Supplemental Indicator of Wastewater Progress for Maryland

The Chesapeake Bay Program Partnership-approved Supplemental Wastewater Indicator is a load-based measure of annual progress toward the 2025 planning targets for wastewater treatment plants and industrial sources. 

  Annual Wastewater Loads discharged to the Chesapeake Bay from MD, given average annual weather conditions throughout the State


Wastewater is the second-largest source of nutrient pollution in Maryland, accounting for approximately 25% of the nitrogen (leaving MDE website) that the State contributes to the Chesapeake Bay. To address this problem, the Maryland has undertaken a major capital improvements program to upgrade all of its major municipal wastewater treatment plants to include state-of-the-art enhanced nutrient removal technologies. Between 2010 and 2017, it is anticipated that these upgrades will reduce the State's annual wastewater nitrogen load to the Bay by over 40%. Because these improvements are critical to Maryland's strategy for meeting its pollution reduction targets, it is important that the State have a reliable metric for estimating annual wastewater pollution in order to measure the benefit of these upgrades.

To assist Maryland in estimating its annual progress towards its targets, the Chesapeake Bay Program has approved an annual measure of wastewater pollution that controls for climatic and hydrological fluctuations. Ordinarily, wastewater pollution levels are affected by factors such as rainfall which can, under extreme conditions, drive total annual discharges of nitrogen up or down by one million pounds statewide. Without controlling for these influences, this variability can completely obscure the results of the work Maryland has undertaken to curb wastewater pollution.

This "Supplemental Indicator of Wastewater Progress" was developed to normalize for the influence of weather in order to more accurately represent the effects of the State's management decisions relating to wastewater. It covers discharges from every permitted municipal treatment plant in Maryland, as well as from industrial and federal facilities. The indicator does not include pollution from sewer overflows. For details on how this indicator is calculated, please read the technical memorandum memo, Proposed Supplemental Indicator for Reporting Point Source Progress.

If you have any questions regarding the supplemental wastewater indicator, please contact Greg Busch at, or at 410-537-3901.​​