Combined sewer overflow

{
  "id": "MLC-T-ENV-005654",
  "term": "Combined sewer overflow",
  "field": "Environment",
  "term_source": "Combined Sewer Overflow",
  "definitions": [
    "1. A discharge of untreated wastewater from a combined sewer system at a point prior to the headworks of a publicly owned treatment works. CSOs generally occur during wet weather (rainfall or snowmelt). During periods of wet weather, these systems become overloaded, bypass treatment works, and discharge directly to receiving waters.\n\n2. A combined sewer system conveys both sanitary sewage and stormwater in one piping system. During normal dry weather conditions, sanitary wastewater collected in the combined sewer system is diverted to the wastewater treatment plant before it enters natural waterways. During periods of significant rainfall, the capacity of a combined sewer may be exceeded. When this occurs, excess flow, a mixture of stormwater and sanitary wastewater, is discharged at CSO points, typically to rivers and streams. Release of this excess flow is necessary to prevent flooding in homes, basements, businesses, and streets. Visit the National Pollutant Discharge Elimination System's Combined Sewer Overflows website for additional information.\n\n3. Discharge of a mixture of stormwater and domestic waste when the flow capacity of a sewer system is exceeded during rainstorms.\n\n4. Overflow from systems designed to collect runoff, domestic sewage, and industrial wastewater in the same pipe system.\n\n5. A discharge of a mixture of stormwater and domestic waste when the flow capacity of a sewer system is exceeded during rainstorms.\n\n6. Discharge from a combined sewer system (CSS) at a point prior to the Publicly Owned Treatment Works (POTW) Treatment Plant (defined at § 403.3(r) of this chapter).\n\n7. A discharge of untreated wastewater from a combined sewer system at a point before the headworks of a publicly owned treatment works. CSOs generally occur during wet weather (rainfall or snowmelt). During periods of wet weather, these systems become overloaded, bypass treatment works, and discharge directly to receiving waters at designed overflow points.\n\n8. A combined sewer system (CSS) is a wastewater collection system owned by a municipality which conveys sanitary wastewater (domestic, commercial, and industrial) and stormwater through a single pipe system to a publicly owned treatment works. A combined sewer overflow (CSO) is the discharge from a CSS at a point prior to the treatment plant. CSOs are point sources subject to NPDES permit requirements including both technology-based and water quality-based requirements of the Clean Water Act. These data are from ICIS-NPDES.",
    "Discharge of a mixture of storm water and domestic waste when the flow capacity of a sewer system is exceeded during rainstorms."
  ],
  "abbreviation": "CSO",
  "subject": [
    "Water",
    "Ecosystems"
  ],
  "references": [
    "National Pollutant Discharge Elimination System (NPDES) Glossary",
    "Greening EPA Glossary",
    "Urban Watershed Management Research Terminology",
    "Watershed Planning Glossary of Terms",
    "EPA Guidance for Federal Land Management in the Chesapeake Bay Watershed Glossary at http://www.epa.gov/owow_keep/NPS/chesbay502/pdf/chesbay_glossary.pdf; Federal Land Management in the Chesapeake Bay Watershed Glossary",
    "40 CFR 122.2 (CFR 2018)",
    "NPDES Permit Writers Manual Glossary",
    "Glossary of Frequent Terms in the Loading Tool",
    "Aquatic Biodiversity Glossary; Terms of Environment"
  ],
  "url": "https://mlchart.com/terminology/environment/combined-sewer-overflow/"
}