Sonoma County supervisors on Tuesday gave final approval to the sale of land on Airport Boulevard to the Sonoma-Marin Area Rail Transit district for a maintenance yard.

The district is buying the site on the southwest corner of Airport Boulevard and the railroad tracks from the Water Agency for $2.7 million.

The facility is expected to cost $15 million and is part of the overall $360 million budget for the Santa Rosa-to-San Rafael service.

Rail cars will be inspected daily, repaired and cleaned and dispatchers at the site will manage SMART's passenger trains and Northwestern Pacific Railroad Co. freight trains.

When service begins in late 2015 or early 2016, the facility will have about 100 workers.