Water tanks play a critical role in the water conveyance system, providing storage to meet a community’s potable water needs, as well as emergency water for fire protection.
Like much of the underground infrastructure, water tanks are aging. Many are being replaced with newer systems; at the same time, a trend is developing where water tank managers are being more proactive about maintaining tanks now in place. There are other concerns, too: the safety of the water supply and how maintenance acts to ensure water quality and increase water efficiency. Choosing the right material for a water tank depends on local considerations—in California, for example, water tanks must meet seismic concerns. With the right maintenance, water tanks can have a long lifespan.
Different tank materials call for different maintenance approaches. Manufacturers of each material type endorse the advantages their company’s product provides to the water conveyance system. For water storage, Containment Solutions manufactures fiberglass tanks of 5,000 gallons and up. The company makes its tanks with an inside/outside mold.
“The outside surface is a little rough, but the inside is smooth,” says David Heiman, marketing manager. “It’s nonporous; there are no holes or gaps. We design these to hold fuel, because there can’t be any contaminants in fuel. We use the same technology for water.”
Xerxes Corporation manufactures underground and aboveground fiberglass storage tanks, for many different water/wastewater applications.
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Photo: Jeran Aero Graphics Inc., San Diego, CA
Six-and-one-half-million gallon tank in Olivenhain, CA |
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Photo: Warren Aerial Photography Inc., Pacoima, CA
Architectural treatment on a six-million-gallon tank in Ontario, CA |
Kristi Peterson, marketing manager for Xerxes, points out that, in a time of water shortages throughout the US, fiberglass tanks are designed not to leak and are thus more water efficient than some products designed for temporary storage.
She also makes the point that, in terms of maintenance, once the tanks are properly installed, they are “worry-free” and do not rust or corrode, thus saving time, money, and extending their life span.
Heiman says water tank materials should be carefully chosen, because tanks are often used for emergency situations, “and if your tank leaks, you don’t have any water.
“If potable water sits long enough, you’ll have to treat it. Water begins to get stagnant regardless of where it’s being held; it’s subject to bacteria or possibly algae or bugs that can get into system. That’s dependent upon filtering components outside the storage tank and is based on how the water moves through the system and is stored in the tank.”
Concrete tanks can be aboveground, partially buried, or completely buried. All of DYK’s tanks are on the ground, says Eric Magee, regional manager of business development for DYK.
United Tank Systems manufactures bolted tanks, typically glass-lined. The company also makes epoxy and stainless steel tanks. Company president Joel Portmann, adds that maintenance inspections should be done every five years.
Landmark Structures manufactures composite elevated water storage tanks—the tank is steel, while the pedestal is made of reinforced concrete. According to the company’s statistics, more than 75% of all elevated water storage applications in North America are now composite tanks.
“It’s been very well accepted as a structurally efficient configuration, because there is a maintenance-free reinforced concrete pedestal that requires no painting or recoating,” points out Bill Restmeyer, marketing director.
Caldwell Tanks’ water compartment is made of carbon steel. David Cull, tank inspection manager, says, “We do build composite elevated tanks with a concrete shaft. Its supporting characteristics make it a very economical material. We still put the water inside a carbon steel container that’s painted, so we can maintain the water quality.”
Cull says he’s inspected tanks that have been in service for more than a century. He notes an evolution of water tank owners becoming increasingly proactive by instituting maintenance programs for regular tank inspections and touch-ups, rather than letting them go.
Caldwell Tanks has a tank asset preservation program. “We are proactive about training all of our applicators and having a management staff that understands the intricacies of the protective coating market,” says Andy Odorzynski, the program’s administrative manager. Significant amounts of money can be saved through proper maintenance, points out Odorzynski.
“It costs money to deliver clean and maintained water to these customers, and it’s a challenge and a benefit to maintain these tanks,” he says. “It is much more financially savvy to maintain these tanks and to take those difficult initial steps of restructuring your budget to be able to afford maintenance, and to realize you have to schedule downtime to provide a system that can handle these things through your budget planning.”
Doing so is an alternative to “finding out you have a catastrophic paint failure and the tank needs to be brought down,” he adds. “There are some tank owners who experienced failure they weren’t expecting and go through the difficult steps of coming up with a large amount of money, just to keep the system running, where they could have broken that cost down over a decade and run smoothly right through it.”
Restmeyer agrees a well-defined maintenance plan is a key factor in avoiding bigger problems in the future. “Given the nature of these tanks, there is labor involved in doing work inside the tanks, so it can be very beneficial to stay on top of that on a planned basis,” he adds.
A typical visual inspection should be done at intervals, whether it’s every year through every five years, Magee says. -Inspections should monitor for water-tightness, cracks, or
delamination. Interior inspections—whether by human divers or robotics—should be done every three to five years to check the condition of the concrete below the water level, he adds.
While discussion of the nation’s aging underground infrastructure focuses on pipes, there also are a number of aging water tanks on the US landscape. Leslie Moulton, senior vice president and director of the California water practice with ESA Water, says while she has no hard data on the condition of water tanks nationwide, “it wouldn’t surprise me if they were insufficient in number, and if they were aging along with the system,” adding she’s seeing more projects calling for replacing and adding more storage points on water distribution systems.
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Photo: Containment Solutions
Maintenance serves two functions: exterior aesthetics and interior water quality. |
In California, where earthquakes and wildfires are of ongoing concern, adequate systems are critical, says Moulton.
Magee says his company is replacing many aging storage tanks. “Anything 40 years or older should be looked at to assess the condition,” he says. “You have to make sure there are no issues with leakage and bacteriological growth in the water system.”
In earthquake-prone regions, seismic concerns underscore the codes that create direction for manufacturers on building seismic resistance in the tanks, says Magee.
Case in point: Calleguas, CA.
Susan Mulligan is the manager of engineering for the Calleguas Municipal Water District, which services 600,000 people in Ventura County, CA.
“We had a seven million-gallon steel tank that was 45 years old and getting close to the end of its life,” says Mulligan. “We’re a wholesale water agency, so there are other water agencies pumping out of that pressure zone. Some hydraulics in our system had changed. We wanted the tank at a slightly higher elevation to give it a little bit more pressure and make it easier for everybody to pump out of that zone.”
California’s seismic standards changed at least twice significantly after earthquakes in the 1970s and 1990s.
“Our tank no longer met seismic standards,” says Mulligan. “We decided to replace it with a cast-in-place concrete tank. The property we own is on a hillside, and the way the site is configured, we needed to raise the reservoir, and the cast-in-place concrete was the only way we could do it. As long as you design it with conservative seismic standards, a cast-in-place concrete tank should be good for 100 years.”
The Calleguas system has redundancies: The older tank was replaced with one 2.6-million-gallon tank and a 4.4-million-gallon tank, partially buried and screened with landscaping.
“The two tanks are required,” says Mulligan. “It was not required 45 years ago—although it should have been—to clean our tanks every five years, and it’s much easier to do that if you have two.”
She adds that problems can be rectified earlier by doing so. “You can clean them, which is critical for water quality. Tiny bits of silt build up in the reservoir over the years, and it’s good to get that cleaned out. The big challenge we have with cleaning reservoirs is the discharge standards that we are subject to for taking the water out.”
Calleguas also has relocated inlet and outlet pipes on opposite sides of the reservoir to allow for better water quality through mixing in the reservoir.
Calleguas uses divers to inspect the reservoir and clean it with vacuums, so that the water can be kept inside the reservoir, Mulligan points out.
Mulligan is concerned that as municipal budgets have been squeezed, their officials will accordingly squeeze down on their water tank budget.
“Hopefully they won’t,” she says. “It’s important for fires and for managing daily peaking. If you have a line break in one place, the reservoir can provide water from a different direction.”
Addressing the nation’s aging water infrastructure, Portmann says his company has found that a lot of infrastructure put into place years ago is now operating beyond its capacity and, due to budget constraints, is not being modified to meet expanded capacity. “There is a lot of mass updating that needs to be done in a short amount of time,” he points out.
Eric Lamon, vice-president of Landmark Structures, says most new tank construction over the past several years has been driven by growth and demographics, not necessarily by the aging and condition of existing tanks. “Only about 10% of our projects involve the demolition and removal of an old tank, and that is typically dictated by the cost-effectiveness of consolidating capacity in the new tank, in line with the trend toward more storage capacity,” he says.
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Photo: Containment Solutions
“As water becomes more scarce, there’s going to be more of an emphasis on longer-life structures with lower maintenance.” |
Lamon adds there are thousands of water tanks throughout the country in need of maintenance and repair, “due, in part, to the fact that procurement over the years has been driven by competitive bids and lowest initial cost, which doesn’t always provide the best value, lowest life cycle, or overall cost.
“In many cases, routine maintenance has been pushed off, which tends to have a cumulative effect and penalty over time,” he adds. “Of course, we see that in our infrastructure situation across the board.”
Maintenance serves two functions, Cull points out: exterior aesthetics and interior water quality. “You want it to be aesthetically pleasing; you want to be a good neighbor,” he says. “From a structural standpoint, you want to make sure the tank is maintained properly to prevent corrosion. The populace does not see that, but it is critical.”
Additionally, water quality maintenance is important. “You want to store it and move it through the tank properly, so you don’t have water quality issues that come with stagnant water,” adds Cull.
Water quality maintenance needs to be done on a regular basis, points out Magee. Sediment builds up in the tank over time. While the tank doesn’t necessarily need to be emptied out, it can be cleaned by a robot that sucks up the sediment or with a vacuum by a diver.
“It allows them to clean up the floor,” says Magee. “They can assess the concrete on the floor and look around for any other issues while they’re in there cleaning the tank.”
By waiting too long to do this type of maintenance, “if sediment builds up too much in the tank and water is drawn from too far down, it pulls up the sediment and compromises the water quality,” he adds.
“While tanks can contribute to the management of water quality by virtue of integrated equipment or processes designed for that purpose—such as mixing systems, treatment, monitoring, regular inspections, and cleaning—quality is really a larger function of the water system itself.”
Systems can be operated “intelligently” by doing production pumping, whereby tanks are refilled at off-peak hours, says Cull.
“Some utilities are doing this very extensively,” he says. “Others, where there is not a financial reason to do so, are not doing so. But a water plant can only produce so much water per hour. There are times during the day where system use far exceeds the ability to produce water.”
Improper maintenance work can wreak havoc on a water utility’s system. That was the case with a paint job gone badly in Conemaugh Township, PA. Conemaugh had two welded steel painted tanks—one built in 1964 with 215,000 gallons of storage, and the other built in 1985 with 300,000 gallons of storage. The municipal authority services 2,575 customers for a total of 7,900 people. Both tanks needed new coating systems on the outside and on the interior. A bid was put out, and the low bidder was awarded the contract. The first tank was painted and finished by the end of September 2008.
Volatile Organic Compound (VOC) testing was conducted, with good results. The tank was quickly placed back in service. But the contractor had scheduling difficulties, which pushed the work back on the second tank, which serviced 60% of the water customers.
“They postponed our painting, hoping to get a break in the weather in November and December and try to finish it. That didn’t occur,” notes Patrick Mulcahy, operations manager for Conemaugh Township Municipal Authority, adding that in his water district’s region, the weather can get especially cold.
“They got behind the eight ball with the weather; they continued to try to fix it,” says Mulcahy. “They tried to get everything finished before the contract expired in February and went through extraordinary measures to try to tent the tank and superheat the exterior and interior in order for the paint to cure. We went with a Tnemec paint system for the exterior and the interior.”
But there were issues with the tank floor curing improperly. “Although they had the coating system on and finished before the end of their contract, when we did the VOC testing, we were getting hits,” says Mulcahy. “As the operator, I was not comfortable with that, and the Pennsylvania Department of Environmental Protection wasn’t going to give us an operations permit.”
The municipal authority went through two different maintenance procedures to try to rectify the problem. The tank didn’t go back online until August 2009. Conemaugh had extended the contractors’ contract, but cautioned that the tank would not be done unless there were a few warm weeks.
“They were insistent upon trying to finish, and it didn’t work out in their favor,” says Mulcahy. “We put liquidated damages against them for a small portion of the contract. They did work with us in order to get this rectified.
“The first time, they re-stripped some of the interior surfaces before the first bottom ring and part of the second ring, in order to try to rectify the areas that had amine blush—the paint system didn’t cure properly,” says Mulcahy. The authority got VOC hits and had the tank repainted and resampled.
“The results we got were still somewhat better, but not where we needed them to be,” he says. “The contractors steam cleaned the entire inside and touched up some of the areas that were still having issues. We had two VOC hits, but they were so minute that the DEP did issue us an operations permit, and we were able to get the tank back online.”
As a result of the experience, Mulcahy recommends that those who operate in a climate such as western Pennsylvania not paint water tanks after October 31. “It’s not worth it,” he notes. “In the end, we do have a good product, but there were a lot of growing pains, and not everybody got along through this whole process.
“Never, as long as I’m involved, will I ever allow someone to paint a tank between November and March.”
Conemaugh had redundancies, however. A bond issue, passed in 2006, provided financing for a number of water system improvements, including a new 540,000-gallon tank adjacent to the one with the VOC problems. Without it, Mulcahy says he’s not sure how the township would have managed.
“That’s what allowed us to delay the contract and get that tank rectified,” he says.
For water authorities, maintenance comes down to budgetary concerns, Mulcahy says. “I don’t care what type of tank you have—they all need to be maintained, cleaned out, and serviced,” he says. “You need to get in and look at them. Too many people don’t do that on the frequency they should.
“We have tried to rectify that on our system; it is absolutely critical,” he adds. “If you have to take a tank out of service and that’s your only tank that services that area, it does give you some issues.”
Portmann says his company avoids the potential of an improper paint job by coating tank components in a controlled environment. “They’re not susceptible to variations in site conditions such as variations involving hot and cold and the accuracy of the surface,” he points out.
Odorzynski says today’s industrial protective coatings put on water tanks “are a much more specialized product than they have been in the past, because of all of the Environmental Protection Agency regulations and evolving technologies.”
There are several factors that ensure coating success, he says: weather conditions, equipment being used, training of the applicators, and safety precautions taken.
“When it’s done properly, these coatings can last much longer and provide a cleanable surface for the water to be held in,” says Odorzynski. “It’s absolutely vital the contractor doing the work has properly trained people, proper equipment, and understands what they’re working with, because if someone is lacking in any of those areas, the customer ends up suffering for it.”
Another issue of concern to water utility managers is water safety. Officials in Kutztown, PA, at one time had to shut its water supply down for 48 hours after discovering a group of people had climbed a large water storage tank that served 15,000 residents.
It was determined that there had been no compromise of the water supply, and Kutztown subsequently upgraded its camera system—which recorded activity on tape—to ‘real-time’ IP cameras embedded with motion analytic technology, which can send alerts to a monitoring station and is subsequently sent out to system administrators, who can call up video stream on their cell phones.
Portmann says his company sees very little being done to provide security for water tanks. “I’m in the business, and I’m afraid of [water tanks being compromised],” says Portmann. “That’s certainly a way to infect an entire population of a municipality. A camera is too late. There needs to be some type of seal on the system to prevent that kind of thing. There is the capability at a relatively low cost to have real-time security, and that certainly should be a part of every system.”
Water supply safety may not be as much of an issue with composite tanks as with “multi-legged” water towers, Restmeyer says. “All access is enclosed and off-limits,” he says. “That’s not to say if someone wants to climb a tank somehow they can’t do it, but it’s more difficult when you’ve got to scale a concrete pedestal that doesn’t have any external ground level access that would be on an older-style configuration.”
Heiman points out that with underground tanks, there is only a single access point, versus the vertical ladder that provides access to tower water tanks. “All of the underground manufacturers are very aware of safety concerns for people, including curious children,” he says. “In general, underground tanks can be hidden more. But safety is a huge issue since you’re potentially contaminating the drinking water of an entire area.”
Odorzynski recommends a locked fence around a tank site. “Access to the structure should be kept locked,” he says. “For tanks with ladders running up the outside, there are devices that shut over the ladder so no one can climb it without having the key to unlock it.”
Magee says in situations where people can gain access to the top of a tank, “everything should be double-locked, and there should be a sensor to make sure the district receives a signal in case the hatch is opened.
“You want to be able to block the access of people stuffing things into the tank through the vent. That can be done with a cage around the vent. Sensors and security cameras cost a lot, but they help in delaying an individual from doing harm to the tank until the authorities can get out there to pick these people up.”
The future of water tanks focuses on redundancy and increased storage capacity. Insufficient storage is an issue for some of ESA’s clients, who can’t take parts of the system down for maintenance or run the system long enough to maintain the water quality because they’re so anxious that they have to keep the one tank they’ve got full, notes Moulton. As such, redundancy has become a catch phrase for most water systems, she says.
“Managers want to have a lot of flexibility to make sure the water is available where and when it’s needed,” she says. “You want to keep water in storage for emergencies like fire, but you can’t keep it in storage too long, or else you can’t maintain the water quality. “There is a constant demand on filling, using, and making sure you’re refilled in advance of an emergency, which nobody can predict. My sense is those running the system are always trying to keep enough water in storage while protecting the water quality.”
System redundancy and increased storage capacity ensures there are parts of the system that can be taken down for maintenance, Moulton points out.
“People are more pro-water conservation and using great sensitivity on the wise use of water,” says Moulton. “We’re in a drought and having water supply issues, so that’s a legitimate concern, but there is a need to understand these systems do better when they have greater flexibility and redundancy.”
That can be a hard sell to people who see expansion or improvement of any kind as serving more people, implying that everyone in drought-stricken areas will get a smaller slice of the “pie.”
Moulton says there is sometimes a perception in California—where water is a precious resource—that new or additional water tanks are put into place to increase capacity—and while that may hold true to provide emergency water for fire fighting, it’s really about “trying to provide system flexibility, maintenance, and proper service delivery,” she says.
Awareness is driving more understanding about water distribution, Moulton says. Many California communities are under voluntary or mandatory water restrictions.
“At the same time we’re fighting on how to develop more water, people are saying they want commitments to conservation,” says Moulton. “Before, people didn’t know much about where their water came from or worry about it too much, but they do worry about it quite a bit now and are getting a lot more knowledgeable about the system because of the conservation sensitivity.
“Municipal water departments are finding themselves with a public that has a lot more interest in what’s in the system and how they run it.”
Manufacturers are responding by building larger tanks. “As water becomes more scarce, there’s going to be more of an emphasis on longer-life structures with lower maintenance,” says Magee.
Watertight tanks will play a key role, he adds. “How can we specify a tank that is known to leak, when we can specify tanks that have a good track record for water tightness?” points out Magee.
Another factor: Computerized operations such as SCADA systems will help utilities monitor and manipulate water systems better, says Cull.
In addition to addressing water shortage concerns, there are other ways tanks can be “green”. Landmark Structures is completing a project in Austin, TX, encompassing new tank design elements, says Restmeyer. The water tank is linked to the city’s water recycling system. Restmeyer points out that this is not unique, but the design is different.
“It’s still a composite tank, and the concrete style is similar to what we typically build,” he says. “However, this is architect-designed, and the tank has an extended upward sweep. It’s almost like a tulip or cup shape tank, which involves some different structural processes.”
The water tank also will incorporate solar power on the roof and other features that haven’t been seen yet in the industry, he adds. “It could very well open up some new opportunities and new thoughts on multiple use opportunities,” says Restmeyer.
Water management is becoming increasingly focused on LEED credits, points out Heiman. “The majority of where water management is leading is to saving potable water and collecting greywater, but more than anything, it is conserving the drinkable water supply, which is very limited,” he says.
With shrinking available space for tank sites, water tanks can play another dual role, says Cull. “We’re going to see more decorative tanks,” he says. “There will be more tanks that blend in with the surroundings, and in some areas, they’re actually going to become focal points of the community.”
Customized designs cost more, but can add marketing value to a community, says Cull. “Aesthetics are a vital part of water tanks and if you have a location where you want your tank to stand out, you can make a unique design,” he says.
Caldwell Tanks has built water towers to resemble whiskey bottles, ketchup bottles, and vacuum tubes. “If you’re near a school, you can use school colors or a logo. You may put accent bands on a water tower to advertise for tourism. If your community has apple orchards, you can paint the tower to look like an apple,” says Cull.
“People are reluctant to spend that much money on a customized tank, but it can be maintained with reasonable costs and with high-performance coatings and a proactive maintenance program,” he adds.