PN-23-03 NAB-2022-61179-M49 (HO DPW Project No. 1165/Ellicott City Site H-4/Earthen Dam)

Published Feb. 6, 2023
Expiration date: 3/8/2023

                       Public Notice
U.S. Army Corps              In Reply to Application Number
of Engineers                    NAB-2022-61179-M49 (HO DPW Project No. 1165/Ellicott
                                           City Site H-4/Earthen Dam)

Baltimore District
PN-23-03                          Comment Period: February 6, 2023 to March 8, 2023

This District has received an application for a Department of the Army permit pursuant to Section 404 of the Clean Water Act (33 USC 1344),as described below:


                                        Ms. Michele Monde
                                        Howard County Bureau of Environmental Services
                                        Stormwater Management Division
                                        9801 Broken Land Parkway
                                        Columbia, Maryland 21046


The flood attenuation facility is proposed in a perennial tributary to Hudson Branch at the location of an existing earthen embankment. The site is located north of Frederick Road, west of US Route 29, and east of Dunloggin Road, in Ellicott City, Howard County, Maryland. (39.272421, -76.820963).


The purpose of the project is to construct a new dry flood attenuation facility in the Hudson Brach watershed to reduce flooding in Ellicott City, without obstructing existing stream baseflows. The facility is proposed in conjunction with other projects constructed under the ‘Ellicott City Safe and Sound’ flood mitigation master plan.


Howard County proposes construction of a dry flood attenuation facility at site ‘H-4’, in accordance with the attached plans. The project is proposed where a perennial tributary to Hudson Branch flows beneath an existing earthen embankment. The facility is designed to capture and slowly release runoff from approximately 122 acres of the Hudson Branch watershed during storm events and pass stream baseflow under typical conditions. The project will construct a new earthen embankment with an impervious clay core and cutoff trench that will span the stream and floodplain directly upstream of the existing earthen embankment. The embankment will feature a 40-foot-wide concrete weir wall outlet control structure and a 5-foot long by 5-foot-wide orifice to allow perennial stream baseflow to pass through the facility unobstructed. The project will grade the stream, floodplain, and valley walls upstream of the embankment to create a basin for necessary flood volume storage. The existing stream will be realigned to flow through the center of the basin in a baseflow channel furnished with gravel streambed material. Where the stream flows into the basin, a series of rock step pools will be installed in the channel to create a stable conveyance to the new floodplain elevation. The project will modify an existing storm drain outfall from Frederick Road and install gabion inflow stabilization in a swale located at the northeast corner of the basin. The basin will be planted with a dense variety of native riparian trees and shrubs to shade the stream channel and stabilize the new floodplain area. The project will grade the existing earthen embankment, replace an existing 60” corrugated metal pipe culvert with a 60” Reinforced Concrete Pipe culvert, and install a rip-rap lined plunge pool at the outfall.

Construction of the facility will permanently impact 835 linear feet (12,210 square feet) of perennial stream. Pump around structures used for dewatering during construction will temporarily impact 12 linear feet (36 square feet) of perennial stream. Realignment of the perennial tributary to Hudson Branch will result in a loss of 145 linear feet of stream length.



Stream Impact (lf)

Stream Impact (Sq. Ft.)


(Section 10/404/408)

Permanent impacts associated with facility construction and stream relocation

835 (perennial)



Section 404

Temporary impacts associated with dewatering

12 (perennial)

36 (perennial)

Section 404



The United States Army Corps of Engineers, as the lead federal agency, is responsible for all coordination pursuant to applicable federal authorities.


Avoidance and minimization: As part of the ‘Ellicott City Safe and Sound’ plan, Howard County evaluated eight potential flood mitigation sites within the Hudson Branch watershed, with the goal of reducing 100-year flood event flows to as close as possible to 10-year flood event flows. The site selection process identified six conceptual in-line flood mitigation ponds and two underground storage facilities. The study evaluated each facility for peak flow reductions to the 100-year storm, site constraints, and property ownership. Results of the study found that Pond H-7 was the most effective in reducing the peak 100-year flows. This pond has been constructed and is on-line as of October 2022. The underground facilities were determined to have significant construction related constraints, including ownership of land, ability to divert the flow into the facilities, presence of bedrock, and significant impacts to stakeholders in the region, and were not considered to be feasible options at this time. The H-4 site (the subject of this public notice) was determined to be the next most feasible and effective flood mitigation pond as it provides the next highest reduction in peak flow and is located on property already owned by the County.

As part of the planning process for the H-4 flood attenuation facility, steps were taken to avoid and minimize impacts to aquatic resources to the maximum extent practicable based on existing conditions. The site is located on a perennial tributary to Hudson Branch where the stream flows through an existing earthen embankment. The site is constrained by Old Frederick Road to the south, steep topography to the north and west, and private property boundaries. No existing wetlands are present within the project site. It is not practicable to construct a facility with sufficient flood-volume storage at this location without impacting the existing stream, but impacts will be limited to a reach of stream and floodplain that is degraded in existing conditions. The existing embankment and degraded corrugated metal pipe culvert create a constriction to stream flow and the site impounds some storm flow in existing conditions. As a result, the stream channel directly upstream of the embankment features an unstable plan form with tight meander bends, actively eroding stream banks, and sparse riparian canopy coverage. Additionally, the stream has migrated up against the roadway embankment of Frederick Road and is currently threatening the stability of the roadway. The realigned stream channel has been designed to improve ecological functions and avoid further impacts to the Frederick Road embankment. Specifically, the baseflow channel will have low bank heights to facilitate frequent floodplain access, minimize erosion, and improve water quality. Furnished gravel material will be placed along the length of the stream bed to provide stable substrate. The gravel lens will be embedded in the floodplain on either side of the stream channel to maintain vertical stability in the event of lateral channel migration. The new floodplain will be planted with 6’-8’ trees to increase native species diversity in the riparian area and to shade the stream channel. Additionally, the facility is designed to maintain aquatic species passage through the site. The baseflow channel orifice will be lined with natural substrate, and a plunge pool will be constructed at the facility outfall to provide a staging area for fish species.

Compensatory Mitigation: No compensatory mitigation is proposed at this time.


This project will be evaluated pursuant to Corps Regulatory Program Regulations (33 CFR Parts 320-332). The decision whether to issue a permit will be based on an evaluation of the probable impacts, including cumulative impacts of the proposed activity on the public interest. That decision will reflect the national concern for both protection and utilization of important resources. The benefit, which reasonable may be expected to accrue from the proposal, must be balanced against its reasonably foreseeable detriments. All factors, which may be relevant to the proposal will be considered, including the cumulative effects thereof; among those are conservation, economic, aesthetics, general environmental concerns, wetlands, cultural values, fish and wildlife values, flood hazards, flood plain values, land use, navigation, shoreline erosion and accretion, recreation, water supply and conservation, water quality, energy needs, safety, food and fiber production, mineral needs, and consideration of property ownership and in general, the needs and welfare of the people. The evaluation of the impact of this project will also include application of the Clean Water Act Section 404(b)(1) Guidelines promulgated by the Administrator, United States Environmental Protection Agency.


A preliminary review of this application indicates that the proposed work will have no effect on federally listed rare, threatened, or endangered species or their critical habitat, pursuant to Section 7 of the Endangered Species Act, as amended. As the evaluation of this application continues, additional information may become available which could modify this preliminary determination.


The Magnuson-Stevens Fishery Conservation and Management Act, as amended by the Sustainable Fisheries Act of 1996 (Public Law 04-267), requires all federal agencies to consult with the National Marine Fisheries Service on all actions, or proposed actions, permitted, funded, or undertaken by the agency that may adversely affect Essential Fish Habitat (EFH), including species of concern, life cycle habitat, or Habitat Areas of Particular Concern. The Baltimore District has made a preliminary determination that the project is not within EFH. The Baltimore District has made a preliminary determination that mitigative measures are not required to minimize adverse effects on EFH at this time. This determination may be modified if additional information indicates otherwise.


Pursuant to Section 106 of the National Historic Preservation Act of 1966 and applicable guidance, the Corps has reviewed the latest published version of the National Register of Historic Places and initially determined that no registered properties listed as eligible for inclusion, therein, are located at the site of the proposed work. The Corps has made the preliminary determination that the proposed project has no potential to cause effects on historic properties. The Corps final eligibility and effect determination will be based on coordination with the State Historic Preservation Office as appropriate and required, and with full consideration given to the proposed undertaking’s potential direct and indirect effects on historic properties within the Corps’ identified permit area.


All Section 408 proposals will be coordinated internally at USACE. The Section 408 decision will be issued along with the Section 404 and/or Section 10 decision. Please see the following link for more information regarding Section 408:


The applicant is required to obtain a water quality certification in accordance with Section 401 of the Clean Water Act.


The Corps of Engineers is soliciting comments from the public; federal, state, and local agencies and officials and other interested parties in order to consider and evaluate the impacts of this proposed activity. Any comments received will be considered by the Corps of Engineers to determine whether to issue, modify, condition or deny a permit for this proposal. To make this decision, comments are used to assess impacts on endangered species, historic properties, water quality, general environmental effects, and the other public interest factors listed above. Comments are used in the preparation of an Environmental Assessment and/or an Environmental Impact Statement pursuant to the National Environmental Policy Act. Comments provided will become part of the public record for this action and are subject to release to the public through the Freedom of Information Act. Comments are also used to determine the need for a public hearing and to determine the overall public interest of the proposed activity.

Written comments concerning the work described above related to the factors listed above or other pertinent factors must be received by the United States Army Corps of Engineers, Baltimore District within the comment period specified above through postal mail at the address below or electronic submission to the project manager email address below. Written comments should reference the Application Number (NAB-2022-61179-M49).


Any person who has an interest which may be adversely affected by the issuance of this permit may request a public hearing. The request, which must be in writing, must be received within the comment period as specified above to receive consideration. Also, it must clearly set forth the interest which may be adversely affected by this activity and the manner in which the interest may be adversely affected. The public hearing request may be submitted by electronic mail or mailed to the following address:

Matt Hynson
U.S. Army Corps of Engineers, Baltimore District
Regulatory Branch
2 Hopkins Plaza
Baltimore, Maryland 21201

It is requested that you communicate this information concerning the proposed work to any persons known by you to be interested, who did not receive a copy of this notice.

General information regarding the Corps’ permitting process can be found on our website at This public notice has been prepared in accordance with Corps implementing regulations at 33 CFR 325.3. If you have any questions concerning this specific project or would like to request a paper copy of this public notice, please contact Matt Hynson at or (410) 689-9532. This public notice is issued by the Chief, Regulatory Branch.