3.0 Affected Environment - Knik Arm Bridge and Toll Authority

Knik Arm Crossing DraftFinal EIS
Affected Environment
Where located near roads or other ground disturbance, forested and scrub wetlands may filter
pollutants from runoff before releasing the water to down slope wetlands.
3.8.2.1.2 Scrub and shrub wetlands
Wetlands dominated by shrubs and by scrub trees in the indirect effects Study Area include
thickets of willow and alder on stream floodplains, alder swamps, extensive bogs with a
dense and diverse cover of deciduous and evergreen shrubs, bogs with a dense sedge cover,
patterned bogs with higher shrubby areas and lower flooded sedge-filled ponds, and bogs
dominated by scrubby black spruce (“muskegs”).
In the direct effects Study Area, most scrub or shrub wetlands are dominated by stunted black
spruce and are similar to the forested wetlands described above. Additional species include
sweetgale (Myrica gale) and shrubby cinquefoil (Dasiphora floribunda). Groundcover
includes bluejoint reedgrass, meadow horsetail (Equisetum pratense), and marsh five-finger
(Comarum palustre). The scrub spruce wetlands in the project corridor have functions similar
to those of the spruce forested wetlands described above. One wetland dominated by shrubheight
paper birch was located in the direct effects Study Area, with bluejoint reedgrass and
meadow horsetail in the understory.
3.8.2.1.3 Sedge and grass wetlands
Wetlands dominated by sedges and grasses in the indirect effects Study Area include
saturated bogs with dense sedge and moss cover, sedge-dominated fens similar to the bogs
but where there is input of relatively mineral-rich water, and seasonally flooded marshes
along streams and surrounding ponds.
Bog- and fen-type sedge wetlands predominate in the direct effects Study Area. Tufted
bulrush (Trichophoum caespitosum), sweetgale, shrubby cinquefoil, and sedges (Carex spp.)
are dominant species in these broad flats. These sedge-dominated wetlands are often found in
the lowest areas of extensive wetlands. Bluejoint reedgrass meadows also occur in the Study
Area in small depressions.
The open meadows provide travel corridors for large mammals such as moose and bear.
Open water occurs in these meadows, providing habitat for waterfowl. Where near roads,
sedge- or grass-dominated wetlands may filter pollutants from road runoff before releasing
the water downstream. No creeks run through these wetlands, limiting the export of nutrients
or organic matter by way of these water bodies.
3.8.2.2 Knik Arm
3.8.2.2.1 Sedge wetland
A narrow fringe of coastal marsh occurs north of POA between the toe of the coastal bluff
and unvegetated intertidal mud flats of Knik Arm. This wetland has been permitted to be
filled during Phase 1 of the POA Expansion Project under Department of Army Permit
POA-2003-502-2 and is not addressed further in this analysis.
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