Officials Break Ground On North Tunnel Project To Alleviate Flooding In Old Ellicott City

ELLICOTT CITY, MD — Howard County officials broke ground on the Ellicott City Safe and Sound North Tunnel project Monday. As voted on by the community, the tunnel boring machine has been named Rocky.

Weather permitting, Rocky is expected to have the North Tunnel excavated and mostly completed by the fall of 2027. Once complete, the 18-foot diameter, approximately one-mile-long subterranean North Tunnel will have the ability to move 26,000 gallons of water per second from the west end of Ellicott City all the way to the Patapsco River. The tunnel will reduce the risk of flash flooding by intercepting water and diverting it underground and away from Main Street.

The work will be executed primarily using a tunnel boring machine that is roughly 300 feet in length and can carve through solid granite. The TBM will be overseen by a joint venture between Kiewit and Traylor Bros., Inc. experts in the tunnel excavation field.

"We worked tirelessly with our partners to create and implement an effective, transparent plan for Ellicott City that will keep people safe and preserve the historic nature of our beloved town. One of seven major public works projects that comprise our Ellicott City Safe and Sound flood mitigation plan, this transformational tunnel will not only enhance our historic town’s resiliency and the community’s protection, but it will also be the single largest public works project in Howard County’s history," Howard County Executive Calvin Ball said during the groundbreaking ceremony.

The extended North Tunnel is one of seven flood mitigation projects in the EC Safe and Sound Plan. Officials broke ground earlier this month on the third and largest stormwater retention pond in Ellicott City's Safe and Sound plan. The H4 dry flood mitigation pond should be completed by late September 2025. It will hold up to 5.5 million gallons, the equivalent of a football field that's 12.8 feet deep, which would otherwise flow directly into the Tiber-Hudson River and down to Main Street. The pond will be constructed along the north side of Frederick Road just west of US 29.

In October of 2022, Howard County finished construction of the H-7 pond located at the interchange of Routes 29 and 40, followed by construction of the Quaker Mill Pond at the intersection of Rogers Avenue and Patapsco River Road in February of 2023. Together, these two facilities have the capacity to collect and control the release of 7.5 million gallons of water during a storm. The completion of the H-4 pond will add another 5.5 million gallons of water capacity, which will bring total retention to approximately 13 million gallons of water during severe storms - equivalent to a football field filled with water that is 30 feet deep.

Related:

• Name The Boring Machine To Be Used For The Ellicott City North Tunnel Project
• Groundbreaking Delayed On Extended North Tunnel Project In Howard Co.
• $50M Cost Increase Disclosed For Extended North Tunnel Project
• 5K-Foot-Long Tunnel To Be Built In HoCo To Help With Flood Mitigation
• Extended North Tunnel Project Meeting Planned For July 6 In Howard Co.
• North Tunnel Extension Would Save 9 Ellicott City Buildings
• Ellicott City Flood Prevention Plan Calls For Tunnel, More
• County Exec Updates Community On Ellicott City Safe & Sound Plan
• Residents Updated On Safe And Sound Plan In Ellicott City