A new riverfront plaza at Denver’s Confluence Park is beginning to take shape as crews lower 25,000-pound precast concrete steps into place at the edge of the South Platte River.

It’s taken nearly two years to reach that symbolic milestone in the long-delayed project. Work stalled for more than a year after the discovery of coal tar buried on the river’s west bank.

But a city parks officials says the now-$9.3 million project, which resumed in August, finally has a clear path ahead.

Contractors, led by ECI Site Construction Management, are aiming to finish the plaza and new ramps for the South Platte Trail by late summer or early fall — keeping to the city’s revised timeline and budget released in July.

“From this point on, passers-by are going to continue to see more plaza coming up and out of the river,” said Michael Bouchard, the assistant director for design and construction for Denver Parks and Recreation. “It’s a critical point for us, because it means we’re past some of the critical deep foundation issues.”

The city set out to replace Shoemaker Plaza and decades-old bike ramps near the REI flagship store, while improving accessibility to the area and adding landscaping.

The plaza project’s budget last summer shot up by 86 percent after officials and contractors finished grappling with what to do to safely remove pockets of the coal tar. The substance is a byproduct of gasification common in industry a century ago, and for a time, it was buried in patches along the river.

The solution has been to remove the tar and treat all water on the site before it’s pumped over metal barriers that have held back the river since spring 2015.

In the end, crews found coal tar in a small portion of hundreds of cubic yards of dirt moved on the site, Bouchard said.

“It was a big question mark,” he said. “That was the tricky part. We had to assume and plan for the worst, and hope as we got into it that things were better than we thought. And that’s how it’s played out so far. Certainly, some was found.”

But with the plaza’s foundation dug out, he said, it’s unlikely crews will find much more.

The next challenge the contractors face is to finish installation at and below the shore, where water is being pumped out, before heavy spring rains return in three or four months. This year’s changes to the project included using precast concrete for most of the lower portions of the plaza — a rounded section of water-level steps still will be poured on site — and Bouchard says that will cut time spent “in the river” by three-quarters.

Pedestrians and bicyclists also have had curtailed access to Confluence Park, where Cherry Creek flows into the river, because of two other projects that the city says should be done in coming months.

The city has pushed back until February the completion of a project to rebuild the trail on the river’s east bank, which was damaged by spring flooding in 2015.

Another plaza on the river’s east side that serves as a main entrance of sorts to Confluence Park also has been fenced off for a private development project. In the spring, Bouchard said, developers of a 35-story, high-rent apartment building called The Confluence — which topped out this week — will reopen that plaza to the public after finishing work to connect the park to the tower’s grounds.