Steel Tanks: The Proven Standard

Safe, Cost-Effective, Durable Water Storage

The Enduring Performer

As water storage tanks go, it’s a fairly modest structure. Most modem water tanks dwarf the 277,000-gallon riveted steel standpipe that serves as a landmark – and vital source of water supply – in Baraboo, Wisc. Nevertheless, the Baraboo tank has a secure place in history. For more than a century, this municipal water tank has delivered reliable performance to about 10,000 Central Wisconsin residents who depend on the vessel for safe storage and water pressure.

“Year in and year out – on the coldest nights and hottest days – we know this tank will be operating for us,” says Terry Kramer, city engineer for Baraboo. “This tank has stood for generations, and we believe it will still be around for many more.”

In continuous service since 1887, the Baraboo standpipe serves as an enduring symbol of steel water storage tanks across America. It stands for safety, cost effectiveness and durability. It stands as historical proof of steel’s superiority for dependable, long-term service.

The Economic Edge

For many cash-strapped municipalities the best cost is less cost. Steel water tanks – in contrast with other materials of construction such as concrete – provide a major cashflow advantage for local government budgets.

The initial costs in Table 1 are based upon recent information from around the country where steel tanks were bid, and a concrete tank alternative was allowed. Costs for the welded steel tank include foundations, painting, cathodic protection and a limited amount of site work.

Besides field-erection expenses, concrete tank costs may include internal linings. There are growing regulatory mandates about materials used in drinking water system components (refer to ANSI-NSF 61). To assure that a concrete tank interior is allowed to hold potable water, it’s advisable to check with state water quality officials for certification requirements on new storage tank projects.

Maintenance Costs

Maintenance is an important responsibility of tank ownership and operation – regardless of the materials of construction. Similar to initial costs, maintenance costs for steel tanks are well-documented. Regular maintenance for a steel tank would include:

  • Professional tank inspection every five years
  • Interior spot repair and exterior wash and paint in Year 10
  • Full-field blast and painting of interior and exterior of tank after 20 years, and
  • Repetition of the previous three steps

Concrete tanks, however, are promoted as maintenance-free. A close look at that claim shows that concrete vessels need more post-installation attention than their marketers may be willing to admit. Concrete tank maintenance can range from external coating rehabilitation – to preserve a moisture barrier and aesthetic appeal – to the inclusion of internal linings for certain storage applications.

Take, for example, the maintenance experience of a concrete tank in Fridley, Minn. In 1989, operators of the 3 million gallon tank had to pay $358,000 for interior reconditioning and $106,000 for exterior maintenance of the concrete structure.

The frequency and depth of maintenance activity will clearly vary from one tank site to the next.

The cost of concrete repairs is not limited to periodic maintenance. For example, owners of concrete tanks that require new manways to comply with Occupational Safety and Health Administration (OSHA) confined-space access mandates can face substantial outlays for such retrofit work.

Performance Leads to Cost Advantages

Owners of water tanks are served best by vessels that are:

  • Virtually unlimited in life cycle
  • Leak-free
  • Designed to minimize potential long-term costs
  • Competitively bid
  • Easily adapted to future water system needs
Virtually Unlimited Lifecycle

As a tank construction material, steel provides unparalleled strength and durability. For example, the STI/SPFA Century Club has spotlighted more than a dozen steel tanks with at least 100 years of continuous service -and dozens more that will reach the milestone in a few years. Ask local water officials about their plans for the sturdy, historic vessels, and they’re likely to cite a recent paint job that will extend the tank’s service life at a fraction of the cost to build a new storage structure.

Leak-Free

There are significant differences in leakage standards for steel and concrete vessels. Steel tanks, for example, do not allow any leakage. However, AWWA D110, the industry standard for construction of concrete water storage tanks, allows leakage of one-tenth of one percent of tank capacity per day. For a 4 million gallon tank, that’s a loss of about 4,000 gallons per day-or 1.46 million gallons a year.

Minimizing Potential Long-term Costs

A leak-free, sanitary steel design eliminates a host of issues associated with other materials of tank construction.

For instance, the leakage of increasingly valuable product- combined with poten- tial environmental damage from soil eroded by thousands of gallons of water – leads the list of a concrete tank’s possible long- term costs:

  • Leakage effects on load-bearing capacity
  • Loss of structural integrity resulting from the shifting of soil designed to support the tank
  • Reinforcement to address the shifting of soil, which could lead to tank cracking and failure
  • Maintenance associated with permitted leakage
  • Lining interior walls to meet state sanita- tion standards for materials that come in contact with potable water
  • Sprucing up exterior moisture-proofing on porous concrete structures

Additionally, in some parts of the country, specifiers must account for freeze-thaw cycles and their effects upon the expansion and contraction of tank materials.

Competitive Bidding

When a new tank is the proper choice for local needs, owners strive to get the best price on projects that serve as major community investments. They often save the most by placing large projects up for competitive bidding. Bid reports show that steel ground storage tank projects can draw several potential contractors – the vast majority of whom are STI/SPFA members. That contrasts sharply with pre- stressed concrete tank construction, which frequently may attract only one quote.

Easily Adapted to Future Water System Needs

The other long-term cost to consider is the future adaptability of a tank. Some water tank owners have discovered how retrofit or repair of existing tanks can trim costs for the local water system. For instance, communities have increased local water pressure simply by raising a steel tank. Other communities have faced government-mandated repairs (e.g., the installation of additional piping, or a manhole for improved worker access), which were easily managed because the tank was made of steel. Similar modifications of a concrete tank would require more-complex preparations.

Unsurpassed Design Flexibility

For thousands of communities across the U.S., the steel water tower provides travelers with the first sign on the horizon that they’re close to home – or some other long-awaited destination. Therefore, besides controlling costs, a steel water tank presents each owner with nearly limitless opportunities to design and send a memorable message – through the actual shape of the structure and the exterior painting.

Elevated water tanks have been shaped as pineapples, baseballs, baby food jars, peaches and even cartoon characters to communicate with passing motorists – and create (or reinforce) a desired image. From the purely functional to the most ornamental, a steel water tank can be easily customized to meet your requirements.

Additionally, design flexibility applies to retrofit considerations, especially for growing communities that wish to add capacity without paying for a completely new tank.

The Zero-Leak Standard

Large-capacity steel tanks employ proven designs to carry out their duties as reservoirs of valuable liquids for the American public and thousands of businesses. The designs have been formulated by experts who develop consensus standards for tank construction, such as the American Water Works Association (AWWA) and the American Petroleum Institute (API).

It is widely recognized that standardization is a cornerstone of design safety.

AWWA Standard D-100 for Welded Steel Tanks for Water Storage provides specifiers with the comfort of zero-leak tolerance – a safeguard available exclusively from steel tank fabricators. In short, this international standard addresses the need for reliable quality in design and construction practices – based upon decades of engineering, manufacturing and construction experience in all types of climates and topography.

State-of-the-Art Stability

Initially developed in 1935 as a standard for riveted steel elevated tanks and standpipes, the D-100 standard was revised in 1940 to include welded construction. Today’s D-100 standard incorporates the latest technology on shell stability and seismic performance to provide the safest, most reliable water tanks built anywhere.

Connections in welded steel tanks have long been proven as dependable – even when tested by earthquakes, hurricanes and tomados. They are made by butting steel plates and welding them together as mandated by the industry’s highest quality standards and widely recognized techniques. The industry’s outstanding product performance record reflects decades of experience with properly engineered and constructed vessels – uniformly created to assure trustworthy storage solutions.

Quality Control and Education

Reinforced Quality

Adherence to quality begins even before a fabricator starts a project as steel producers monitor and certify materials shipped to individual plants. Tanks are made of grades of steel that are chemically tested and standardized from years of industry experience. This contrasts sharply with the use of concrete- the quality of which typically varies depending upon supplier, geographic location and contractor. The quality issue is driving many of the sanitation concerns linked to state requirements for certification of materials used in drinking-water systems.

As an internationally recognized standard, AWWA D-100 establishes minimum quality assurance and quality control requirements for steel water tanks. Each manufacturer provides quality inspection during plate fabrication, and field-erection activities. Both destructive and non-destructive testing of the product reinforces the ability of fabricators and constructors to provide a durable tank system that will deliver decades – if not a century – of storage.

Ongoing Industry Education

Because of the importance in sharing inno-. vation and manufacturing experience, member companies of the Steel Tank Institute/Steel Plate Fabricators Association (STI/SPFA) are active in industry standards organizations. In addition to assisting with standards development, STI/SPFA members volunteer their time to collect design data and methods.

With joint funding from the American Iron and Steel Institute, they publish reference materials for use by tank designers, fabricators, erectors and purchasers. STI/SPFA and AISI also conduct seminars on topics related to the design, construction and maintenance of steel water storage tanks.

The Proven Product

Across America, the tanks that have followed the steel Baraboo standpipe continue to provide service to communities large and small.

Tank after tank has truly stood the test of time.

The steel tanks of today embody the heritage established in the 1800s – durable, reliable, economical, versatile storage structures of enduring quality.

They have proven performance from arctic regions to tropical locales. Each has been designed to squarely meet the immediate needs of a community, and the far-off requirements of generations to come.

“Networking at STI/SPFA meetings has given us new ideas to manufacture our products more efficiently.”

Sonny Underwood
Mid-South Steel Products, Inc.

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