Union Square station (Somerville)

Planned station site in December 2011 before clearing

In August 2012, the City of Somerville, MassDOT, and the MBTA reached a memorandum of agreement about the station. Through the Somerville Redevelopment Authority, the City will acquire $8 million worth of land for the station and grant the MBTA a permanent easement, while retaining the rights for transit-oriented development overhead. In return, the MBTA and MassDOT will pay for cleanup costs at the site, begin construction by the spring of 2014, and open the station no later than "late 2016-early 2017".[5]

In October 2012, the Somerville Board of Aldermen approved the Union Square Redevelopment Plan and authorized an $8 million bond, including $6 million to purchase the land and $2 million for cleanup and station planning.[6] In May 2013, the Board of Aldermen announced that the North Prospect block - a mostly industrial area bordered by the railroad tracks, Prospect Street, Somerville Avenue, and the rear of residential properties on Allen Street - had been acquired by the city via eminent domain for $4.5 million. The properties were to be vacated by August. The city also received a $1 million EPA grant to clean up one of the properties.[7] Site cleanup began in September 2014.[8]

After major cost increases due to contractors increasing costs above estimates became public in 2015, MassDOT cancelled contracts and scaled back sections of the project. A new design released in May 2016 removed direct access from the Prospect Street overpass (which required elevators, escalators, and stairs) and platform canopies.[9] In December 2016, the MBTA announced a new planned opening date of 2021 for the extension.[2] As of November 2019, a private developer will fund an elevator connecting the station to the overpass. The elevator may open later than the station.[10]

Extant steps leading to the long-gone commuter rail station

Union Square was formerly a commuter rail stop on the Fitchburg Railroad (now the Fitchburg Line). It opened in 1835 as one of the original stations on the line and was originally called Prospect Street.[11][12] Service to Somerville and Union Square stations ended on July 9, 1938, in concert with the end of passenger service on the Watertown Branch.[13][14][15] A set of steps which led to the station is still extant next to Webster Avenue.

Restoring commuter rail service to Union Square has been considered; by 2003, a stop was expected to opened within five years.[16] The 2004 state Program for Mass Transportation estimated such a station would attract 390 daily riders.[13] A Union Square commuter rail station was listed as a possibility in 2012 as an interim air quality mitigation measure in response to delays in building the Green Line Extension.[17] However, such a station would not be popular with riders from the rest of the Fitchburg Line, which is already slow due to closely spaced stations. The station could also not have been completed by the 2015 deadline, and was not supported by MassDOT.[17]