(Photos by Bob Hubner, WSU Photo Services, and Robert Frank)
Okay, it’s been 30-59 years and the dust is about 16-17 inches deep. It’s time to clean.
Trouble is, the room is 114 X 114 feet in size and the dust has settled underwater, so divers are needed.
(Photo: Richard Peterson shows diving helmet equipped with lights and cameras.)
Obviously, we’re not talking about your everyday get-out-the-Hoover-and-vacuum project. We’re talking about cleaning Washington State University’s east water reservoir.
Located adjacent to the Jewett Observatory, the 21-foot-deep reservoir has an estimated 2,041,553-gallon capacity. The reservoir isn’t completely full, so the silt is under about 13-15 feet of water.
To tackle the job, WSU contracted Liquivision Technology, based out of Klamath Falls, Ore. A three-man Liquivision Technology (LT) crew has been on campus for several days and will continue here, off and on, over the next couple weeks as it cleans not only the east reservoir, but repairs a 2 million-gallon water chiller reservoir a few blocks west.
The east water reservoir was built in 1947, along with the water tower that stands adjacent to it. And, as far as records show, this may be its first official cleaning and inspection. No one working at Facilities Operations remembers it ever being cleaned, which takes it back at least 30 years.
(Diver decends into reservoir)
This week’s cleaning comes via a high-powered water vacuum that sucks out 250 gallons of water a minute. Manning the vacuum is one of the LT team, decked out in a dry diving suit and diving helmet.
(Photo: Giant bladder bags sift out sediment from water.)
Before entering the water, the diver is sprayed down, head to foot, with a 200 ppm chlorine solution, killing any bacteria and protecting the purity of the water supply. The helmet features a built-in light, video camera, microphone and receiver. That equipment allows a second member of the LT team to watch and record everything the diver is seeing, his location and how the project is going.
The third team member keeps the air and water pumps fueled and running and connects the hose expelling water and sediment to a giant 3 x 90-foot porous bladder bag. Because these bags fill up regularly, this team member monitors and reconnects the hose to new bags as necessary.
(Cameron Hagerman, left, and Jason Fitzpatrick, move expulsion hose to a new bag.)
Over time, the water drains out of the bags and the silt dries in the sun. Tests will be done on the sediment to determine its makeup. At that point, Facilities Operation crews will shovel it into a truck and move it to an appropriate destination, said Howard Gossage, director of maintenance and utilities services.
An LT diver usually remains in the water for 2 or 3 hours. The length of his stay normally is determined by his ability to “hold water” or how he feels. The three crew members rotate positions and duties every few hours throughout the project.
Is 16-17 inches of sediment on the bottom of a reservoir in 30-59 years a lot? Cameron Hagerman, one of the LT crew, put it this way: “Well, we currently are working on a project near Quinault where the reservoir is five years old and there is about 5 feet of silt.”
(Cameron Hagerman monitors diver’s cleaning progress.)
David Larson, vice president of LT, said his company regularly cleans a reservoir in Nevada that was accumulating about one foot of silt every six months. That problem has been corrected and now it is cleaned every one to two years.
The difference Larson noted is that these other reservoirs draw their supply from surface water. Pullman draws its water from an aquifer that naturally filters the water before it arrives.
WSU’s west water reservoir, approximately the same capacity as the east reservoir, was built in 1963. Unlike its counterpart, it has been drained and cleaned at least three times, said Gossage, most recently in 2003. During that project the reservoir’s roof was torn off and replaced, and the walls and floor were cleaned, inspected, patched and painted.
The American Water Works Association, in its most recent manual, recommends that reservoirs be cleaned and inspected every three years. “This is a recommendation, not a regulation,” said Tim McCandless, standards engineer with AWWA. “Depending upon the quality of the water you are drawing from, you may need to clean the reservoir less frequently.” He pointed to a couple examples where cities have been able to delay their inspections to every 5-10 years.
“The key thing is that you have a plan in place and implement it.”
Given these recommendations, Gossage said, WSU plans to clean and inspect the reservoirs on a more frequent basis. Facilities Operations will review the data they receive from LiquiVision Technology and establish a schedule.
Data from future cleanings, in turn, will allow them to further fine tune the schedule.
“Until recently, there hasn’t been the technology to put a diver in the reservoir to clean it,” said Ev Davis, executive director of Facilities Operation. “That is an enormous advantage. It’s not a simple thing to drain one of these reservoirs.
“You can’t just start dumping 2 million gallons of chlorinated water into the sanitary system or release it and have it drain into the surface water. It could have a huge impact. So, the question is,
where do you put all that chlorinated water?
“This (diving) procedure has much less of an impact on the environment,” said Davis. “And, by doing it more frequently, we can ensure the reservoir is in good shape and catch necessary repairs early on.
“Much of the cost for cleaning it this way is based on how much silt is in the reservoir. The more silt, the more cost. So by doing it frequently, we reduce that cost and keep the reservoir in good shape,” Davis said.
In this case, the university expects to pay about $40,000-$55,000. More than $20,000 of that is for the cost of the bladder bags, which run $450 each.
Although the cleaning is overdue, the university has always kept close, precise tabs on the water quality. Marty O’Malley, environmental health specialist with WSU’s Environmental Health and Safety, said the water in the WSU system is tested:
* monthly for bacteria in 25 locations (in June-July it is reduced to 10)
* quarterly for disinfection byproducts
* once a year for nitrates
* once every three years for other inorganic and organic chemicals, as well as lead and copper
(A full copy of EHS’s annual consumer confidence report on the WSU drinking water system can be seen at www.ehs.wsu.edu/waterreport.asp.)
“Relatively speaking, WSU’s water quality is very good,” said O’Malley. “Any monitoring of it, at any point in time, shows we’re not even close to any maximum contaminant levels.
“The biggest problem we have is with iron. It’s not a health hazard at the levels found in our water, but as it oxidizes over time, the iron can turn the water a brownish color.”
If a system sits idle for several days and someone turns on the faucet, the water can come out a brownish color for a few seconds. Hot water follows that trend more, because the heat accelerates the oxidation process.
“We recommend that people just turn on the water faucet and let it run for several seconds. Normally, this action will take care of the problem. We tell them if they continue to see the sediment or brownish color to call us back and EH&S will investigate the problem further.”
EH&S reminds everyone that only cold water should be used for drinking and food preparation. Never use hot water because of the heavy metals that can leach from the pipes and fixtures.
Silt not hazardous
“Because of the depths of the wells from which we draw water, the water is very clean and there is little chance of anything (hazardous) ever getting in,” O’Malley said. “All of our current production wells are over 500 feet deep.”
He noted that the silt settles out to the bottom of the reservoir and is “not hazardous.”
The water is drawn out of the reservoir through two standpipes that are 2-feet tall, therefore above the level of the sediment.
“If we’d have seen a problem of any kind with the water (in our testing), we’d have done the cleaning much sooner,” said O’Malley.
“It’s important for the public to have confidence in the water supply,” said Davis. “Our drinking water is very clean; it goes through very little treatment. It’s chlorinated and fluoridated and that’s it. It’s not like many municipalities where it has to go through various processes at a water treatment plant.”
The good news is, virtually all the sediment in the reservoir will soon be gone — vacuumed clean by Liquivision Technology’s crew — with another diver scheduled to visit, clean and inspect in several years.