Street Surface Storage for CSO Control

Abstract

This paper presents a discussion of the use of on-street storage as an effective means to control stormwater runoff. It focuses on the success achieved by using street storage in two communities in Illinois and includes a description and evaluation of how this technology eliminated surcharging and basement flooding, complied with regulations and proved to be a cost-effective solution which earned public support. Wet weather flow (WWF), including combined sewer overflow (CSO) and stormwater discharges, is one of the leading causes of water-quality impairment in the United States today. Improvement of controls is one of two priority water focus areas cited by the EPA’s Office of Water in its National Agenda for the Future. Pollution problems stemming from WWF are extensive throughout the country. Many CSO occurrences can be eliminated, or their impacts attenuated by flow retardation techniques. However, even as these retardation techniques may attenuate the CSO, they usually exacerbate other problems. e.g., basement flooding. In addition, CSOs provide relief only for sewer systems; upstream areas may not have overflow routing and thus, the system is relieved by surcharging into basements, or to the ground surfaces. Surcharging and flooding cause health hazards, structural damage (due to hydrostatic pressures and/or washouts) and damage to personal property. Over the past several years, numerous investigations have been undertaken to determine cost-effective methods of abating CSO. Much of this effort has concentrated on methods of controlling and retaining upstream stormwater. One such cost-effective method is source control. This approach avoids upstream flooding by not allowing stormwater into sewers until capacity is available, and avoids downstream surcharging and CSO by permitting downstream flow to be conveyed away before upstream flows can arrive. Source control temporarily stores stormwater in urban areas on the surface (on-street and off-street) and, as needed, below the surface, close to the source. “Close to the source” refers to the stormwater prior to its entry to a combined sewer or storm sewer. This on- and off-street storage may be an effective means to control stormwater runoff, protecting intercepting sewers from surcharging and/or creating CSO conditions.