ELLICOTT CITY, MD – Howard County’s Department of Public Works’ (DPW) Stormwater Management Division (SWD) has begun the preliminary design phase of the Ellicott City (EC) Safe and Sound plan’s Tiber One (T-1) flood mitigation pond. Located along the Tiber tributary just west of historic Ellicott City, the T-1 Pond will enhance safety for downstream residents, businesses and landowners by capturing and detaining nearly 22 million gallons of water from the upper parts of the Tiber Branch Watershed during extreme rainfall events.
One of the seven major infrastructure strategies included in my EC Safe and Sound Plan, the T-1 Pond is an important piece to our ongoing efforts to mitigate flooding in Historic Ellicott City. This important first step of the project will help the County evaluate the scope of this work and begin capital planning for the cost of construction.
As part of the preliminary design phase, DPW SWD has partnered with County contractor GreenVest LLC to oversee Phase 1 of the T-1 Pond project, set to launch this month. The goal of Phase 1 is to define the scope, cost and schedule for the project’s final design and implementation.
GreenVest will conduct a thorough evaluation of comprehensive flood mitigation and stormwater management opportunities within the Tiber Branch Watershed, including stream stabilization and other stormwater management and resilience treatments. As part of this work, Greenvest will carry out preliminary assessments of existing natural resources, topographic surveys, evaluations of existing stormwater infrastructure and associated stream networks, and geotechnical investigations required to inform the design process. Weather permitting, Phase 1 is expected to take approximately 14 months to complete.
In addition to the construction of a large flow detention pond, the T-1 Pond project will also include corresponding stormwater management improvements in the project area and the stabilization of eroding stream and outfalls to proactively offset any environmental impacts of the new facility.
In addition to T-1, Ball’s Ellicott City Safe and Sound flood mitigation plan calls for four other stormwater retention ponds (H-7, Quaker Mill, H-4, and NC-3), the Ellicott City North Tunnel and Maryland Avenue Culverts water conveyance projects, 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.
In October of 2022, Howard County completed construction of the H-7 pond located at the interchange of Routes 29 and 40; followed by the Quaker Mill Pond at the intersection of Rogers Avenue and Patapsco River Road in February of 2023. The County initiated construction of the H-4 project in June of 2024.
Together, the H-7 and Quaker Mill ponds have the capacity to collect and control the release of seven and a half million gallons of water during a storm. Upon the completion of the H-4 Pond in fall of 2025, the pond will add another five and a half million gallons of water capacity. The three ponds together will have the ability to retain approximately 13 million gallons of water during severe storms, which is equivalent to a football field filled with water 30 feet deep.
The County also broke ground on the North Tunnel project in June of 2024. The 18-foot diameter approximately one-mile-long subterranean facility 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. Expected to be substantially complete in fall of 2027, the tunnel will reduce the risk of flash flooding by intercepting water and diverting it underground and away from Main Street.
As for the remaining projects, NC-3 Pond is currently in the final design and permitting stage and the Maryland Avenue Culverts project is in final design. Enhanced stream inspections and debris removal are initiated following each storm and the Outdoor Tone Alert System and high-ground signage and access points have also been installed.
For questions or concerns about the T-1 Pond, contact Mark Richmond, Chief, SWM Division, msrichmond@howardcountymd.gov or 410-313-6413. To learn more about the EC Safe and Sound plan, visit www.howardcountymd.gov/county-executive/ellicott-city-safe-and-sound.