May 8, 2008
Cleaning the Alamo Water Tank

Photo by Dave Maxwell Crew working on cleaning Alamo water tank.

By Dave Maxwell, Staff Writer

Alamo Sewer and Water District hired Advanced Diving Services (ADS) out of St. George, Utah to inspect the 450,000-gallon water tank that sits atop Pearson Knoll at the south end of town. Federal law requires municipal water tanks to be cleaned inside and inspected for structural defects or stresses every five years.

ADS completed the job on May 1 and Supervisor Dave Gonyon explained that they send a diver into the water tank with a hose “Cleaning out all the sediment and debris, any of the buildup that comes in naturally. It’s typical for any water tank in any city anywhere you go.” Following the suction cleanout Gonyon said they then check the “structural integrity of the tank, looking for any kind of holes and repairs that are needed and make recommendations to the city water authority.”

Advanced Diving Services is a full-service commercial water diving company Gonyon said. “We do everything from pipelines, underwater welding, water tanks, waste water treatment plants, Hazmat structures, nuclear power plants, etc.; pretty much anything. It doesn’t matter where it is. Anything you can think of on the surface, we can do it in the water,” he said. ADS can also fix any problems they might find during their cleaning and inspections. If repairs are necessary, ADS puts in a competitive bid. However, in the Alamo case, they found the structure sound and not in need of repair.

Coming to Alamo was a bit of a break for his crew Gonyon said. He explained that ADS had been doing a job on several 10 and 20 million gallon tanks in Riverside, California. ADS is one of about 16 companies in the U.S. performing this type of work, and only a few companies work year-round and coast-to-coast.

Diver Cory Martin, part of the four-man crew, went into the Alamo tank wearing a wet suit and diving helmet equipped with a video camera so pictures could be recorded on a DVD or VHS in the control center. The pictures give visual evidence for later review of what they did and what problems they might have found; he used a series of suction and cleaning tools for the job.

In addition to federal regulations mandating cleaning municipal tanks every five years, Gonyon said, “Tanks in areas where they get a lot of sediment, a lot of buildup (like Alamo), chlorine will only penetrate 1/4 inch of sediment and anything below that could be building up bacteria and other things that you don’t want in your water.” He said some tanks he has worked on have had an inch or more of sediment and the chlorine is only taking care of one-quarter of that.

He said the Alamo tank showed minor calcium deposits but did have an amount of sediment “a little bit higher than we like.” The tank has an inside white epoxy coating that helps to prevent rust.

“It’s pretty important to have these tanks looked at,” Gonyon said, “especially when they are up on a hill like this one. If they split open, it’s going to make quite a mess.”