waters in the United States should be “fishable and swimmable.”3 These two broad uses have been significantly elaborated on by the states, such that in Pennsylvania all surface waters have been designated for uses that include warm-water fish and other aquatic life use, recreational use, and drinking water supply. In addition to these uses, some waters are of exceptional quality (designated as high quality or exceptional value waters), and some of these may be protected for cold-water fish. As described later, water designated for these higher-end uses must meet more stringent water quality criteria. The most common designated uses are described below, with particular attention to drinking water uses of waters in southwestern Pennsylvania.

Drinking Water

Public health depends on provision of adequate quantities of drinking water free of harmful concentrations of human pathogens and chemical pollutants. Provision of clean, safe drinking water depends on the quality of both the source water and the treatment and distribution systems. Thus, assigning the appropriate use designation and then meeting water quality standards in source waters is the first step in providing safe drinking water (EPA, 2002a).

In southwestern Pennsylvania, drinking water is taken from a variety of sources. While the urban core in Allegheny County (see Chapter 6 for further information) is served predominately by public water services utilizing surface water sources, other counties in the area rely more heavily on public and private groundwater sources. Figure 3-1 shows the distribution of sources by population served for each county. Because population density for the region is highest in Allegheny County, which relies heavily on surface water, the majority of people in the region rely on treated surface water for their drinking water (see Figure 3-2). Major surface water sources of drinking water in the region include the Allegheny River, the Monongahela River, the Ohio River, the Youghiogheny River, Beaver Run, and Indian Creek.

Section 1453 of the Safe Drinking Water Act (SDWA) Amendments of 1996 requires states to develop a Source Water Assessment and Protection (SWAP) program to assess the drinking water sources (not “finished” waters already treated to meet various drinking water standards) serving public water systems for their susceptibility to pollution.4 A state’s SWAP is required to (1) delineate the boundaries of the areas providing source waters for all public water systems, and (2) identify (to the extent practicable) the origins of regulated and certain unregulated contaminants in the delineated area to determine the susceptibility of public water systems to such contaminants. The key objective for conducting source water assessments is to support the development of local, voluntary source water protection programs. In conducting such assessments, each state must use all reasonably available hydrologic information (such as water flow, recharge, discharge) and any other information deemed necessary to accurately delineate the source water assessment areas.

In order to protect public health, treatment of surface waters used for drinking water is mandated. Large water service suppliers in the region that utilize surface water are listed in Table 3-1. While these large systems provide significant populations with water, there are also many smaller water service providers in the region, many of which rely heavily on groundwater


It should be noted that exceptions to the fishable, swimmable use exist. For example, in Pennsylvania a portion of the Delaware Estuary and water in the vicinity of the harbor at Erie do not fully support and are not expected to support the “fishable and swimmable” goal of the CWA.


Further information on SWAP can be found at http://www.epa.gov/safewater/protect/swap.html.

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