October 2010 Vol. 65 No. 10
Features
Solutions For Lateral Rehab
In many American cities, the sanitary sewer laterals that connect homes and commercial structures to sewer main lines have been allowed to deteriorate and become a significant source of sewer system inflow and infiltration (I&I), along with other problems.
Editor’s Note: This is the second in our three-part, exclusive series on the complicated laterals issue facing municipalities across North America. Read part one here. Part three will be published in the November issue of Underground Construction, and will examine what needs to be done to speed the process of repairing the nation’s ailing laterals.
A primary cause of the neglect of laterals is that many municipalities and water and sewer districts take the position that laterals are the responsibility of property owners and, therefore, exclude them from sewer repair and rehabilitation projects.
A summary of the factors that contributed to the nationwide lateral crisis was published in the September issue of Underground Construction — the first of our three-part lateral series about sewer laterals. This report covers how the problem is being addressed today.
Typically, a lateral is repaired and replaced only when it becomes a necessity — usually when the property owner no longer has the ability to flush facilities without backups and flooding.
It is reasonable to believe that the number of laterals reaching that point is increasing and thus a growing number of laterals have to be replaced or rehabilitated. In most cases, property owners are paying the bills.
“Unless the municipality has initiated a program to renew or replace private sewer laterals, it is the homeowner’s responsibility to maintain, repair or replace the lateral pipe in the event it no longer functions,” said Gerry Muenchmeyer, P.E., Muenchmeyer Associates LLC, and technical director of NASSCO (the National Association of Sewer Service Companies). “Today, more and more plumbing companies now offer a lining or renewal technology to the homeowner that is quick and relatively inexpensive when compared to excavating and replacing not only the lateral sewer, but the associated landscaping that may be encountered.”
The position of service providers, that property owners are responsible for lateral repairs, continues to impede progress on solving lateral issues. However, there are progressive system owners who recognize it is to their benefit to take responsibility for laterals in their systems.
Regardless of who ultimately is responsible, there are three basic methods for replacing or rehabilitating sewer laterals:
• Open-cut construction;
• CIPP (cured-in-place pipe) lining; and
• Pipebursting.
Open-cut construction
For years, the only way to install new sewer laterals or repair/replace old pipe was to dig a trench and put in pipe or make necessary repairs, and fill in the excavation. It’s a simple, straightforward process that all contractors have the equipment and knowhow to do. However, excavation damages lawns and if the lateral pipe is buried under drives, walks or patios the job becomes more complicated. If excavations are not properly compacted, fill can settle, causing continuing problems.
CIPP rehabilitation
Rehabilitating a lateral with CIPP lining involves inserting an inverted felt tube liner saturated with epoxy-based resin into the lateral where it is cured by heat to form a new “pipe” within the old pipe.
CIPP lateral rehabilitation causes the least surface disturbance of any rehabilitation/repair method available.
CIPP can be successfully employed on most lateral projects, said Gil Carroll, director of business development at Applied Felts, a pioneer in the CIPP process and manufacturer of MaxLiner systems.
“Given that most laterals are within four to six inches in diameter and go directly to property line clean-outs where lengths are typically no more than 40 feet,” said Carroll, “there are really no special circumstances that limit the use of CIPP for lateral rehabilitation and repair. CIPP can be used for every standard and non-standard length required by a lateral.”
Carroll said one point of access is needed — either from the clean out on the property or the main line if a seal also is being produced. In most cases, it is possible to shoot a blind shot from one point to the other without limitation.
Most laterals needing attention exhibit a variety of problems, including broken pipe and root intrusions which are identified by inspection prior to the lining process.
To line a lateral, the pipe must be clean and clear of blockages, and the first step is a careful CCTV inspection.
Preparation includes measuring and cutting the felt tube liner to the specified length. The proper epoxy resins for the job are combined with specific hardeners with “pot lives” ranging from 15 to 180 minutes. A max vac pump is used to remove all air from the felt liner to assure complete resin impregnation, and the impregnated felt is fed through a calibration roller to ensure even distribution of epoxy resins throughout the tube.
The impregnated liner then is inverted into the lateral and cured. Following the curing process, any side entrances to the repaired pipe are reopened and openings at each end are finished.
“The most critical piece of equipment is the liner gun which inverts the liner into the existing pipe,” said Carroll. “But we recommend a complete system. The MaxLiner system includes the gun, calibration rollers, max vac pump, mobile hot box heating unit to speed curing time, control box to maintain even air pressure through curing and cutting tool to reinstate service of newly lined and cured pipe.”
When sealing lateral connections, the process begins inside the main line where it is launched and then continues out into the lateral for seamless installation of 30 or more continuous feet of cured-in-place pipe.
In addition, MaxLiner offers a self-contained trailer providing a mobile CIPP unit that adheres to ASTM F1216 for lateral relining.
Time to complete a lining depends on length, diameter and condition of the pipe.
“Assuming a 40-foot, four- to six-inch diameter pipe, the entire process can be completed in just a few hours,” Carroll said. “With our system, installers typically complete two, three or more relining jobs each day. The flexibility of the materials used, portability of the equipment, and the ease of use make CIPP lateral lining systems extremely adaptable and user-friendly in a variety of pipe conditions, weather patterns and soil types.”
Pipebursting
Pipebursting is a well established trenchless method of installing new pipe to replace old, deteriorating laterals. The process involves pulling a bursting tool through the old pipe, cracking or bursting it into pieces while pulling in a new length of pipe behind it.
A major benefit of using the pipebursting process is the capability of upsizing new pipe — how much pipe size can be increased depends on soil conditions.
While pipebursting is included in the “trenchless” category, it does require excavations for starting and receiving pits.
“For a 60-foot pipebursting lateral installation, about 45 feet will be trenchless with excavations necessary at each end,” said Chris Brahler, president of TT Technologies, a leading manufacturer of pipebursting equipment and technology.
Compact bursting equipment and tools have been developed specifically for sewer laterals. Brahler said there are two basic types of bursting methods for laterals: pneumatic and static.
“The pneumatic method employs a pneumatic piercing tool as the bursting device,” he explained. “An entry pit is dug and the tool inserted in the old pipe with new pipe attached to the rear with the air hose enclosed in the new pipe. The hammering action is activated and a small lateral winch pulls the tool through the old pipe to the exit pit. Once in place the new lateral pipe is connected at the property end and to the sewer main.”
This method is best suited for straight runs, said Brahler.
Static (also called hydraulic) bursting is preferred for laterals with bends and curves. This method’s shorter bursting tools can better negotiate changes in direction than longer piercing tools.
The TT Technologies Grundotugger static pipebursting system includes a hydraulic winch unit, bursting heads for various sizes and types of pipes, and cable to connect to tool and winch. A 20-horsepower gasoline power pack and extraction cage also are available. To make a burst, the winch unit is placed in the exit pit, and then cable is passed through the old pipe and connected to the bursting head. With new pipe attached to the rear of the head, it is pulled through the pipe by the winch, busting old pipe and pulling in new pipe. When new pipe is in place, connections are made at each end.
“Entry and exit pits are the most time consuming of a bursting project,” said Brahler. “For pneumatic jobs, the entry pit is the largest to accommodate the length of the piercing tool. It’s just the opposite with hydraulic equipment because the exit pit holds the winch.”
Because pneumatic jobs are straight, they take less time to complete.
“A straight shot of 50 feet or less with a pneumatic tool can be completed in an hour or less,” he said. “A lateral the same length with bends could take two to four hours with static equipment. There’s more set up time, and the pipe pull-through is slower.”
For difficult straight static installations, a pneumatic piercing tool can be placed inside of the product pipe behind the expander to provide a percussive assist during a lateral burst.
One contractor’s operating procedure
Mark Metcalfe, vice president of operations for Hoffman Southwest Corp., said all the company’s shops are equipped to service laterals by CIPP, pipebursting and excavation. Hoffman Southwest operates Roto Rooter franchises in California, Oregon, Arizona and Utah.
Metcalfe said on most service calls, a CCTV inspection is made after the line is opened. Video inspection usually confirms the cause of stoppage and whether the line is clean. If the line is damaged, inspection results can be used to identify repair options.
“Most customers,” Metcalfe said, “are receptive to inspection when its cost is included in the cleaning service. When there is a separate charge they normally are only receptive if they have had repeated backups. For lines that were full of roots, the old practice was to clean them once a year. The trend now is to rehab them.”
When a lateral is found to be damaged, have severe root problems or is an obvious source of I&I, the recommendation is rehabilitation.
Generally the first choice of rehabilitation is CIPP, pipebursting is second, and excavation last.
“Advantages of CIPP are that it can be done with little or no excavation and can rehabilitate the entire line without going into easement or public right-of-way,” Metcalfe explained. “With pipebursting, material is less expensive than CIPP, but it is more labor intensive and is more unfriendly to the landscape. Excavation generally is the last choice because the landscape damage is the most severe.”
Figuring in all factors, Metcalfe said costs for the three procedures are much the same, although repairs to surface damage after excavation can add to the cost when excavation is used.
“CIPP and pipebursting generally can be completed in one day versus excavation which may take several days including relandscaping,” said Metcalfe.
Signs of progress
Laterals continue to age and fail, but there is a greater recognition today of the serious problems they cause.
“Considering the cumulative effect of the infiltration from most laterals in a system, the failing laterals must be considered community problems,” observes George Kurz, P.E., DEE, senior technical leader, Barge Waggoner Sumner & Cannon Inc. “Therefore, reducing lateral infiltration and recapturing capacity of public sewers must be recognized as a community benefit.”
There is evidence that sewer system operators are beginning to understand that.
“In recent times,” said NASSCO’s Muenchmeyer, “some municipalities, particularly in areas served by regional treatment facilities, have taken legal steps to allow them to repair lateral sewers and thereby reduce infiltration and subsequent flow to the regional facility. The reduced costs associated with these flow reductions more than justified the cost or the lateral sewer repair or replacement by the municipality.”
FOR MORE INFO:
TT Technologies, (800) 533-2078, www.tttechnologies.com
MaxLiner, (276) 656-1225, www.maxlinerusa.com
Hoffman Southwest Corp., (800) 784-7473, www.pro-pipe.com
NASSCO, (410) 486-3500, www.nassco.org
Barge Waggoner Sumner & Cannon Inc. (George Kurz), (615) 252-4441, gekurz@bwsc.net
Setting an Example
The city of Avalon on Catalina Island off the coast of California provides a good example of how a progressive city can address the issue of failing laterals, said Gil Carroll, Applied Felts director of business development.
Following discovery that the waters of Avalon Bay were polluted to levels unhealthy by human standards, the city had to determine the causes of the pollution and determine how to correct them. A study of the city’s sewer system was a priority.
On Catalina Island, wastewater was being flushed into sewer laterals and main lines using salt water, and video inspections of laterals revealed that the salt water had corroded the laterals. In addition, a majority of the laterals were broken or cracked, causing wastewater from the homes in Avalon to enter the groundwater system.
“Even though the homeowners were considered the responsible parties,” said Carroll, “the city made the decision to fund the relining of virtually every lateral. They went down entire streets and relined laterals in the all of the Flats area of Avalon. Even though the state of California had cut off funding, the city of Avalon made the decision to move forward in the best interest of its residents and visitors.”
Carroll said the Catalina Island project clearly demonstrates that when someone takes responsibility for the health of lateral pipes, the rehabilitation process moves along quickly and efficiently.
“However,” he said, “this is an isolated case and, unfortunately, indecision regarding ownership is a more common situation today.”
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