Moving Forward with Collection System Solutions

Agencies owning and operating public infrastructure, in particular sewer systems, are facing great challenges today in the U.S. This issue highlights challenges and emerging technical practices to address planning, operating, and maintaining sewer systems.  While there are numerous challenges, three significant areas have emerged as demanding immediate attention and are changing the way agencies make decisions.

Aging Infrastructure. Past growth patterns in cities are now mirrored by waves of aging pipes—1890, 1920, and 1950 population surges mean large percentages of system inventory are 120, 90, and 60 years old. While designers assumed a standard design life for sewers (60 to 100 years in most cases), studies reveal a national trend in underfunding maintenance and repair of these systems, so that pipes are failing well in advance of their design life. Huge “balloon” payments will come due for communities as large proportions of their system simultaneously arrive at their true service. In response, asset management is emerging as a means for proactively addressing this trend and prioritizing both low cost maintenance and higher cost replacement/rehabilitation. Several papers in this issue present tools and practices to assist in grappling with this challenge (Elsayegh et al., Lee & Ferry).

Elimination of Unregulated Overflows. Agencies have inherited sewer systems designed over 120+ years. Who knows what design standards were applied? What population density and water consumption patterns were assumed? What peak flow capacity, and when was a sewer/pump station allowed to overflow? What rain patterns and imperviousness? Not only are agencies dealing with upgrading or backstopping such legacy systems, they are further challenged to create new design standards adapting to overflow regulations, all while climate experts predict dramatic changes in our assumed rainfall patterns. This moving target means current design practices must evolve rapidly, utilizing powerful tools to predict statistically likely flows in order to prevent overflows. If your agency is still designing sewers using IDF curves and d/D lookup tables, you might want to focus on papers in this issue that stress the value of continuous simulation and long-term rainfall analysis (Goulding & Kepner, Schultz & Nelson, Tsay et al.).

Public Perception and Tolerance.  Sewers tend to be out of sight and out of mind. Citizens will clamor for road and traffic improvements and be blind to potentially disastrous underground problems. Their willingness to pay rising sewer fees is linked either to catastrophe (sewer collapse, or beach closings) or to economic impact (growth moratorium). Further, planners attempting to lay out new interceptors, locate pump stations, and excavate and rehabilitate existing sewers are confronted by resistant citizen groups. To cost-effectively address the first two challenges—aging sewers and elimination of overflows—agencies will need to add new practices to their toolkits. These include active campaigning for expanding sewer funds, advisory committees to assist in route selection, and direct and frequent communication with affected property owners throughout planning and construction. Several papers in this issue illustrate the benefits of this proactive approach, which in some cases resulted in sewer routes with less community impact while ensuring agency goals of reliability and operability were still met (Aurit et al., Kennedy et al.).

The WEF Collection Systems community is a diverse but highly cooperative group of water professionals. We endeavor to share new techniques in engineering (pipe materials, design, and construction methods), in balancing private/public investment (rehabilitating private laterals vs. public mains), in public outreach (educational materials and decision-science tools for alternatives evaluation), and in regulatory compliance (rainfall and flow monitoring and prediction). We anticipate a dynamic 10 years ahead of us, as more sewers reach their useful life and agency resources are stretched further. We also know that the WEF community will use its history of successful collaboration to devise the necessary responses.

Claudia L. Zahorcak, Issue Editor
City of Albany, Oregon