Water Quality Analyses (WQA) with EPA Concurrence of MDE's Findings: Conowingo Dam/Susquehanna River

The Conowingo Dam Susquehanna River watershed is located in the Lower Susquehanna sub-basin (02-12-02), which drains approximately 5,916 square miles starting at Sunbury, Pennsylvania and ends where the Susquehanna River empties into the Chesapeake Bay in Havre de Grace, Maryland.  The watershed draining to the mainstem Susquehanna River between the Pennsylvania-Maryland border and the Conowingo Dam covers approximately 125 square miles, of which only 18 square miles are located in Maryland. 

The Conowingo Dam Susquehanna River watershed (basin code 02120204) was identified on the State’s 2010 Integrated Report as impaired by nutrients (1996) and sediments (1996).

The report, available below, provides an analysis of recent monitoring data to address whether or not the watershed is still impaired by nutrients. The study demonstrates that both applicable criteria for nutrients and the designated uses supported by this criteria are being met in the Conowingo Dam Susquehanna River 8-digit basin; therefore, a nutrient TMDL is not required.

Although the waters of the Conowingo Dam Susquehanna River do not display signs of eutrophication, the State reserves the right to require future controls in the Conowingo Dam Susquehanna River watershed if evidence suggests nutrients from the basin are contributing to downstream water quality problems. Other substances not addressed at this time, but identified on Maryland’s 303(d) list as impairing the Conowingo Dam Susquehanna River 8-digit basin, will be addressed in the future.

WQA of Eutrophication for Conowingo Dam Susquehanna River watershed, Cecil and Harford Counties, Maryland

(EPA Concurrence: May 18, 2012)

EPA's Decision Letter EPA's Decision Letter

Main Report 

Conowingo_Susquehanna_NutWQA_final.pdf (1227KB)

Comment Response Document

Conowingo_Susquehanna_Nut_CRD_final.pdf (7KB)

Contact Information

Please direct questions or comments concerning this project to Maryland's TMDL Program at (410) 537-3818.