North Shore Infrastructure - It's More than New Stadiums
by Geoffrey B. Nara, P.E., L.A. Pittsburgh Section

Several new jewels are rising on the Pittsburgh skyline, with their construction adding to the excitement of an already vibrant city. Two that get a lot of attention as they take shape on the North Shore, across the river from the city's central business district, are the new Pirate's baseball field, PNC Park, and the new Steelers Stadium for football. It's easy to loose sight of the other critical engineering efforts going on at ground level, the North Shore Infrastructure Project.

The project encompasses all roadway, utility, and infrastructure improvements associated with construction of the new sports stadiums. But it needed to be more than that. The North Shore infrastructure work is intended to extend Pittsburgh's downtown area across the Allegheny River to include the North Shore. Streets, sidewalks, lights, trees and utilities are integrated into the designs, intended to expand the downtown area across the river and to provide for future development of the site between the new stadiums. Project amenities include granite curbs throughout the project, brick cross walks, decorative pedestrian and street lighting, and the use of various species of trees to accentuate the new facilities and provide mixed fall coloration throughout the project.

From the outset, the project was a coordination challenge. In addition to the existing surface streets, which were to be modified for the new sports facilities and planned future development, elevated approaches to several linked highways cross the site on overhead structures. Underground are existing electrical duct banks servicing the city, water, sanitary and storm sewers, and thermal lines servicing the existing Three Rivers Stadium, in addition to all the new utilities servicing the new stadiums. Two 120" sanitary sewers cross the site, one 30' deep brick sewer (constructed around the turn of the century) and the other 120" sewer which was tunneled approximately 100' deep, crossing nearly under an existing pedestrian underpass structure. Adding to the challenge, an ongoing improvement to Pittsburgh's riverfront parks along the Allegheny River in the project area needed to be accommodated in the designs.

Initially, all the roadways in and around the site were developed as a single project. As the plans progressed, it became apparent that to accommodate existing traffic and construction of the new stadiums, the roadway system as initially planned would be inadequate. Furthermore, the existing system did not provide sufficient space for the park improvements proposed along the riverfront. The plans were subsequently developed as four separate construction phases, each to address specific construction sequencing.

• Phase 1 was developed to accommodate the opening of PNC Park on March 31, 2001. A new connector street, perpendicular to the river, was added to the infrastructure to provide traffic relief for closure of existing roadways during future construction phases.
  
  
• Phase 2 was also designed to accommodate the opening of PNC Park. Phase 2 included relocation of the main circulation roadway around the stadiums, North Shore Drive, further north away from the Allegheny River through an existing parking lot to provide room for the riverfront park. It was also critical to the schedule to relocate the roadway in advance of riverfront park construction for the opening of PNC Park
  
  
• Phase 3 consisted of the roadways around Steelers Stadium and through the existing Three Rivers Stadium. This section was realigned to provide room for a future "great lawn" area adjacent to the Allegheny River near the new Steelers Stadium, adding to the riverfront park feature. Another key roadway was also realigned to provide space for a future amphitheater. This section was designed, from preliminary through final design in three months, to accommodate demolition of Three Rivers Stadium in early 2001 and opening of Steelers Stadium in August of 2001.
  
  
• Phase 4 is a pedestrian underpass structure carrying North Shore Drive over the pedestrian walkway from the riverfront park to the new Steelers Stadium. The structure was initially a single span structure that evolved into a three-span steel continuous multi-w-beam structure. The beams are sized and the steel details along the parapets were designed to match the steel shapes used throughout the Steelers Stadium. In addition, the skew angles of the abutments as well as the piers vary based on splay lines from the center of the stadium. The structure is clad with stone veneer matching the stadium. Phase 4 was designed to accommodate the construction schedule of the bridge, to be opened by the first Steeler game in the new stadium in August 2001.

Three separate sewer projects were bid: one sanitary project and two storm projects. The sanitary sewer project involved placement of deep sewers, a portion of which were jacked and bored from a downshaft along the Allegheny River. A 42" storm sewer was jacked and bored nearly 700'. Another advanced storm system connected an existing outfall to the Allegheny River, with the new roadway system designed to accommodate construction of a stormwater detention basin required for demolition of Three Rivers Stadium.

As with any project of this magnitude that also has an extremely aggressive completion schedule, total commitment is required by all parties. The City of Pittsburgh Department of Engineering and PennDOT District 11-0 especially deserve tremendous recognition for cooperating and providing timely reviews and approvals, enabling the project to move ahead on schedule.

Although the two stadiums get nearly all the attention, significant effort is being spent to ensure that construction proceeds smoothly, that sports fans will have good access to the facilities, that utility service meets all the user's needs, that the new riverfront park improvements will be able to be enjoyed year-round, and that all these pieces "fit" together. The North Shore Infrastructure Project does all this successfully. People will notice this extension of downtown Pittsburgh.

With thanks to Michael Baker Jr., Inc. for their support and information in the development of this article.