After two years of construction work and months spent carving out shafts and staging areas, Howard County officials say the real underground action is finally about to start. This summer, mining is set to begin with the massive tunnel-boring machine nicknamed "Rocky" as crews enlarge the North Tunnel to steer floodwaters away from Ellicott City's historic Main Street. The Extended North Tunnel is billed as the largest public works project in county history and a cornerstone of the Safe and Sound flood mitigation plan. County leaders say the underground conduit is designed to intercept stormwater and direct it straight to the Patapsco River, providing the town with a long-term buffer against sudden flash floods.
What the tunnel will do
Plans call for the tunnel to run roughly a mile beneath the West End, with a diameter of about 18 feet and the capacity to carry roughly 26,000 gallons per second into the Patapsco River, according to Howard County. Construction on the North Tunnel started in June 2024, and the county is targeting substantial completion in the fall of 2027. Officials describe the conduit as a way to capture upland flows and send them underground rather than letting torrents charge straight down Main Street.
The machine and the mining
The work will be handled by a tunnel-boring machine known as "Rocky," which officials and contractors say will be assembled on site before mining starts. As reported by WMAR-2 News, the machine weighs roughly 140,000 pounds, measures about 300 feet at launch (eventually stretching to around 460 feet), and can chew through about the equivalent of 90 dump-truck loads of granite in a single day. County crews have been working six days a week to clear the deep launch shaft and create enough room for the massive rig to be put together, according to local coverage.
"The water came so fast, so violently," survivor Heather Owens told WMAR-2 News, recalling the 2016 flood that killed her fiancé, Joe Blevins. Residents and elected officials regularly point to those losses when arguing for aggressive engineering fixes and state support for the Safe and Sound program. County leaders say the tunnel is meant to avoid a repeat of that kind of sudden, violent flooding that shattered businesses and lives a decade ago.
Who is building it and the timeline
The project is being delivered by a Kiewit-Traylor joint venture. Traylor Bros., Inc. notes that the tunnel-boring machine is a refurbished Robbins main-beam unit that has completed factory acceptance testing and will be assembled at the launch site. Industry reporting indicates that tunneling operations are expected to start this year, with substantial completion eyed for 2027, although the schedule depends on weather and site conditions. Contractors emphasize that the deep-rock work is complex and will move forward in stages to protect surface structures above the tunnel alignment.
Cost, funding and local impacts
Funding for the Safe and Sound program pulls from county money, state grants, and federal loans, including a $75 million WIFIA loan and additional state aid, according to Howard County. Officials say they have chased grants and partnerships to cover much of the multi-year price tag and that construction timelines will be adjusted as funding and permits come through. Local businesses say the tunnel promises long-term protection but also brings short-term headaches from staging areas and periodic closures in the West End.
What residents should expect
County leaders say most of the tunneling will happen deep underground, but residents will still notice staging, equipment deliveries and shaft work in nearby neighborhoods and parking areas. As WBAL reported at the project groundbreaking, business owners describe the effort as a necessary tradeoff for greater resilience. Officials are urging residents to follow county project updates for details on planned closures and detours. The hope is that once "Rocky" finishes its run, Ellicott City will be far less vulnerable to the kind of sudden floods that have defined the town's recent history.
