3.0 Affected Environment - Knik Arm Bridge and Toll Authority

Knik Arm Crossing DraftFinal EIS
Affected Environment
• plan for future development of the port district and wise utilization of its coastal
resources
The Point MacKenzie AMSA Plan identifies as one of its 12 issues, “providing access
between Point MacKenzie and the Anchorage area.” To address this issue, the plan set forth
Goal 2.5: “Develop a direct transportation connection between Point MacKenzie and the
Anchorage urban area as the need arises.”
The plan goes on to state that “The Knik Arm Crossing proposal … could in the future be
very important to the future growth and development of the Point MacKenzie area by
improving access to the heavily populated areas across Cook Inlet.” Applicable enforceable
policies are listed and discussed in Section 4.8.6.
3.8.6.3 Anchorage
3.8.6.3.1 Anchorage Coastal Management Plan
The Municipality of Anchorage approved its first Coastal Management Plan in 1980 and
subsequently updated the plan in 1982, with the addition of the Anchorage Wetlands
Management Plan. In 1987, the Anchorage CMP was revised with additional maps but no
substantive changes to the policies or standards (MOA 1987). The Municipality is currently
revising its CMP to comply with the 2003 ACMA amendments and 2004 ACMP regulatory
changes. A revised CMP is scheduled for release in March 2006. For this Draft EIS, the 1987
enforceable policies will be used. Applicable enforceable policies are listed and discussed in
Section 4.8.6.
3.8.7 Habitats
3.8.7.1 Marine habitat
3.8.7.1.1 Intertidal zone
The most prevalent intertidal habitat types within Knik Arm are mud and sand flats, which
usually begin at the mid- to lower intertidal zone. 41 From Eagle Bay and Goose Bay
southwest, intertidal substrates vary above elevations of about +4 to +6 feet MLLW. In
general, the middle and upper beaches north of the POA, on the southern shore, and north of
Point MacKenzie, on the northern shore, consist of gravel and cobble mixes with occasional
bands of sand at the high tide line and more widespread silt/clay deposits in the middle
intertidal range. The extreme conditions of tide, currents, icing, and beach instability result in
a very low primary productivity on the beaches and in the water column (e.g., Bakus et
al. 1979; FHWA and ADOT&PF 1983a).
Field observations completed for this project indicate that intertidal habitat and vegetation of
the upper beach on the east side of Knik Arm consist of gravel and cobble with scattered
larger boulders (KABATA 2005b). The middle beach is composed of soft or hard clay, while
the lower beach often has large boulders and a broad and irregular gravel, boulder, and sand
41 In general, the intertidal zone is the area between highest observed tide and lowest observed tide.
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