Menlo Park transportation engineers and consultants unveiled three conceptual designs for a bike and pedestrian crossing beneath the Caltrain tracks at Middle Avenue on Monday, May 13.

Concept 1 would take up the smallest amount of land, so was established as the preferred option of the city staff. It would have a curved out-and-back ramp and a staircase, leading down about 12 feet into a tunnel with a height of about 10 feet.

Early estimates indicate it could cost between $20 million and $25 million, but with significant cost-minimization efforts, the cost could be lowered to $14 million to $18 million. It could be built using a method that limits impacts to the Caltrain line to a four-day weekend. The cost estimates cover construction, moving utilities, acquiring the needed right-of-way, design services, a construction manager, and additional expenses for the project in 2022.

Concept 2 is the most expensive option, at an estimated $35 million to $40 million. With this option, the tunnel would be lowered to a deeper level, but the construction could be done using a method that wouldn't disrupt Caltrain operations. The ramps and stairs would have to be significantly steeper to accommodate the deeper tunnel, however.

Concept 3 is similar to Concept 1, with a similar cost estimate – $20 million to $25 million – but would move the tunnel about 200 feet north of the Concept 1 location, which would minimize the impacts on the rail's crossing track. But it would require other utilities to be relocated and cause more right-of-way impacts, so cost-savings options would be more limited.

Each concept design also has options to make the ramps more curved or straight, and to make turns right angles or switchbacks.

Cost savings are relevant for this project because in the city's negotiations with Stanford, the university committed to provide $5 million or half the cost of the tunnel – back when the project was estimated to cost around $10 million.

Where the rest of the funding for constructing the tunnel would come from is a question still under discussion. According to Senior Transportation Engineer Angela Obeso, the project is currently funded by a grant from the San Mateo County Transportation Authority, which is expected to carry the project through its environmental analysis phase and plans that are 30% complete. If the tunneling portion of the project gets lined up in time for Caltrain's current electrification process, the city could also save some money, Obeso explained.

According to Assistant Public Works Director Nikki Nagaya, other funding sources include county sales tax revenue from Measures A and W, as well as private funding. The city has also asked for funds from Stanford as part of its negotiations with the university in its general use permit application process. "We have limited resources. We want to make sure we're investing them smartly," Nagaya said.

Community members in attendance at the May 13 meeting expressed preference for separate ramps for cyclists and pedestrians as well as facilities to accommodate wider e-bikes and cargo bikes. Some objected to curved ramps, bollards and tight hairpin turns.

When asked how the project would be affected by whatever the city decides to do about grade separations at the city's vehicular crossings with Caltrain, Obeso noted that it's something staff and consultants have been thinking about a lot: She's project manager of both, she said.

Whatever happens, she said, the goal is for the crossing to be compatible with a hybrid or fully elevated grade separation. The city can get this bike and pedestrian crossing built in the next two or three years, while, even in the best-case scenario, a grade separation project will take eight to 10 years to build, she explained. Having bike and pedestrian access at Middle Avenue will be a big benefit to the community during whatever construction phase lies ahead for the grade separation plans for city roads, she added.

The goal is to bring the project to the Complete Streets Commission on June 12, to the City Council in July to choose a preferred concept, and for construction to be complete around the time Stanford's new buildings are ready for occupancy, likely sometime in 2022, according to Obeso.