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

Final Environmental Impact Statement Rio de los Pinos Vegetation Management Project
(WIZ), mainly roads. The amount of road disturbance in the WIZ is 7.4%, under the 10%
concern level for this parameter.
This “watershed of concern” designation does not preclude new land disturbance within the
watershed but does require specific watershed analysis prior to any new land disturbing activities
(Dobson, 1996). This watershed was evaluated carefully during field work completed for the
County Line Vegetation Management Project. In the summer of 2003, the watershed was
assessed in detail to: 1) determine current stream health; and 2) identify concern areas that may
need restoration or additional design criteria to correct stream health concerns. A summary of
this analysis is provided in the following section. The County Line EIS was the NEPA prepared
to allow for the Spruce Park and two other sales that are currently under contract.
The main channel in this seventh-level watershed varies from an E-type high in an upper
meadow to A3/B3 type with large-medium cobble in the lower reach below Forest Road 118.1C.
In the upper E-reach, bank stability is impacted by a high-use dispersed camp site. At its mouth,
this stream flows into a large beaver dam complex on the Rio de los Pinos. Stability of small Estream
reaches and B-streams with large cobble and small boulder is excellent in the analysis
area.
Forest Road 118.1C that parallels the main stream channel is well-maintained, and work
completed in 1998 and 2007 reduced impacts from this sediment source. Although the channel is
close to the road, thick willow and sedge provide an effective buffer. In smaller subwatersheds
within this watershed of concern, stable E-stream channels within well-vegetated meadows are
present. Small trout were observed during field evaluation of these streams.
Fine sediment sources are limited to a few trail crossings and some steeper slopes where
vegetation is sparse. Rill and gully sources were not seen. Sediment impacts of road crossings
on the smaller tributaries are minor. Good vegetation cover is present on several roads in the
upper parts of the watershed, including Forest Roads 118.1Q, 118.1R, and 118.1S.
Two natural factors that influence sediment availability in this watershed are rapidly weathering
bedrock in many areas and soils prone to mass movement. One example of sediment input to
streams by natural weathering is the sandy conglomerate outcrop along Forest Road 118.1C
adjacent to the main channel. Slopes prone to mass movement are present in upper parts of the
watershed and are a natural factor in fine sediment contribution to the overall system.
To determine relative sediment load impact by the current road system and previous disturbance,
stream channels above all road disturbance were used as “reference” reaches in analysis of
stream health. Examination of one B-4 stream reach above all roads and below indicates bedload
is very similar in composition and that fine sediment is inherent to the streams. Fine sediments
are present in lower energy areas of the channels and fine to coarse sands and gravels in higher
energy sections.
Stream observations conducted in 2003 and 2008 indicate that current input of fine sediment to
streams in this watershed from previous forest management activities appears to be minor and
not a major factor influencing fine bed load in streams. A pebble count conducted in 2003 on a
Chapter 3 – Affected Environment & Environmental Consequences Page 3-20