Due to depth of the pipe and prevailing environmental conditions, and the fact that the pipeline flowed directly into the Detroit River, conventional open cut construction methods (dig and replace) were ruled out. Not only would this method be environmentally challenging, it would also have been high impact and more expensive. The city also considered another variety of slip lining called discreet barrel lining, which implements a smaller pipe that is pushed into the host pipe. This method was ruled out because of the resulting loss of hydraulic capacity, as well as concerns over efficient placement of an annular space grouting system, making it difficult to ensure grout placement. If grout is not used to fill in the annular space, the smaller pipe will not be secured, and movement and leakage may occur.
The city needed to find a solution that was low impact, yielded maximum hydraulic efficiency, had standalone structural capabilities and economy, all with minimal disruption. That solution turned out to be cured-in-place pipe (CIPP) relining, which was proposed and provided by the Detroit Water and Sewage Department (DWSD), Lanzo, and Lakeshore Engineering Services, a team specializing in large diameter projects. The team utilized Applied Felts custom liners to create a standalone tight-fitting pipe within a pipe.
The DWSD identified the problems and were instrumental in providing the preliminary model of the solution that was utilized. They also provided support services, which included handling the permitting phases, conducting field surveys and initial pipe inspection, and locating all major defects. These services were essential in enabling the team to complete the rehabilitation in a timely manner.
Lanzo was the general contractor and principal in the construction effort that coordinated the design team and handled rehabilitation efforts, including the CIPP lining and design, bypass pumping, shaft installation, point repairs, inspection and testing. Lanzo provided bypass pumping and plugging systems to one barrel at a time for pipe rehabilitation/lining installation activities, so that the remaining two barrels continued to provide service.
Lakeshore Engineering Services worked closely with Lanzo in the field investigation and surveying, liner design, cofferdam sheet piling, inspection and testing.
The team implemented a field inversion of a resin-impregnated CIPP 32-mm-thick liner tube, which was custom designed by Lanzo and Lakeshore in partnership with Applied Felts. The liner was designed with a 32-mm thickness, thick enough to serve as a standalone tight-fitting pipe capable of structurally rehabilitating the pipe, yet maintaining maximum hydraulic flow. Once Lanzo had the liners, the team of experts constructed an onsite wet out facility and utilized portable resin batching and impregnation equipment to repair the damaged barrels.
As with any large diameter CIPP job, the team, led by Project Manager Ali Feiz, raced the clock to impregnate and install each of the 850-foot barrels in the ground within 24 hours, ensuring long-term catalyzed stability of the resin system utilized, which allowed for placement of 850-foot monolithic shots.
Time was not the only challenge facing the team. At least one barrel had to remain operational while rehabilitation was underway. Lanzo constructed a cofferdam, which enabled them to isolate the pipeline from the river, enabling the flow to continue downstream while the team conducted point repairs.
As a result of the work completed by Lanzo, DWSD and Lakeshore, the city of Detroit now has a standalone pipe within a pipe that has a 100-year design life expectancy with maximum hydraulic capacity. Site development can now commence without further concern about the potential collapse of a 100-year-old sewer. From design to permitting, cleaning and pipe preparation, lining, site cleanup, and restoration, the entire job was completed in a 60-day cycle.
As a result, the successful CIPP rehabilitation of large diameter barrel outfalls like this one means that municipalities now have a proven methodology for completing such projects in a timely, low impact, cost-efficient manner with minimal disruptions to the city.