Dames & Moore, 1999 - USDA Forest Service

Aquatic Habitats
Surface Water
The potentially complete exposure pathways for PCOCs at the Site include aqueous and sediment contact
and ingestion by aquatic receptors. The toxicological benchmarks against which aquatic exposures were to
be compared in this baseline ERA included 1) the water hardness adjusted criteria (WAC 173-201A) that
were derived to protect aquatic receptors regardless of the specific exposure pathway, and 2) published.
species-specific, toxicity test results. Because fish species move within the water column, the 95 percent
upper confidence limit (UCL) of the Site data and the median surface water concentmtions, were compared
to acute and chronic water quality criteria. Where the sample size was too small to calculate the UCL. the
highest value was used for screening purposes. Since plants and animals are not directly exposed to
groundwater, this media was not considered as an exposure source in itself.
Surface water data were separated into those that are representative of the mainstream of Railroad Creek
(not including samples collected adjacent to seeps emanating from the south bank of Railroad Creek)
(Tables 7.2.2- 1 B 1, B2, B3), and those that are associated with seeps along the south bank of Railroad Creek
(Table 7.2.2-1A). In addition, Railroad Creek was divided into three reaches: (1) upstream of Site
(including RC-I 1, RC-6, RC-I and USGS and Ecology samples collected within this reach); (2) adjacent to
Site (RC-4, RC-7, RC-2 and Ecology samples collected within this reach); and (3) downstream of Site (RC-
10, RC-5, RC-8, RC-3 and Ecology samples collected within this reach). As specified in WAC 173-20IA.
metals concentration criteria were hardness adjusted for the mean measured hardness of 14.5 mg/L for those
metals that are hardness dependent: cadmium, copper, lead, nickel, and zinc. These screening values and
95 percent upper confidence levels of surface water data are shown in Table 7.2.3-1A. Elements were
eliminated if they did not exceed these criteria, or if there is no toxicity benchmark by which to judge
toxicity.
While USGS (1996) samples collected from 'locations 603 and 628 exceeded water quality criteria for
manganese and had the highest concentrations of most other metals analyzed, these samples were collected
from the creek bank immediately downstream from seep areas, not in the main stream where fish and
invertebrates would be found. Because of the large dilution effect of Railroad Creek, these samples and
other samples collected directly from seeps or portals were not considered as riverine habitat for
invertebrates or fish. All metals except lead fell below the federal criteria in Copper Creek and were not
further analyzed for risk to aquatic or terrestrial receptors.
In summary, there was no need to further evaluate the following metals because concentrations were below
federal criteria or toxicity benchmarks are not available to evaluate toxicity.
Fish Bioassavs
Surface Water - aluminum; arsenic; barium, beryllium, chromium, iron, mercury;
manganese, nickel; and silver.
Comparison of Tables 7.2.2-lB1, B2 and B3 with 7.2.3-1A shows that all of the UCLs for surface waters
where copper was detected, including Holden Creek, exceeded the chronic water quality criterion for copper
and lead at a hardness of 15 mg CaCOfi. This was also true for Bridge Creek, Company Creek, and the
south fork of Agnes Creek, reference streams at a hardness of 14 mg CaCOJL. This is largely attributable
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17693-005019Uuly 27.1999,5:16 PMDRAFT FINAL RI REPORT