PITTSBURGH - When Lisa Schroeder arrived here 16 years ago, she said, the city's rivers were viewed as little more than a "toxic highway."

Back then, the riverfronts were a "pretty dreary" lot as well, she recalled. Developers shied away from them. And whatever riverside amenities existed probably occurred more by accident than design.

Schroeder, former president and CEO of Riverlife, marvels at how things have changed since she first arrived from Portland, Maine. These days, Pittsburgh's riverfronts have gone from dreary to dynamic. From the North Shore to the South Side to the East End, developers who once spurned the land along the rivers now are clamoring to build on it.

A study done for Riverlife, the organization formed in 1999 to shepherd riverfront development, estimates about $130 million has been invested in trails and other improvements in the last 15 years. That, in turn, has helped to spur nearly $4.1 billion in development.

The numbers include major projects like the Rivers Casino, the David L. Lawrence Convention Center, and the North Shore attractions - PNC Park, Heinz Field, the riverfront park, and more than $140 million in investment in office buildings, Stage AE, the Hyatt Place Hotel, and restaurants between the stadiums by Continental Real Estate Cos.

And that's just on the Allegheny and Ohio Rivers.

The last 15 years also have seen the rise of SouthSide Works, the redevelopment of the old LTV steel mill on the Monongahela riverfront into an eclectic mix of offices, retail, restaurants and entertainment, and residences.

New office buildings have gone up across the Monongahela at the Pittsburgh Technology Center. And Station Square, one of the city's oldest riverfront retail and entertainment complexes, has added such features as a marina to take advantage of its location.

Some of the most ambitious projects are still to come. In all, more than $1.5 billion worth of waterfront development is in the works.

Orphans no more

The biggest is the $1 billion redevelopment of the former LTV Coke Works along the Monongahela in Hazelwood into a mix of offices, housing, and research and development space, all built around cutting-edge environmental standards.

In the Strip District, Oxford Development Co. has completed the first of four office buildings at 3 Crossings, a $160 million mixed-use development that will include 300 apartments and a 575-space multimodal transportation facility.

A few blocks away, the Buncher Co. has initiated its $450 million Riverfront Landing project, with plans to turn acres of parking into offices and apartments.

New apartments also are in the works at Station Square, on the North Shore, and in Lawrenceville, with new office buildings planned at SouthSide Works and the North Shore. Pittsburgh Technology Center soon may be home to apartments and a hotel.

With most projects will come plans for expanded riverfront trails and other features.

Riverfronts were once treated as orphans, but developers and businesses now see them as great amenities for employees, said Steven Quick, an adjunct professor of architecture and a research fellow with the Remaking Cities Institute at Carnegie Mellon University.

Quick helped put together the Allegheny Riverfront Vision plan, a blueprint for redevelopment of 80 acres stretching from the Strip District to Lawrenceville initiated by then-Mayor Luke Ravenstahl.

He hopes the plan will push waterfront neighborhoods to turn themselves "inside out," seeing the river as a front door rather than the back end.

Matthew Galuzzo, executive director of the Lawrenceville Corp., has said the Foundry at 41st project - a $35 million residential development at a former 19th-century foundry site featuring 182 luxury apartments - represented some of the first fruits of the plan.

A push from Riverlife

No organization has been more instrumental in raising awareness of the riverfronts and prodding developers to add such amenities as trails than Riverlife.

The nonprofit spearheaded the development of Three Rivers Park, the 13-mile interconnected network of trails, green space, and other improvements that includes Point State Park, the North Shore riverfront park, the Monongahela Wharf, South Shore riverfront park at SouthSide Works, Station Square, and the Rivers Casino promenade.

Vivien Li, who took over from Schroeder as Riverlife president and CEO in October, has been impressed with the city's river-related development since arriving from Boston, a town renowned for its waterfronts. She envisions the riverfronts becoming more neighborhood-like, with 24/7 living and companies maintaining offices.

Toward that end, Riverlife is focused on bringing more restaurants, restrooms, and perhaps even playgrounds to the water's edge. Li predicted more water taxis could sprout up in the next five to 10 years, noting that Uber experimented with a water-taxi service using private yachts during an annual art fair in Miami this month.

Riverlife also will be working to coordinate planning for the major park in the Strip that will involve the Buncher and Oxford properties, and provide open space, public access, and connections to adjacent neighborhoods.

The group hopes to start construction in early 2016 on a switchback ramp providing bicyclists and pedestrians direct access between the Smithfield Street Bridge and Mon Wharf, filling a key missing link in the Three Rivers Park network.

Falling behind?

But not all is well, according to former Mayor Tom Murphy, perhaps the biggest champion of the city's riverfronts and trails.

Murphy, who revitalized miles of trails during his 12 years as mayor, said the city must do more to fill missing links. Those include a connection to the Glenwood Bridge and a gap in the South Side trail near Station Square.

And while redevelopment of the Hazelwood Almono site has been on the drawing boards for more than a decade, there is still no trail through it, he noted, although work has started on a $27 million "signature boulevard" that will include bike and pedestrian connections. He said he was concerned about deterioration of the North Shore trail beyond the casino toward the West End Bridge and Alcosan.

Murphy, who now is a senior resident fellow at the Urban Land Institute, sees Pittsburgh falling behind other cities. "There are lots of cities very aggressively doing great trail systems," he said, mentioning Denver and Chicago as two examples.

On the commercial development side, Murphy said the proposed Buncher and Almono projects represent great opportunities "but stuff needs to start happening there." He expressed frustration with the lack of progress at the 178-acre Hazelwood site, owned by a consortium of local foundations.

The redevelopment was first pitched to Murphy when he was mayor.

"I just hope that someone at some point in my lifetime pulls the trigger and does something," he said.

The Regional Industrial Development Corp., which is managing the Hazelwood site, hopes to have deals in place for the first tenants in the first quarter of next year.

Riverlife, meanwhile, is working with the Army Corps of Engineers on a possible demonstration project to stabilize, revitalize, and incorporate some recreational amenities to the North Shore riverbank from Heinz Field to the West End Bridge.

A better front door

Despite the gaps and concerns, Schroeder, now president and CEO of the People and Parks Foundation in Baltimore, saw first hand in her 15 years heading Riverlife how the city and its riverfronts had changed - along with outsiders' impressions.

When she first started and told people she was from Pittsburgh, they "would search for something positive to say," she recalled.

"Now when I say I'm from Pittsburgh, eyes light up and they have wonderful things to say. I like to think the riverfronts are an important ingredient in that transformation."