West Interceptor Rehabilitation - Gammon Extension to Pumping Station 5


  Madison Metropolitan Sewerage District owns a sanitary sewer pipe that runs under the middle of Lake Mendota Drive. The pipe, which serves the Spring Harbor neighborhood and adjoining areas, is 87 years old and has started to corrode. The district will install a new pipe liner inside the existing pipe from Baker Avenue to Spring Harbor Park using a process called cured-in-place pipe. In the end, the liner is essentially a new pipe inside the existing pipe. 

The district’s contractor, Visu-Sewer, is planning to begin cleaning the pipe on April 8, 2019 in preparation for the lining installation. For the week of April 8, 2019, pipe cleaning is the only activity planned. Pipe cleaning is accomplished with a tanker truck. A high pressure water jetter is inserted into the pipe through a manhole and rotary cutting tools are required for heavier deposits. Mendota Drive may be restricted to one lane at the location of the tanker truck. There will be no other traffic or sewer impacts during pipe cleaning.    

The new pipe liner installation is scheduled to begin on April 15, 2019 and is expected to take three to four weeks to complete.  The liner will be installed in sections from one manhole to the next, and each section will take two to three days to set up, complete the installation and break down. The installation takes place completely within the existing pipe through existing manholes and there will be no excavations. Equipment used in the process includes refrigeration trucks, boilers, pumps and possibly generators.  

The boilers provide hot water or steam to cure the new liner pipe, which is soft when first installed but hard, similar to fiberglass, after curing. The new pipe liner needs to be refrigerated during storage and transportation to prevent premature curing. Sewer laterals that are connected to the pipe section being lined will be blocked by the liner during the installation. A sewer lateral is the pipe from individual houses to the sewer pipe in the road. Laterals may be blocked for up to 16 hours while the liner is installed and cured. After the liner is fully cured and drained, robotic cutters with cameras will be used to reopen the laterals. Affected residents will be notified at least a day before their laterals are blocked by the liner installation.   

While the pipe liner is installed and cured, wastewater from the existing pipe upstream of the section being lined will be bypassed around the work area by pumps. Bypass hoses will run down the center of Lake Mendota Drive in lengths up to 1,000 feet or more. Once each new pipe section is complete, the whole set-up will be moved down the line to the next section. 

In some locations, the existing pipe runs more than 20 feet beneath the street and is below the groundwater table. The new pipe lining will improve flows, prevent infiltration of groundwater into the pipe and extend the life of the existing pipe. 

Additional work that will be done as part of this project includes coating the inside of existing manholes with epoxy and testing and sealing lateral connections to the existing pipe. The additional work is currently scheduled to begin in June and will take about one to two months to complete. Traffic and sewer disruptions from the additional work will be minimal.

Process protects environment, saves time and money
Since the cured-in-place process does not require digging, it is significantly less costly, time consuming and disruptive to the public and the environment than excavation and pipe replacement with traditional open-cut methods. However, the use of bypass pumps and other equipment is expected to have short term traffic impacts and to generate some noise between 7 p.m. and 7 a.m. The lining process also will temporarily (up to 16 hours) limit sewer use for some residents.

The project reflects the district’s efforts to maintain aging infrastructure in a way that protects public health and the environment while delivering reliable services at an acceptable cost. Questions may be directed to project engineer Eric Hjellen, Madison Metropolitan Sewerage District, at (608) 222-1201, ext. 348 or at erich@madsewer.org.