The cool morning air was filled with excitement in a clearing near the intersection of Lexington Road and Grinstead Drive on the morning of September 22. After 21 months of carving its way through four miles and 625,000 tons of rock 18 stories underground, the Bumblebee machine had just thirty feet to go to complete the path of the Waterway Protection Tunnel under Louisville.
By 2 p.m. there were less than three feet to go. A growing crowd of project crew members and MSD personnel peered over the high edge of a wide shaft down 200 feet to where Bumblebee would break through the shaft wall.
Jesse Salai of contractor Shea-Traylor and several others climbed into a yellow metal cage and were lowered by a crane into the shaft to give the command for the final push.
Dangling in the cage near the bottom Salai lifted his cellphone to call the man inside the machine on the other side of the remaining rock. “Let her rip,” he said.
A deafening roar filled the shaft as the 22-foot face of the tunnel boring machine began grinding against the rock. Fine cracks appeared around a green plus sign marked on the wall.
Small, then larger and larger bits of rock fell from the wall until more and more of the massive machine appeared. Within an hour Bumblebee was quiet and the hole-through was complete.
It marked a breakthrough for MSD.
“This is the largest capital project in MSD history,” said Project Manager Jacob Mathis, noting that the Waterway Protection Tunnel is three times the size of the Shawnee Park basin project completed last year. “The breakthrough is a big accomplishment for the project.”
Bumblebee—the nickname given the tunnel boring machine in a nod to Louisville boxing great Muhammad Ali—began its journey in January 2019 at 12th and Rowan streets.
Alston Noronha, construction manager for Black & Veatch, compared the work on the project to childbirth.
“We’ve been building this project for three years, and we’ve been excavating since January 2019, and now it’s like birthing a 900,000-pound baby,” he said. That’s how much Bumblebee weighs.
Noronha said lining the tunnel with 12-inch-thick concrete has already begun, starting at 12th and Rowan’s work shaft. When complete, the Waterway Protection Tunnel will capture and store up to55 million gallons of combined stormwater and wastewater during rains, preventing the water from flowing untreated into the Ohio River and Beargrass Creek
The captured water will be released into the sewer system as capacity becomes available and treated before it is released into the waterways. The tunnel is expected to go into service during the second half of 2021.
Chief Engineer David Johnson congratulated Mathis and the Engineering Division on the milestone. “Without their efforts and dedication, this project would not be a success,” he said. “The tunnel breakthrough was not only an engineering feat for MSD, but it was a momentous celebration for MSD in achieving safe clean waterways for our community and those downstream of us.”
Next will be the disassembly and removal of Bumblebee. It will take six to eight weeks to take apart the 400-foot-long machine.
MSD approved the tunnel project to take the place of four previously planned storage basin projects and provide more storage capacity and greater operational efficiency along with significant cost savings. The $200 million project is part of MSD’s Consent Decree with the federal government to significantly reduce sewer overflows caused by heavy rains.