DRBC's Designated Use Study
The Next Chapter in Delaware Estuary Water Quality Improvements

The DRBC approved a resolution in September 2017 (pdf 249 KB) recognizing the significant water quality improvements in the Delaware River Estuary and providing for a formal review of the designated aquatic life uses and water quality criteria necessary to support these uses.

The resolution outlines a deliberative, scientific process to further study evidence on the reproduction of resident and migratory fish in a 38-mile section of the tidal Delaware River stretching from Wilmington, Del. to just above the Tacony-Palmyra Bridge connecting Philadelphia and New Jersey; this area includes DRBC Water Quality Zones 3, 4, and the upper portion of Zone 5. This study will allow the commission to determine the "designated use" of this reach of the river and provide data and information to establish revised water quality criteria to protect that use. It also affirms the important goal of continued water quality improvement.

DRBC is leading this groundbreaking effort through a collaborative process informed by expert scientists and engineers, and in close consultation with its Water Quality Advisory Committee, a group representing state and federal co-regulators, NGO's, academic institutions, municipal and industrial dischargers, and water purveyors.

The DRBC-approved resolution provides for scientific and technical studies to be performed over the next 3.5 years for the following purposes:

  • To conduct additional field studies of the occurrence, spatial and temporal distribution of the life stages of important fish species that utilize the estuary;
  • To determine the dissolved oxygen (DO) requirements of these fish species and the oxygen-depleting nutrient loadings form point (end-of-pipe) and non-point (runoff) sources that can be discharged into the tidal river while maintaining the DO levels in the water;
  • To conduct an analysis to determine the attainability of DO requirements and water quality standards that would result in an upgrade in the designated aquatic life use in this 38-mile section of the river, including technical, social, and economic factors; and
  • To identify and evaluate opportunities for early action to reduce discharges of oxygen-depleting wastes to this stretch of river in the short term

The resolution directs the initiation of DRBC rulemaking to revise the designated aquatic life uses consistent with the results of these scientific and technical studies, as well as with the federal Clean Water Act. The commission seeks to issue a final rule and an implementation strategy within six years, dependent on the availability of resources to fund the effort.

When the DRBC was created in 1961, little or no DO was present in the Delaware River from Wilmington to Philadelphia for periods of up to six months each year. To combat this serious challenge, DRBC in 1967 established designated aquatic life uses for the estuary and associated numerical water quality criteria necessary to protect those uses. The designated use in this 38-mile stretch of river was "maintenance" (survival) of resident fish and movement of migratory fish through these waters to and from spawning areas.

Significant improvements in DO levels have occurred throughout this stretch of river since 1967. By the late 1980s, over one billion dollars had been spent on improving wastewater treatment facilities throughout the basin, which benefited communities along the river and strengthened fish populations.

The scientific and technical studies to be undertaken as the result of the approved resolution will help to better inform decision makers on DO requirements of various life stages of resident and migratory fish species since the early life stages of estuarine fish species are generally more sensitive to DO levels than are the adults living in the river stretches or just passing through these waters to reach spawning areas.

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