Friday, November 6, 2009

Workers dive deep into tunnel system to clean out debris: Down, down we go. USA, LLC

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Sep. 5--It is one of Milwaukee's most dangerous and dirty jobs, but someone has to do it every three to four years. Divers -- dressed in full, heavy rubber dry suit, gloves, boots and metal helmets -- took turns last week working brief shifts more than 300 feet below the surface of the Jones Island sewage treatment plant. Each walked with no visibility into a 10 foot in diameter pipe filled with a mix of sewage and water. Plastic bags and soda bottles, other trash, leaves, sand and gravel had accumulated to depths of 2 to 6 feet at the bottom of the pipe since it was last cleaned in 2004, said diver supervisor Ed Stowitts. Stowitts and the four other divers on his team for this job are employees of Veolia Environmental Service's marine division out of Schererville, Ind. It was a diver's job to drag a high-pressure water hose with him as he slowly advanced into the pipe, blasting water at the floor ahead to loosen mounds of debris so wastewater pumps could suck it out. This is the sole drainpipe for the Milwaukee Metropolitan Sewerage District's deep tunnel system, 26.5 miles of underground caverns capable of storing 494 million gallons of wastewater until it can be treated at the Jones Island or South Shore plants. When pumps begin draining the tunnels after a storm, all of the wastewater flows through this 280-foot-long pipe to a pumping chamber, where the flow is lifted to the surface. As debris accumulates and restricts flow in the drainpipe, however, the three massive pumps in the chamber can begin to vibrate and must work harder to empty the tunnels. The dangers encountered in cleaning the drainpipe start with an uncommon ride to work, Stowitts said. The diver stands in a steel basket that is lifted by a crane and suspended above a 20-foot-wide shaft that provides access to the bottom end of the deep tunnel and the start of the drainpipe. Then the crane slowly lowers the basket 324 feet down to the bottom of the shaft. "I don't like heights. That's why I like to dive in water," Stowitts said. As the basket descends, workers on the surface feed the diver's lifeline down the hole. A breathing hose, communication line, depth indicator, video line and other safety features twisted into a cable and held together with duct tape serve as the diver's umbilical cord and only link to the surface, Stowitts said. Tension on the line snapped the video cord on the first dive of the week. The basket reached standing wastewater about 31 feet from the bottom of the shaft. At the bottom, the diver walks out of the basket with the lifeline trailing behind, and enters the drainpipe, pulling the hose. At that depth of water, divers are able to work no more than 3 hours, 15 minutes before returning to the surface, Stowitts said. While one diver is in the drainpipe, a second diver waits on the surface, suited up and ready to go down the shaft to pull out the other if there is an emergency. Stowitts inspected the shaft before work began. Even with a helmet-mounted light, visibility in the wastewater was no more than 5 inches during the inspection, he said. When he returned to the bottom of the shaft for the first working dive, Stowitts walked into the drainpipe and turned on the high-pressure hose. Visibility immediately fell to zero as leaves and plastic bags were stirred up from the bottom of the pipe. "There's anywhere from 2 feet deep to 6 feet deep of this stuff" in the pipe, Stowitts said. After blasting the trash and vegetation with water, Stowitts walked back to the basket in the shaft, and the crane raised him several feet above the water so a pump could be turned on. After 15 minutes, the pumping stopped and Stowitts returned to the pipe. Little of the debris had been removed. He blasted another 60 feet of the debris and left the pipe. But much of the debris was simply spread out more evenly on the bottom of the pipe, he said.

A second diver that night blasted debris along the same length of pipe with slightly better results. Two other divers worked the second and final night and succeeded in dislodging and removing much of the rest of the debris. A few mounds of small gravel less than 1 foot deep remained, Stowitts said.

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Source Citation
"Workers dive deep into tunnel system to clean out debris: Down, down we go." Milwaukee Journal Sentinel [Milwaukee, WI] 5 Sept. 2008. General OneFile. Web. 7 Nov. 2009. .

Gale Document Number:CJ184465362

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