SCARBOROUGH — The Eastern Trail Alliance announced Tuesday that it is close to a fundraising goal that would allow the trail to run 16 miles uninterrupted from Bug Light in South Portland to Saco.

The alliance needs just over $600,000 to complete a $3.8 million capital campaign that would allow for construction of a difficult section of the trail that spans a railroad track and the Nonesuch River.

The Eastern Trail is envisioned as a 64-mile off-road bike-and pedestrian path reaching from South Portland to Kittery. Already 22 miles of the trail runs through portions of South Portland, Scarborough, Old Orchard Beach, Saco, Biddeford, Arundel and Kennebunk. The non-profit Eastern Trail Alliance and the municipalities along the southern Maine coast are behind the effort to extend the trail.

By far the trickiest section to build is the 1.6-mile stretch that will run over the Pan Am Railroad and the Nonesuch River in Scarborough, said Dan Bacon, Scarborough’s town planner and a member of the alliance.

“Getting over the railroad is a huge feat for many different reasons,” said Carole Brush, the Eastern Trail Alliance executive director. “Obviously crossing an active rail line with a trail that has to be … made a certain grade and also has to be a certain number of feet above the railroad tracks makes it a really long bridge. It will be longer than the Eastern Trail bridge over the (Maine Turnpike). The trail will then be wonderful for recreation and commuting on a section of the trail that is heavily used.”

The Eastern Trail Alliance estimated through a 2014 survey that roughly 90,000 people use the trail annually and spend a total of $1 million while using it, Brush said.

The 1.6-mile section will connect the trail from the Wainwright Sports Complex in South Portland to the other side of the Nonesuch River in Scarborough off Black Point Road.

Roughly $2 million of the estimated $3.8 million cost of the project will go toward the railroad bridge due to the bridge’s height – rising 20 to 22 feet above the tracks, said Bacon, who has worked with the engineering firm – HNTB Corporation of Westbrook – that designed the new section of trail.

The bridge over the Nonesuch River, which can use existing stone abutments, will cost around $100,000, Bacon said.

The 1.6-mile section also will cut through wetlands, three private residential properties and land owned by Central Maine Power. The alliance is working on securing easements.

“We’ve been working with private landowners and knitting together a passable route for this trail that will have minimal impact,” said Scarborough Town Manager Tom Hall. “There are three landowners and there have been hurdles to get over, but I’m confident we will.”

The project received $1.5 million from the Maine Department of Transportation and $1.2 million from the Portland Area Comprehensive Transportation System, a federally mandated organization that works to improve transportation in Greater Portland.

Joyce Taylor, the Maine transportation department’s chief engineer, said there’s no time frame for the alliance to secure the $1.5 million grant.

“I think it’s a very important section and it helps close the gap in an area where we think people will get the most use and it will really make a difference,” Taylor said. “We’re in it for $1.5 million if they’re willing to match it. We want to see this done. We want to work with them. They’re showing a great effort.”

The campaign also received $216,000 this year from the town of Scarborough as well as $44,000 from the town in 2014. South Portland contributed another $26,000, and the alliance contributed and raised $100,000 through donations, Brush said.

Jessy Brewer, 18, grew up in Portland and only discovered the Eastern Trail in the last year. But as she walked along it Tuesday she said she’s fallen in love with the quick escape it provides, putting her deep in nature within minutes from her door.

“I wish we had something like this near home when I was growing up,” Brewer said. “All we have in Portland in pigeons. There is so much wildlife here: foxes and chipmunks and all the beautiful birds in the marsh. I’ve never seen anything like it.”

As Scarborough High sophomore John Goff ran along the trail in the rain Tuesday, he got a lift to learn the trail soon would extend into South Portland and on to Casco Bay.

“Wow, I’m psyched. Our track team runs along it all the time and normally we go (across the Scarborough Marsh),” Goff said.

He mused about the excitement of running all the way to Bug Light from his high school.

“We definitely would take it the other way,” Goff said. “It would be something different. On our long days we go six miles, sometimes the older runners go 10. We certainly could run as far as the ocean.”