Dames & Moore, 1999 - USDA Forest Service

on available and similar aquatic habitat. The selection of reference locations having habitats similar to
the potentially affected locations was also performed and is a critical component of the analysis.
Five aquatic sampling locations considered to be potentially affected by mine activities and two reference
locations were selected within Railroad Creek. These sampling locations are described in Section 4.6. ,
Reference Reach Selection
Three additional reference locations were identified within streams located outside the Railroad Creek
drainage area for comparison 'to habitat conditions in Railroad Creek downstream of the Site. The
selection process included review of existing literature, interviews with knowledgeable parties, the
development of key habitat variables, the analysis of candidate reaches. and final selection after a field
reconnaissance was completed. The results of the process are described in Section 4.6.
3.9.1.3 Phase II
Phase I1 aquatic biota field investigations were conducted during September and early-October 1997 and
consisted of habitat analysis, benthic macroinvertebrate sampling, and fish sampling.
Aquatic Habitat
Habitat quality influences benthic macroinvertebrate and fish communities within Railroad Creek
regardless of physical or chemical perturbations associated with the Holden Mine. Although it is
desirable to select sampling locations with similar or comparable habitat quality, not all habitat
components will be identical between sampling locations. Therefore, habitat analyses were conducted at
each sampling site to provide data as to the relative capability of reference and affected locations to
support benthic macroinvertebrate and fish communities in the absence of chemical perturbations.
Therefore, the intent of the habitat analyses was to investigate non-mine related factors potentially
limiting the establishment of benthic macroinvertebrate and fish communities.
Habitat analysis methodologies were employed to provide data for both qualitative and quantitative
assessment of benthic macroinvertebrate and fish habitat conditions at each of the sampling locations.
Macroinvertebrates are affected by a variety of habitat conditions including: substrate composition,
substrate embeddedness and cementing, and current velocity (Bjornn et al., 1977; Minshall, 1985; Platts
et al., 1983; Kiffney and Clements, 1996). Fish are also affected by these habitat conditions, in addition
to poollriffle and runlbend ratios, and bank stability conditions (Plafkin et al., 1989, and Rosgen, 1994).
To determine the physical habitat conditions at the aquatic biota sampling locations, procedures described
in the rapid bioassessment procedure guidance document, "In-stream Biological Monitoring Handbook -
For Wadable Streams in the Pacific Northwest" (EPA, 1993) were generally followed. Accordingly, the
following parameters for rifflelrun prevalent streams in the Pacific Northwest were assessed:
Bottom Substrate - percentage of bottom substrate that is fines
Instream Cover - percentage of the stream that provides stable fish habitat
Embeddedness - the degree to which boulders, rubble, or gravel are surrounded by fine
sediment indicating suitability of the stream substrate as habitat for benthic
macroinvertebrates and for fish spawning and egg incubation
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