Dames & Moore, 1999 - USDA Forest Service

Reference Reaches - Upstream Railroad Creek
RC-1. and RC-6 as References for. RC-9 and RC-7
Control areas or reference reach segments of Railroad Creek were selected in order to evaluate the aquatic
biota data collected from the segments of Railroad Creek adjacent to and downstream of the site. The
selection process was based on ten primary factors, including channel slope, valley width, watershed area
size, presence of glaciers, presence of lakes, dominant geology, elevation, drainage network, aspect, and
presence of downstream fish barriers. Based on these criteria, it was discovered that the pool of candidate
reference streams were situated both upstream of the site within the Railroad Creek watershed and in the
North Lake Chelan Basin, north of the Railroad Creek watershed.
It appears that the stream and habitat conditions observed at the RC-6 and RC-1 sampling stations are
generally similar to those observed at the RC-9 and RC-7 stations in Railroad Creek, and are, therefore,
considered appropriate control or reference reaches. Benthic macroinvertebrate communities appear
suppressed within the reach of Railroad Creek that extends adjacent to tailings piles 1, 2, 3, compared to
the reference stations based on the 1997 aquatic sampling results. While the density of benthic
macroinvertebrates at station RC-7 indicates an affected community, it should be noted that the RC-9
sampling station includes an apparent transition into the influence of tailings pile seepage originating near
the south bank of the sampling station. The downstream portion of the station has obvious indication of
staining fiom the tailings pile seeps, while the upstream portion is relatively free of any staining or
flocculent-like material on the substrate. Of the eight benthic macroinvertebrate samples collected at this
station, four were collected either upstream fiom the initial staining or near the north bank, while the
remaining four were collected within the staining or along the south bank. The density of benthic
macroinvertebrates within the samples collected upstream or along the north bank ranged from 260 to
1,s 10 organisms per m2, while the density of benthic macroinvertebrates within the staining or along the
south bank ranged from 10 to 300 organisms per m2. The benthic macroinvertebrate results indicate that
the communities may be similar to the reference communities, while those immediately downstream of
the flocculent are reduced compared to the reference stations.
The 1997 fish survey results at RC-9 and RC-7 varied widely between the two stations (RC-9, 114
trouthectare and RC-7, 10 trouthectare); however, the density of trout at RC-9 was within the range of
the reference trout densities (64-93 troutfhectare). As indicated by the habitat evaluation scores, station
RC-9 had the least desirable habitat (score 77) of all stations sampled, while RC-7 had the third lowest
score (94). The reference stations for the reach, RC-6 and RC- 1 scored 1 1 1 and 105, respectively.
Water quality samples were not collected at RC-9 during the 1997 investigation. The results of samples
collected from RC-7 indicate exceedances of water quality criteria for acute toxicity during April (zinc),
May (cadmium, copper, and zinc), and July (copper and zinc). Based on the benthic macroinvertebrate
sampling results from RC-9, the physical conditions of the substrate within these stations may also
adversely influence these communities. Comparison of the individual benthic macroinvertebrate and fish
sampling results with the iron-stained and non-iron stained portions of RC-9 indicate that the occurrence
of iron flocculent within a portion of the reach has a greater influence on fish and macroinvertebrate
populations than dissolved metal concentrations.
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17693-005-019Uuly 28. 1999;10:24 AM;DRAFT FINAL RI REPORT