Making the Leap from Hindsight to Foresight with Balfour Beatty’s Wastewater Experts
In Meda, Ethiopia, one of the only sources of clean drinking water is located at the bottom of a steep, 100-story gorge. To collect that water each day, residents must traverse treacherous dirt paths down a 700-foot cliff. But the people of Meda aren’t alone. It’s estimated that over 1.1 billion across the globe lack access to safe and potable water.
In Loudoun County, Virginia, however, clean water is always within reach thanks to wastewater treatment plants like the Broad Run Water Reclamation Facility. There, solids are removed and water is cleansed of harmful bacteria and toxins. For most, these processes are out of sight, out of mind. But for our project team that is currently expanding Broad Run’s solids treatment capacity, water isn’t just a profession—it’s a passion.Equal parts contractors and chemists, their routine workplace vernacular includes terms like denitrification and alkalinity. Masters of a subterranean underworld of polyethylene piping systems, Balfour Beatty’s wastewater experts orchestrate the magical process that keeps the county’s faucets flowing.
When Broad Run was originally constructed in 2008, the 11MGD plant—that’s a million gallons per day—met the most stringent water reuse standards in the world. Although it was the first large-scale facility to employ membrane bioreactor technology with carbon treatment and disinfection by ultraviolet light, Broad Run could never achieve the 11MGD process capability with a mere two digesters. Cognizant that Loudoun County’s rapidly growing population would result in increased water needs, civic leaders planned and designed Broad Run with future expansion in mind.
Enter Balfour Beatty. As any contractor knows, it’s never a seamless process to build upon a template someone else created, and for our team, the Broad Run Interim Biosolids project—which includes the construction of two new anaerobic digesters among other major mechanical improvements that will achieve the full 11MGD capacity—has been no exception to that rule. From the outset, our team discovered major discrepancies in what they presumed true about the project based upon their review of as-builts, design drawings and other data versus the realities of the site. Although these inconsistencies resulted in scope modifications, the allocation of additional manpower and other challenges the team hadn’t anticipated, through a highly intentional approach to project management, they’ve overcome them while establishing a standard of excellence on which to benchmark future wastewater projects.
Muddying the Waters
Their challenges began in the soil itself. Although the contract drawings noted that the location for the new digesters had been previously excavated to an elevation of 219 feet above sea level, our team discovered copious amounts of rock over six feet above that point. Because Balfour Beatty was required to excavate to 218.5 for the base elevation of the new digester tanks, our team had no option but to utilize a hydraulic breaker hammer to demolish the rock—a process that took roughly four days per tank. Further complicating matters, the team discovered that the presence of these boulders—and the large pockets they left in the earth—made it impossible to achieve a level elevation at 218.5 feet. To create an even surface, the team devised a solution to pour additional concrete as they placed the mud mat for the new digesters.
But there would be more surprises in store that impeded the team’s installation of a new condensate vault adjacent to an existing duct bank. Although the as-builts reflected the location of the duct bank outside of the excavation zone, after moving dirt, the team determined that it was very much inside their footprint. Working in lockstep with the engineer, Balfour Beatty determined that the duct bank ran off into the existing electrical building—a marked departure from what the as-builts indicated. As a result, four major modifications became necessary: moving the condensate vault approximately five feet; repositioning the wall penetration for the 16-inch digester gas line that connects the vault to the existing digester; relocating the existing duct bank; and offsetting the new electrical duct bank.
What’s more, when the team began the process of tying into a PSM or primary scum line—which they believed from the drawings to be a three-inch glass line—they observed that it was actually a four-inch HDPE or high-density polyethylene line. This was problematic on a number of levels. First, the owner had experienced challenges with primary sludge getting stuck in the piping, causing blockages. While a glass pipe has a relatively low coefficient of friction that allows the sludge to flow with relative ease, an HDPE pipe’s friction factor is much greater. But there weren’t just complications due to the differing materials. Transition points also pose risks for blockages when material catches in the gaps, and the current scheme would have created a series of those. Many options to execute the tie-ins to incongruous lines were vetted. Ultimately, the team chose to maintain the four-inch diameter but to change over to a glass lined ductile iron pipe.
The most consequential discrepancy affected the ease with which the team was able to tie in to the existing digester building. Based upon the contract drawings, our team understood that this building had been built with knockout walls to accommodate future tunnels. Popular in tilt-up construction, this design feature helps accommodate the need to knock out or remove a segment of a wall with minimal cost, effort and impact to its structural integrity. During the demolition phase, the Broad Run team realized that the presumed knockout walls were actually #5 double mat steel reinforced walls, requiring extensive efforts to cut and remove inlaid rebar. For the first tunnel, this process took an additional five days. In order to maintain the critical path on the second tunnel, the team was forced to deploy smaller equipment and dismantle the wall from the inside, resulting in an additional seven days of work.
“There are a lot of intricacies in treatment plants due to the fact that it’s common for them to be built out over a long span of time,” affirms Denis Moffett, project manager at Broad Run. “The P&IDs or piping and instrumentation drawings don’t always cover everything, and the specs aren’t always graphically there. The obstacles we encountered at Broad Run have ultimately made us stronger and sharper builders.”
Perseverance Fuels Purpose
And that’s due in large part to a groundbreaking initiative called the “BBII Project Lifecycle,” which debuted across the Balfour Beatty Infrastructure business in 2016. This web-based, internal platform was created with the goal of empowering Balfour Beatty teams to improve the safety, quality and profitability of their jobs. Broad Run was one of the first civils projects nationwide to apply this tool from its inception. At the project’s beginning, for example, the team used the tool to download templated commissioning and kick-off documents, saving valuable time that helped facilitate the achievement of early milestones. The Broad Run team has also leveraged the Project Lifecycle to “pay it forward,” documenting the importance of obtaining comprehensive definitions of terms like “knockout walls” that carry a degree of inherent ambiguity during the bidding phase.
“We take each day as an opportunity to learn a new lesson and to find value to share with our teammates,” praises Denis. “Our mentality can be described in one word: accountability.”
Hindsight is 20/20, as the saying goes, but as our Broad Run team has proved, foresight is half the battle when it comes to navigating the complex world of wastewater construction. It’s precisely this attitude of continuous improvement that makes Balfour Beatty such a trusted construction partner for the systems that provide millions of Americans with clean water and environmentally safe wastewater management. And thanks to them, our wells won’t ever run dry.