From Stormwater Collection Systems Design Handbook

Larry W. Mays
Department of Civil and Environmental Engineering
Arizona State University
Tempe, Arizona

18.1 COMBINED SEWER OVERFLOW ( CSO)

Sewer systems that convey both sanitary sewerage and stormwater through a single pipe are referred to as combined sewer systems (CSSs). During dry weather a CSS is able to convey all flows to the waste water treatment plant. However, during periods of heavy rainfall or wet weather flow (WWF), the CSS capacity may be exceeded, resulting in a combination of untreated sewage and stormwater flowing in the same pipe(s), and may be discharged directly into nearby receiving water. These overflows are referred to as combined sewer overflows (CSOs). Manuals on CSO control have been published by the Water Environment Federation (WEF) (1989) and the U.S. Environmental Protection Agency (USEPA) (1993).

Retention storage facilities capture and dispose stormwater runoff through infiltration, percolation, and evaporation, whereas detention storage is temporary storage for stormwater runoff and CSO. In CSOs, temporarily stored flows are subsequently returned to the sewerage system at a reduced rate of flow, or the flow is discharged to a receiving water with or without treatment. The common elements of a typical CSS that are generally found in older cities are illustrated in Fig. 18.1.


Figure 18.1: Common elements of a combined sewer system. (From USEPA, 1998)

The solution to WWF problems most often include a combination of best management practices (BMPs). The backbone of integrated WWF management plans should be storage...


Products & Services
Machine Shop Services
Machine shop services use machinery or equipment to perform custom removal of material to fabricate a finished part.
Metal Sheet
Metal sheet is metal or alloy stock supplied or available in the form of sheet or foil. It has a thickness between 0.006" and 0.250", and a width of 24" (609.6 mm) or more.
Metal Strip
Metal strip is narrow, thin stock that is usually 3/16 in. (4.76 mm) or less in thickness and under 24 in. (609.6 mm) in width. Metal strips are formed to precise thicknesses and/or width requirements.
Plating Services
Plating services apply a thin coating of metal to the surface of a substrate in order to improve conductivity, prevent rust and corrosion, and facilitate soldering. There are two basic plating techniques: electroplating and electroless plating.
Abrasive Files
Abrasive files are small stick or stone made of bonded abrasives or superabrasive coatings for deburring, finishing, lapping and polishing in hard to reach places and recesses.

Topics of Interest

Neil Armitage Department of Civil Engineering University of Cape Town Private Bag Rondebosch, 7701, South Africa 19.1 INTRODUCTION In years to come, archaeologists sifting through the remains of late...

Inspection Process Enhances Machining Services With the aid of CNC equipment, a company provides machining services to OEMs with capabilities complemented by 3-D CAD software. Milling, turning,...

Precision Swiss-machined components are produced with tolerances from 0.002 mm, lengths to 600 mm, and diameters from 0.1 to 150 mm. Equipment includes multiaxis lathes, precision grinding, and...

Tip-entry machining of blisks can be practical for shorter blades. Machining blades in a single operation improves efficiency and reduces head movements and chance of collisions. KENNETH J. KORANE...

CUTTING FLUIDS Cutting Fluids Recommended for Machining Operations. Soluble Oils: Types of oils paste compounds that form emulsions when mixed with water: Soluble oils are used extensively in...

New Privacy Policy

We have adopted new policies. Please read each one carefully.

OK