$75 million loan signed; tunnel construction in flood-prone Ellicott City set to begin


Funding has been secured, and ground is expected to begin this year to build a 5,000-foot tunnel in historic Ellicott City. It will carry water away from flood-prone Main Street and into the Patapsco River.

The largest and potentially most-effective aspect of Howard County, Maryland’s $165 million plan to minimize flooding along Main Street in historic Ellicott City will break ground later this year, WTOP has learned.

Howard County Executive Calvin Ball will announce Tuesday that the county has secured funding to build a 5,000-foot tunnel that will carry water away from Main Street and into the Patapsco River, according to county officials.



The county has signed a $75 million Water Infrastructure Finance and Innovation Act Loan with the U.S. Environmental Protection Agency to pay for the tunnel. Construction is expected to begin later this year.

Ellicott City was devastated by floods in 2016 and 2018 — two people died in the 2016 event, one died in 2018. Founded in 1772, the former mill town’s topography has made it perpetually prone to flooding.

Ball is expected to provide more details on the 18-foot-diameter tunnel, which is able to carry about a swimming pool’s worth of water every second. The tunnel running parallel to Main Street will be, at points, up to 100 feet below ground level.

Since taking office, Ball has committed more than $160 million in local, state and federal funds to protect Ellicott City.

In May 2019, Ball announced the plan, which will include razing four buildings on lower Main Street. An earlier plan would have called for the destruction of 10 buildings to widen the channel that carries water toward the Patapsco River during heavy rains.

The intake for the tunnel will be located in the vicinity of current Parking Lot F near the intersection of Ellicott Mills Drive and Main Street. The flood-swollen Tiber Creek washed away a portion of Ellicott Mills Drive in 2018, which resulted in a sturdier, larger concrete waterway beneath the road.

Emergency sirens were installed in 2019 to provide warning to residents and business owners of flash flood warnings. After a July 2019 incident, in which emergency sirens didn’t sound, the county and National Weather Service implemented a new protocol to differentiate “Historic Ellicott City” from the more widespread city.

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