Bay States: The Bay States are the states that contribute to the Chesapeake Bay watershed: Maryland, Virginia, Pennsylvania, Delaware, West Virginia, New York, and the District of Columbia. Also referred to as “Bay Jurisdictions.”

Loads: A term used to represent the amount of a pollutant that enters the Bay watershed, typically expressed in pounds.

TMDL: A Total Maximum Daily Load, or TMDL for short, is an information tool used to determine how many pollutants can enter a body of water without impairing the water. “Impaired waterbody” is a term of legal significance under the Clean Water Act. Any body of water classified as “impaired” must have a TMDL developed by either the state or the EPA. Informally known as a “pollution diet,” it works in a similar way to a human diet: instead of measuring how many calories, fat, and added sugar a human boy can absorb and still be healthy, a pollution diet measures how many nutrients (e.g. nitrogen, phosphorus, and sediment) a body of water can absorb without being impaired.

The Chesapeake Bay TMDL is the largest and most detailed TMDL ever written by the EPA. It was developed in collaboration between the EPA and the Bay States, which each state contributing a Watershed Implementation Plan (WIP) to establish how pollution reduction targets will be achieved. Implementation of the Bay TMDL will occur in three phases: Phase I runs from 2010-2014; Phase II runs from 2014-2017, and requires each Bay State to have at least 60% of practices in place by 2017; Phase III runs from 2017-2025, when all practices are expected to be in place by 2025. Importantly, the Bay TMDL does not require that the Chesapeake Bay be healthy by 2025; rather, it merely requires all practices to be in place by then so that the Bay will eventually attain a healthy water quality.

WIP: A Watershed Implementation Plan, or WIP, is the framework through which the Bay States implement practices to ensure that pollution reduction targets under the TMDL will be met on time. Each Bay State has its own WIP, which the EPA assesses to ensure that the Bay States are taking steps necessary to achieve the required pollution reductions.