Bypass Pumping: Key to Solving Washington, D.C., Sewer Emergency
What began as an otherwise nondescript Thursday afternoon in mid-February this year in a municipality near Washington, D.C., ended with an unexpected catastrophe that area officials were not prepared to handle alone: A 20-in. cast iron pressurized sewer main ruptured at a Maryland wastewater treatment plant.
The Washington Suburban Sanitary Commission (WSSC) and Maryland Department of Environment (MDE) were called in, as were emergency maintenance crews employed by the wastewater treatment plant, and Ross Contracting Inc. Everyone quickly came to the consensus that this was a much larger issue than they could fix by themselves — this was going to be a serious multi-day repair requiring outside help and some heavy machinery.
Enter Florida-based Thompson Pump, manufacturer of top-quality pumps and related equipment that also provides engineering expertise for construction dewatering, bypass, and emergency operations.
“When we arrived, there was no equipment onsite, but once we were advised of the situation we knew we had to react and get control of the situation,” said Howard Brown, sales manager of Thompson Pump’s Baltimore/Washington, D.C., branch. “With the municipality and Ross’s team’s help, we determined the flow of the treatment plant was 12 MGD based on the existing conditions. We mobilized four Thompson 8-in. dry prime pumps with the Thompson Enviroprime System and 1,200 lf of 8-in. Quick Connect Pipe that allowed us to route the wastewater into a nearby overflow/retention lagoon. Everything was installed by 11 p.m. that evening and the immediate issues were under control.”
This was a major victory by anyone’s standards, but Brown knew the solution was only temporary. That’s because the wastewater continued flowing and within a day, the retention/overflow lagoon was already close to maximum capacity. Brown and the Thompson team deployed five additional Thompson 6-in. dry priming pumps with the Enviroprime System to pump the contents of the first overflow lagoon into a second one, increasing the holding capacity of the sewer.
Long-Term Solution Needed
While this was another milestone achieved, it was also another short-term solution. Before anything could even be repaired, the existing sewer lines needed to be inspected to allow the team to understand the extent of damage that occurred in the line. The engineers, along with the team of city employees and the contractor, concluded that the construction of a 30-MGD pump-a-round was needed to allow for the inspection and repair of the existing sewer line.
Brown and his team met with all involved and the decision was made to begin the construction of the bypass immediately. Pumps and pipe would need to be installed, thereby diverting the sewage flow from the influent pump station to the grit facility.
The next morning, the massive multi-day undertaking began. Six Thompson 12-in. dry prime pumps with the Enviroprime System and three discharge lines (each measuring 2,000 lf) were mobilized. A forklift, two Bobcats and two fusion machines were brought in. Light towers were set up to ensure the safety of the workers, who were routinely working deep into the night.
“The entire system took six long days to set up and the bypass began,” Brown said. “As much as we would have liked to have done it more quickly, you cannot rush the pipe fusion process, which creates an exceptionally durable bond (making them much less susceptible to leaking). In our line of work, particularly in a job as big and complex as this, it is vital that everything works as it is supposed to.
“We also had to make sure we were always in compliance with the government’s guidelines, eliminating spills or sewage leakage and ensuring that our team was working safely.”
All three of Thompson’s discharge lines/pipes were installed aboveground. This part of the process was completely trenchless allowing the team to complete the project in a shorter time frame. From beginning to end, the Thompson Pump and Ross crew operated the pumps around the clock, monitored the system and fueled the equipment being used to perform the bypass. The project lasted about 30 days without disruption.
Pump technicians were charged with conducting hourly checks, allowing them to promptly spot any irregularities; and quickly and efficiently fix mechanical issues and release the occasional clog. In addition to installing the 16 dry prime Enviroprime System pumps with Silent Knight sound enclosures used to pump the sewage and the 8,000 lf of pipe and hose, Brown says it took thousands of man hours to install, operate and tear down the project.
The Ross team was pivotal in the success of this project. “We worked side by side from the first phone call to the completion of the job,” Brown said. He considers that the effectiveness of the project was due to both teams being able to function as one.
“Playing an instrumental part in fixing large-scale problems like this is what motivates me and why I love what I do,” Brown said. “It is such a fantastic feeling when everyone tells you how grateful they are to you and your team for solving what was a very serious problem – and hearing about how they couldn’t believe how well our trenchless bypass worked. The municipality and contractors very much appreciated our fast response time and the fact that we stayed and ensured that there were no interruptions in our products’ operation throughout the entire process.”