Fact-Based Planning Enables Long-Term Savings for Water Pipe Systems

Perhaps the three most important questions facing a municipal water department today are, ?How do you predict how long our water distribution system will last?,? ?When must we start planning for replacement?? and ?What?s the true cost over the lifetime of the system??

Naturally, one would like to have these answers long before water starts cascading down streets due to broken pipes or roads collapsing into sinkholes from degraded water and sewer lines. Of course, by then it?s too late to save damaged property, crippled businesses and, under the direst circumstances, lost lives. That is why it is so important to have a well defined assessment of current underground assets and awareness about available materials that may prove to be better long-term performers, delivering enhanced sustainability and paramount savings.

A full analysis that accounts for all the components that make up a water pipeline network is absolutely necessary when seeking to provide responsible and enduring infrastructure systems. Understanding the complete costs for flawless functioning, from installation, through maintenance, into system expansion and over the full lifetime, is critical. Plans for possible repair and replacement should be built in to the annual budget. Looking only at initial installed cost is short-sighted, irresponsible and potentially more expensive. Making a selection based solely on the lowest price or product familiarity can lead to future consequences like improper installation, compromised pipeline quality, higher repair costs and increased water losses.

Also essential to any cost efficiency analysis for a water distribution system is a complete understanding of the multitude of variables that have an effect on a water pipeline including water chemistry, operating parameters, environmental influences, advancements in materials and installation techniques. Once all of these considerations are encompassed, a truer picture emerges that allows sound decision-making for best economical system options.

From the perspective of the whole-life-cycle cost analysis approach, a medium-sized, high-density polyethylene (HDPE) pipe network frequently ends up costing much less overall than many other systems, including ones that use a mixture of different types of pipes. This lower cost is due to two main reasons as referenced in a number of recent research studies and investigations. One such study, conducted during the past decade by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) (Victoria, Australia) and sponsored by the PPI, found exactly that: HDPE pipelines offer premium life-cycle savings, first, because failure rate is low, thereby making cost per mile for repair or replacement low. Keeping repairs to a minimum yields significant benefits and cost savings since repairs generally represent 70 percent to 80 percent of the total costs experienced by a network.

The second major benefit, according to the CSIRO report, is that the leak-free performance of HDPE pipe due to fusion-welded joints diminishes loss and eliminates the need for an ?acceptable leak rate,? a term commonly referenced and understood as a suitable standard in the industry. Ultimately, as water becomes more and more scarce, this ability for the system to protect from infiltration or exfiltration, conserving the resource and guarding it, once treated, will be recognized as an invaluable inherent feature. Greater economical reserves over the life-term can be anticipated.

As more and more utilities investigate the lifetime performance of their pipe systems, the realization that 50 years of service life, previously considered the norm, is no longer the common benchmark will be understood. Today, when calculating potential future costs over service life projections for HDPE pipe, the milestone used is 100 years. This marker was highlighted in a recently released 2011 report by Jana Laboratories (Ontario, Canada). A paper encompassing results of four years of study was just published. It details a project PPI sponsored in collaboration with the Alliance for PE Pipe (Alexandria, Va.), which examined PE pipe materials and performance beginning with early use in the late 1950s and continuing through generations of materials development, each providing advanced performance capabilities into the modern era. The research yields data that projects today?s high performance generation of HDPE pipe materials can, conservatively, provide more than 100 years of service in the vast majority of our country?s potable water systems when properly designed and installed. It also supplies a predictive model that takes into account the various specific factors that impact a water system. [The report is available at: http://www.janalab.com/hdpe-finalreport]

Even the resin used to make the pipe is a critical factor that must be considered in gaining an understanding of best cost-efficiencies. The latest development in PE pipe resin classification is PE 4710. PE resins that qualify for the PE 4710 designation offer a high level of ductility and toughness when compared to previous generations of PE materials. This translates to the ability, if desired, to utilize a thinner walled pipe and still meet the same performance requirements while delivering increased flow capacities without compromising safety or long-term service.

With regard to installation costs, because HDPE pipe is both flexible and strong, it is preferred when using horizontal directional drilling (HDD) techniques. Starting the pipe run with just a small hole about 3 feet wide, a crew can easily pull the pipe several hundred feet under the surface, either bursting an existing deteriorated line to replace it or boring to install a new line. These underground methods reduce expenses in labor and minimize needs for equipment. Plus, they eliminate the need for digging trenches. Installations done by HDD can reduce total job cost by 50 percent with savings ranging upward into significantly higher ranges. Dependent upon the circumstances for any given scenario, like repaving requirements, which often are necessary when using traditional dig-and-replace methods, savings can be far more dramatic.

Overall, HDPE pipe has been found to have the lowest life-cycle cost for any pipe material and the lowest failure rates for water mains. Understanding this fact is motivating cities to implement conversions, rehabilitations and expansions with HDPE materials. The City of Palo Alto, Calif., is one in which a program to convert its complete municipal potable water system to HDPE materials is under way. The city started to use HDPE pipe because it could be installed by boring instead of the open-trench method.

According to Greg Scoby, P.E., manager of water, gas, wastewater engineering for the City of Palo Alto Utilities Department, ?We have been using this installation method since around 1997. Before, we were doing about 20,000 ft a year with cut-and-cover. Now we are able to increase our replacement rate by 50 percent with the move to directional drilling. Not only is the installation time much faster, but we also are realizing a significant reduction in costs since we no longer have to completely tear up our streets, re-route traffic or replace surfaces. Said another way, directional drilling allows us to do a better, faster job and install more feet of pipe for about the same dollar amount.?

Another example can be found in the city of Livonia, Mich. Because of increasing leaks in the water system, it could not maintain pressure or flow rates, and the loss of treated water became financially crippling. The worry there, too, focused on the possibility of contamination because of infiltration. The city identified HDPE pipe for replacement of some 27,000 ft of water mains to deal with these problems and selected it as the most sustainable and safeguarding solution.

?During the past 20 years we experienced an increasing number of incident reports of broken water mains that required digging up the streets to do the repairs,? Mayor Jack Kirksey said. ?At first it was manageable. But during the past five years the failing sections were reaching a catastrophic stage. Not only were we losing water, a valuable resource, but the cost to our taxpayers was significant. We had to find a way that would solve this problem and also be financially prudent. In other words, find the best system that would last the longest and have the most realistic cost.?

These are just two examples, but there are hundreds of other cities large and small, urban and rural, where HDPE pipe is solving cost and performance issues for the long haul. The choice of pipe material for any application, whether underground or above ground, can be the most important decision for the entire project ? and many times it has influence over the complete life-cycle economics for a system. So when contemplating and planning for sustainability, a comprehensive approach incorporating full life system considerations is imperative.

Palo Alto, Calif.

The City of Palo Alto Utilities (CPAU) services 60,000 people in northern California and has been replacing its entire 214-mile water main system with PE 4710 pipe. According to city officials, lower costs for both installation and material life cycle are notable. The material is resistant to internal build-up and abrasion, plus it provides a leak-free, fully self-restrained system. Using the model presented in the Jana study, performance projections are in excess of 100 years based on the water chemistry and operating parameters of their system.

Livonia, Mich.

The city provides more than 16 million gallons of water daily (MGD) to more than 38,000 residential, commercial and industrial customers through some 400 miles of water main pipe that varies in size from 3 to 36 inches. Like many other communities today, it was faced with potentially expensive decisions concerning sections of the water system nearing the end of its useful life. Nearly 23,000 feet of deteriorated water main was replaced with HDPE pipe to reduce costs and improve its water infrastructure with a long-life product

Tony Radoszewski is the executive director of the Plastics Pipe Institute Inc., the major trade association representing all segments of the plastic pipe industry. PPI is dedicated to promoting plastics as the material of choice for pipe applications and is the premier technical, engineering and industry knowledge resource publishing data for use in development and design of plastic pipe systems. Web: www.plasticpipe.org.

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