Dive Brief:
- Crews led by Omaha-based infrastructure heavy hitter Kiewit-Shea and a tunnel boring machine dubbed Nora, according to the Times Herald-Record, are in the process of digging a $1 billion bypass tunnel 55 stories under the Hudson River to get around the leaking, 85-mile Delaware Aqueduct, which serves New York City, the Associated Press reported. Via gravity, the aqueduct delivers 600 million gallons of water from the Catskill Mountains region to New York City residents and businesses, which is half the city's daily requirement.
- The tunnel boring machine is digging a path through solid rock around the worst of the aqueduct's leaks. Once the tunnel is complete in 2022, the city will divert water out of the aqueduct and into the bypass tunnel. Vincent Sapienza, the commissioner of the city Department of Environmental Protection, called it "the largest and most complex water tunnel repair that the city of New York has ever done."
- The section of the aqueduct that is leaking does not have the same steel sleeve that the rest of the World War II-era tunnel has. As a result, the aqueduct has been losing 18 million gallons of water a day, but too many city residents rely on the tunnel for their water supply and repairs would have taken years. Consumers will have to deal eventually with a months-long shutdown of the Delaware Aqueduct in preparation for the switch to the bypass tunnel, but city officials said they have been preparing for that event with low-flow plumbing devices and a water-use reduction program.
Dive Insight:
Tunnel boring machine work can be tricky and one misstep can derail a project for years. Bertha, the machine used to carve out the tunnel for the $2.2 billion Alaskan Way (SR 99) project in Seattle broke down in 2015 and stalled the job's progress for approximately two years. After Bertha was up and running again in 2017, Washington Gov. Jay Inslee briefly shut down tunneling operations after a sinkhole appeared near the machine. Bertha finally completed her tunneling work in April 2017, almost 30 months past the originally scheduled finish date.
But potential problems haven't stopped transportation agencies from planning tunnel projects of their own. In fact, the Los Angeles County Metropolitan Transportation Authority has incorporated tunnels into all three phases of its Purple Line light rail extension project. First-phase tunneling will begin this August with two tunnel boring machines carving out parallel paths between Beverly Hills and Los Angeles' Koreatown neighborhood.
