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Comprehensive Assessment

We apply the watershed perspective to monitoring, spanning scientific disciplines as well as political boundaries in order to characterize conditions within our watersheds as comprehensively as possible.


Assessing the integrity of our waterways is integral to the long-term sustainability of our aquatic ecosystems. Thorough measurements of our aquatic communities and infrastructure allow to us determine whether or not a particular waterbody and the lands around it are headed toward improvement or degradation. The Philadelphia Water Department (PWD) considers such assessments a top priority and is committed to monitoring sites within and beyond Philadelphia County lines.

The Philadelphia Water Department has carried out extensive sampling and monitoring programs to characterize conditions in seven local watersheds (Figure 1), both within the county boundaries and outside counties/municipalities. The program is designed to document the condition of aquatic resources and to provide information for the planning process needed to meet the regulatory requirements of EPA and PADEP. The program includes hydrologic, water quality, biological, habitat, and fluvial geomorphological aspects. The Office of Watersheds is well suited to manage the program because it merges the goals of the city’s stormwater, combined sewer overflow, and sourcewater protection programs into a single unit dedicated to watershed-wide characterization and planning.

Regulatory Basis for Watershed Monitoring

Under the provisions of the Clean Water Act (CWA), the National Pollutant Discharge Elimination System (NPDES) requires permits for point sources that discharge to waters of the United States. In the six watersheds entering Philadelphia, stormwater outfalls and wet weather sewer overflow points discharging to surface waters are classified as point sources and are regulated by NPDES.

EPA's Combined Sewer Overflow Control Policy, published in 1994, provides the national framework for regulation of CSOs under NPDES. The policy guides municipalities and state and federal permitting agencies in meeting the pollution control goals of the CWA in as flexible and cost-effective a manner as possible. As part of the program, communities serviced by combined sewer systems are required to develop long-term CSO control plans (LTCPs) that will result in full compliance with the CWA in the long term, including attainment of water quality standards. PWD completed its LTCP in 1997 and is currently implementing its provisions. The strong focus of the National CSO Policy on meeting water quality standards is a main driver behind PWD’s water quality sampling and monitoring program.

Regulation of stormwater outfalls under the NPDES program requires operators of medium and large municipal stormwater systems or MS4s to obtain a permit for discharges and to develop a stormwater management plan to minimize pollution loads in runoff over the long term. Partially in administration of this program, PADEP assigns designated uses to water bodies in the state and performs ongoing assessments of the condition of the water bodies to determine whether the uses are met and to document any improvement or degradation. These assessments are performed primarily with biological indicators based on the EPA’s Rapid Bioassessment Protocols (RBPs) and physical habitat assessments.


PWD’s Office of Watersheds (OOW) and Bureau of Laboratory Services (BLS) are responsible for characterization and analysis of existing conditions in local watersheds to provide a basis for long-term watershed planning and management.