Chesapeake Bay Total Maximum Daily Load (TMDL)

This TMDL is the largest and most complex ever developed by EPA, and covers six states and the District of Columbia. Pennsylvania's Department of Environmental Protection has been tasked with developing a Chesapeake Bay Watershed Implementation Plan (WIP) that will assist Pennsylvania in meeting the pollution reduction goals as set forth in the Chesapeake Bay TMDL.

Check with PADEP's Chesapeake Bay Program Office's webpage for the latest status. To understand the progress and steps taken since 2010, PADEP prepared a timeline infographic.

PADEP is currently working with USEPA to develop the Phase III WIP and finalize it in 2019. The WIP will be developed to include load reductions subdivided to the local (county) level to assist with implementation efforts to improve water quality.  

In Chester County, 6 watersheds, comprised of 142 square miles of land area, ultimately drain to the Chesapeake Bay Basin. These 6 watersheds include portions of 20 municipalities of Chester County and drain to either: Eastern Shore of the Chesapeake Bay or the Susquehanna River Basin.
Farm in the Octoraro Creek watershed

Draining to the Eastern Shore of the Chesapeake Bay:


  • Big Elk Creek,
  • Little Elk Creek, and
  • Northeast Creek
These Chester County watersheds represent the only land areas in Pennsylvania that drain to the Eastern Shore and include portions of 10 Chester County municipalities. Therefore, in the Pennsylvania WIP, the load reductions assigned to the Eastern Shore of the Bay will be shared exclusively by municipalities, landowners and operators located within these 3 watersheds in Chester County, Pennsylvania.


Draining to the Susquehanna River Basin:


  • Conestoga Creek,
  • Octoraro Creek, and
  • Pequea Creek
These Chester County watersheds represent only a very small portion of the Susquehanna River Basin and include portions of 15 Chester County municipalities. Therefore, in the Pennsylvania WIP, the load reductions assigned to this drainage area will be shared by many PA municipalities and landowners.

Resources to Improve the Waters of Chester County and the Chesapeake Bay
To improve the waters of Chester County and the Chesapeake Bay, it is essential to understand the Chesapeake Bay TMDL and how it will affect Chester County residents and its municipalities. To assist with this, several resources are available here: