ICIS-NPDES Limit Summary and Data Element Dictionary

The Enforcement and Compliance History Online (ECHO) system provides a compendium of the effluent parametric limits that are identified in the NPDES permits issued to entities (municipal, federal, and commercial facilities) that discharge pollutants into the navigable waters of the United States. These limits identify what pollutants can be discharged and how much of each pollutant can be discharged as well as certain water conditions such as pH and dissolved oxygen content that must be maintained at the locations where the discharges occur. At EPA, the official source of NPDES limit data is stored in the Office of Enforcement Compliance Assurance, Integrated Compliance Information System (ICIS) where it is extracted by ECHO.


Limit File Description

The Limit download data file is comprised of limit information that was in effect starting from FY 2009 until the present day. In the zip file, npdes_limits_fy2009plus.zip, there is one CSV file named, NPDES_LIMITS_FY2009PLUS.csv. The zip file is updated each week, typically over the weekend.

The data contained in the download file is comprised of selected data columns from the following ICIS tables:

IDEA_ICIS ICIS_LIMIT
IDEA_ICIS ICIS_LIMIT_SET
IDEA_ICIS ICIS_LIMIT_SET_SCHEDULE
IDEA_ICIS ICIS_LIMIT_SET_STATUS
IDEA_ICIS ICIS_LIMIT_VALUE
IDEA_ICIS ICIS_PERMIT
IDEA_ICIS  ICIS_PERM_FEATURE

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ICIS-NPDES Data Elements

NPDES DMR (NPDES_DMR_FYxxxx.csv)

Element Name Data Type Length
ACTIVITY_ID Number 22
EXTERNAL_PERMIT_NMBR VarChar2 9
VERSION_NMBR Number 22
PERM_FEATURE_ID Number 22
PERM_FEATURE_NMBR VarChar2 4
PERM_FEATURE_TYPE_CODE VarChar2 3
LIMIT_SET_ID Number 22
LIMIT_SET_DESIGNATOR VarChar2 2
LIMIT_SET_SCHEDULE_ID Number 22
LIMIT_ID Number 22
LIMIT_BEGIN_DATE Date 7
LIMIT_END_DATE Date 7
NMBR_OF_SUBMISSION Number 22
NMBR_OF_REPORT Number 22
PARAMETER_CODE VarChar2 5
PARAMETER_DESC VarChar2 100
MONITORING_LOCATION_CODE VarChar2 3
STAY_TYPE_CODE VarChar2 1
LIMIT_VALUE_ID Number 22
LIMIT_VALUE_TYPE_CODE VarChar2 3
LIMIT_VALUE_NMBR Number 22
LIMIT_UNIT_CODE VarChar2 2
LIMIT_UNIT_DESC VarChar2 13
STANDARD_UNIT_CODE VarChar2 2
STANDARD_UNIT_DESC VarChar2 13
LIMIT_VALUE_STANDARD_UNITS Number 22
STATISTICAL_BASE_CODE VarChar2 3
STATISTICAL_BASE_TYPE_CODE VarChar2 3
LIMIT_VALUE_QUALIFIER_CODE VarChar2 3
STAY_VALUE_NMBR Number 22
OPTIONAL_MONITORING_FLAG Char 1
LIMIT_SAMPLE_TYPE_CODE VarChar2 2
LIMIT_FREQ_OF_ANALYSIS_CODE VarChar2 5

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Limit Data Element Definitions

The following is a list of the data elements and ICIS-derived elements that appear in the NPDES DMR download.

ACTIVITY_ID - The unique identifier for an activity performed at or related to a particular site.

EXTERNAL_PERMIT_NMBR - The unique identifier for a Permit.

LIMIT_BEGIN_DATE - The date on which a limit starts being in effect for a particular parameter in a limit set.

LIMIT_END_DATE - The date on which a limit stops being in effect for a particular parameter in a limit set.

LIMIT_FREQ_OF_ANALYSIS_CODE - The frequency with which the permittee must analyze the sampled data. The general format is XX/YY, where XX=number of times sampled and YY=Period of time sampled. Note: When opening the file in Excel, values may display as dates due to the formatting (E.g., "01/30" describes monthly frequency sampling, but may display in Excel as "30-Jan".)

LIMIT_ID - The unique identifier for a limit parameter record.

LIMIT_SAMPLE_TYPE_CODE - The sampling method required by the permit to be used to provide values on the DMR for the limit. For a list of all codes and descriptions, download the Sample Type Reference Table (CSV) (1.7 K).

LIMIT_SET_DESIGNATOR - The alphanumeric field that is used to designate a particular grouping of parameters within a limit set.

LIMIT_SET_ID - The system-generated unique identifier for a limit set. 

LIMIT_SET_SCHEDULE_ID - The system-generated unique identifier of the Limit Set Schedule.

LIMIT_UNIT_CODE - The code representing the unit of measure applicable to quantity or concentration limits and measurements as entered by the user.

LIMIT_UNIT_DESC - The short description of the unit of measure applicable to limit or DMR values.

LIMIT_VALUE_ID - The system-generated unique identifier for the Limit Value.

LIMIT_VALUE_NMBR - The actual limit value number from the Permit or Enforcement Action Final Order.

LIMIT_VALUE_QUALIFIER_CODE - The unique code identifying the limit value operator (e.g., <, T, >, E, =).

LIMIT_VALUE_STANDARD_UNITS - The limit value expressed in standard units as calculated by the system.

LIMIT_VALUE_TYPE_CODE - The indication of the limit value type (e.g., Quantity 1, Concentration 2).

MONITORING_LOCATION_CODE - The code that the monitoring location at which the monitoring requirement (and effluent limit if limited) applies. One parameter may have several monitoring location requirements pertaining to the same permitted feature. Valid code values are:

Code Description
0 Intake
1 Effluent Gross
2 Effluent Net
3 Intake Public Water
4 Pretreatment, Process Complete
5 Upstream Monitoring
6 Downstream Monitoring
7 Intake from Stream
8 Other Treatment, Process Complete
9 Phosphate Removal, Process Complete
A Disinfection, Process Complete
AP Alternate Process
B Prior to Disinfection
C Nitrogen, Removal Complete
D Tertiary/Advanced Process Complete
E Secondary/Biological Process Complete
EG Effluent Gross
F Primary/Preliminary Process Complete
G Raw Sewage Influent
H During Manufacturing
I Intake from Well
IN Allowed Increase
J Intermediate Treatment, Process Complete
K Percent Removal
L Digestor
N In Aeration Unit
O See Comments
P See Comments
Q See Comments
R See Comments
RS Beneficial Reuse
RW Receiving Water
S See Comments
SC See Comments
SL Sludge
T See Comments
U See Comments
V See Comments
W See Comments
X End of Chlorine Contact Chamber
Z Instream Monitoring
Y Effluent Gross (Supplementary)
GW Groundwater
II Industrial Influent
IM Internal Monitoring Point
PI Prior to Irrigation
PR Prior to Reuse
LA Land Application Soil

NMBR_OF_SUBMISSION - The attribute stores the number of months for submitting the DMRs for the limit set (e.g., monthly = 1, quarterly = 3, semi-annually = 6). This data element will be blank for Unscheduled Limit Sets.

NMBR_OF_REPORT - The number of months in the monitoring periods for the DMRs for the limit set (e.g., monthly = 1, quarterly = 3, semi-annually = 6).

OPTIONAL_MONITORING_FLAG - The flag allowing users to indicate that monitoring is optional but not required (i.e., effluent violation generation will be suppressed for optional columns).

PARAMETER_CODE - The unique code identifying the parameter being limited and/or monitored.

PARAMETER_DESC - The description of the parameter.

PERM_FEATURE_ID - The unique system identifier of a permitted feature.

PERM_FEATURE_NMBR - The identifier assigned for each location at which permit conditions are being applied.

PERM_FEATURE_TYPE_CODE - The code indicating the type of permitted feature (e.g., External Outfall, Sum). Valid code values are:

Code Description
ARW Receiving Water (Ambient)
CDS Co-disposal Site
DOF Discharge to Offsite Facility
EXO External Outfall
INC Incinerator
INF Influent Structure
INO Internal Outfall
INS Intake Structure
LAS Land Application Site
MOD MODU
OTR Other
PLA Platform
SDS Surface Disposal Site
SUB Subsea
SUM Sum
WEL Monitoring Well

STANDARD_UNIT_CODE - The code representing the standard unit of measure applicable to quantity or concentration limits and measurements as entered by the user.

STANDARD_UNIT_DESC - The short description of the standard unit of measure applicable to limit or DMR values.

STATISTICAL_BASE_CODE - The code representing the unit of measure applicable to the limit and DMR values entered by the user (e.g., 30-day average, daily maximum). For a list of all codes and descriptions, download the Statistical Base Code Reference Table (CSV) (10 K).

STATISTICAL_BASE_TYPE_CODE - The code indicating whether the statistical base code is a minimum, average, or maximum for purposes of calculating compliance against the limit value. For a list of all codes and descriptions, download the Statistical Base Code Reference Table (CSV) (10 K).

STAY_TYPE_CODE - The unique identifier of the type of stay applied to a limit (e.g., X, Y, Z), which indicates whether the limits do not appear on the DMR at all, are treated as monitor only, or have a stay value in effect during the period of the stay.

STAY_VALUE_NMBR - The numeric limit value imposed during the period of the stay for the limit; if entered, during the stay period, the system will use this limit value for calculating compliance rather than the actual limit value.

VERSION_NMBR - The version of the permit when a modification or reissuance is applied to the permit.

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