The Great Lakes Water Authority (GLWA) manages a large and complex water distribution system vital to the delivery of drinking water to communities across the Detroit metropolitan region including 803 miles of transmission mains, three intake facilities, 19 booster pump stations and 32 water storage reservoirs. The majority of the water transmission system was installed during decades of urban growth in Detroit, most notably during the 1920’s and 1960’s. There are several different types of water transmission pipe in the GLWA system. Many of these pipes are well over 50 years old with some over 100 years old.

Because the region has such an aging inventory of critical water infrastructure, GLWA is looking for ways to rehabilitate large diameter water mains without actually having to dig up city streets which can disrupt the lives of community members, is expensive and time consuming. For this project, GLWA selected a 218 foot section of four foot diameter cast iron pipe on Kercheval Ave. between St Clair and Harding Streets in Detroit. The pipe is approximately ten feet below the paved street. This section of water main was initially installed in 1913. Cast iron pipe was installed for transmission of potable water from the 17^th through the mid-20th century and represents some of the oldest pipe in the GLWA system. Two different renewal technologies were installed by Structural Technologies, Inc., a nationally known structural repair company. One is a more traditional process of manually installing reinforcing steel wire and concrete mortar. The other is a more experimental technique using robotically installed modern fiber reinforced polymer materials.

The U-M team developed a unique structural monitoring system to assess strain, pressure, and temperature to evaluate the structural performance of the rehabilitated sections of pipe. A total of 15 strain channels with numerous individual strain gages were installed. In addition, temperature sensors were installed to gather data from both inside and outside the pipe. Finally, pressure is measured inside the pipe. Construction activities and the monitoring equipment installation occurred over a four week period between July and August of 2020. The Kercheval Ave. water main was brought back into service (i.e., re-pressurized to roughly 65 psi) on October 7, 2020. UM will evaluate the performance of the pipe sections over a period of one year. Following this evaluation period, the pipe will again be taken out of service to allow for detailed visual inspections inside the pipe.