FEIS Summary - Knik Arm Bridge and Toll Authority

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Knik Arm Crossing Final EIS Summary regarding this alternative’s potential to adversely affect beluga whales. FHWA identified the 8,200-foot-long pier-supported bridge as the Preferred Alternative in the Draft EIS because, in addition to its constructibility (lower construction costs, shorter construction time), a shorter bridge will have fewer piers, resulting in less construction noise and shorter in-water construction time. Less noise and shorter construction time mean less potential to disrupt beluga whale behavior and movement patterns. As discussed above, this bridge alternative is not expected to affect tidal flows or naturally occurring sedimentation in the vicinity of the POA. Identification of Recommended Alternative FHWA identified the 8,200-foot-long Bridge Alternative as the Recommended Alternative for the reasons noted in the “Comparison of Impacts” section, above. Based on agency comments on the Draft EIS and results from additional hydrodynamic modeling, close agency coordination will continue during the design and permitting stages. Anchorage Description of Anchorage Alternatives The Draft EIS evaluated two Anchorage approach alternatives: Degan Alternative and Erickson Alternative. As Exhibits S-17 and S-18 depict, the logical termini for both alternatives is the intersection of the A-C Couplet with 3rd Avenue during Phase 1 (opening day) and the intersection of the Ingra-Gambell Couplet with 3rd Avenue during Phase 2. For either alternative, construction of Phase 2 would occur as traffic volumes warrant. Exhibit S‐19. Transportation Features and Traffic Flow Characteristics Degan Alternative Erickson Alternative (Recommended Alternative) Phase 1 Includes a 790-foot-long, four-lane, cut-and-cover tunnel under Degan Street, connecting to East Loop Road with an at-grade signalized intersection south of the existing intersection with Hollywood Drive. Motorists use East Loop Road to drive to the A-C Couplet. Traffic from the KAC bridge has access to Government Hill through the at-grade signalized intersection with East Loop Road south of the existing Hollywood Drive intersection. The alternative, up to the intersection, has a design speed of 50 mph. Controlled-access ROW varies along the alignment as necessary. Intersections and ramps vary from 125 to 1,000 feet. Includes a 790-foot-long, two-lane, two-way, cut-andcover tunnel under Erickson Street, connecting to the A-C Couplet by way of East Loop Road. Ramping would be provided to allow access to the Government Hill neighborhood. East Loop Road is modified for the south tunnel approach. To maintain free-flow traffic, two on/off ramps are constructed between East Loop Road and Government Hill. Traffic from the KAC bridge has access to Government Hill through two on-off-ramps constructed on the north side of the two-lane, two-way, cut-and-cover tunnel. The design speed is 70 mph, transitioning to 50 mph north of Government Hill prior to the tunnel. Controlled-access ROW varies along the alignment. Intersections and ramps vary from 125 feet to 600 feet. (continued on next page) S-12
Knik Arm Crossing Final EIS Summary Exhibit S‐19. Transportation Features and Traffic Flow Characteristics (continued) Degan Alternative Erickson Alternative (Recommended Alternative) Phase 2 Phase 2 modifies Phase 1 construction to allow a connection to a viaduct traversing the Ship Creek industrial area to tie into the future Glenn-Seward Highway-to-Highway Connection (proposed by the Municipality of Anchorage in its 2025 LRTP) at the Ingra-Gambell Couplet and 3rd Avenue (EIS Figure 2.35). The signalized intersection constructed in Phase 1 is removed and East Loop Road is elevated to cross over the Degan Alignment to facilitate free-flow traffic from the proposed KAC bridge to the Ingra-Gambell Couplet. Government Hill and A-C Couplet through-traffic has access to or from the KAC bridge by way of ramps on the north side of the tunnel. Mat Su and A-C Couplet through-traffic uses Government Hill surface streets and a signalized intersection at Loop Road and Hollywood Drive to continue down East Loop Road and gain access to the A-C Couplet. Traffic traveling north from the Ingra-Gambell Couplet uses ramps to gain access to Government Hill. Phase 2 necessitates an additional tunnel with four more lanes. The tunnel expansion (two additional parallel tunnels with six total lanes needed for Phase 2) then connects to the proposed viaduct that traverses the Ship Creek industrial area and ties into the future Glenn-Seward Highway-to-Highway Connection (proposed by the Municipality of Anchorage in its 2025 LRTP) at the Ingra-Gambell Couplet intersection with 3rd Avenue. Some alignment modifications of the initial construction and additional ramp construction are necessary to allow free-flow of traffic to the termini at the A-C and Ingra-Gambell Couplets. Government Hill traffic gains access to or from the KAC bridge by way of ramps on the north side of the tunnel. A-C Couplet through-traffic has access to the KAC bridge through the two-lane, two-way, cut–andcover tunnel, bypassing Government Hill. Mat Su and A-C Couplet through-traffic uses the free-flow condition, two-lane, two-way tunnel through Government Hill to gain access to the A-C Couplet. Traffic heading north from the Ingra-Gambell Couplet does not have direct access to Government Hill. Northbound Government Hill traffic needs to travel west to the A-C Couplet and then use ramps from the A-C Couplet to gain access to Government Hill. The existing lanes of the southbound East Loop Road at Hollywood intersection are not changed from what presently exist—two lanes, with the left lane having a left turn or through-movement and the right lane allowing a right turn onto Erickson Street or a throughmovement. The alternatives’ locations were selected because their topographic and site conditions would be conducive to constructing a cut-and-cover tunnel less than 800 feet long (a controlling design feature). A cut-and-cover tunnel is proposed to minimize impacts to the Government Hill community. The Draft EIS did not identify either Anchorage approach alternative as preferred, and, during the Draft EIS review phase, FHWA requested comment on the Anchorage approach alternatives to assist the agency in selecting an alternative. Comparison of Traffic Characteristics Exhibit S-19, on pages S-12 through S-13, describes the alternatives in more detail by comparing the key features and S-13
Page 1 and 2: Knik Arm Crossing Final Environment
Page 3 and 4: Exhibit S‐1. Final EIS Document O
Page 5 and 6: Knik Arm Crossing Final EIS Summary
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Page 15 and 16: Exhibit S‐22. Reasons for Preferr
Page 17 and 18: Findings, Compliance, and Permits E
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Page 33 and 34: The preliminary design includes pla
Page 35 and 36: Summary Initial Construction (Phase
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Knik Arm Crossing Final EIS Summary
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FEIS Summary - Knik Arm Bridge and Toll Authority

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