SOMERVILLE — Mayor Joseph A. Curtatone stood on a bridge in Union Square that can be seen from Prospect Hill, where George Washington ordered his troops to raise the Grand Union flag on New Year’s Day in 1776.
As its chief decision maker, Curtatone understands that he presides over a city that many expect will experience its largest economic growth in more than a century in the coming years. The catalyst for the expected financial boom is the $1.43 billion Green Line extension, a project that will bring new subway stations to Union Square, Washington Street, Gilman Square, Lowell Street, and Ball Square on the border with Medford, where a station will be built on College Avenue near Tufts.
From the bridge, where the new Union Square station is expected to be completed in 2017, Curtatone pointed to a gritty metal scrapyard and a used plumbing and heating supply shop next to a set of commuter rail tracks. “This will change,” said Curtatone, looking over the 3.8-acre site, where up to 600,000 square feet of new development is expected — including buildings as high as 10 stories — with the subway stop as its hub. “It’s the transformation that we all dreamed about.”
In economic terms, Somerville has been able to quantify the benefits. By 2030, the city projects that 17,300 new jobs and 3,600 residential units will be created around Union Square and at the Washington Street station nearby, which is also expected to open in 2017.
The new jobs are expected to help keep more people in the city. These days, just 15 percent of the workforce works in Somerville or lives within walking distance of Davis Square or Sullivan Square, according to the city. By 2019 — when the Gilman Square, Lowell Street, and Ball Square stations are expected to begin operating in Somerville — 85 percent of the city will live within walking distance of an MBTA station.
Investors will have a chance to redevelop 192 acres throughout the city.
“This will have a huge impact on our environment, our social fabric, and on our economy as a region,” said Curtatone.
Sheila Borges, whose family has owned the Neighborhood Restaurant in Union Square since 1983, said the Green Line extension has been the talk of the town. She thinks when the new stations open, more people will visit the city daily.
“People will be able to get in and out of here without using their cars, and we’ll get people in here who don’t have cars. It will be a lot easier for everybody,” she said.
In Medford, the city has yet to study the potential economic impact of the Green Line extension. Lauren DiLorenzo, director of Medford’s Office of Community Development, said the city is more focused on having the project completed. A proposal to further extend the Green Line to Route 16 is still being studied by the state.
To date, the state has committed $617 million to the Green Line extension. The proposed federal funding — about 50 percent of the entire project — has yet to be secured.
For a city that lost its last trolley to Boston in 1958 and was shut out of the subway system until Davis Square put Somerville on the Red Line in 1984, the Big Dig was its unlikely champion. In 1990, as part of an agreement to widen Interstate 93 next to Somerville, the state promised to extend the Green Line into the city. That promise was repeated in the ensuing decades, and finally last year, the state broke ground.
Meanwhile, the state is set to open the first new subway stop in decades at Assembly Square this summer. The Orange Line station will serve a section of Somerville that already is undergoing a $1.2 billion
development renaissance — with high-rise apartments, retail, and office space —
“Increasing affordable transportation leads to economic growth and opportunity and an improved overall quality of life,” said MBTA general manager Beverly A. Scott. “Making it easier for residents of Boston’s neighboring communities to get to both work and play in the city will provide a whole host benefits for generations.”
By giving people the option to take the light rail to work, it will cut down on car pollution — which has taken its toll on Somerville residents, especially those who live near I-93 and routes 28, 38, and 99, said Wig Zamore, a Somerville real estate project developer who has volunteered to help coordinate studies with Tufts University on the health impact of cars and diesel trains on the city’s roughly 77,000 residents.
According to Zamore, for those who live near Somerville’s highways, heart disease mortality is highest. On I-93 alone, 150,000 vehicles pass by the city each day, and up to 60,000 cars and trucks travel along Route 28 in Somerville. In addition, up to 200 commuter-rail diesel trains rumble through the city each day.
The impact of the air pollutants from the vehicles has been deadly, according to a study prepared by Zamore. Results ranked Somerville as the city with the highest rate of lung cancer and heart attack deaths in the region, with 35 excess deaths — those over the number that are statistically expected per square mile, compared with just 3 in Milford.
With the Green Line extension is expected to add 45,000 daily riders by 2030 and eliminate 25,728 daily vehicle miles from the roads, the project will reduce congestion and pollution emissions, according to Ellin Reisner, director of the Somerville Transportation Equity Partnership . Zamore, who also volunteers for the partnership, is also working with Tufts University on a new study to help improve air quality next to Somerville’s busiest roads, such as I-93.
“We’re looking at things like indoor air filtration to make sure everybody has healthy air,” said Zamore, who added that highway sound walls and green barriers also could improve the quality of life in the city.
Stephen Bremis, operations manager at Bremis Realty in Somerville, expects real estate prices will go up after people see substantial construction occurring at the new stations.
“It won’t have an impact until people see the station being built,” said Bremis. “There’s no question if you’re within half to three quarters of a mile of a Green Line stop, your prices will go up 5 to 10 percent.”
Prices already are climbing in Somerville, where the Warren Group, a Boston-based firm that tracks real estate data, reported the median sale price of a single-family home jumped nearly 20 percent from $450,000 for the first 10 months of 2012 compared with $539,000 through October 2013. Condo prices rose dramatically for the month of October, from $339,000 for 27 units in 2012 compared with $396,000 for 29 units in 2013; the median price for 2013 through October was $405,000, up from $382,500 in 2012.
With the Green Line extension and redevelopment of blocks of properties, some longtime residents have been asking how the city can maintain its traditional neighborhoods and funky squares and keep them affordable. In recent years, the city has seen an increase in the number of younger, better educated single residents. According to the 2010 US Census, 44 percent of the population is ages 20 to 34. Also, 53 percent have a bachelor’s degree or higher, compared with 41 percent in the city a decade earlier.
Howard Horton, who has lived in the city for 40 years, said some gentrification will occur as new businesses and residents enter the city. Still, he hopes the city will develop a strategic plan to retain families.
“Somerville doesn’t want to become a victim of its own success, becoming only the hip place,” said Horton, who is president of New England College of Business and Finance, an online degree program based in Boston. “It wants to be a place that retains a wide variety of types of citizenry, including a lot of families.”
As part of the new growth, the city anticipates that 20 percent of all new housing expected to be built in Somerville by 2030 — or 1,200 of 6,000 units — will be affordable.
Curtatone said the Green Line extension is not the city’s panacea. But the mayor — who recently announced a drop in property taxes for residents because of business growth — said the new subway stations will help create jobs, housing, and strengthen the infrastructure that will allow long-timers to stay.
“We want rising tides and to raise prosperity for everyone,” he said.Steven A. Rosenberg can be reached at srosenberg@ globe.com. Follow him on Twitter @WriteRosenberg.