Dames & Moore, 1999 - USDA Forest Service

accessed, including the RM-3 "Dan's Camp" station sampled by Pacific Northwest Laboratories (1992),
during the initial reconnaissance of the creek. Beqause of the steep gradient and flows, both of which were
considered a potentially unacceptable risk to the sampling team, no aquatic sampling locations were
identified within these reaches. However, based on field observations, RC-10 could be considered
representative of reach "C" and. thus, the reference locations at Bridge Creek and South Fork Agnes Creek
could be considered suitable references for reach "C."
Reach "A" is at the mouth of Railroad Creek and is unique due to channel slope, valley width, the
percentage of glaciers, and the proximity of the lake. A reach of Company Creek, a tributary to the Stehekin
River, was identified as a potential reference reach based on the evaluation of the ten hydro- and geological
parameters previously described. This particular reach was approximately 4 miles upstream From the
confluence with the Stehekin River and was the only reach within Company Creek considered to qualify for
reference based on the evaluation of the ten parameters. However, during field verification, the Company
Creek reach was determined inaccessible and of substantially lower discharge than any of the Railroad
Creek reaches. Therefore, the Company Creek reach was eliminated as a reference reach candidate.
Subsequent to the final selection of stream reaches determined to be qualified as reference reaches, the
USFS identified the need to select a reference reach to represent Railroad Creek reach "A" with the primary
criteria being the potential for migratory species to frequent the reach during the spawning season. The
migratory species of particular concern in this case was the Kokanee salmon. Although the importance of
the ten criteria and its application for selecting reference reaches were recognized, the primary
criteria for selecting a reference reach for lower Railroad Creek (which is accessible to Lake Chelan
spawning kokanee salmon) was the documented occurrence of kokanee salmon in the reference reach. The
lower segment of Company Creek has historically served as a quality spawning tributary to the Stehekin
River for Lake Chelan kokanee salmon. Therefore, a reach of lower Company Creek was selected as a
possible reference for lower Railroad Creek with the qualification that Company Creek was not similar to
lower Railroad Creek with respect to the ten hydrologic and geologic parameters and the stream discharge
but with respect to the potential for kokanee salmon to access the stream.
4.6.1.2 Habitat Evaluations
Aquatic sampling locations were selected in an attempt to minimize variations attributable to habitat.
However, since not all habitat variables could be held constant, habitat was evaluated to estimate the
potential for supporting viable aquatic resources based on physical habitat quality in comparison to
reference locations. As previously described, habitat was qualitatively evaluated using the guidance
provided in the U.S. EPA (1993), Region 10 In-stream Biological Monitoring Handbook for Wadable
Streams in the Pacific Northwest. Furthermore, the evaluation of habitat was not intended to indicate
trout carrying capacity but was employed merely to contribute to the weight of evidence used to assess
the conditions of the aquatic communities within Railroad Creek and the various reference streams.
All ten locations (including the reference locations) were evaluated. The average (five transects per
location) habitat parameter ratings by location are presented in Table 4.6-2. Again, it is emphasized that the
habitat scores do not represent potential trout biomass or carrying capacity but are used only to compare
stations with respect to overall habitat quality. Furthermore, although certain stations may appear to be
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