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Skip Navigation LinksDNREC : Division of Watershed Stewardship : Watershed Assessment : Watershed Assessment TMDLs

Total Maximum Daily Loads (TMDLs)

When monitoring reveals that waterways do not meet Delaware's water quality standards, they are reported on a list of impaired waterways (303(d) List). For each impaired waterway, the Federal Clean Water Act (CWA) requires states to develop Total Maximum Daily Loads (TMDLs) for the pollutants of concern. A TMDL sets a limit on the amount of pollution that can be discharged into a waterbody such that water quality standards can still be met. A non-scientific definition for TMDL could be "pollution limit." 

Pollutants in Delaware waters are often chemicals, such as nitrogen and phosphorus from fertilizer runoff and wastewater, but TMDLs could also be set for other pollutants such as bacteria, sediments, or even heat – anything that can injure a waterway's natural health. Pollutants can come from specific point sources or from nonpoint sources. Point sources are discrete sources of pollution, and include facilities that have a National Pollution Discharge Elimination System (NPDES) Permit, such as municipal and industrial wastewater treatment plants.

Nonpoint source pollution travels over and through the ground from many diffuse sources, including human activities on agriculture and developed lands like septic systems and runoff from lawns, farms, parking lots, and golf courses.

TMDLs consist of three parts: a wasteload allocation (WLA) for point sources, a load allocation (LA) for nonpoint sources, and a margin of safety (MOS): TMDL = WLA + LA + MOS

Delaware has been establishing TMDLs for our State's impaired waters since 1998.  Monitoring and other types of data are used to develop models that can predict how water quality will change under a variety of pollutant loading scenarios. These models help us determine TMDL levels that will achieve water quality standards. The table below lists all of the TMDLs that have been established in Delaware and provides links to technical analysis documents and the resulting regulations. Maps summarizing reductions in nonpoint source nitrogen, phosphorus, and bacteria required by TMDLs in order to achieve water quality goals are also shown below. 

Watershed 

Developed by

Year

Analysis Documents

Regulations

Piedmont Drainage

Naamans Creek (1)

DNREC

2005

Nutrients and Bacteria

Nutrients and Bacteria

Shellpot Creek (2)

DNREC

2005

Nutrients and Bacteria

Nutrients and Bacteria

Brandywine Creek (3), Red Clay Creek (4), White Clay Creek (5), and Christina River (6)

EPA

2005 

High Flow Nutrients and Bacteria 

Red Clay Creek (4)

DNREC

1999, Amended 2009

Zinc

Zinc

White Clay Creek (5)

DNREC

1999

Zinc

Zinc

Delaware Bay Drainage

Army Creek (8)

DNREC

2006

Nutrients and Bacteria

Nutrients and Bacteria

Red Lion Creek (9)

DNREC

2006

Nutrients and Bacteria

Nutrients and Bacteria

Dragon Run Creek (10)

DNREC

2006

Nutrients and Bacteria

Nutrients and Bacteria

Appoquinimink River (12)

EPA

DNREC

2003

2006

Nutrients

Bacteria

 

Bacteria

Blackbird Creek (13)

DNREC

2006

Nutrients and Bacteria

Nutrients and Bacteria

Smyrna River (15)

DNREC

2006

Nutrients and Bacteria

Nutrients and Bacteria

Leipsic River (16)

DNREC

2006

Nutrients and Bacteria

Nutrients and Bacteria

Little Creek (17)

DNREC

2006

Nutrients and Bacteria

Nutrients and Bacteria

St. Jones River (18)

DNREC

2006

Nutrients and Bacteria

Nutrients and Bacteria

Murderkill River (19)

DNREC

 

DNREC

2001,
Amended 2005

2006

Nutrients

 

Bacteria

Nutrients

 

Bacteria

Mispillion River (20)

DNREC

2006

Nutrients and Bacteria

Nutrients and Bacteria

Cedar Creek (21)

DNREC

2006

Nutrients and Bacteria

Nutrients and Bacteria

Broadkill River (22)

DNREC

2006

Nutrients and Bacteria

Nutrients and Bacteria

C&D Canal East and Lums Pond (11) 

DNREC

2012

Nutrients 

Nutrients 

Chesapeake Bay Drainage

Chester River (28), Choptank River (29), Marshyhope Creek (30), Nanticoke River (31), Gum Branch (32), Gravelly Branch (33), Deep Creek (34), Broad Creek (35), and Pocomoke River (37)

DNREC

2006

Bacteria

Bacteria

Chester River (28)

DNREC

2005

Nutrients

Nutrients

Choptank River (29)

DNREC

2005

Nutrients

Nutrients

Marshyhope Creek (30)

DNREC

2005

Nutrients

Nutrients

Nanticoke River (31), Gum Branch (32), Gravelly Branch (33), Deep Creek (34), and Broad Creek (35)

DNREC

1998

Nutrients in the mainstem of the Nanticoke River and Broad Creek

Nutrients in the tributaries and ponds of the Nanticoke River and Broad Creek

 

Nutrients

Pocomoke River (37)

 DNREC

2005

Nutrients

Nutrients

Inland Bays/Atlantic Ocean Drainage

Lewes-Rehoboth Canal (38), Rehoboth Bay (39), Indian River (40), Iron Branch (41), Indian River Bay (42), Buntings Branch 43), Assawoman Bay (44), and Little Assawoman Bay (45)

 DNREC

2006

Bacteria

Bacteria

Lewes-Rehoboth Canal (38), Rehoboth Bay (39), Indian River (40), Iron Branch (41), and Indian River Bay (42)

 DNREC

1998

Nutrients

Nutrients

Little Assawoman Bay (45)

DNREC

2005 

Nutrients

Nutrients

Indian River (40)

EPA

2004

Temperature

Buntings Branch (43)

DNREC

2004

Nutrients

NA

Delaware Estuary

Zones 2-5

EPA

2003

PCBs

Zone 6

EPA

2006

PCBs

 

PROPOSED ACTIONS

Proposed Amendment of the Murderkill River Watershed TMDL

The Department of Natural Resources and Environmental Control (DNREC), Watershed Assessment and Management Section, will conduct a Public Hearing regarding proposed amendments to the Waste Load Allocation (WLA) of the 2005 Murderkill River Total Maximum Daily Loads (TMDLs) Regulation on Tuesday, April 29, 2014 at 5:00 pm, in the DNREC Auditorium, 89 Kings Highway, Dover, Delaware.

If you cannot attend the hearing, you are encouraged to submit written comments. All written comments must be received by May 16, 2014.  Please send written comments to:

Hassan Mirsajadi
DNREC/Division of Watershed Stewardship
Watershed Assessment and Management Section
820 Silver Lake Boulevard – Suite 220
Dover, DE 19904-2464
Phone: (302) 739-9939
Facsimile: (302) 739-6140
Email: (Hassan.Mirsajadi@state.de.us)

You are encouraged to submit comments electronically.

Maps:  The maps below show the amount of reduction needed from nonpoint sources across the state to achieve TMDLs for nitrogen, phosphorus, and bacteria.

Click on the maps to view a larger image.

Setting pollution limits is just the first step toward improving water quality.  Once the pollutant limits are established, efforts must be taken to reduce the pollutant loads from point and nonpoint sources. The Watershed Assessment Section works with Tributary Action Teams to identify voluntary and regulatory actions for each impaired region of the state. Collectively, these actions are called pollution control strategies (PCS) and they are designed to achieve TMDLs and water quality standards. In addition, other types of watershed plans and strategies have also been developed across the state.

 Related links:

Learn more about Delaware's Watersheds!

 
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