September 2010 Vol. 65 No. 9
Features
Dealing With Laterals: Abundant Challenges
Failing sanitary sewer systems are confronting American cities of all sizes. Many systems are operating beyond capacity and old underground infrastructure is crumbling with infiltration causing overflows following heavy rains and leaking sewage contaminating groundwater. Many systems are operating under U.S. Environmental Protection Agency consent decrees in which customers ultimately pay for correcting serious deficiencies.
Laterals that connect sewer mains with homes and buildings of customers are an essential part of every sewer system. But as major projects replace and rehabilitate thousands of miles of sewer mains, the condition of laterals is largely ignored, even though failing laterals may be responsible for a significant portion of a system’s inflow and infiltration (I&I). Every sewer system is different, but estimates of I&I attributed to laterals range from 25 to more than 50 percent.
Why aren’t sewer laterals receiving the same attention as main lines?
This report is the first of three that will ponder that question and options to address failing laterals. This report considers the condition of sewer laterals in the U.S. and factors that contributed to today’s problems.
Integral part
Laterals clearly are an integral part of a sanitary sewer system, yet most municipalities and water and sewer districts consider laterals the property and responsibility of the owner of the property through which they pass.
“Laterals are on private property and, therefore, generally considered the responsibility of the property owner,” says Gerry Muenchmeyer, P.E., Muenchmeyer Associates LLC, and technical director of NASSCO (National Association of Sewer Service Companies). “In many municipalities sewer laterals — other than vertical riser connections — are not accepted as the responsibility of the city. In other areas, the municipality assumes responsibility for the lateral sewer only from the mainline to the property line.”
Unless the municipality has initiated a program to renew or replace sewer laterals, it is widely considered the property owner’s responsibility to maintain, repair or replace lateral pipe in the event it no longer functions, an obligation most property owners are unaware of and unprepared to do.
Most people, Muenchmeyer observes, take sewers for granted, including main lines and laterals.
“Many homeowners are probably not even aware of what happens when a facility is flushed in their home,” he continues. “Certainly maintaining the condition of their sewer laterals is not a priority. Money is more readily spent for landscaping and surface improvements that can be visually appreciated, rather than a pipe which is only important when a flush is no longer available.”
As a result of system owners avoidance of responsibility for laterals and property owners unawareness that in case of a failure they may be responsible, a large percentage of laterals in the U.S. are old and have received no maintenance since they were put in the ground.
In addition, the piping used for laterals and the ways in which they were constructed has contributed to their generally poor condition.
“Pipe material for laterals generally has been lower in cost and quality and installed without any municipal inspection,” says Muenchmeyer. “Unlike mainline sewers that were typically installed in a straight alignment between manholes, lateral sewers were installed with a multiple number of bends and fittings. And though generally infrequent, mainline sewers have received some measure of maintenance by the municipality while lateral sewers typically deteriorate to a point where major renewal or replacement is required.”
I&I
George Kurz, P.E., DEE, senior technical leader, Barge Waggoner Sumner & Cannon Inc., has conducted extensive research and documentation of lateral I&I issues.
“Leaking sewer service laterals represent a significant component of I&I in sewer systems,” says Kurz. “Also, I think that it is possible to estimate the percentage of I&I that can be attributed to failing laterals, and better yet, it has been demonstrated that the percentage can be measured under certain circumstances.”
Kurz cautions that methodology of previous studies has varied widely influencing the resulting estimate of I&I levels.
“The real message,” he says, “is that lateral and manhole rehabilitation must always be a part of the overall rehabilitation project. I call this the ‘system approach’.”
Hoffman Southwest Corp. operates Roto Rooter franchises in California, Oregon, Arizona and Utah and its personnel service hundreds of sewer laterals every day.
“The majority of sewer laterals in the Western U.S. are more than 30 years old and are in poor condition,” says Mark Metcalfe, vice president of operations. “Heavy root intrusion, cracked pipes and offset joints are common. When blocked, most of these laterals can be opened with routine cleaning but can be a source of I&I as can roots that travel from the lateral into the main line.”
Laterals receive no maintenance because cities or sanitary districts do not have inspection programs for laterals on the public side and owners of the private side laterals are not aware of laterals until there is a problem.
“Most cities consider the lateral the property owners responsibility from the home or building until it enters the city easement or street mainline,” Metcalfe continues. “Another problem is that most cities do not have a lateral program that requires inspection and repair after a backup or when the property is sold.”
Excavation replacement of laterals is very difficult and expensive, but Metcalfe says his company finds many city building departments are not familiar with trenchless technologies.
“Education about trenchless options would help property owners be aware of alternatives for rehabilitation,” Metcalfe believes.
In fact, trenchless procedures of rehabilitating old sewer laterals by relining and replacing old laterals with new pipe are being used today, but their full potential has not been realized.
Lack of standards
Gil Carroll, director of business development at Applied Felts says from his company’s perspective, the most glaring issue holding back the advancement of lateral rehabilitation with linings is the lack of the same standardization, inspection and quality assurance that has been established for cured-in-place pipe (CIPP) rehabilitation of mainline sewers. Applied Felts is a leading manufacturer of CIPP liners.
“For example,” says Carroll, “we don’t see the industry adhering to the ASTM 1216 in lateral relining. We still see installers using ambient cure, which will never be as effective as heat curing and could create negative impressions of the CIPP process overall on the part of those not familiar with the process. This could result in CIPP being disallowed in areas where improper installation techniques have been followed.
“The lateral market needs to follow suit in order to ensure complete integrity of installations, which is critical to improving the condition of sewer laterals in the U.S.”
Chris Brahler, president of TT Technologies, a leader in developing the pipebursting market in the United States, says this trenchless procedure provides a cost effective, socially responsible and green alternative to typical open-cut methods of installing new lateral pipe.
“Although pipebursting laterals has been used since 1994, from our perspective we are only scratching the surface for sewer lateral applications,” Brahler says. “There are still many contractors, municipalities and engineers that have never heard of pipebursting. They are unaware that pipebursting is a viable proven alternative, another tool for their tool box. For contractors, the procedure can save time and money.”
However, awareness is growing. The best “advertising” for the process, Brahler believes, comes from satisfied system owners and contractors who have successfully executed lateral pipebursting projects.
“Our buried infrastructure,” he concludes, “will be addressed and pipebursting can play a significant role in restoring sewer system infrastructure, including both laterals and mains.”
FOR MORE INFORMATION:
Muenchmeyer Associates LLC, (252) 626-9930, www.muenchmeyerassoc.com
Barge Waggoner Sumner & Cannon Inc. (George Kurz), (615) 252-4441, gekurz@bwsc.net
Hoffman Southwest Corp., (800) 784-7473, (949) 380-4161, www.pro-pipe.com
Applied Felts, (203) 426-5948, www.appliedfelts.com
TT Technologies, (800) 533-2078, www.tttechnologies.com
NASSCO, (410) 486-3500, www.nassco.org
Comments