Customized machinery developed to meet challenges of working 300 ft underground
A once-in-a-decade maintenance project in the Milwaukee Metropolitan Sewerage District's (MMSD) Deep Tunnel drew to a conclusion last week, as crews removed the final pieces of floating debris that accumulated in the end of the system near the Jones Island Water Reclamation Facility.
Completed in 1993, Milwaukee's Deep Tunnel stores storm water and wastewater during heavy or prolonged rains. Designed to hold more than 520 million gal, the Deep Tunnel has prevented 92 billion gal of pollution from entering Lake Michigan. Ranging in diameter from 17 to 32 ft, the Deep Tunnel system is 28.5 miles long and sits 300 ft below ground.
Maintenance and clean-out are performed on the tunnel every 10 years. In early November, Veolia specialists (along with two flat-bottomed and one pontoon boat) began setting up to remove two decades' worth of plastic bottles, balls, wood and other floating debris that had accumulated in the tunnel. During this project, the Veolia crews were typically hundreds of feet from an outside exit, working in what would otherwise be complete darkness, and prepared to evacuate at a moment's notice in the event of rapidly developing storms.
Because of the uniqueness of this maintenance effort, specially trained crews from Veolia planned for months in advance of this effort—bringing in confined space and water treatment experts to ensure the safety of the crews working underground.
"Performing this critical underground infrastructure maintenance is important to properly maintaining the Deep Tunnel, a valuable piece of Milwaukee's infrastructure," said Scott Royer, general manager of Veolia Water Milwaukee. "Although this project was an unusual challenge, we are proud to be able to bring to bear expertise and knowledge from across Veolia's organization to meet that challenge safely and efficiently.
Veolia Water North America operates the Milwaukee Metropolitan Sewerage District's Jones Island and South Shore Water Reclamation Facilities.