California Department of Transportation  >  District 4 Home Page The alternatives to be considered in the environmental document include construction of a two-lane tunnel north of the existing bores (Alternative 2N), construction of a three-lane tunnel north of the existing bores (Alternative 3N), and a “No Build” Alternative. Tunnel Alternative “2N” This alternative envisions construction of a new tunnel with two westbound lanes and standard shoulders on an alignment north of the existing tunnels. The proposed tunnel would have two mixed-use 12-foot lanes, a 10-foot shoulder on the right, a 5-foot shoulder on the left, a 3-foot emergency walkway on the south, and a 2.5-foot emergency walkway on the north side of the tunnel. The total tunnel width would be 44 feet and the length would be approximately 3,389 feet. Tunnel Alternative “3N” This alternative envisions construction of a new tunnel with three westbound lanes and standard shoulders on an alignment north of the existing tunnels. The proposed tunnel would have three 12-foot lanes, 10-foot shoulders on each side of the tunnel, a 3-foot emergency walkway on the south, and a 2.5-foot emergency walkway on the north side of the tunnel. The total tunnel width would be 61 feet and the length would be approximately 3,389 feet. "No Build" Alternative This alternative represents existing conditions with no project-related construction. It would not provide any improvements to existing Route 24, nor would it provide any relief for traffic congestion and delays, which are expected to increase substantially during the next twenty years. The “No Build” Alternative provides the baseline for existing environmental conditions against which other alternatives are compared. Additional alternatives were considered during the early stages of the environmental process, however, they were not carried forward to the environmental review process because they were not feasible alternatives. Criteria used to screen alternatives included preliminary costs, traffic operations, timeframe to complete construction, geotechnical considerations and environmental impacts. A preferred alternative will be identified in the final environmental document. Home | Project Overview | Alternatives | News & Library | Glossary | FAQs | Get Involved | Contact Us Caltrans District 4 Home | Caltrans Information | Bay Area Projects ©2005 Caldecott Improvement Project. All rights reserved.