Keeping the integrity of a water conveyance system is critical, says John Kurdziel, director of Technical Services and Market Development for Advanced Drainage Systems (ADS). “You put a lot of money into treating the water,” he says. “The last thing you want to do is lose it.”
An aging underground infrastructure, a focus on water efficiency as a conservation effort to offset ongoing water shortages, and a concern for water quality are all factors that come into play as public and private water utilities consider how they will address their own water conveyance systems. Advances in pipes, pumps, and storage tank systems offer many options.
Plastic Performance
The biggest advancement in plastic pipe comes with the advent of a high performance polyethylene that meets ASTM PE4710 standards, says Tony Radoszewski, executive director, Plastics Pipe Institute (PPI).
“The advancements in technology have brought out a more robust polymer that delivers a higher-strength performance in pipe as a finished product,” he says. “Because it can handle higher stresses, it allows the change in design factor from a 0.5 to a 0.63, which means you can effectively have a thinner wall in the pipe.”
In addition to water and wastewater, applications include pressure and non-pressure installations in the electrical, industrial, and telecommunications industries as well. One such application is Underground Solutions’ (USGI) piping project in Sacramento, CA. The city had been working for several decades to replace approximately 63,000 lineal feet (LF) of riveted steel water transmission lanes that were installed between 1870 and 1950. Some 37,000 LF have been replaced, with many sections of removed pipe displaying severe corrosion, including some holes penetrating through the entire pipe wall.
One recent project involved replacing 2,500 LF of 24-inch riveted steel man constructed in 1903 in the downtown area. To minimize disruption, slipline installation was selected for a 1,500-LF section of the project. City officials had considered a slate of options that included ductile iron, HDPE, and Fusible PVC. The city had selected the C-905 pipe for a downtown potable water slipline project. Its installation was completed in June 2010. The pipe had offered a 235-psi pressure rating while providing the largest flow area per outside diameter and enabled the city to use standard mechanical joint connections for fire hydrant and valve connections, eliminating the need for specialty fusion skills or stocking of specialty parts for future maintenance.
Sacramento is one of many clients for which Underground Solutions has provided Fusible PVC pipe for sliplining projects. Bob Walker, P.E., vice president of engineering applications for USGI, says the company has supplied more than one-half million feet of water and wastewater pipelines to renew water and wastewater pipelines in 200 projects, particularly in cases where adjacent utility lines have made “no-dig” the preferred option. Municipalities that have used the sliplining technology include El Paso, TX; Harrisburg, PA; Newport, RI; Hamilton, OH; Secaucus, NJ; Laguna Beach, CA; Atherton, CA; Helena, MT; Bremerton, WA; South Jordan, UT; Albuquerque, NM; and Bakersfield, CA.
Prior to 2004, pipeline rehabilitation was primarily accomplished using such lining technologies as cured-in-place-pipe (CIPP), epoxy coatings, cement mortar lining, or swaged/folded HDPE. While viable in applications such as gravity sewer and other non-pressurized pipe rehabilitation, Underground Solutions endeavored to provide an option for water transmission and distribution lines and many force mains where higher pressures are common. The company points out that liners typically rely, to some degree, on the host pipes and–with the exception of HDPE liners–are generally not stand-alone systems.
There are ongoing political efforts to ensure the integrity of the nation’s water conveyance system. Members of the National Association of Water Companies (NAWC) recently took to Capitol Hill to encourage lawmakers to take actions to support policies on environmental, finance, and tax issues of benefit to the companies and the communities they serve.The private water companies of NAWC service nearly 73 million customers in
the United States, almost one quarter of the nation’s population.
Among its recommendations:
• Support legislation to expand the use and availability of tax-exempt financing
for water projects. It is estimated that by removing existing restrictions to this financing, $5–6 billion in private capital would be unlocked to be deployed
towards water infrastructure projects.
• Reauthorize the Clean Water State Revolving Loan Fund and enable private water service providers to extend much-needed wastewater solutions and service to under-served communities and noncompliant systems.
• Consider the development of an infrastructure bank that would act as a real bank and encourage public-private partnerships.
Fit to Scale
End-users have chosen sliplining using Fusible PVC pipe for its strength-to-weight ratio, longevity, corrosion resistance, flexibility, resistance to the oxidizing effects of chlorine-based disinfectants, and to gasoline and gasoline-saturated groundwater. ADS, which manufactures corrugated HDPE pipe, has introduced a product line and specifications for sewer pipe and high-end stormwater usage.
“The key is these chambers now are coming in sizes that are equivalent to large diameter pipe,” says Kurdziel. “That’s going to give a lot of advantages. The economics of that almost make them a win for everybody, because they can store more water in a smaller footprint. There have been numerous changes in the specifications as of late. In the past, there weren’t really any design requirements, but these now are being designed structurally the same way all of the major piping products are designed.”
ADS manufactures pipe products for use in water systems that serve as low-pressure distribution lines. In Lexington, SC, ADS is installing the MC4500, the first installation of the largest injection molded stormwater retention/detention chambers in the world at the site of a new middle school, says David Mailhot, national engineering manager for ADS. The 320 chambers being used are 60 inches tall and 100 inches wide, Mailhot notes.
“You’ll see structures like that, that are maybe 30 inches tall, and this is twice the size of what’s been normally available in the marketplace,” he adds. “This is useful where water must be retained onsite or treated before discharge and the subsurface systems become valuable, in that you won’t have to purchase additional land to essentially develop the site.”
Such products are commonly used for urban retrofits, Mailhot notes. “We have a tight site, and one of the problems is how much water can you store in a given footprint. Historically, smaller chambers have been used, but you can only get so much water into the footprint because they are not very deep, not very tall. These new chambers enable significantly more volume to be stored in a given footprint.”
The chambers are not only storing water underground, but also in open-graded stone surrounding the structure. The open-graded stone provides a dual role of support for the structure, and because it’s open-graded, there’s about 40% veracity for additional storage. The system also includes an outlet control structure and helps to achieve better water quality, Mailhot says.
“If you’re infiltrating, then you’re not discharging water that contains sediments or other pollutants, so for retention, we’re putting it back into the ground and that certainly minimizes impact on receiving water bodies,” he says.
When used as detention systems with an outlet, “You get very good separation of sediments as water travels through the subsurface system,” says Mailhot. “The system has an isolator row–a row of chambers wrapped in fabric and stormwater passes through that row before it reaches the rest of the system.”
The sediment filter out as the water passes through a filter media.
“These systems can be easily retrofitted to take out some of the pollutants that would otherwise be discharged to receiving water bodies,” says Mailhot.
Additionally, the systems have been used increasingly more for rainwater harvesting.
“For rainwater harvesting, an engineer would design a liner system around the perimeter of the excavation,” says Mailhot. “Now the chamber system and the surrounding stone is surrounded by an impermeable liner. The water is captured in the system and pumped out as needed, usually for irrigation purposes.”
Strength and Stability
Ductile iron pipe is being used more frequently in trenchless applications and rehabilitations, notes Paul Hanson, regional director of the Ductile Iron Pipe Research Association (DIPRA).
“Due to its great strength, ductile iron is the pipe of choice for horizontal directional drilled and pipe burst installations,” he says.
“There are a lot of different products on the market, and each one has relative strengths and weaknesses,” says Kurdziel. “Some of them are overkill for some of their applications and carry the price with them. They are certainly good products, no question about it.
“For high-pressure applications, you would have a concrete cylinder pressure pipe or ductile iron pressure pipe,” he says. “Both of those do a phenomenal job in typical water pipe in the street. They also are using those for low-flow applications, and as such, it’s an overkill. That’s the target market where we come in, and our products are considerably less expensive. There are a number of different products coming from the upper end, and we’re coming from the lower end. Both are feeding into this middle target area.”
“As important as water efficiency is water quality,” says Hanson. “Cement-lined iron pipe has been providing excellent water quality and hydraulics for as much as 89 years of service.”
“Field testing in working systems on pipe in service as much as 77 years has shown the cement mortar’s protective qualities are maintained for the life of the pipe,” he says. “DIPRA’s brochure on cement mortar lining goes into the details of these tests, which revealed an average “˜C’ value of 140.”
To ensure water quality, “Certification to NSF Standard 61 should be required for all pipe products that are used to transport potable water,” says Walker. “PVC pipes have been thoroughly evaluated and certified by NSF for more than 50 years.”
Repairing, Replacing, Rehabilitating
In determining whether to repair, rehabilitate, or replace water conveyance structures, entities consider projected, ongoing frequency and costs of reactive repair versus the costs associated with rehabilitation or replacement, Walker points out.
Owners also consider such factors as the state of the existing line, future growth, depth, and cost of each alternative, says Kimberly Paggioli, vice president of marketing and quality control for Hobas Pipe USA. Hobas has been manufacturing centrifugally cast, fiberglass reinforced, polymer mortar pipe for the past 25 years.
The best approach is an asset assessment to determine the existing pipe’s condition, following up with a prioritization list, says Radoszewski.
“Once they make that assessment, then they put in place that plan to start upgrading those assets as necessary,” he says.
If it’s a gas pipe, the driving factor is safety. If it’s a sanitary sewer pipe, it may be an EPA consent decree. When water leaks, while it may not be a safety or health issue, it’s a loss of valuable water, he adds.
“Of course the challenge that’s facing us is right now is a lack of a revenue source because they are all struggling–some are struggling more financially than others,” says Radoszewski. “The ones that are struggling financially are only doing repairs when a failure occurs. That’s all they have the resources for.
“In some of the more stable communities or ones that may have financial challenges but are stepping up to get their assets up to speed more quickly, they are taking the approach where they’re going to rehab the system much in the same manner of the gas system–they identify the assets and are doing a dedicated renewal process,” he continues.
“Sustainable infrastructure is dependent upon a sustainable level of funding that covers operation, repairs, and replacement/rehabilitation,” adds Walker. “The out-of-sight, out-of-mind nature of buried pipe utilities has resulted in their neglect and lower-than-deserved priority. As more pipe failures occur and the consequences get worse, attention and funding priority will eventually grow. Unfortunately, this postponed reaction and response will substantially increase the cost and disruption that will be required to deal with the problem.”
In determining whether to repair, rehabilitate, or replace, many engineering factors come into play, Hanson points out.
“But it is an economic question that requires good information,” he adds. “The better the utility records are on the infrastructure and its performance, the easier this question is to address. Generally, the decision is made on the basis of which alternative is the least expensive in the long run.”
Proper inspection and assessment plays a key role in a systemized, managed approach to pipeline replacement and rehabilitation, says Walker.
That begins even as pipes go into the ground.
“Construction supervision is necessary to ensure that the funds for engineering, materials, and installation have been spent properly,” points out Hanson. “It has been said, “˜You have no right to expect, if you do not inspect.'”
The criticality of inspection continues long after pipe installation or repair in mitigating small problems before they become major issues.
“Pipe inspection is necessary on a routine basis to detect issues within the line,” says Paggioli. “If you catch the problem when it is small, you can prevent catastrophic failures.”
With public and private dollars being stretched to the limit these days, that’s critical. Public and private entities struggle to address the conflict between the need to address an aging infrastructure and strained funding resources.
“Many entities lack the funding necessary to rehabilitate existing lines or construct new ones,” points out Paggioli. “They are allocating funds to the projects that they determine are of the utmost importance.”
Hanson says concerns over the nation’s water conveyance system are not necessarily dominated by an aging infrastructure.
“More than 600 North American utilities are members of the “˜Cast Iron Century Club’ and much of that 100-plus-year-old pipe is still doing fine,” says Hanson. “Other pipes that are much younger may need to be replaced due to issues such as breaks, water quality, size, and fire flow requirements.”
Hanson cites EPA estimates that most utilities will have to double their rates over the next 20 years to keep up with infrastructure needs.
“This would require a rate increase of 3% per year over inflation,” he says. “Involving the stakeholders in this process and getting their support is paramount to its success.”
By demonstrating the need based on an economy analysis, water utilities can make a strong argument for the need for pipe replacement, Hanson points out. He adds that the American Water Works Association (AWWA) and other professional organizations can provide assistance with tools and ideas for involving stakeholders in the needs of their systems.
Factoring in maintenance costs offers a true picture of the total cost of a water conveyance system. Manufacturers say improvements in their systems minimize those costs.
“Proper recordkeeping in maintenance will greatly assist in making educated decisions for use of the available rehabilitation and replacement funding priorities,” points out Hanson.
Maintaining any kind of distribution line entails cleaning out debris. “The pipes–especially the polypropylene–have extremely good long-term properties, both from the durability standpoint as well as from structural performance,” says Kurdziel. “I wrote up the ASTM standards for this; I wanted to make sure these pipes were structurally sound.
“If you go into a lot of the websites, you’ll see testing to an ASTM D3212, and it goes up to a standard and it goes up to a 10.8-psi test, but it’s short-term,” he continues. “Most form of plastics are time-dependent materials. We put a 1,000-hour test in there under pressure, which is superior to anything else most tests do. Any that pass that would be the water pipe people, and that would be the ductile iron and the concrete pressure pipe.”
Non-Revenue Water
Water loss can have a significant impact on utilities. “Water loss has a direct economic impact on water systems, and it is fortunate that ductile iron pipe joints must be bottle tight at installation to pass pressure testing requirements,” says Hanson. “Make up water allowed in AWWA C600 is for the rehydration of cement mortar lining and the increase in system volume as the pressure is raised during testing.”
Adds Walker, “Water loss is an unnecessary expense and wastes both energy and resources.”
In order to maximize water efficiency, “Underground pipes need to be leak-free, have long-life, low-maintenance durability, and be capable of providing a sustainably smooth, low-friction, inner-wall to minimize the energy used for pumping,” says Walker.
The PPI published reports last fall regarding a research project to identify the long-term performance of polyethylene-type systems based on water conditions in municipalities across the country.
“Water is not the same in one area of the country as it is in the other,” says Radoszewski. “We had to take into consideration the water chemistry, the temperature, and the pressure that the system operates on, but we’ve been able to identify the parameters that can deliver more than a 100-year service life for polyethylene pipe, and that’s becoming more important to the municipality.”
Kurdziel points out that anytime a pipe has joints, there is potential for leaks, adding that the ideal situation is to have the least amount of joints possible.
“You have to have a joint configuration that maintains long-term integrity, and long-term integrity means preventing root intrusion or intrusion into the joint that opens it up and causes leaking or some kind of mechanical type seal that prevents any deterioration of that joint configuration,” he says.
Going forward, the industry will produce products that will be completely watertight, Kurdziel says. Already, municipalities spend a lot of money to make sure water lines have high integrity, he adds.
“There’s not going to be a leakage allowance,” he says. “We see that from the storm side already where people don’t want to have any leakage of stormwater because you get pollutants from pipes going in or out of the area. That also includes sewer lines where they are paying for treatment of sewage.
“You want to keep everything where it is and keep the water in the pipe. Watertight integrity is going to become even more critical than it is already.”
Equally critical in the water conveyance system are water storage tanks. That sector of the industry is introducing new technologies to minimize maintenance and maximize water efficiency, quality, and safety.DN Tanks is a recent merger of the DYK and Natgun companies. The merger enables the newly formed company to combine expertise from each firm on constructing prestressed concrete tanks to provide more options to tank owners, notes Eric Magee, a regional manager with DN Tanks. Since the merger, the company has been working on new prestressing technologies, says Magee.“We’re working on new tank options that are still within the standards that we can offer, such as a Type 1 tank with a dome roof, which is not typical,” he says. We’re also looking at wrapping a Type 3 tank, which is a precast tank, with galvanized strand, and that’s not typically done, with a few exceptions.”
Magee says the benefit of concrete is that it doesn’t require maintenance and it doesn’t need coatings, “Concrete has no corrosion issues at all, inside or out. The concrete tank that is painted on the outside is purely aesthetics. It has nothing to do with the protection of the concrete. Once the concrete tanks go into service, they can remain in service pretty much their entire lives.
“We prestress it, so we’re compressing the concrete, which will keep the tank wall crack-free and enhances longevity, and it makes for a very durable tank,” he says. “We call them 100-year tanks.”
Fiberglass tanks are becoming more common on the landscape. Xerxes manufactures fiberglass tanks for a range of water storage applications that include potable water, rainwater harvesting, fire protection systems, and stormwater detention.
The tanks themselves have a National Sanitation Foundation (NSF) listing for the storage of potable water, which differs from those on the market whose linings or materials are NSF listed, but not the tanks themselves, says Tom Tietjen, vice president of sales and marketing for the Xerxes Corporation.
“When it comes to potable water, the significance of a third-party listing is very important, and NSF is viewed as the standard for that,” he points out.
One of the benefits of fiberglass tanks is that they require little maintenance or inspection, notes Tietjen.
“Fiberglass does not rust or corrode, so properly installed, periodic inspections, and maintenance shouldn’t be necessary,” he adds.
Containment Solutions Inc. (CSI) manufactures fiberglass solutions for the storage of petroleum, water, wastewater, and other applications. CSI now offers aboveground fiberglass water storage tanks to compliment its line of underground tanks. The aboveground products include residential rainwater harvesting tanks with a capacity of 300 to 1,050 gallons and commercial water storage tanks ranging from 1,200 to 20,000 gallons.
Clients chose CSI products because “fiberglass is often sought for its inherent ability to resist rust and corrosion,” says David Heiman, director of marketing for the company.
Determining whether to repair, rehabilitate, or replace a tank is a case-by-case consideration, says Magee.
“In the context of concrete tanks, a lot of times, if the wall is usually in good shape, you have a solid floor and a good roof, and maybe the tank is worth saving and rehabilitating,” he says. “However, if you have a tank that has a cracked floor, then the tank may not be worth the money to save because if it’s a catastrophic crack, and then the tank may be not feasible to repair. Likewise, if the wall or the roof is in distress it may not be cost-effective to repair the tank.”
In deciding whether to repair, rehabilitate, or replace a storage tank, Heiman points out that corrosion can cripple a tank’s structural integrity.
“In some cases, leaks in tank walls or liners can be repaired, but often when corrosion has caused structural deterioration, the entire tank will need to be replaced,” he says. “If you are purchasing new, you need to consider corrosion in your product life cycle cost. How long do you want the tank to last? Corrosion resistance in building materials can vary. For long-term projects, fiberglass is usually the best option because it is non-corrosive and will not degrade over time.”
As water utilities struggle with budgetary concerns, the impact of water loss in dated and degraded structures can set up a Catch-22.
“Our experience as it relates to lift stations that are part of a municipal collection system is that infiltration and exfiltration can be very expensive for the owner to deal with,” says Tietjen. “To the extent that it requires building or expansion of new wastewater treatment facilities, the cost impact is significant.”
Too often, says Tietjen, water infrastructure seems to be a less important upgrade to prioritize, versus other demands on funds.
While the majority of his company’s tanks are slated for new facilities and needs rather than replacing existing ones, “the lack of state funds across the country is certainly a limitation on infrastructure upgrades,” he adds.
Typical DN Tank clients include local municipalities, water departments, water districts and sanitation districts. These days, capital purchases are a challenge for cash-strapped municipalities. Many of them qualify for grants and loans, Magee says. Some districts are putting in rate increases. Public partnership agreements between municipal entities and developers are becoming more common, he says.
“With populations growing and water supplies shrinking in nearly every community, municipalities and utility districts are quickly realizing that current water management plans are unsustainable,” says Heiman. “The bottom line is that it simply costs too much to treat and supply drinking water to the public without help.
“All levels of government are facing the same question—invest now with tighter budgets or hope that the money will be there when water rates escalate to record levels?”
Some areas have immediate problems and are forced into funding projects or at least phases of projects, Heiman points out.
“For areas with the luxury of a choice, the approach many local communities are taking is to incentivize homeowners and businesses to proactively conserve drinking water by reusing collected rain/runoff water,” he says. “Rebates on sales tax, water bills, and even government subsidies can persuade individuals and corporations to capture water, which in turn reduces the burden on utility companies.”
As for those entities that do upgrade or replace, they’re doing so with tank materials that require little to no maintenance. Another consideration is planning for areas that will experience more population growth.
When it comes to sizing of tanks, Magee notes that civil engineers who design the water systems require a certain amount of storage for the peak daily use of water, and then sometimes add on 2.5 times that amount for fire storage.
“But you don’t want to oversize the tank either; so there’s a balance between sizing it just right and sizing it too big,” says Magee. “You want to be in between the two, so you can get proper turnover of the water. Otherwise, water sits too long, disinfection starts to decrease, and it can cause water quality issues.”
When it comes to maintenance, concrete tanks need very little, says Magee.
“Prestress keeps the concrete in compression and, therefore, adds durability to the structure, so the only inspections that need to be done at a minimum of every five years is to make sure that there are no cracks,” he says.
“You want to do an inspection on the inside of the tank with a diver or a robot to take a look at the interior of the concrete and make sure there’s no issues associated with that. With any tanks, you want to go in and clean out the silt and the build-up of biofilm and inspect the floor to make sure there are no issues down there,” continues Magee.
As for inspection of water tanks, Heiman points out that, “for many underground water storage structures, the act of inspecting is not as important as the ability to be inspected.
“A water storage system designed and installed properly should not need much inspecting, however Murphy’s Law tells us that problems can happen even in the best system,” he says. “Some underground storage options rely on a sealed bladder membrane. These systems can be effective at storing water, but once the system is infiltrated, there is not a simple way of inspecting or treating the contamination shy of unearthing the buried system. The proper storage solution should have watertight access openings at grade or ground level.”
As long as water districts operate the tanks with proper turnover and use the proper disinfection, there are “very few issues” with concrete tanks, Magee notes.
“I know some districts put in certain mixing systems and baffle walls to keep water moving in one direction and other features such as that,” he says. “There are aftermarket tank mixing systems that are available that keep water moving. All of these enhance the water quality of the tank.”
Safety problems also are minimized through concrete tanks, Magee says.
“Prestressed tanks have a history of performance in an earthquake without damage,” he says. “We’ve got several case studies where we have had several tanks near epicenters, and all of them have performed excellently. They were able to supply water in emergencies where there are fires and dire water needs in the communities. As far as safety, concrete tanks have also been shot at with guns, and the penetration of the bullets into the concrete doesn’t do any damage to the contents.”
As for employee safety, as long as water district workers are properly trained, there should be no problems, Magee says.
“There are some OSHA standards for the ladders, and they’re usually safe climbing systems and workers wear harnesses,” he says. “They also use air monitoring systems to make sure there’s enough oxygen in the tank in case someone wants to go inside of it. Everyone is harnessed. Some districts put in those little crane systems where they can hoist someone out if they pass out, or if there’s a problem medically they can lift them out. We’ve seen some of that put on our systems.”
Water efficiency often translates to the need for storage, either short-term through stormwater storage or lift stations, or long-term through rainwater collection, greywater systems, and fire protection, Tietjen points out.
“Reduction in use is critical to efficiency,” he says. “To the extent that collection and storage of water can be utilized to retain water supplies for later use in lieu of new potable water sources, efficiency is achieved.”
Heiman agrees, adding that water efficiency and containment structures go hand-in-hand, Heiman says.
“There are ways of slowing down runoff water using retention ponds, ditches, even underground drain chambers, but to truly manage water efficiently, the system should store water for reuse,” he says. “By collecting and then reusing the stored water, a vast amount of potable water can be offset. The ultimate goal should be to use non-potable water for non-potable needs. Slow dispersal of runoff water is certainly helpful, but not efficient.”