FEIS Summary - Knik Arm Bridge and Toll Authority
FEIS Summary - Knik Arm Bridge and Toll Authority
FEIS Summary - Knik Arm Bridge and Toll Authority
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The preliminary design includes plans for potential future expansion (Phase 2) when<br />
traffic volumes would warrant its completion. For the crossing, two more lanes of<br />
bridge decking could be added, without having to install additional piers.<br />
This section rendering gives an idea of what the bridge might<br />
look like. Final bridge design has yet to be determined. Future expansion (Phase 2)<br />
<strong>Knik</strong> <strong>Arm</strong> Crossing Final EIS<br />
<strong>Summary</strong><br />
Proposed crossing (Phase 1)<br />
Mat‐Su side<br />
Mat-Su<br />
~8,200 feet<br />
50 foot clearance 250 feet<br />
Anchorage side<br />
Anchorage<br />
Navigation channel<br />
Add two lanes <strong>and</strong> pathway<br />
for future expansion<br />
14,000-foot <strong>Bridge</strong> Alternative 1<br />
2<br />
Key Costs <strong>and</strong> Impacts for <strong>Bridge</strong> Alternatives<br />
8,200-foot <strong>Bridge</strong> Alternative<br />
North<br />
North<br />
Sources: Imagery from SMB June 2004<br />
MSB GIS, HDR Inc.<br />
Anchorage side<br />
0 0.25 0.5 Mile<br />
14,000-foot bridge<br />
approach 1<br />
Costs<br />
Construction<br />
Design, engineering, <strong>and</strong><br />
construction administration<br />
Contingency<br />
Total (by phase)<br />
(Note that Phase 2 includes future<br />
build-out of project through 2030)<br />
In-Water Construction Methods<br />
14,000-foot <strong>Bridge</strong> Alternative 1<br />
Phase 1: $478.8M<br />
Phase 2: 174.3M<br />
Phase 1: 69.4M<br />
Phase 2: 25.3M<br />
Phase 1: 93.2M<br />
Phase 2: 63.1M<br />
Phase 1: 641.4M<br />
Phase 2: 262.7M<br />
Barges <strong>and</strong> temporary<br />
construction trestles in mud flats<br />
(would require fill)<br />
8,200-foot <strong>Bridge</strong> Alternative<br />
(Recommended Alternative)<br />
Barges only<br />
Phase 1: $319.3M<br />
Phase 2: 85.9M<br />
Phase 1: 46.3M<br />
Phase 2: 12.5M<br />
Phase 1: 61.2M<br />
Phase 2: 31.1M<br />
Phase 1: 426.8M<br />
Phase 2: 129.5M<br />
Construction Time 3 construction seasons 2 construction seasons<br />
Number of Piers 66–76 piers 33 piers<br />
Marine Fill ~ 45 acres total ~ 90 acres total<br />
Beluga Whale<br />
(Pile driving is a key concern<br />
because pile-driving noise will<br />
adversely affect belugas most.)<br />
Essential Fish Habitat<br />
Estimated Sedimentation<br />
(silt accumulation over time around<br />
bridge approaches)<br />
• 440–508 hours pile-driving<br />
noise<br />
• Less fill in habitat<br />
• Subtidal waters ~ 0 acres filled<br />
• Estuarine shores <strong>and</strong> mud flats:<br />
~ 45 acres would be filled<br />
• 220 hours pile-driving noise<br />
• More fill in habitat<br />
• Subtidal waters ~ 8 acres filled<br />
• Estuarine shores <strong>and</strong> mud<br />
flats: ~ 82 acres would be filled<br />
20 acres around abutments 260 acres around abutments<br />
North<br />
North<br />
Sources: Imagery from SMB June 2004<br />
MSB GIS, HDR Inc.<br />
0 0.25 0.5 Mile<br />
Anchorage side<br />
8,200-foot bridge<br />
approach<br />
Exhibit S-16 The Crossing Alternatives<br />
<strong>Knik</strong> <strong>Arm</strong><br />
The 8,200-foot <strong>Bridge</strong> is part of the Recommended Alternative because:<br />
• installation of fewer piers will reduce in-water noise <strong>and</strong> other construction<br />
impacts on species inhabiting <strong>Knik</strong> <strong>Arm</strong> waters within the Project Area<br />
• shorter construction time (two construction seasons will be required)<br />
• construction cost ($426.8M total will be reasonable)<br />
<strong>Knik</strong> <strong>Arm</strong><br />
1<br />
The 14,000-foot <strong>Bridge</strong> Alternative was found to not be financially feasible <strong>and</strong> did not meet stated purpose <strong>and</strong> need criteria; however, this alternative was carried forward solely for comparative evaluation based on requests from environmental<br />
resource <strong>and</strong> permitting agencies.<br />
2<br />
Only one or the other bridge approach alternative would be constructed—i.e., the portion of the “Y” corresponding to each respective approach alternative.<br />
Exhibit S-16 The Crossing Alternatives<br />
S-33