Long-delayed efforts to restore train service on the Dumbarton Rail Corridor, which links the mid-Peninsula to the East Bay, could get a boost as Facebook looks to add housing and offices along the tracks in Menlo Park.

This spring, the San Mateo County Transportation Authority will study how to bring service to a 4.5-mile segment of the Dumbarton tracks between the Redwood City Caltrain Station and Willow Road in Menlo Park, as recommended by the Dumbarton Policy Advisory Committee. Restoring service to that segment would not require the replacement of sections of the Dumbarton Rail Bridge or major track reconstructions. (Both would be needed to restore service on the full 20.5-mile Dumbarton corridor between the Redwood City Caltrain and Union City BART stations.)

Facebook is rapidly expanding its “East Campus” headquarters in Menlo Park, where roughly 4,600 employees now work. The campus is located within walking distance of a proposed Dumbarton Rail station at Willow Road, a source of potential ridership unforeseen in a 2011 study of the project [PDF]. The company still has room to grow to 6,600 employees at the East Campus and add another 2,800 at its nearby West Campus. One parcel over, Facebook plans to add another 1,500 employees at a refurbished warehouse on a ten-building, 59-acre site purchased in September.

Facebook wants to develop up to 3,500 housing units on its East Campus parking lots and at the adjacent 56-acre Menlo Science and Technology Center, a sprawling 21-building commercial site purchased from Prologis in February. The company sees these sites, as well as another another site owned by developer David Bohannon near Marsh Road to the west, an opportunity to create mixed-use neighborhoods within a half-mile walk of potential Dumbarton Rail stations.

“We very much want to preserve the option of studying housing on the site and on our campus,” wrote Fergus O’Shea, Facebook’s director of campus facilities, in a February e-mail to members of Menlo Park’s General Plan Advisory Committee. “Housing not only would allow for our employees to live near the campus, but would also reduce traffic, increase the overall supply of housing in Menlo Park, and present an opportunity to deliver below market rate units.”

An environmental review of the proposed 4.5-mile Dumbarton Rail segment could begin this May, if planning funds are available for the project. SMCTA staff are expected to deliver a funding update on May 29.

After environmental approval, money to construct and operate the passenger rail service would still need to be raised, since the original Dumbarton Rail Corridor Project was defunded in 2014 to help pay for other regional transportation projects, including BART’s extension to Warm Springs.

If restoring Dumbarton rail service is not feasible, Facebook supports “the transformation of the Rail Corridor into a Community Transit Corridor, running from either the Redwood City CalTrain Station or Marsh Road to Willow Road,” which could include “a Bus Rapid Transit line on rubberized tracks, along with a bicycle/pedestrian trail,” according to an October letter from Vice-President of Real Estate John Tenanes.