Final Environmental Impact Statement Rio de los Pinos Vegetation ...

Final Environmental Impact Statement Rio de los Pinos Vegetation Management Project
steeper reach of the main channel dominated by large cobble (B3 stream type) showed 18% sand
and 4% silt fractions, close to the average fine sediment (15%) determined on reference reaches
of the same type on the Forest.
To further evaluate stream water quality and macro invertebrate habitat in the tributaries,
Tarswell substrate ratios (TSR) were estimated during field evaluation and rocks examined for
aquatic insects. The T-Walk diversity screen includes a procedure where 10 cobble sized-rocks
within a riffle reach of stream are examined for macro invertebrates (Ohlander, 1996). Stonefly,
mayfly, and caddis fly nymphs, larvae, and casings are counted. This information, provided in
the watershed specialist report, showed substrates productive to biota were present and water
chemistry is in good condition.
Overall, streams within watershed 130100050501 are healthy. Sediment sources associated with
current system roads or other surface disturbances are minor. Although watershed condition has
been affected by past activities, watershed work completed in 1998 and natural recovery of the
watershed since timber operations were conducted (see Timber and Silviculture section)
contribute to the present condition. Stream banks are stable, with healthy riparian vegetation in
proper functioning condition present along intermittent and perennial stream reaches.
In the 7 th level watershed of concern where spruce beetle mortality has resulted in a high basal
areas loss, streams remain healthy and stable. A monumented cross-section established in 2003
was again surveyed in 2008 and stream width and gradient have not been affected to date by
reduction in live basal area due to spruce beetle infestation.
Main Stem
The main stem of Rio de los Pinos does not lie within but is adjacent to the analysis area. This
stream is classified as a B4/C4 stream type with much of its watershed within wilderness and
backcountry. Stream bank stability on the main stem of Rio de los Pinos below the proposed
treatment area is good, with healthy riparian vegetation in proper functioning condition able to
withstand high flows. In localized steep areas, bank instability attributable to natural bedrock
weathering is present, which adds fine and coarse sediment to bedload through sheet erosion and
slumping. In addition, above Trujillo Meadows Reservoir there are localized unstable bank
sections present on outside bends of meanders where the stream channel has migrated into higher
elevation ground. Unstable bank and impact to riparian vegetation due to livestock grazing in
this area appear to be minimal.
Upstream from the project area, this stream currently holds a population of Rio Grande Cutthroat
trout. Stream health is robust.
Existing Conditions
Fisheries: The Rio de los Pinos above the analysis area provides habitat for Rio Grande
cutthroat trout, which is listed as a Region 2 sensitive species, and was recently petitioned for
listing as a federally endangered species. The Clean Water Act requires that chemical, physical,
and biological integrity of all waters, stream channels, and wetlands be protected. Standards and
guidelines that have proven effective would provide that protection. By following these standard
design criteria impacts to stream health are expected to be minimal.
Chapter 3 – Affected Environment & Environmental Consequences Page 3-21