The geographic location of the Township of Berlin, Mich., poses some interesting challenges for those responsible for the maintaining the condition of its underground sewer system.
The Township — located approximately 20 miles south of Detroit — sits at the western end of Lake Erie, as well as at the Huron River at its north end. The result of all this neighboring water is an extremely high groundwater table that can and has affected the overall condition of the Township’s sewer mains and service leads.
Berlin Township was known for many years as a “cottage community” with many such residences still dotting its landscape. The size of the Township is fairly large, covering more than 30 sq miles. With a population of nearly 9,000, the township combines a highly populated residential base of single-family dwellings with a rural community.
The age of the township sewer system, which is primarily concentrated along the southern portion of the township’s borders, is relatively young when you compare it to those in the Northeast United States, which are more than 100-plus years in some areas. Here, the township system ranges in age of 30 to 40 years, with mostly reinforced concrete pipe with the older service leads being clay.
When you combine the system’s age, the high groundwater table and the clay service leads, the resulting inflow-and-infiltration issues involving its main lines and service laterals are not that surprising, township officials say. Among the problematic issues involve root intrusion, offset joints and infiltration, which ultimately created calcification at the joints.
“It is unusual to have as many I/I problems with such a relatively young system but in the conditions that [the township is] is in, it is not surprising,” explains Township engineer Jim Hollandsworth, who is engineering and surveying manager with Hennessey Engineers. “We’re having some issues in a couple of our other nearby communities that have the same problem with the groundwater table, experiencing a lot of infiltration. One of those communities has sewers that were installed in the 1990s.”
He says today the Township uses PVC and HDPE pipes, which creates a tighter system and lessens the threat of infiltration. “We can get a much tighter system with the new rubber seals and the plastic pipes and we don’t get near the amount of infiltration you would get in the old, clay pipes,” Hollandsworth says.
In the areas with the clay pipe, the township was having serious issues with infiltration during large rain events for nearly a decade, with the wastewater treatment plant having to treat the excess flows. “During our large rain events, the wastewater treatment plant was receiving between 1.5 million and 1.8 million gallons of excess flows,” Hollandsworth says. “Not only is treating the excess flows costly but [the situation] was also putting the wastewater treatment plant out of compliance with its Michigan Department of Environmental Quality (MDEQ).”
The Township undertook an extensive CCTV project in 2012 to determine the extent of the I/I and to identify the specific areas in the system that needed immediate attention. “Most of the infiltration we are seeing is coming from the sanitary service leads with a little bit from the sewer joints,” says Ryan Kern, senior project manager with Hennessey Engineers. “We televised all of the sewers in early 2012 and found 220 service leads in a lot of the older sewers installed in the 1970s that were leaking, with some of them having pretty heavy flows coming through them. They were leaking either at the connection with the mainline sewer or within a few joints inside of the lead.”
Trenchless technology would serve as the rehabilitation methods for this project, which would involve cured-in-place pipe (CIPP), lateral lining and manhole repair. The Township is familiar with the use of trenchless methods, having employed CIPP technology in 2001 and 2002 in Estral Beach and Lilly Patch to reline the entire system in that area. “We found that the excessive I/I in those areas were reduced considerably,” Hollandsworth says.
Four separate contracts were let for bids to address this current I/I project: 1) full length sewer lining (CIPP); 2) sectional sewer lining/lateral lining; 3) rehabilitation of manholes and 4) wastewater treatment plant upgrades. Trenchless technology was used in the first three projects, employing cured-in-place pipe (CIPP), lateral lining and internal mechanical seals.
Inland Waters and Pollution Control in Detroit was awarded the mainline relining, which involved approximately 2,300 ft of 10- to 27-in. diameter pipe. LiquiForce Services USA, Romulus, Mich., was awarded the contract for the sectional lining, lateral lining and manhole rehabilitation. Multiple contractors are being used in the upgrade on the wastewater treatment plant.
The sectional lining project involved relining 51 locations in the sanitary sewers ranging in size from 10 in. to 24 in. LiquiForce Services used its LFS Point Liner rehabilitation system on this portion of the project, says LiquiForce Services business development manager John Thompson. This process involves the inversion of a resin-saturate, felt point liner into the existing pipeline at the repair point. The inverted point liner is ambiant-cured; the resin is specially formulated for each pipeline application and the point liner is custom-made to the exact pipeline diameter being repaired. The ends of the point liner are tapered to ensure that effluent flow is not impaired in any way.
The project also involved rehabilitating 217 service laterals from the mainline sewer, ranging in size from 10 in. to 48 in. Rehabilitation of 137 service laterals are to be completed using LiquiForce’s LFS Junction Liner CIPP rehabilitation process a CIPP process for lateral pipelines that cleans the existing lateral connection, measures it for a new, custom-made replacement liner and installs the new CIPP lining system all from the existing access points (manholes) on the main pipeline. The LFS Junction Liner mechanically bonds the junction liner to the main pipeline through the lateral connection as well as in excess of 100 ft of the lateral pipeline to a home or business, resulting in a one-piece pipeline system that is impervious to infiltration or leakage. There is no gradient separation between the junction and lateral liner, which ensures maximum capacity flow.
Thompson notes that 80 service laterals are connected to the Township’s interceptors and are to be rehabilitated from a cleanout using the LFS Lateral Repair System. Although the LFS Junction Liner was preferred, the interceptor diameter and excessive flow made it use cost-prohibitive.
Prior to the lining work being done, crews cleaned the mains to remove any debris or hard obstructions that had accumulated since the 2012 cleaning so a proper lining could be completed. Crews used remotely controlled robotic units for the work, either hydraulically driven or air grinding tools for man entry cleaning.
With both of these lining processes, the need for access to homes and/or businesses is not needed, eliminating the need to dig a traditional clean-out on the property. “That is why our process was so favorable for this project. All the work is done from within the mainline without the need for a cleanout,” Thompson says.
Thompson and Hollandsworth both note the importance of eliminating the need of the cleanouts in this project. “This is an area where the groundwater table is very, very high and our ability to do everything from the main was key,” Thompson explains. “We didn’t have to get into these excavations like a lot of other traditional technologies and deal with dewatering, etc. Also, with eliminating the need for the cleanouts, the residents don’t have to worry about the cleanouts being a potential source of inflow and infiltration in the future and they don’t have to worry about the cleanouts failing in the future.”
“[The LiquiForce] system definitely helped because with the smaller diameter pipes, we did not have to do a separate dig up to install a cleanout. We just installed the liners into the laterals. With this system, they can do it from inside the pipe itself,” Hollandsworth says, which makes the community happy.
LiquiForce also rehabilitated 45 large diameter mainline joints using the Cretex Internal Mechanical Sealing System and 250 manholes using external wraps. The manholes were experiencing significant infiltration through the joints, frame seal and cover. About 60 of the manholes were buried as much as 2 ft below the ground surface, requiring crews to raise them up to grade before repairing them.
The project started in January and to date, approximately 75 percent of the work is completed. Crews did the sectional repairs first; they are now in the process of lining the laterals. “We are looking to have the project wrapped up by the end of the year,” Kern says. “So far it has been going very well. The Township has definitely seen a reduction in flows as far as the work we have completed, more so than was even anticipated.”
Sharon M. Bueno is managing editor of Trenchless Technology.