The Enforcement and Compliance History Online (ECHO) system incorporates Combined Sewer Overflow (CSO) data from EPA's Integrated Compliance Information System National Pollutant Discharge Elimination System (ICIS - NPDES) as well as information on certain closed CSOs that are not in ICIS - NPDES.

The National Combined Sewer Overflow Inventory was first published to ECHO in May 2023 to reflect the most current inventory of CSOs across the United States. These data are updated weekly, as described on About the Data.

On this page:

• Guidance on the National Combined Sewer Overflow Inventory
• Download File Structure
• Data Element Dictionary

ICIS-NPDES Description

ICIS - NPDES is an information management system maintained by the EPA Office of Compliance to track permit compliance and enforcement status of facilities regulated by the National Pollutant Discharge Elimination System (NPDES) under the Clean Water Act (CWA). ICIS - NPDES is designed to support the NPDES program at the state, regional, and national levels.

Guidance on the National Combined Sewer Overflow Inventory

The National Combined Sewer Overflow Inventory is a comma - separated value (CSV) file labeled as "ALL_CSO_DOWNLOADS.csv". This file is packaged in a ZIP file and available on ECHO Data Downloads. 

Please note that state are actively working to update and correct data in ICIS - NPDES. EPA estimates that approximately 80% of CSOs are included in the National Combined Sewer Overflow Inventory (as of May 2023). 

Some states have elected to manage closed CSOs outside of ICIS - NPDES. These are marked as such in the National Combined Sewer Overflow Inventory. EPA's Office of Wastewater Management periodically verifies these outfalls with state Water Data Stewards and updates the inventory as appropriate. The last update was May 2023. 

Missing attribute data (e.g., CSO latitude and longitude data) means that the authorized state has not yet entered these data into ICIS - NPDES or that the authorized state has elected to manage the closed CSO outside of ICIS - NPDES.

Download File Structure

Data Element Dictionary

The following is a list of the data elements in the National Combined Sewer Overflow Inventory. They are listed in column order (left to right). 

NPDESID_PFID

This is the concatenation of the NPDES_ID and the PERM_FEATURE_NMBR for the CSO. For CSOs that do not have a PERM_FEATURE_NMBR (i.e., they are managed outside of ICIS - NPDES), this field uses the following convention: [NPDES_ID] - [NO_PFID].

NPDES_ID 

This NPDES number may reflect the permit associated with the CSOs. This element is also identified as EXTERNAL_PERMIT_NMBR in other ECHO download files. 

PERMITTING_STATE

This is the state that issued the NPDES permit associated with the CSOs. 

AGENCY_TYPE_CODE

A three - character code indicating the type of organization issuing or granting a permit. All CSOs are permitted by authorized states so AGENCY_TYPE_CODE = "ST6". 

FACILITY_UIN

The number assigned by the Facility Registry Service (FRS) that is used to associate facility records from multiple environmental database systems that are known or believed to represent the same facility.

FACILITY_NAME

An 80 - character field that contains the name of the facility. 

LOCATION_ADDRESS

The street address of the facility.

SUPPLEMENTAL_ADDRESS_TEXT

The name of the supplemental location for the facility.

FACILITY_CITY

A 60 - character field that contains the name of the city that is permitted for the CSO. 

COUNTY_CODE

A five - digit field that contains the FIPS county code in which the permitted facility is located, used in conjunction with the facility state code. A list of codes and descriptions can be found at 2017 FIPS Codes for Counties. 

STATE_CODE

A two - character field that contains the state postal abbreviation for the state in which the permitted facility is located.

EPA_REGION_CODE

A two - character field that contains the EPA Region in which the permitted facility is located.

FACILITY_TYPE_CODE

A 3 - character code indicating ownership type of the facility. The values for permitted facilities with CSOs are:

• CTG - Municipality
• MWD - Municipal or Water District 

FACILITY_LAT

The horizontal (latitude) of the permitted facility as maintained in ICIS-NPDES.

FACILITY_LON

The vertical (longitude) of the permitted facility as maintained in ICIS-NPDES.

PERMIT_NAME

This is the name of the facility having the NPDES permit to discharge pollutants in the water of the United States.

VERSION_NMBR

The version of the permit when a modification or reissuance is applied to the permit. A "0" indicates the most recent or current permit version. 

PERMIT_TYPE_CODE

Text description for PERMIT_TYPE_CODE. Valid code values and descriptions are below. The values for permitted facilities with CSOs are:

• NPD - NPDES Individual Permit
• UFT - Unpermitted Facility 

EFFECTIVE_DATE

The date the permit became effective or is scheduled to become effective (MM/DD/YYYY). 

EXPIRATION_DATE 

The date the permit expired or is scheduled to expire (MM/DD/YYYY). 

PERMIT_STATUS_CODE

ICIS - NPDES designates a permit as Effective (EFF), Administratively Continued (ADC), Expired (EXP), Not Needed (NON), Pending (PND), Retired (RET), or Terminated (TRM). Active facilities are those currently in operation (indicated by any status code except NON or TRM). 

FACILITY_TYPE_INDICATOR

A 10 - character code indicating if the permitted facility is either a POTW, non-POTW, or federal entity. 

MAJOR_MINOR_STATUS_FLAG

A 1 - character code that designates the facility as a major discharger (M), non - major discharger (N), or that no data is available (null values), such as for unpermitted facilities.

Under the Clean Water Act, a major facility is any NPDES facility or actively classified as such by the regional administrator, or in the case of approved state programs, the regional administrator in conjunction with the state director. Major municipal dischargers include all facilities with design flows of greater than one million gallons per day and facilities with EPA/state approved industrial pretreatment programs. Major industrial facilities are determined based on specific ratings criteria developed by EPA/state. Non-major facilities are those not designated as major.

PERMIT_TRACKING

This is a Y/N field that identifies if ICIS - NPDES is configured to track any violations associated with the permitted facility. 

PT_START_DATE

This is the latest date when the PERMIT_TRACKING was created or updated by the authorized state. 

DMR_TRACKING

This is a Y/N field that identifies if ICIS - NPDES is configured to track DMR non-receipt violations associated with the permitted facility.

DMR_NR_START_DATE

This is the latest date when the DMR_TRACKING was created or updated by the authorized state.

PERMIT_DESIGN_FLOW

This is the design flow (in million gallons per day) for the permitted facility associated with CSO.

PERMIT_AVG_FLOW

This is the average flow (in million gallons per day) for the permitted facility associated with CSO. 

PERM_FEATURE_NMBR

This is the identifier for the CSO and is unique for a given NPDES_ID.

PERM_FEATURE_TEXT

This is additional text that describes the CSO location or other attributes.

PF_LAT

The horizontal (latitude) position coordinate for the CSO in units of decimal degrees. 

PF_LON

The vertical (longitude) position coordinate for the CSO in units of decimal degrees. 

PF_CHARACTER

This is the ICIS - NPDES Characteristic code that the authorized state used to describe the CSO. EPA identifies CSOs for the National Combined Sewer Overflow Inventory when they have one of the following Characteristic codes in ICIS - NPDES:

• CSO - Untreated CSO: A combined sewer overflow is a discharge from a combined sewer system at a point prior to the POTW Treatment Plant. CSOs consist of mixtures of domestic sewage, industrial and commercial wastewaters, and storm water runoff. CSOs are point sources that discharge to waters of the US and need to be tracked in ICIS - NPDES. For data entry purposes, if a CSO does not meet the definition of treated CSO (TCS) or closed CSO (CLS), then it should be classified as a CSO. The majority of CSOs will have the characteristic code CSO. 
• TCS - Treated CSO: Treated CSOs are outfalls that receive the minimum CSO treatment described in the CSO Policy, which consists of: primary clarification, solids and floatables disposal, and disinfection, where necessary (see 59 Fed. Reg. 18692-3.II.C.4.a).
• CLS - Closed CSO: Closed CSOs are former outfalls that have since been removed or plugged such that they cannot discharge combined sewage into the environment. Outfalls can be marked with multiple other codes if a closed CSO needs to also be recorded because of other discharges (e.g., SW - MS4 outfall) in addition to the CLS characteristic code.

The full set of ICIS-NPDES Characteristic codes are provided below:

NPDES Characteristic Codes

Code	Descriptions
BIO	Sludge/Biosolids
CCW	Contact Cooling Water
CLB	Closed Bypass
CLS	Closed CSO
CSO	Untreated CSO
DEW	Dewatering
DSW	Domestic (Sanitary) Wastewater
GRW	Groundwater
INT	Intermittent Flows
MNR	Manure
MOB	Mobile
NCW	Noncontact Cooling Water
NDP	Non - Domestic Process Water
NPD	Nonprocess
PRC	Percolation Pond
SW	Storm Water
TCS	Treated CSO
TRB	Treated Bypass
UTB	Untreated Bypass
WEL	Monitoring Well

PERM_FEATURE_TYPE_CODE

This is the type for the permitted feature. This value is set to "External Outfall" (EXO) for all CSOs. 

PF_STATE_WATERBODY_NAME

The state's name for the water body into which the effluent is discharged for a CSO.

PF_STATE_AUTO_NAME

This is the name of the water body as determined by EPA based on the facility or CSO latitude and longitude data and a spatial analysis using the United States Geographical Society's (USGS) National Hydrography Dataset (NHD).

PF_REACH_ID

This is the REACH code associated with the CSO. This is the unique 14 - digit code that identifies a continuous piece of surface water with similar hydrologic characteristics. It is assigned to each receiving water body by the United States Geographical Society's (USGS) National Hydrography Dataset (NHD).

IN_ICIS

This is a Yes/No field that identifies if the CSO is managed in ICIS - NPDES. The CSOs that are marked with "No" (i.e., not managed in ICIS - NPDES) are periodically reviewed by EPA's Office of Wastewater Management.