During the planning and design phase, the program’s engineers worked to obtain and use all available information about existing and planned utilities in the area. This included reviewing utility atlas information, obtaining topographic and subsurface utility surveys, performing manhole inspections and reconciling those observed conditions with records to help confirm routing. This information allowed for a more detailed and well-thought-out engineering design plan for both the civil work and electrical tasks.
Once preliminary routing was established, extensive test hole work was performed to confirm exact locations and depths of utilities at critical areas in the design. Because of the unique hazards when working underground, a focus was placed on addressing risks and identifying internal team members who had the experience to properly manage and mitigate those risks. With coordination of public, municipal and other utilities a key aspect of the project, Burns & McDonnell brought on a full-time utility coordination manager with a critical focus on safety. The program team also worked closely with local subcontractors and selected partners with a track record of safe execution of similar work.
The cable scope included work on dozens of circuits, with voltages ranging from 600 V to 23-kV. In total, this included more than 51,000 linear feet of new cable and associated splices within the new manhole and conduit systems. Complicating the electrical work on the program was the interconnection of the new cable into the existing system. Many circuits branch off multiple times and are comprised of several different cable types, so special attention had to be paid to successfully re-connect into existing cable.
In some areas, existing underground utility congestion made new cable distribution and manhole installation impossible, such that dozens of existing brick manholes had to be carefully demolished and rebuilt larger in place in order to accommodate the new cables. Engineering and construction teams closely coordinated this effort and others, with safety top of mind at all times.
As a crucial part of the work, installing new manholes, cables and services had to be performed while minimizing customer power outages. Regular status calls and outage tracker technology was used to help the team plan outages in a proactive, strategic way to cause the least amount of disruption to DLC’s customers.
To help make working conditions safer, extensive maintenance of traffic planning and close coordination with other entities who shared the right-of-way was critical. Burns & McDonnell and DLC hosted weekly meetings with the City of Pittsburgh and all affected utilities, with the Burns & McDonnell utility coordinator managing the work map for the area. This coordination effort was key to keeping the public safe and informed, in addition to helping all utilities meet their scheduled commitments ahead of the roadway work.
Results
This major infrastructure investment will enable DLC to continue fulfilling the electricity needs of Pittsburgh — home to more than 300,000 residents as well as Duquesne University, University of Pittsburgh and Carnegie Mellon University campuses.
Work to expand electrical subsurface infrastructure included 18 months for planning and permitting, and 30 months for construction. In addition to installing 216,000 feet of conduit and 51,000 feet of new cable, the construction team installed 12 precast manholes, eight new build-in-place brick manholes, and 37 rebuild-in-place brick manholes. With DLC's work taking place in the same footprint and concurrently with gas, water and sewer work, robust utility coordination resulted in safe and successful execution. All work was completed on time and within budget.
