FEIS Summary - Knik Arm Bridge and Toll Authority

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Knik Arm Crossing Final EIS Summary Richardson from the roadway will be controlled access. The roadway will include construction of an intersection to allow northern access to the POA. Exhibits S-10 through S-14 show the ROW to be acquired, the locations and types of structures that will be the subject of relocation decisions, and the entities that will have the option of being acquired (with compensation) or of being temporarily relocated during construction. Right-of-way acquisitions for Phase 2 are not scheduled until future development of the Anchorage Approach, however, advance ROW acquisition and relocation may be made available during Phase 1 for hardship cases, protective purchases, or property owners requesting advanced acquisition. In Phase 1, the cut-and-cover tunnel will be a minimum of two lanes wide (Exhibits S-11 and S-12). Roadway on and off-ramps will be constructed north and south of Government Hill. Traffic will flow freely between East Loop Road and the roadway (i.e., no traffic signal will be required). In Phase 2, the cut-and-cover tunnel to be constructed along the Erickson Street alignment during Phase 1 would be expanded to the east (Exhibits S-13 and S-14) to accommodate an additional four lanes of traffic for the increased traffic volume and to facilitate connection with the Ingra-Gambell Viaduct. The first two lanes would continue to provide free-flow traffic through the tunnel to and from East Loop Road. The additional four lanes would provide free-flow traffic through the tunnel to and from the Ingra-Gambell Viaduct. On- and off-ramps would be expanded north of Government Hill. No direct access would be available between Government Hill and the Ingra-Gambell Couplet. Note that the Phase 1 design calls for a sidewalk along the west side of the roadway from the cut-and-cover tunnel south to the existing A C Viaduct. In Phase 2, that sidewalk would be connected to a multiuse path which will be constructed on the west side of the roadway, and which would extend north over the cut-and-cover tunnel, to the bridge, and along the roadway on the Mat-Su side. No sidewalk or path is planned as part of the Ingra- Gambell Viaduct in Phase 2. Reasons for Selection of Recommended Alternative The EIS provides a detailed discussion of each reasonable alternative’s direct, indirect, cumulative, and construction impact on the natural and human environment. The discussion that follows presents distinguishing characteristics of the reasonable alternatives and reasons for the selection of the Recommended Alternative. This information is presented tabularly and graphically in Exhibits S-15 through S-18, beginning on page S-32. Mat-Su Alternatives Comparison of Impacts The EIS evaluated two Mat-Su approach alternatives: the Point MacKenzie Road Alternative and the Northern Access Alternative (see Exhibit S-15). Wetlands impacts, ROW impacts, and construction costs are similar across both alternatives, as summarized in the “Key Costs and Impacts” table included on the exhibit. Of the 92,580 acres of wetlands in the Mat-Su Borough, only 0.004 percent would be affected by the project. Both alternatives were located to avoid wetlands and minimize impacts to wetlands when avoidance was not possible. Because of the undeveloped nature of this area, no residential or business acquisitions or relocations would be required under either Mat-Su side alternative. S-10
Knik Arm Crossing Final EIS Summary FHWA identified the Northern Access Alternative as the Preferred Alternative in the Draft EIS for the alternative’s consistency with Mat-Su Borough and Port MacKenzie planning objectives (wetland impacts, ROW impacts, and construction costs are similar under both the Point MacKenzie Road Alternative and Northern Access Alternative). The Northern Access Alternative will remove through-traffic from Port MacKenzie operations, will be more conducive to Port MacKenzie development, and is favored by Mat-Su Borough and Port MacKenzie officials. Identification of Recommended Alternative No adverse comments were received during the Draft EIS comment and review period regarding the identification of the Northern Access Alternative as the Preferred Alternative. The Northern Access Alternative has been identified as the Recommended Alternative for the reasons noted in the “Comparison of Impacts” section, above. Crossing Comparison of Impacts Two bridge crossing lengths were evaluated for the Southern Alignment Crossing of Knik Arm: a 14,000-foot, 3 pier-supported bridge spanning the entire width of the arm, and an 8,200‐foot, pier-supported bridge with armored, 4 gravel-fill roadway sections 3 The 14,000-foot bridge length was found to not be financially feasible and did not meet stated purpose and need criteria. This alternative was, however, carried forward solely for comparative evaluation based on requests from environmental resource and permitting agencies. 4 Armor rock (3–5 feet in diameter) will be placed on the slopes of the gravel-fill roadway sections to prevent undercutting and erosion resulting from tidal currents, storm surges, wave run-up, and ice floes. completing the Crossing. 5 Either bridge length (see Exhibit S-16) could cross the intertidal zone perpendicular to the shoreline and connect to either Mat-Su side alternative. In the EIS, the Study Team considers the project’s impact to hydrologic and sedimentation processes of Knik Arm. Through alteration of natural tide-driven flows in their immediate vicinity, both bridge crossings studied are capable of disturbing hydrologic and sedimentation processes. Neither bridge alternative, however, is expected to affect tidal flows or naturally occurring sedimentation in the vicinity of the POA. As the table on Exhibit S-16 shows, construction costs, construction time and methods, the use of and impact from more fill versus the driving of more piers, and impacts to essential fish habitat and to beluga whales, are key impact categories evaluated in the EIS. While the 8,200-foot Bridge Alternative will have a lower construction cost and will be easier to construct, it will also be associated with more marine fill placed in essential fish habitat (including subtidal waters, estuarine shores, and mudflats). More fill, however, means fewer piers to be driven. The 8,200-foot Bridge Alternative will require only about half the number of piers as would the 14,000-foot Bridge Alternative. Fewer piers also means a shorter duration of pile-driving noise, a key consideration 5 An intermediate single-embankment option was also considered, consisting of a 1,400-foot, gravelfill portion of the bridge crossing on the west side of Knik Arm with a 12,500-foot pier-supported bridge linking to the eastern shoreline. This option was not carried forward for further evaluation because of high operation and maintenance costs and because its estimated cost-to-impact ratio suggests that it would likely achieve only a marginal cost savings as compared with the 14,000-foot bridge alternative and would do so without reducing environmental impacts below an intermediate level. For more information please refer to KABATA’s Crossing Options Technical Report (2005d in the Draft EIS). S-11
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FEIS Summary - Knik Arm Bridge and Toll Authority

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