From the very beginning, Dig 'Em the frog was determined to make a name for himself. During his twenty-year, on-again/off-again, career as the mascot for Kellogg's popular Sugar Smacks cereal, the ball-cap wearing amphibian worked diligently to catapult his catch-phrase "Dig 'Em" into the world's vocabulary.
Armed with a number of distinctive features including a cereal stealing sidekick aptly named "Kitty" and the uncanny ability to jump from bowl to bowl while heaping lavish praise on his favorite puffed-wheat cereal with all the fire and fury of a beat poet, his was a rising star.
However, times have changed and as many folks in the water and wastewater business have noticed...the lovable frog's ever popular catch-phrase "Dig 'Em!" has slowly begun to fade from industry lingo—despite his years of hard work.
These days, the folks who are responsible for moving water to—and from—our nation's homes and businesses are slowly laying aside their shovels and are taking a greater interest in recent developments in trenchless rehabilitation and replacement technology.
Trenchless technology, often referred to as the "no dig," approach to replacing and repairing buried infrastructure, is an attempt to reduce and/or eliminate the need for surface excavation.
By doing so, the myriad of traffic problems, risks to employee safety, and damage to area roads and sidewalks that is often associated with infrastructure repairs can often be reduced.
Although the processes are still not universally embraced, with much of the nation's water and wastewater infrastructure located beneath residential areas or covered over by asphalt, trenchless technology is slowly gaining momentum as a practical, cost-effective, and often safer alternative to traditional methods of getting at the root of the problem.
In this issue of the Safe Drinking Water Trust eBulletin we will take a look at this trend, some of the more common methods of trenchless repair, and how it all just might change the way your system tackles leaky pipes in the future.
Additional Resources
EPA: Collection Systems O&M Fact Sheet—Trenchless Sewer Rehabilitation
www.epa.gov/owm/mtb/rehabl.pdf [1]
North American Society for Trenchless Technology: Fact Sheets for Trenchless Methods
www.nastt.org/resources.html#5 [2]
To Dig, or Not to Dig...
There is a growing concern in our nation over the ongoing need to replace or repair substantial portions of the nation's aging drinking water distribution and wastewater collection systems in the coming years. Because of the potential public health and safety implications, maintaining these systems in good working order must be given a high priority.
A recent study conducted by the U.S. Environmental Protection Agency found that an estimated $274 billion will be needed to rehabilitate water mains over the next 20 years. When you think about it...that could add up to an awful lot of digging.
In the United States, 24 percent of the waterborne disease outbreaks reported among community water systems over the past decade were attributed to contaminants entering the water distribution system--not due to poorly or under treated water.
Addressing this problem will require the replacement or rehabilitation of many miles of buried infrastructure. Whether this task is completed through traditional open-cut or trenchless methods remains to be seen.
The idea of replacing sub-standard water or sewer lines is nothing new. However, the notion of simply rehabilitating the lines has taken on new meaning over the past few years.
Rehabilitation is generally defined as an improvement to the functional service of an existing pipeline system, by creating a new interior surface, or lining—without requiring extensive excavation.
Replacement is generally defined as installing a new pipeline either by open-cut or trenchless methods.
Additional Resources
Ohio Transportation Engineering Conference: What is Trenchless Technology?
www.otecohio.org/2006%20presentations/Sess32/Saber.pdf [3]
Parsons Brinckerhoff Construction Services: Economic Evaluation of Trenchless Technonogy
www.pbworld.com/library/technical_papers/pdf/68_EconomicEvaluation.pdf [4]
Digging for the Truth: Unearthing the History of Trenchless Technology
The first know use of pipes to transport water dates back to around 2500 BC. You can bet that even back then installation would have required a large number of toga wearing people armed with shovels. During the height of the Roman Empire a system of 11 aqueducts covering roughly 360 miles were able to deliver 50 million gallons of water a day to large storage cisterns. Pipes made of lead were then used to carry the water from the cisterns to public fountains and baths.
Throughout the centuries, conventional wisdom has been clear—if you want to install water or sewer lines, or simply need to replace the ones that are already buried under ground, then you had better grab a shovel and start digging—it was just that simple.
Proving the notion that "necessity is the mother of invention," back in the mid-1800s a group of workers needing to get water from one side of a railroad track to the other, without disrupting rail-service, devised a way to push pipes under the tracks with the help of hydraulic jacks.
And there you have it--the introduction of trenchless technology to the water and wastewater industry. If only those toga-wearing folks had thought to invent a hydraulic jack rather than structural arches, fast curing cement, and chariots, back in 300 AD, a lot of blisters and long days spent on the business end of a shovel could possibly have been avoided.
While traditionally ignored by the "wet" utilities until much more recently, the idea of trenchless technology has boomed in the mining, oil, and communications fields for many years.
Additional Resources
Underground Construction Magazine: History, Choices for Underground Infrastructure Pipes
www.oildompublishing.com/uceditorialarchive/June05/June05_history.pdf [5]
Burying the Trench
When you take into account that the Occupational Safety and Health Administration (OSHA) consistently ranks water, sewer, and pipeline construction (essentially open-trench work) as one of the top ten most dangerous occupation in the U.S., it starts to become clear why many systems are exploring alternative methods.
Factoring in the cost, dangers, and potential for public disruption created by conventional open trench excavation, interest in trenchless methods for the replacement and rehabilitation of underground utilities simply adds up.
"It has been estimated that trenchless construction methods have gained a market share of around 20 percent by cost in pipe installation and renewal for utility services," said EPA Water Administrator Ben Grumbles in an interview for Insituform, a trenchless technology leader. "It is likely that this share will continue to increase in the future as advancements in technology and improvements in obtaining geotechnical data and development of new equipment continue."
Remember, there are no magic answers for how best to repair ailing water and sewer lines. Each project needs to be evaluated specifically by an engineering professional.
Additional Resources
Occupational Safety and Health Administration Excavation Guide
www.osha.gov/Publications/osha2226.pdf [6]
Going Trenchless
Trenchless options for rehabilitating water and sewer lines are generally broken down into two categories:
Structural Methods: Required when the host pipe is considered to have inadequate structural capacity.
Non-structural Methods: Processes used when the host pipe is considered to be structurally sound and doesn’t need reinforcement.
It is important to remember, that in most cases of rehabilitation, the pipe you are repairing must first be thoroughly cleaned to remove scale, tuberculation, corrosion, and other foreign matter.
Examples of structural methods of rehabilitation include slip lining, cured-in-place pipe, pipe bursting, and horizontal directional drilling. In each of these methods, either the existing pipe is replaced or a liner is installed inside the existing pipe that adds to the overall integrity of the pipe.
Cement mortar and epoxy liners are the most common examples of non-structural trenchless rehabilitation. In these cases, the liners simply seal the interior walls of the existing pipe and do not add to, or take away from, the overall strength of the pipe.
For many years, non-structural methods clearly represented the largest portion of the trenchless rehabilitation work being completed in the water and wastewater industries. However, due to a number of recent improvements in the materials and processes, this trend is slowly changing.
Additional Resources:
IDS Water Information’s Guide to Trenchless Technology
www.idswater.com/water/us/ISTT/Trenchless_Technology/10_0/g_supplier.html [7]
End of an Era...or Simply Time for a New Catch Phrase
The creation of new developments in trenchless technology over the past 25 years has been dramatic. However, many planners, systems, and engineers are not yet accustomed to using them. Accordingly, there is clearly a need for further technological refinements, better information, and greater public awareness of the possibilities this technology holds for the water and wastewater industries.
While there is little chance that the world's shovel manufacturers are in danger of going out of business any time soon, there is clearly a movement away from conventional trenching methods for underground utility rehabilitation and replacement.
Much like the nearly forgotten Sugar Smacks' mascot, proponents of trenchless technology must work hard to stand out from the crowd and prove their effectiveness.
There was never any question that Dig 'Em clearly had big shoes to fill before he would attain the spotlight generally reserved for the ranks of breakfast cereal greats such as Tony the Tiger, Toucan Sam, Trix the Rabbit, and the immortal Snap, Crackle, and Pop--But, trenchless technology has even bigger trenches to fill before it will truly become a universally accepted practice.