Targeting pollution, one load at a time

Established in 2010, the Chesapeake Bay Total Maximum Daily Load, or Bay TMDL, set limits for major sources of nitrogen, phosphorus and sediment pollution entering the Chesapeake Bay. Pollution reductions are critical in order to meet water quality standards, which ensure the water of the Bay is healthy for humans, plants and animals.

These pollution limits, or allocations, were divided across the six Chesapeake Bay watershed states – Delaware, Maryland, New York, Pennsylvania, Virginia and West Virginia – as well as the District of Columbia. These allocations were set using state-of-the-art modeling tools, extensive monitoring data and peer-reviewed science.

The six watershed states and the District of Columbia prepare Watershed Implementation Plans (WIPs), which include detailed, specific steps they will take to reduce their pollution loads and meet these allocations. Currently in the process of developing their third WIP since the establishment of the Bay TMDL, these jurisdictions now have new targets to meet for pollution reduction.

These new planning targets were set based on refinements made to the most recent version of the model, Phase 6, which uses the most up-to-date science, land use, land cover and monitoring data available to replicate the conditions of the Bay. The Chesapeake Bay Program partnership's Phase 6 Model includes more insight on how pollution loads have changed as pollution control practices have been implemented across the region. The new planning targets take into account the importance of location and geography in the effectiveness of pollution control, so implementing the same action in different areas could have varying levels of impact. For example, a pound of nitrogen reduced in the James River might not have the same impact as a pound of nitrogen reduced in the Potomac River.

Currently, each jurisdiction is reviewing the draft version of their planning targets, with the final versions on track to be issued in May 2018.

Learn more about planning targets.