Marin planners propose review of I-580 connector options

Marin transportation planners are working to weed out weaker project options in an effort to streamline environmental review of a proposed connection between northbound Highway 101 and eastbound Interstate 580 in San Rafael.

For more than two years, Transportation Authority of Marin staffers have focused their attention on four project alternatives that propose flyovers varying in height and length linking the highways around the area of Bellam Boulevard and Andersen Drive.

After a closer analysis, staff concluded that two of those options raise too many questions about cost, gridlock and aesthetics. TAM staffers are asking the Board of Commissioners on Thursday to discontinue its study of those alternatives.

Staff also wants to throw into the mix a new option that proposes improvements on Bellam Boulevard, but with no direct connector between the freeways. The new alternative “7” is expected to be considerably less expensive.

The agreed upon alternatives would then be studied in a formal environmental impact report, or EIR. A scoping session is planned this summer.

“We really thought it was important to head into the EIR process with a more streamlined approach, taking into account the local feedback we received,” said Anne Richman, executive director of TAM. “We’ve done a fair amount of outreach and we really wanted to reflect that in the options we’re bringing forward.”

The four project alternatives were narrowed down from 13 options.

One known as “Modified 3B” is among the two that could be headed to the chopping block. Costing an estimated $200 million, the proposal would add an exit lane from Highway 101 that connects to Interstate 580 via a newly created eastbound offramp. Studies showed the configuration could create offramp backups, and the proposal garnered little community support.

Project alternative “6,” which also could be cut, is the most expensive option estimated at $315 million. It would call for a 60-foot-high flyover structure crossing Andersen Drive above the Golden Gate Transit bus facility.

The height raised concern about aesthetics, and Golden Gate Transit officials worried there could be potential impacts to its bus lot. The high cost could also potentially delay the project, TAM staff said.

Richman said these two project alternatives “don’t really offer any significant benefit from the other alternatives.”

With that in mind, staffers said they are still interested in considering project alternatives “2” and “3A.”

Alternative “2” proposes a flyover between Cal Park Hill and the Bellam Boulevard exit that crosses Andersen Drive and follows Simms Street to merge onto Interstate 580. That option costs $241 million.

Alternative “3A” is the least expensive option at $192 million. It proposes a connector near Bellam Boulevard that crosses over the existing northbound Highway 101 and eastbound Interstate 580 offramp.

Each of the options also include improvements on the Bellam Boulevard corridor. Those upgrades on Bellam are being proposed as the new standalone alternative “7.” A direct connection between the freeways is not part of the plan.

The improvements that would be included involve replacing the eastbound 580 bridge over Bellam Boulevard, transit improvements, as well as intersection and bicycle and pedestrian upgrades between Andersen Drive and Kerner Boulevard.

“The series of local improvements in the Bellam corridor area will provide significant benefits on travel times, regional traffic and local traffic,” Richman said of the newly proposed alternative “7.”

“That also contributes to the reason to drop the two alternatives ‘Modified 3B’ and ‘6,’” Richman said.

As it stands, northbound Highway 101 drivers must use Bellam Boulevard in San Rafael or Sir Francis Drake Boulevard in Larkspur to get to Interstate 580 and onto the Richmond-San Rafael Bridge. The regional traffic clogs local streets with backups into communities.

If there is no project, traffic patterns on northbound Highway 101 are expected to get worse, increasing the travel time between the Tamalpais Drive interchange and the Bellam Boulevard exit from 13 minutes to 25 minutes by 2040, according to TAM.

Officials have secured $135 million in Regional Measure 3 funding and $16.5 million in Measure AA funding for the project.

San Rafael Mayor Kate Colin, who is a member of the TAM board, said city officials are pleased that the local improvements on Bellam Boulevard are being considered.

“The traffic data shows that these improvements will improve travel times for both commuters and local residents,” Colin said. “In addition, the timeline is shorter for implementation, so the benefit will be realized sooner.”

“The city is committed to working with our partner agencies to find effective and near-term solutions and believe the Bellam corridor alternative is an excellent option,” Colin said.

The board meets at 5:30 p.m. Thursday in the Board of Supervisors chambers at the Civic Center in San Rafael. Meeting information is at tam.ca.gov/.

Additionally, TAM staffers are leading a separate $9.1 million project to add a lane and improve traffic flow at the existing Bellam Boulevard offramp. That project is being designed and is expected to be ready for construction this fall.

TAM has secured about $5.2 million for the project, including $4 million from Measure A and AA tax dollars.