Indiana sewer replacement project implements customized bypass solutionp
The city of Evansville, situated in the southernmost tip of Indiana, was founded in the early 1800s and is home to nearly 120,000 people. Like many municipalities, the city has its share of aging infrastructure, with much of the sanitary sewer system dating back nearly 100 years. As part of an effort to proactively upgrade the system, the Evansville Water and Sewer Utility needed to replace a 60-by-48-in. brick combined sewer line with two new separate lines: a 12-in. sanitary sewer line and a 60-in. storm sewer.
The major trunk line, with its proximity to the Evansville East Wastewater Treatment Plant, was at the confluence of multiple smaller feeder lines. As a result, any water event in the area tended to increase flow, sometimes exponentially depending on its severity. Average daily flow rates in the eight-block junction ran at levels of roughly 1 million gal per day (mgd), and the system would rapidly rise to upwards of 20 to 25 mgd within minutes during significant rain events.
This was a high-profile project for the city due to the size of the new lines versus the narrow right-of-way, challenges with the rapid increases in flow, and proximity to an assisted living facility, high-rise apartments, and the new Ford Center entertainment complex. Blankenberger Brothers Inc., a local firm with experience in municipal infrastructure, won the construction bid. With the high-profile nature of the project, Blankenberger needed a partner that could handle the bypass effort.
“The city was very concerned about getting the project right,” said Brian Fox, project manager for Blankenberger Brothers Inc. “So we knew we had to choose a partner that could take care of the bypass, allowing our team to focus on the system upgrades.”
The rapid flow increases of the trunk line had to be addressed with the bypass, and Blankenberger assumed the pumps would need to be watched 24/7. As it went through the vetting process for bypass partners, it was provided a proposal from the local Xylem branch that included Godwin Field Smart Technology (FST), a remote control and monitoring system that would monitor crucial pump operating data, including system levels and flow; anticipate increases; turn pumps on and off as needed; and provide remote access to monitor system activities through a website, accessible via smartphone or any device with internet access. It hired Xylem to deliver a turnkey solution for the bypass, from design through installation and ongoing system monitoring and pump maintenance.
Engineers developed a bypass solution that employed a tiered pump approach. The plan called for the daily “dry-flow” requirements of 1 mgd to be handled by a Godwin 6-in. CD150M Dri-Prime pump. To handle the initial onrush of increased flow, the team installed two 8-in. CD225M Dri-Prime pumps to kick on sequentially. As a severe weather event continued to bring on additional water, two 18-in. CD400M Dri-Prime pumps and an additional CD400M as a lag standby pump were set up as the primary workhorses of the bypass. These pumps could move upwards of 10 mgd each. However, they typically take 8 to 10 minutes to prime. With the rapid influx of water into the system during rain events, the team did not have the luxury of time, so Xylem devised a solution in which the CD400M pumps would turn on when the smaller CD225M pumps kicked on, ensuring the system could handle a sudden increase in flow. The bypass pumping solution provided a time buffer for the larger pumps to cycle through and get primed to move water.
Suction points for the pumps were out of the new 26-ft-deep drop structure that Blankenberger installed as part of the upgrade, and the discharge point was approximately 400 ft down the line.
Diagnostics, Monitoring & Control
The team set up each pump with Godwin FST. Fed by data from MJK flowmeters in the discharge line and level transducers in the 26-ft-deep drop structure, the FST automatically stopped and started the pumps as necessary based on preset levels in the structure and preset flow rates.
The FST provided real-time diagnostic and reporting information about each of the pumps, as well as monitoring data. This enabled Blankenberger to prepare for upcoming storm events with contingency planning measures, such as pumping down the system to the lowest possible levels in advance of the event, to provide maximum storage space and reduce the likelihood of a sanitary sewer overflow. The data could be accessed remotely, which ultimately eliminated the need for onsite 24/7 pump watch duty, saving the firm—and ultimately the city—more than $100,000 in man-hours. Auto-dialers also were set up to alert Fox via text message when the pumps were started, giving him remote visibility to pump activity and reassurance that the system was working as designed.