Howard County, Ma., breaks ground on “massive” underground stormwater tunnel project

(UI) – Howard County Executive has broken ground on the Ellicott City Safe and Sound plan’s highly anticipated North Tunnel stormwater conveyance project. This is the largest public works project in Howard County’s history.

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 area 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 (TBM) 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.

“Our Kiewit-Traylor team is proud to partner with Howard County to bring our breadth of resources and tunneling expertise to construct the North Tunnel and realize the vision of the Safe and Sound Program for the Ellicott City community and future generations,” said Matt Swinton, Senior Vice President and District Manager, Kiewit.

The TBM, named “Rocky,” is expected to have the North Tunnel excavated and substantially completed by the fall of 2027.

“This crucial project was made possible through $27 million in state grants and $28.5 million in state loans. I am especially proud because these loans were made possible because of the Resiliency and Revolving Loan program. Together, we are building a safer, more resilient future for Ellicott City and all of Maryland,” said Maryland State Senator Katie Fry Hester, District 9.

“This massive, 18-foot tunnel will be transformational in moving tens of thousands of gallons of rainwater away from Main Street directly into the Patapsco River.  As state partners on this effort, we look forward to continuing to work with county leaders to ensure that this project has the resources and support it needs to safeguard the future of Ellicott City,” said Maryland State Senator and Howard County Delegation Co-Chair Clarence Lam.

The Ellicott City Safe and Sound flood mitigation plan is designed to provide a comprehensive solution for flood control in historic Ellicott City, following recent catastrophic floods in 2011, 2016 and 2018.

In addition to the North Tunnel, the city has plans for five stormwater retention ponds (H-7, Quaker Mill, H-4, NC-3 and T-1), the Maryland Avenue Culverts water conveyance project, enhanced stream inspections and debris removal following storms, an Outdoor Tone Alert System, high-ground signage and access points, and drainage improvements throughout the watershed.

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