SSOs is well documented, the data presented to the committee and those uncovered by its own research as summarized in Chapter 3 are inadequate to arrive at a definitive conclusion as to (1) the impact of these discharges on water quality in receiving streams and (2) what should be done to address the issue in the context of federal CSO policy.

Investing large sums of capital based only on currently available data may not ultimately solve the most important problems or provide appropriate solutions. Although it is true that no amount of additional data and analyses would remove all uncertainty about water quality investments, it is clear that currently available information is lacking in several critical areas, including the following:

• the nature and magnitude of CSO effects on receiving streams during wet weather events;

• whether effects are limited to indicator microorganisms (i.e., bacterial indicators of fecal contamination and, indirectly, the presence and quantity of fecal pathogens) and the extent to which they include floatable and settleable solids;

• how much surface water runoff from separate stormwater conveyances affects water quality in receiving streams during wet weather events;

• whether present discharges constitute a threat to the public as evidenced by health data; and

• the extent of the effects of present and potential small community and on-site systems.

The causes and nature of water quality impairments, the parties responsible, and the individuals and waterways affected differ for each of the problem contaminants in the region. A comprehensive watershed-based approach is needed to address the spectrum of water quality problems; such a systematic approach should recognize interrelationships among problems and the need for the parties responsible for each water quality problem to share in its solution. Responsible groups may be the public at large, a segment of the population, individuals, or a particular industry or group of industries. Recognition of payment capacity of individuals and the region as a whole should also be considered in reaching equitable solutions (see Chapter 6 for further information).

The Commonwealth of Pennsylvania and local governments in the Pittsburgh region have a long history of planning, regulations, capital investments, and development of managerial expertise to control water pollution. It is evident that more is needed, particularly in the management of CSOs, SSOs, separate storm sewers, and other sources of pollution. Future actions will build on or modify existing infrastructure and managerial institutions. Some of those facilities and arrangements are discussed in the sections that follow.

Sewer systems that convey wastewater or combined wastewater and stormwater to sewage treatment plants generally have multiple components and multiple owners. First, pipes within a residence collect wastewater and carry it to a house lateral pipe (see Figure 4-5). House lateral pipes are underground and owned by the homeowners. Laterals typically comprise 50 percent of the total length of pipe in a sewer system and are connected to a street sewer pipe; as a general rule, they may account for a substantial portion of the total infiltration and inflow into