Work is proceeding this fall on a 1.3 mile extension of the Neponset River Greenway. Above, a Department of Conservation and Recreation supervisor walked along the trail on the Mattapan side of the Neponset River on Monday. The $14 million segment will be completed next spring, according to current projections. Jennifer Smith photo

The elaborate riverside boardwalk connecting Blue Hill Avenue in Boston to Central Avenue in Milton – the “missing link” in the Neponset River Greenway trail between Pope John Paul Park II and Mattapan Square – is under construction and expected to be completed by spring 2016.

On Monday, Department of Conservation and Recreation officials took the Reporter on a tour of the long-awaited 1.3 mile stretch that will fill in the public way.

The project, estimated to cost $14 million, is “on schedule and more or less on budget,” said project manager Stella Lensing. Costs are higher than initially expected due, in part, to the “canopy-walk” portion, which will rise 18 feet above the ground over the trolley tracks at the Mattapan Square T station.

This section has been a complicating factor as it involves raising the path over the trolley line and bus station, grading its descent, and cantilevering it across the river bank to where it ends near Mattapan Square at Blue Hill Avenue. The overpass route is the result of a compromise between the MBTA and the DCR, after the T opposed an at-grade crossing at the station.

The former comfort station at the Blue Hill Avenue intersection has not yet been designated for a specific use. The DCR is not actively soliciting proposals for the space, Lensing said, but the agency is open to community members reaching out with suggestions.

Access to the riverwalk is available from several points, including from the Ryan Playground field, the playground parking lot, and the Mattapan T station, from which pedestrians will climb to the raised canopy-walk section. The MBTA insisted on access from the station, Lensing said.

“There’s so much enthusiasm for this from the community,” Lensing said, reflecting the years of discussions between Dorchester, Mattapan, and Milton residents to expand this much-used path from Central Avenue. Standing amid the concrete pillars that will support the canopy-walk, she estimated that the project is between 30 to 40 percent complete.

Along the trail, which has been cleared out by community members, the river laps at the bank a few yards away, with new apartment buildings and the playground abutting the Mattapan side of the path.

On Monday, support structures were rising from the dirt, where construction has been underway since early this year. A dramatic arched bridge, similar in style to the Blue Heron Bridge in Waltham, will cross the Neponset and join the path at a trail already in place on the Milton side of the river.

The canopy-walk unit and the bridge will both be installed in single chunks lifted by cranes, Lensing said. Like the rest of the walk, which traces an informal path through the woods along the riverbank, they will measure 10 feet across and be made of burnished, red, wood-like material.

Work will continue throughout the winter, weather permitting, with temporary shut-downs of the trolley line possible as the canopy-walk is constructed. The DCR expects the canopy portion to be completed by late winter, with the span, to be called the Harvest River Bridge, installed in the spring.

For the duration of construction, the Ryan Playground field will remain covered with displaced dirt, metal, and large rocks. The dirt will be replaced along the trail, and under the skywalk, with the rocks placed on the bank for drainage purposes. In the end, a grass playing field will sprawl out behind the tennis courts, Lensing said, which should be ideal for soccer.

Officials discussed two other Greenway projects on Monday:
• A section of the Lower Neponset Trail between Granite Avenue and the Shawmut Junction Bridge had fallen victim to various adverse conditions and was shut down, but it has since been repaired and pedestrian access restored.

• The proposal for a cantilevered walkway connecting Victory Road and Morrissey Boulevard along Tenean Beach around the gas tank is on hold pending funding, Lensing said.

In addition, the land on which the trail would be constructed is owned by National Grid, granted to the DCR through an easement. Though the department is staying up-to-date on the design and permitting side of the process, no construction is slated to begin at this time, Lensing said.