Dames & Moore, 1999 - USDA Forest Service

Area background values for arsenic, cadmium, copper, lead, manganese, and zinc are above the Yakima
Basin background values published by Ecology. Additionally, area background arsenic and cadmium levels
are above MTCA Method B and MTCA Method A cleanup levels, respectively.
5.1.2 Surface Water
The assessment of background surface water quality conditions for Railroad Creek is complex due to the
presence of a number of tributaries that enter Railroad Creek upstream and downstream of the Site.
Additionally, historic prospecting and mine activities in the area unrelated to the Howe Sound Company
and the Holden Mine preclude the assessment of natural background as defined under MTCA. Area
background related to Railroad Creek was evaluated by collecting water quality data from Railroad Creek
and various tributaries upstream and downstream of the Site and from creeks located in the Stehekin
valley that have similar characteristics to Railroad Creek.
The specific sampling locations are further described in Section 5.3. Area background data were compared
to federal freshwater acute and chronic water quality criteria (AWQC and CWQC, respectively) specified in
40 CFR Part 131.36 and Washington State freshwater criteria (WAC 173-201A) to assess if background
metal concentrations were above the criteria. Site data collected fiom reaches that appeared to be influenced
by the Site were then compared to the background data and the ARARs described below.
Table 5.1- 1 presents preliminary ARARs and TBCs for surface water. The table includes:
Area background surface water concentrations
Washington State freshwater acutelchronic criteria as described in WAC 1 73-20 1 A
Federal freshwater acutelchronic criteria as described in 40 CFR Part 13 1.36
MTCA Method B Surface Water Cleanup Levels. CLARCII update, February 1996
The federal freshwater AWQC and CWQC focus specifically on the protection of aquatic life.
Freshwater AWQC and CWQC are established for arsenic. cadmium, chromium, copper, lead, nickel, and
zinc and are based on dissolved concentrations. The AWQC and CWQC for selenium are based on total
recoverable concentrations. The AWQC for mercury is based on dissolved concentrations, however the
CWQC is based on total recoverable concentrations. Only an AWQC (no CWQC) is established'for
silver and is based on dissolved concentrations. The criteria for cadmium, chromium, copper, lead, nickel,
silver, and zinc are corrected for water hardness.
The State of Washington criteria for surface water generally adopted the federal criteria; however, actual
hardness values for metal-specific criteria calculations are used as compared to the use of 25 ppm
minimum hardness for federal criteria where actual hardness measurements are less than 25 ppm. The
comparison of Site surface water data to the AWQC and CWQC is considered to be a conservative
assessment as the AWQC is based on short-term exposure of 1-hour average and the CWQC is based on a
4-day average.
In addition to the metals discussed above, criteria for beryllium and iron are specified in WAC 173-201A
by reference to an EPA document "Quality Criteria for Water, 1986." As with the metals criteria
specifically ide,ntified in WAC 173-201A, the criteria specified for beryllium and iron is derived primarily
for the protection of aquatic life.
\WM~SEAI\VOLI\COMMOMWP\WPDATA\OOSREPORTSWOLD-2 5-3 DAMES & MOORE
17693-005-019Uuly 28. 1999;11:09 AMDRAFT FINAL R1 REPORT