The 170,000-pound steel frame swung slowly over the Neponset River. A high arch settled over a long, straight stretch that will later support pedestrians and bicyclists alike joined the Mattapan path to one on the Milton side of the river.

And the Harvest River Bridge was in place late afternoon Thursday, the second of two bridges included in this stretch of the Neponset River Greenway. The bridge’s purple hue matches the canopy walk bridge in place over the Mattapan trolley tracks, which was installed over the winter.

Neponset Bridge: The Harvest River Bridge crosses the Neponset River, connecting the path between Mattapan and Milton. Photo credit Lee Toma

The lengthy riverside boardwalk will connect Blue Hill Avenue in Boston to Central Avenue in Milton. It is considered the “missing link” in the Neponset River Greenway trail between Mattapan Square and Pope John Paul Park II in Neponset.

Jessica Mink, chair of the Neponset River Greenway Council was among those occupying Ryan playground during the hours-long installation. Other community groups, including Mattapan Food and Fitness, joined DCR officials watching the proceedings.

The Greenway is a pull even for those outside the immediate neighborhood, Mink said, looking at the mountains of dirt and rock displaced by the construction.

“Everybody stays connected to it,” she said. It’s sort of a forgotten place, but it's really beautiful, and if we can make it more accessible without hurting it -- which I think this trail is going to do, even though it doesn’t necessarily look it right now standing here -- it’s really going to be a great thing for the city.”

Still to come for the 1.3-mile, $14 million extension: completing the Harvest River Bridge with Ipe timber decking, paving the general walk, and adding finishing touches like benches along the riverway path.

Project manager Stella Lensing said the whole project is expected to be completed in October, including resurfacing the field portion of Ryan Playground to an athletic grade natural turf field.