MILWAUKEE, Wisconsin (29 Nov 2004) -- Think you have a crappy job? Tell that to Al Sebrechts, who will have an eight-man diving crew in Milwaukee next week to descend into the deep tunnel system and dislodge sewage solids under 20 feet of wastewater. Officials at the Milwaukee Metropolitan Sewerage District hired Sebrechts' firm to do the cleaning in hopes of curing a vibration problem on one of the three giant pumps that suck wastewater from the tunnel to the Jones Island or South Shore treatment plants. The job will be done by divers in special suits dipping into the stuff that sits at the base of the tunnel. Despite the obvious hazards, Sebrechts said, his divers operate in a much less germy environment than ordinary scuba divers swimming in polluted lakes or streams. "We are as clean as whatever is inside of that suit," he said. Divers don heavy rubber wetsuits, as well as leather over suits, heavy boots, gloves and sealed helmets. It's the same gear his workers use to service water intakes at nuclear power plants, Sebrechts said. "It's like armor," he said, and is pretty much impervious to puncture by errant syringes or other detritus. Sebrechts' firm - Sea Brex Marine Inc. of Stevensville, Mich. - will earn up to $60,000 for what they hope will be about a five-day job. If heavy rains hit, the job will be postponed until a dry spell when the tunnel isn't needed. Though the tunnel is relatively dry now, it always has about 4 million to 5 million gallons running through it from groundwater leakage, which accumulates at its deepest point adjacent to the pumps on Jones Island. Two-person diver teams will be lowered by crane 300 feet through a Jones Island tunnel drop shaft and into the drink, linked to the surface with air tubes and communications gear. The teams are relieved every 3 hours or so and are assisted by other team members at the surface. | | Visibility ranges from 6 inches to maybe 4 feet, meaning divers are pretty much working by feel. While underwater, the divers will use blasts from air hoses and follow up with high-pressure water hoses to remove what MMSD's John Jankowski delicately referred to as "silt" that's accumulated in the tunnel floor and crevices. It's that stuff - "I guess you could call it crap," Sebrechts said - that MMSD officials think might be hindering operation of one of the tunnel pumps. The material actually is a mix of hardened grease, grit and other sewage byproducts. "It's almost like sticking your hand into a bucket of lard," he said. "The sand and gravel stick to it. That's what gives it that dark, black color." Although vibrations cause the pump to heat up to the point it sometimes can't be used, Jankowski said, the problem hadn't contributed to raw sewage overflows. Each of the Japanese-made pumps is worth more than $1 million, and officials don't want to damage them, he said. MMSD has dumped nearly 18 billion gallons of untreated waste since the tunnel was put in service more than a decade ago. Officials have said limitations on pumping out the tunnel during last May's heavy rains contributed to the record 4.6 billion gallons of raw sewage that were dumped. Next week's deep tunnel cleaning will be only its third since the system opened. The last was done in 2003. Sebrechts suggested more regular maintenance might be a good thing to help guard against sewage dumping. Jankowski said the tunnel may be accumulating more of the gunky sediment because in recent years it has been used as a sewage holding tank during sewer construction projects. When the tunnel is used for its primary task of holding rain-swollen wastewater flows, the mix isn't as clogged with solids, he said. SOURCE - JS Online |
