Final TMDLs Approved by EPA: Lower Gunpowder Falls

​The Lower Gunpowder Falls watershed is located entirely within the central eastern portion of Baltimore County, Maryland. The watershed is located in the Coastal Plain and Eastern Piedmont regions, two of three distinct eco-regions identified in the Maryland Department of Natural Resources (MDDNR) Maryland Biological Stream Survey (MBSS) Index of Biological Integrity (IBI) metrics. The Loch Raven Dam divides the Loch Raven watershed from the Lower Gunpowder Falls. The watershed begins at the Loch Raven Reservoir dam and flows generally towards the east. Where it meets the tidal portions of Gunpowder River, it becomes the Gunpowder River watershed. Major tributaries in the watershed include Minebank Run, Long Green Creek, Sweathouse Run, Haystack Branch, Jennifer Branch, and Bean Run. The watershed is within the Gunpowder River Basin (Maryland 6-digit 021308), which also includes the Prettyboy Reservoir, Loch Raven Reservoir, Little Gunpowder Falls, Bird River, Middle River – Browns, and the mainstem Gunpowder River as subwatersheds.

The Maryland Department of the Environment (MDE) identified of the waters of the Lower Gunpowder Falls watershed on the State’s 2014 Integrated Report as impaired by multiple pollutants. The Lower Gunpowder Falls watershed is associated with two assessment units in Maryland’s Integrated Report: a non-tidal 8-digit watershed (02130802) and an estuary portion (Chesapeake Bay segment: Gunpowder Oligahaline (GUNOH)). A data solicitation for total suspended solids (TSS)/sediment was conducted by MDE in December 2014, and all readily available data have been considered.

The TMDL, available below, will ensure that watershed sediment loads are at a level that supports the Use Class I/III/IV designation for the Lower Gunpowder Falls watershed. The TMDL will address water clarity problems and associated impacts to aquatic life in Lower Gunpowder Falls caused by high sediment and TSS concentrations. The sediment TMDL for the Gunpowder River Oligohaline Chesapeake Bay segment in the 2010 Chesapeake Bay TMDL addresses the Use Class II impairment.  Other pollutants identified for the watershed either have been addressed or will be addressed in the future.

Total Maximum Daily Load of Sediment in the Lower Gunpowder Falls Watershed, Baltimore County, MD

(Approved on May 4, 2017)

EPA's Decision Letter EPA's Decision Letter (4370KB)
​Fact Sheet Lower_Gunpowder_Sed_TMDL_FactSheet.pdf (171KB)
Main Report

Lower_Gunpowder_Sed_TMDL_final.pdf (1383KB)

Point Source Technical Memorandum Lower_Gunpowder_Sed_TMDL_PS_TechMemo.pdf (37KB)
Nonpoint Source Technical Memorandum Lower_Gunpowder_Sed_TMDL_NPS_TechMemo.pdf (27KB)
Comment Response Document Lower_Gunpowder_Sed_TMDL_CRD.pdf (30KB)

Additional Supporting Information

Biological Stressor Identification Lower Gunpowder Falls Watershed Report (656KB)

Biological Stressor Identification Methodology (459KB)

Nontidal Sediment TMDL Methodology Report (361KB)

Addendum to the Nontidal Sediment TMDL Methodology Report (23KB)


Contact Information

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