After the destruction of Superstorm Sandy, hundreds of thousands of residents along the East Coast were without power. Public Service Electric & Gas' (PSE&G) Sewaren Switching Station was hit especially hard.
Superstorm Sandy, the most destructive and deadliest hurricane of the 2012 Atlantic hurricane season and second-most expensive in U.S. history, pummeled the East Coast in late October 2012. Hundreds of thousands of residents along the coast were forced from their homes and left without power.
Public Service Electric & Gas' (PSE&G) Sewaren Switching Station, on the New Jersey side of the Arthur Kill waterway, was hit especially hard. A 14-foot tidal surge and subsequent flooding caused significant equipment damage and threatened power reliability.
At the time, Burns & McDonnell was already designing and procuring materials for an expansion of the Sewaren Switching Station, including two bays of a breaker-and-a-half configuration; a new, half-mile-long, three-circuit 230-kV XLPE underground transmission line; three new 230-/26-/11-kV transformers; and expansion of the 26-kV yard. The primary goal of the expansion project was to improve reliability of the existing 26-kV yard through new 230-kV feeds.
Reworking the Plan
Phase I of the expansion project, energizing of the first 230-/26-kV transformer, originally was scheduled to be completed by December 2013. However, the storm damage created critical issues within the station, and repairs alone would not be sufficient for the higher summer loading demands. To provide reliable power, PSE&G needed to move up the Phase I energize date to June 1, 2013.
"That decision was based not only on a need for repairs to the existing facility, but also a need to improve reliability during peak summer loads," says Andrew Wedekind, Burns & McDonnell's project manager for the Sewaren 230-kV expansion project.
In addition to accelerating the project schedule, PSE&G wanted to be prepared for similar storms in the future. The decision was made to elevate all new equipment 1 foot above the Sandy flood level elevation, meaning critical equipment would be installed approximately 6 feet above its existing grade elevation.
"This required a large-scale redesign effort while maintaining the already-expedited June 1 energize date," says Vern Mulkey, Burns & McDonnell senior project manager. "All foundations for major equipment had to be redesigned, which was further complicated by the poor soil conditions, requiring all foundations to use concrete-filled pipe or helical piles."
"The work itself was nothing unusual - design Burns & McDonnell is accustomed to and has done at a number of other sites," Wedekind adds. "It was the order and speed at which it needed to be done that created challenges."
Need for Speed
During the critical construction months, it was common to have 150 personnel on-site working six or seven 12-hour days weekly, with a night shift working the other 12 hours. Duct bank construction looked similar to an assembly line with crews staggered along the route installing sheeting, excavating soil, installing helical piles, pouring the reinforced mud mat, setting conduits, placing manholes, establishing the concrete encasement and backfilling the trench.
Advancing the schedule meant more than doing the work faster. It affected the design process, scheduling, procurement processes, work flow and a host of other elements.
Most notably, design work could not be completed before construction began. To streamline this, Burns & McDonnell relocated Paul Pansing, lead design engineer, to New Jersey as an on-site engineering liaison to coordinate design requirements and changes between the on-site construction management team and Burns & McDonnell's design offices.
"Communication was critical to maintaining the construction team's access to the latest drawings since the design was being implemented as it was completed," Pansing says.
"(Burns & McDonnell) kept the lines of communication open with the different members of the PSE&G project team to identify issues, prioritize work and come up with out-of-the-box solutions to meet the aggressive in-service date," says Lauren Thomas, senior project manager at PSE&G.
In addition to the schedule constraints, the work site presented challenges that required PSE&G and Burns & McDonnell management teams to work as partners. The half-mile-long underground transmission line ran underneath an existing road flanked by environmentally sensitive wetlands, meaning work access posed unique problems.
"Something as simple as removing soil became a major procedure because of the congested site conditions," Wedekind says. "The construction required intricate staging to remove more than 18,000 cubic yards of soil for installation of the duct bank and other Phase I foundations."
Between rainfall and the groundwater table, dewatering was another major concern. The entire duct bank was excavated using a sheet piling system using more than 3,000 individually driven, 2-foot-wide sheet piles.
The sheet piles reduced groundwater infiltration from the sides of the duct bank excavation, but infiltration still occurred through the bottom of the trench. To mitigate that and the occasional rainfall, a custom-designed pump system ran the length of the trench.
"We provided construction and office support to respond to issues in almost real time," Wedekind says. "PSE&G took their response to the storm seriously with dedication to their customers. We had constant communication among all teams."
That communication and partnership with PSE&G became crucial when the design and construction teams had to again make adjustments after the Federal Emergency Management Agency declared new flood hazard elevations even higher than Sandy's level. The new requirements were embraced and design was revised again to reflect critical equipment being raised to 1 foot above the new flood hazard elevation requirements, or approximately 9 feet above the existing grade.
Despite the challenges Superstorm Sandy presented, an enormous amount of dedication and teamwork between PSE&G and Burns & McDonnell enabled Phase I of the Sewaren 230-kV expansion project to be energized on May 29, 2013 — three days ahead of schedule.
"The ability of the project team to not only meet, but beat, the aggressive in-service date after Sandy is a testament to the teamwork and dedication of all project team members," Thomas says. "The Burns & McDonnell team worked side by side with PSE&G throughout the project, and their innovative problem solving and dedication to quality was critical to the project's success."
For more information, contact Andrew Wedekind, 816-349-6673.