Reliable power connections are essential today as technology makes everything we do possible. But the power transmission lines beneath many U.S. cities were buried a century or more ago. To serve growing needs, and be able to accept renewable energy from other sources, electric utilities must update the lines between substations to ensure continuous service. With the route to a better, cleaner and dependable electricity grid underground, that means tunneling for miles to accomplish this goal.
Upgrades can be billion-dollar investments for power companies and unique challenges for program management and construction management (PMCM) teams. Completing infrastructure projects on time and on budget is especially fraught when new power transmission lines must cross highways and waterways. Boring underneath these obstructions, excavation crews make way for new conduit. Along the way, they must be careful to prevent disruptions. That means steering clear of old utility lines that are not always well mapped out and streets that offer access to nearby businesses and homes.
McKissack & McKissack’s infrastructure projects for Baltimore Gas and Electric Co. had all these challenges—and many more—to build out a long-planned power distribution substation south of Camden Yards. The two-year, $160 million project, completed in June 2020, improved the reliability of a system about to outgrow its capacity and prepared Southwest Baltimore businesses and communities for continued growth.
Drilling Deep Below Ground to Bring Power to the People
As prime contractor, McKissack supervised the buildout of a new electrical substation with four \distribution lines and infrastructure for an additional future 32 distribution lines to energize the station and 2.4 miles of high-voltage transmission lines.The infrastructure project extended underground transmission lines from the new Wilkens Avenue substation past scores of historic homes to an existing power substation in the bayfront Westport neighborhood. We managed a retrofit of the existing substation and construction of the new substation.
Crews bored under Interstate 95,Maryland Route 295, Carroll Park, Gwynns Falls and multiple railroad lines to bore a path for the new conduit. For much of the construction project, crews avoided digging trenches through a combination of auger boring—pushing a segment of pipe forward, with a large, rotating corkscrew bit in the pipe to clear a path —and horizontal directional drilling (HDD),in which a remote-control drill steers a narrower path 60 feet below the surface, providing a 48-inch diameter void to house the sizable cables and conduit.
When Daniel Day-Louis’ oilman character in the highly acclaimed 2007 film “There Will Be Blood” proclaimed “I drink your milkshake!” he was boasting about how he could cut a lateral drilling path across miles of open farmland.Drilling below the urban landscape near Baltimore Harbor using HDD, a trenchless technology that prevents a drill from hitting and breaking existing electrical lines, was far more challenging. It also required along consensus-building process to guarantee community buy-in.
The program management team first secured permissions from local government and other utilities. The process limits street closures during construction and assure a smooth process to power up the new substation. Knowing the region, our experience with aging infrastructure helped us limit the impact of underground work at street level and protect the foundations of older or historic homes.
Program Management Expects the Unexpected
Public hearings, community meetings and notices to individual residents kept neighbors informed on the energy project’s progress. A community outreach specialist was on hand during construction to resolve noise complaints or other issues. The new substation site, a full city surface grading to beautify the area with a site specific, sustainable ecosystem.
Contractors acquired engineering drawings to reach agreement on the easiest path with the least potential to disrupt buried utility lines or street-level businesses. McKissack’s PMCM team then conferred with the general contractors, talking through the time involved, to hire contractors with the time and manpower to make the deadlines.
To prevent business disruptions, some street-level work was scheduled for night hours when merchants were closed. To route copper cable past two businesses that needed 24-hour road access, program managers scheduled three weeks of staging activity so the street would close only during the two days when the facilities were shut down for inventory.
Tunneling under roads can minimize traffic disruption, but it can be done only from a stable excavation site. Crews dig a large pit to hold drilling equipment and debris. It also keeps the fluid—which keeps the drills cool—from running into sewers and streams. When rock is in the way, often the only route available is to slowly drill through it. That was the case here: In a number of places we had to punch through it.
Even in the sections where concrete and metal duct banks for conduit could be placed in open-cut trenches, there were hidden roadblocks—unmapped, nearly century-old utility lines. Early engineering drawings were unreliable or simply didn’t exist. When digging revealed an unmarked utility crossing, the crew had to avoid it and keep digging, documenting the layout as they went. We also discovered cobblestones under the streets and old gravel roads under open land.
Substation Construction Builds for Next Generation
Finally, the new Wilkens Avenue distribution substation and the existing Westport substation needed connections to the upgraded supply lines. To prepare the former factory site at Wilkens Avenue, construction crews removed soil contaminated from old industrial processes. New soil and stone improved the site’s drainage and keep electrical systems safe from water damage today.
With experience in substation design as well as construction, McKissack adapted plans drafted for the site earlier to include state-of-the-art power and communication equipment. Next-gen equipment monitors equipment for engineers to control offsite, improving reliability by giving power multiple paths to follow.
Both the electrical substations and the transmission lines between them are now in operation, providing energy sustainability to older neighborhoods that had been prone to power outages. Although the scope of the project grew near the end, but we never missed a date and were always within budget. We wrapped up with a review of lessons learned along the way, especially as plans allow capacity to add more distribution feeder lines later this decade.
In a game plan with a lot of wildcards, the PMCM team played its hand well. The winners were Baltimore’s residents and businesses, who have new infrastructure in place to meet their power needs.
Paul Strong is a PMCM project manager at McKissack& McKissack. MichaelCarter is vice president of program management and construction management for McKissack’s Mid-Atlantic region.