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

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.

Howard County Executive Calvin Ball announced 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.



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 provided 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.

During the announcement, Ball said the tunnel “will have the capacity of carrying approximately 26,000 gallons of stormwater per second away from the streets and foundations.”

“It will be one of the most important, impactful and transformational projects that Public Works has done in the history of Howard County.”

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.

Water will enter the tunnel in at least two locations — the primary intake structure located on the north side of the 8800 block of Frederick Road, and one 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.

“I’m so incredibly grateful for our federal and state and local partners, our community, which has actively participated in developing these plans,” Ball said.

“And this year, Ellicott City is celebrating its 250th anniversary, a meaningful milestone for this cherished historic town. Two hundred and fifty years is a big deal. Together, we are writing that new next chapter in the story of Ellicott City, making it a national model of cooperation, resilience and ensuring its vibrancy for another 250 years and beyond.”

Editor’s note: Clarifies the two locations where water will enter the tunnel.

Neal Augenstein

Neal Augenstein has been a reporter at WTOP since 1997. Through the years, Neal has covered many of the crimes and trials that have gripped the region. Neal's been pleased to receive awards over the years for hard news, feature reporting, use of sound and sports.

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