Cities across the country depend on decades-old water reservoirs, ponds, and tanks to store potable water as well as for fire suppression. 

Although steel and fiberglass are mostly used for smaller tanks, the largest and most enduring outdoor tanks and reservoirs that contain millions of gallons are constructed of cement or asphalt. Unfortunately, several factors can cause these constructions to develop sizable cracks through which large quantities of liquid can escape (exfiltration) or enter the water supply.

When this happens, facility managers must decide whether to demolish and reconstruct the aging structure or find a way to extend their service time. Fortunately, advanced polyurea coatings and liners are showing ideal for the tank, pond, and reservoir restoration by presenting strong, flexible waterproofing that not only links large existing cracks but can elongate up to 400% without breaking.

Concrete/asphalt cracking

Cracks can occur in aging concrete reservoirs and tanks for numerous reasons ranging from ground movement to daily or seasonal heat changes that cause expansion and contraction. The weight of water in a big reservoir or tank can also cause concrete to move many inches. In doing so, tiny cracks in a drained tank can open to cracks 1/4" or larger when filled with water.

To address the issue, waterproof layers such as epoxies are often applied to the exterior. However, these traditional coatings lack the flexibility to budge and sway with concrete or asphalt and crack.

Instead, water facility managers turn to polyurea coatings and linings, one of the few protective coatings that can work on the expansion and contraction cycles of substrates such as asphalt, steel and concrete. Some advanced polyurea coatings have high tensile strength and the flexibility to stretch 400% and sizable bridge cracks.

Rehabilitation instead of demolition

Redstone Arsenal, a large U.S. Army base in Huntsville, Alabama, had a decision to make: demolish or repair an important, working, 5-million-gallon water tank. The tank, built-in 1941, has had a beneficial life as a water storage tank for fire suppression, as well as a back-up water supply. However, the tank had numbers of cracks and leaks and was losing water at an significant rate.

The tank was missing a significant amount of treated drinking water, which is more expensive. The Army base had attempted to use different liner types over the years, but those were not working adequately.

Redstone Arsenal's Public Works Department evaluated their options for more than ten years with no apparent solution. After the current success of a polyuria-rehabilitated water storage pond adjacent to the tank, they recognized that they could use a similar approach. The contractor on the pond was also awarded the tank project.

The spray-applied waterproof coating creates a seamless, waterproof, durable protective liner that stops leaks and strengthens the entire storage structure's integrity. It is designed to withstand decades of freeze-thaw cycling, wide variations of heat and humidity. In the late 1990s, Parsons Brinckerhoff issued a 75-year lifespan on the famed Boston Tunnel Project.

With minimal crack repair and surface preparation, the polyurea coating can be thick film-applied directly to the concrete, asphalt, or similar substrate. An alternative application method that can sometimes mitigate the need for surface or crack repairs is to pre-spray the polyurea to geotextile fabric panels placed above the onsite substrate, fusing the panel edges with more polyurea.

With either application process, the polyurea coatings exhibit preferred physical properties such as high elongation, crack bridging, hardness, and tensile strength to create a robust industrial liner that protects, strengthens, and waterproofs concrete reservoirs and vessels.

The polyurea's ability to set and cure fast also reduces water tank or reservoir downtime. This can translate into thousands of dollars per hour savings in facilities requiring potable water and a source of emergency water for fire protection.

The polyurea sets up in seconds and can be put back into service as fast as an hour. It can take days for epoxy to cure enough to do the equivalent. The time saved can provide tremendous savings to a facility. 

After repairing all cracks over 1/8″ wide with a concrete repair grout, the contractor primed the 5-million-gallon water tank's concrete surfaces with primer and applied 80-100 mils of pure polyurea. The walls were completed first. Next, they removed the heavy equipment from the floor. The tank base was re-cleaned and primed before the polyurea's last application was applied to the floor. From start to finish, the project lasted two months.

Two years later, both Redstone Arsenal's polyurea-rehabilitated 5-million-gallon water tank and the water storage pond adjacent to the tank have been investigated and remain in excellent shape, with decades of extended life expected.

Learn more about ArmorThane protective coatings here.