↑ Return to ISSUES

Chesapeake Bay TMDL

Chesapeake Bay Total Maximum Daily Load (TMDL) 

On December 29, 2010, the U.S. Environmental Protection Agency (EPA) established the Chesapeake Bay Total Maximum Daily Load (TMDL), a pollution diet to initiate actions to restore water quality in the Chesapeake Bay and the region’s streams, creeks and rivers.

  • 2011: EPA completes TMDL and model revisions;  States submit Phase II Watershed Implementation Plans (WIPs) detailing actions proposed at a local scale;
  • States submit Phase III WIPs; EPA modifies TMDL allocations;
  • States complete implementation actions

What is a TMDL? The Clean Water Act (CWA) sets an environmental goal that all waters in the United States be fishable and swimmable. It requires states to establish appropriate uses for their waters and adopt water quality standards that are protective of those uses. Every two years, states are required to develop a list of waterways that are impaired by pollutants and do not meet water quality standards. For those waterways identified on the 303(d) list of impaired waters, a TMDL must be developed. A TMDL is essentially a pollution diet that identifies the maximum amount of a pollutant the waterway can receive and still meet water quality standards.

Why was a TMDL developed for the Chesapeake Bay and its tidal tributaries? Despite extensive restoration efforts during the last 25 years, the Bay TMDL was prompted by insufficient progress and continued poor water quality in the Chesapeake Bay and its tidal tributaries. The TMDL is required under the federal Clean Water Act and responds to consent decrees in Virginia and the District of Columbia from the late 1990s.

How large is the Chesapeake Bay? How big is the watershed that drains into it? How many people live within the watershed? The Bay itself is about 200 miles long, home to more than 3,700 species of plants, fish and other animals. The Bay watershed totals about 64,000 square miles, stretching from Cooperstown, New York, to Hampton Roads. Nearly 17 million people live in the watershed. The Bay TMDL and its implementation plan will be enacted throughout the entire Chesapeake Bay watershed.

How long has the Bay TMDL process been underway? Since 2000, the seven jurisdictions in the Chesapeake Bay watershed (Delaware, the District of Columbia, Maryland, New York, Pennsylvania, Virginia, and West Virginia), EPA, and the Chesapeake Bay Commission, have been planning for a Chesapeake Bay TMDL. During the October 2007 meeting of the Chesapeake Bay Program’s Principal Staff Committee, the Bay watershed jurisdictions agreed that EPA would establish the multi-state TMDL.

What about the Susquehanna?  The Susquehanna contributes over 50% of the Bay’s freshwater and around 43% of its pollution. Reducing nitrogen, phosphorus and sediment loads from the Susquehanna is critical to TMDL success. Reductions will require serious ratcheting of regulatory controls on polluters like big agriculture, deforestation and landscape conversion, stormwater and erosion and sediment.

Our Role

What Are We Doing About the Bay TMDL? We actively participate as a stakeholder in Watershed Implementation Plans on the state, county and local level. We are the sole NGO stakeholder participating in Bay TMDL implementation who is specifically dedicated to ensuring the health and vitality of the Susquehanna Watershed. In line with that mission, our …

View page »

TMDL Implementation

How will the Bay TMDL be implemented? What is the relationship between the TMDL and the Watershed Implementation Plan (WIP)? The accountability framework includes Watershed Implementation Plans (WIPs) developed by the states, two-year milestones identified in the WIPs, EPA’s tracking and assessment of restoration progress and, as necessary, specific federal actions if jurisdictions do not meet …

View page »

Water Quality

What water quality problems affect the Bay? Nitrogen and phosphorus pollution are the most serious problems facing the Bay. Too much nitrogen and phosphorus cause algae blooms that block sunlight to underwater grasses. When the blooms decompose, they create dead zones where dissolved oxygen levels are too low to sustain fish and shellfish. Excess sediment also …

View page »