The Maryland Department of the Environment (MDE) has completed its administrative review of the Clean Water Act, Section 401 Water Quality Certification (WQC) 17-WQC-02 issued to Constellation Energy Generation, LLC (Constellation (formerly Exelon)) in 2018.​ On October 2, 2025 MDE issued with conditions a Revised WQC, 17-WQC-02(R1), to Constellation Energy Generation, LLC, certifying the Conowingo Hydroelectric Project, FERC No. P-405 in accordance with Section 401 of the Clean Water Act.​ The Revised WQC, which is accompanied by a settlement agreement between Maryland, Constellation, Waterkeepers Chesapeake, and Lower Susquehanna Riverkeeper Association, ensures that water quality standards will not be adversely impacted by the dam’s discharge and operations.  The revised WQC will be filed with F​ERC for the dam’s operating license to be renewed.​

• ​Reconsideration Fact Sheet
  

The Revised WQC, Attachments, and Settlement Agreement are available below:

17-WQC-02(R1)_Conowingo Dam WQC Package with Attachments

17-WQC-02(R1)_Conowingo Dam WQC

Conowingo Dam WQC Reconsideration Order

2025 Settlement Agreement​

WQC Attachments (Individual Files)

A_Fish Passage Diagram

B_Minimum Stream Flow Operational Plan (“MSFOP”) dated Mar. 18, 2022

C_DOI Modified Prescription for Fishways, dated Jun. 8, 2016

D_Conowingo Hydroelectric Project (FERC Project No. 405) Fishway Effectiveness Monitoring Plan (“FEMP”) dated Sept. 2021 

E_Conowingo Hydroelectric Project (FERC Project No. 405) Fishway Operations and Maintenance Plan (“FOMP”) dated Jan. 2023 

F_Conowingo Hydroelectric Project (FERC Project No. 405) Final Study Report Maryland Darter Survey Revised Study Plan (“RSP 3.10”) dated Aug. 2012 

G_Conowingo Hydroelectric Project (FERC Project No. 405) Fish Kill Notification Plan dated Mar. 2022 

H_Conowingo Hydroelectric Project (FERC Project No. 405), American Eel Passage and Restoration Plan (“EPRP”), dated Sept. 2021 

I_Conowingo Hydroelectric Project (FERC Project No. 405) Project’s previously-filed Chlorophyll-A Monitoring Plan dated Mar. 2023

J_Quality Assurance Project Plan for Lake Nutrient Monitoring for Integrated Report Assessment and Total Maximum Daily Load Development dated Feb. 26, 2025 

K_EPA Region 3 QAPP Standard Template Final 

L_MDE-provided MS Excel data template 

M_Conowingo Hydroelectric Project (FERC Project No. 405), Debris Management Plan, Revision (“Debris Management Plan”), dated Oct. 2021 

N_Conowingo Hydroelectric Project (FERC Project No. 405) Sediment Management Plan, dated August 2012 and Revised Sept. 2021 

O_Conowingo Hydroelectric Project (FERC Project No. 405) Shoreline Management Plan (“SMP”) dated Aug. 31, 2012, revised Sept. 2021

P_[WITHHELD] Conowingo Hydroelectric Project (FERC Project No. 405) Revised Bog Turtle Protection Plan dated Jul. 2022

Q_[WITHHELD] Conowingo Hydroelectric Project (FERC Project No. 405) Northern Map Turtle Protection Plan dated Mar. 2022

R_[WITHHELD] Conowingo Hydroelectric Project (FERC Project No. 405) Waterfowl Nesting Protection Plan dated Mar. 2022​​

A limited public notice related to the reconsideration of Clean Water Act, Section 401 Water Quality Certification 17-WQC-02​ was issued by MDE on June 30, 2023. Public comments in response to the notice as well as supplemental briefing materials from parties to the reconsideration can be found below.

Public Comments

Please note that personally identifiable information (such as e-mail addresses and mailing addresses) has been removed from individual citizen comments.​

More information is available on MDE's Conowingo Dam Impacts web page:

 https://mde.maryland.gov/programs/water/TMDL/TMDLImplementation/Pages/Conowingo-Dam-Impacts.aspx

For information on MDE’s freshwater mussel restoration efforts, please visit:

 https://mde.maryland.gov/programs/water/WetlandsandWaterways/Pages/freshwater-mussel-restoration.aspx

Legal Challenges

• ​​Judg​ment, No. 21-1139- DC Circuit Court (December 20, 2022)

• ​Order, No. 21-1139- DC Circuit Court (December 20, 2022)
  

• ​Opinion, No. 21-1139- DC Circuit Court (December 20, 2022)
  

• ​Administrative Appeal of Final Decision to Issue Clean Water Act Section 401 Certification for the Conowingo Hydroelectric Project (6/8/2018) - Stewards of the Lower Susquehanna, d/b/a Lower Susquehanna Riverkeeper Association, and Waterkeepers Chesapeake

• ​Protective Petition for Reconsideration and Administrative Appeal (5/25/2018) - Exelon Generation Company, LLC
  

Conowingo Hydroelectric Project Water Quality Certification Application​​​​​

​Related Docume​nts

• Conowingo Settlement Agreement (PDF)
• ​ FERC License Application Vol 1 and Vol 3​​​
• ​ FERC License Application Supporting Studies ​
  

Conowingo Pilot Dredge Project

• Additional information is available on the Conowingo Innovative and Beneficial Reuse Pilot Project web page.