowest technically achievable detection limits in an attempt to be at or below the AWQCICWQC. As the RI
data collection and data evaluation progressed, analytical methods were adjusted to facilitate recognized
data needs such as reducing detection limits to clearly evaluate exceedances as compared to water quality
criteria. The method changes were documented in the SAPS and QAPPs associated with each field phase.
The detection limits for lead and mercury were above the aquatic life chronic criteria (CWQC) in 'April
1997. Following this round, the lead and mercury methods were revised to provide lower detection limits.
During subsequent sampling rounds in MaylJune and July 1997; mercury and selenium were not detected or
were detected at concentrations that were orders of magnitude below WQC. These analyses were then
eliminated from fbture sampling events. The lead concentrations detected in surface water samples
collected during 1997 were suspect due to intermittent problems with laboratory method blank
contamination. Additionally, the detection limit provided by the method selected was often at or above
the CWQC., The method was reevaluated prior to 1998 sample collection and revised to a draft low-level
EPA method. The revised method resulted in detection limits well below the CWQC for lead. The May
1998 data allowed data evaluation to clearly determine if exceedances for lead were apparent in surface
water in Railroad Creek during the spring.
The surface water discussion is organized and presented beginning with a discussion on the assessment of
area background surface water quality. Following the background discussion, individual sections discuss
the chemical data collected from the Stehekin River watershed, Railroad Creek, portal drainage, Copper
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17693-005-019Uuly 28. 1999;11:09 AM;DRAFT FINAL RI REPORT