The city of Memphis, TN, like all major cities across the U.S., is faced with aging infrastructure that requires constant attention and proactive initiatives for upgrades and rehabilitation. In September 2012, the United States Environmental Protection Agency and the Tennessee Department of Environment and Conservation issued a Consent Decree to the city requiring the implementation of an “investigation and rehabilitation program” with the objective to eliminate sanitary sewer overflows (SSOs).
To address the Consent Decree requirements, the city implemented the Sewer Assessment and Rehab Program (SARP10) to proactively work through the critical projects in and around the greater Memphis area. Black & Veatch was chosen as the Program manager and Overland Contracting Inc. was chosen as the construction manager. Black & Veatch, Overland and the city identified the Mud Island Interceptor and Manhole Rehab project as a priority on the list.
This job required the rehabilitation of a 35-year-old monolithic reinforced 60-inch diameter concrete sanitary sewer pipe that served as a critical trunk line for the city’s sewer network. The entire 3,500-linear foot length of the 60-inch diameter pipe needed to be upgraded, along with 24- and 36-inch diameter laterals. A bypass pumping operation would have to be put in place in order to access all three lines during the rehabilitation project.
A winning team
Insituform Technologies LLC (Insituform), a subsidiary of Aegion Corporation, with its cured-in-place pipe (CIPP) solution, was chosen for the SARP10 Mud Island project. Insituform was contracted by, and worked closely with, Overland to build the project. Insituform needed a bypass pumping partner to handle all aspects of the bypass – from upfront design and ground preparation, to installation, to 24-hour pump watch duty once the bypass was up and running. Insituform contracted the bypass pumping activities to Xylem due to its bypass pumping expertise and unique solution, with significant cost savings for the city.
“In order for us to provide our quality CIPP solution, we needed a quality bypass pumping contractor with an intimate knowledge of the project and the city’s sanitary system,” said Ryan Miller, business development manager at Insituform. “We had worked with Xylem in the past, so we felt confident in their ability to provide a safe and effective bypass pumping solution. When they showed us their unique idea that would also save the city a significant amount of money, we felt it was not just the most effective, but also the most cost-effective way to go.”
The 60-inch sanitary sewer line to be rehabilitated ran off of a 30-foot deep drop structure. Insituform initially expected that the bypass would need to start upstream from the drop structure, tap into the upstream line and bypass it along with the entire length of 60-inch pipe. This was estimated to be a very costly part of the bypass. Xylem’s design had the bypass starting from within the 30-foot deep, 60-inch drop structure – with the suction point directly in the structure – eliminating the need for the costly upstream tap. This solution helped save the city over $100,000 and won Xylem the job.
In order to handle the 47.5 million gallons per day of flow, Xylem brought in six Godwin diesel-driven critically silenced CD400M pumps, and four Godwin diesel-driven critically silenced DPC300 pumps. Five of the CD400M pumps were set up to draw suction from the 30-foot deep drop structure, and the sixth CD400M pump was a redundant back-up should any of the other pumps fail. Xylem installed a 60-inch sewer plug at the drop structure exit with a ½-inch steel plate above the plug to help keep it secure. The CD400M pumps utilized five 18-inch high-density polyethylene (HDPE) suction pipes that entered through a hole cut in the concrete at the top. They were set into the drop structure and were cut with a 40-degree chamfer on the ends, so they could support their own weight yet still have open pipe exposed for suction.
The discharge was into a 48-inch manifold with check valves and gate valves for directional flow only. The manifold then discharged into three lines of 24-inch HDPE pipe that ran approximately 3,500 linear feet along a greenway to the discharge structure at the Wolf River siphon. Two of the DPC300 pumps were used on the 24-inch lateral line and were connected to the manifold. The two other DPC300 pumps were connected to the 36-inch lateral and had discharge lines of 24-inch HDPE pipe that ran directly to the discharge point.
The bypass system utilized Godwin Field Smart Technology to monitor pump engine operating parameters such as hours, speed, engine temperature and fuel consumption, as well as pump parameters such as suction and discharge pressure. The data was communicated via cellular and satellite networks back to the city of Memphis and Xylem personnel to ensure optimum pump performance. Xylem also installed MJK flow meters to monitor flow rates to assess system efficiency and capabilities.
In addition to providing turnkey site excavation, construction and bypass setup, Xylem also provided 24/7 system monitoring and pump watch duty while the bypass was online. The bypass took three weeks for the Xylem team to install and it ran for four weeks while Insituform installed the 60-inch CIPP solution. When the Insituform team rehabilitated the 400 linear feet of 24-inch diameter CIPP, the bypass pumps were again fired up.
“Having the bypass pumping system set up and ready to go for all three components of the Mud Island project allowed for a smooth project flow, minimizing any downtime,” said B.J. Kerstiens, project manager, Insituform. “We were able to move from one piping rehabilitation section to the next, with the Xylem team providing a seamless bypass pumping solution. It was a good project from start to finish, and we feel Overland, Black & Veatch and the city of Memphis were pleased with the end result.”
About the author: Ken Albaugh is the central regional director for Xylem, and he can be reached at kalbaugh@Xyleminc.com.
FOR MORE INFORMATION:
(914) 323-5700, xylem.com
(800) 234-2992, insituform.com
Black & Veach,
(913) 458-2000, www.bv.com
Overland Contracting Inc.,
(800) 790-2149, overlandcontracting.com