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_SCHEDULE_ID Number 22
LIMIT_ID Number 22
LIMIT_BEGIN_DATE Date 7
LIMIT_END_DATE Date 7
NMBR_OF_SUBMISSION 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

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

LIMIT_ID - The unique identifier for a limit parameter record.

LIMIT_BEGIN_DATE - The date on which a limit starts being in effect for a particular parameter in 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, semi-annually = 6, quarterly = 3). This data element will be blank for Unscheduled Limit Sets.

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). Valid code values are:

Type Code Long Description
AVG 1A 1 Day Geometric
AVG 1C 12 Day Average
AVG 1D 12 Month Average
AVG 1E 12 Month Daily Water Flow
AVG 1F 120 Day Average
AVG 1G 180 Day Arithmetic Mean
AVG 1H 1 Day Average
AVG 1I 1 Hour Average
AVG 3A 30 Day Geometric Mean
AVG 3B 30 Day Arithmetic
AVG 3C 30 Day Average
AVG 3D 30 Day Geometric
AVG 3F 30 Day Arithmetic Mean
AVG 3G 30 Day Median
AVG 3H 30 Day Average Geometric
AVG 3I 3 Hour Average
AVG 4A 4 Day Average
AVG 4D 4 Hour Average
AVG 5B 5 Day Average
AVG 5Y 5 Year Average
AVG 6A 6 Month Median
AVG 6B 6 Hour Mean
AVG 6C 6 Hour Geometric Mean
AVG 6D 6 Month Average
AVG 6E 6 Hour Average
AVG 6F 6 Hour Geometric
AVG 7A 7 Day Average
AVG 7B 7 Day Geometric
AVG 7C 7 Day Median
AVG 7F 7 Day Arithmetic
AVG 7G 7 Day Arithmetic Mean
AVG 7I 7-Day Average Geometric
AVG 9B 90 Day Average
AVG 9D 96 Hour
AVG A1 Average (Data Migration)
AVG AB Annual Average
AVG AE Arithmetic Mean
AVG AF Average
AVG AG Average Below Detectable
AVG AGM Annual Geometric Mean
AVG AH Average Value
AVG AN Annual Median
AVG CA Allowed Concentration
AVG DA Daily Geometric Average
AVG DB Daily Average
AVG DF Daily Median
AVG DG Discharge Per Day Average
AVG DH Discharge per Day Geometric
AVG DM Daily Geometric
AVG DP 14 Day Average
AVG G5 5 Day Geometric Mean
AVG GA Geometric Mean
AVG HA High 7 Day Average
AVG HB High Weekly Average
AVG LA Logarithmic Mean
AVG LB Logarithmic Monthly Median
AVG M3 Monthly Median
AVG M4 Monthly Average Geometric
AVG MC Mean
AVG MD Median
AVG MK Monthly Average
AVG ML Monthly Geometric
AVG MM Monthly Geometric Mean
AVG NA Non-Specific Average
AVG QA Quarterly Average
AVG QR Quarterly Rolling Average
AVG RA Rolling Average
AVG RB Reported Average
AVG RE Indiv 12 Mo Rolling Ave
AVG RF Aggregate 12 Mo Rolling Avg
AVG RM Aggregate 12 Mo Rolling Median
AVG SC Semi-Annual Average
AVG SD Single Sample Geometric
AVG WA Weekly Average
AVG WB Weekly Geometric
AVG WE Weekly Average Geometric
AVG WK Weekly Geometric Mean
AVG WL Well Average
MAX 1B 10% of Samples
MAX 2A 20% of Samples
MAX 2P 2 Hour Peak
MAX 3E 30 Day Maximum
MAX 4B 4 Day Maximum
MAX 4C 48 Hour Maximum
MAX 5A 50th Percentile
MAX 7E 7 Day Maximum
MAX 7H 75th Percentile
MAX 7J 70th Percentile
MAX 8A 80th Percentile
MAX 95P 95th Percentile
MAX 9A 90th Percentile
MAX 9C 90% of Samples
MAX AC Annual Maximum
MAX AX Annual Average Maximum
MAX DD Daily Maximum
MAX DI Discharge Per Day Maximum
MAX EX Seasonal Maximum
MAX GX Maximum Monthly Geometric Mean
MAX HX Hourly Avg Maximum
MAX IA Instantaneous Maximum
MAX M0 Maximum Value
MAX M1 Maximum 30 Day Average
MAX M2 Maximum Monthly Average
MAX M6 Maximum (Data Migration)
MAX MA Maximum Bdl
MAX MB Maximum
MAX MN Monthly Maximum
MAX MQ Maximum Daily Average
MAX MR Maximum Hourly Rate
MAX MS Maximum Weekly Average
MAX MT Maximum 7 Day Average
MAX MU Maximum 7 Day Geometric
MAX MV Maximum 7 Day Geo. Average
MAX MW Maximum Single Sample
MAX MX Monthly Geometric Maximum
MAX NB Non-Specific Maximum
MAX QB Quarterly Maximum
MAX RD Rpt Allowed/Rpt Actual
MAX SA Single Sample
MAX SB Single Mv Conc. Sample
MAX SE Single Reading
MAX SF Successful Readings
MAX SG Single Grab
MAX SX Semi-Annual Maximum
MAX VA Value
MAX WC Weekly Maximum
MAX X1 Positive Results
MAX XA >Background
MIN 1J 1 Day Minimum
MIN 2E 24 Hour Minimum
MIN 4E 48 Hour Minimum
MIN 7D 7 Day Minimum
MIN AM Annual Average Minimum
MIN BA Median (Minimum)
MIN BB Average (Minimum)
MIN BC 90Th Percentile (Minimum)
MIN BD 70Th Percentile (Minimum)
MIN BE 50Th Percentile (Minimum)
MIN DC Daily Minimum
MIN DE Daily Average Minimum
MIN DJ Discharge Per Day Minimum
MIN DL Daily Geometric Minimum
MIN HM Hourly Avg Minimum
MIN IB Instantaneous Minimum
MIN IC Instantaneous Min. Geom
MIN M5 Minimum (Data Migration)
MIN ME Minimum
MIN MF Minimum Percent Removal
MIN MG Minimum Weekly Average
MIN MH Minimum 7 Day Average
MIN MI Minimum 7 Day Geo. Average
MIN MJ Monthly Average Minimum
MIN MO Monthly Minimum
MIN MZ Minimum Value
MIN NS Minimum Single Sample
MIN QC Quarterly Minimum
MIN RC Reported Minimum
MIN SM Semi-Annual Minimum
MIN TM Monthly Total Minimum
MIN WD Weekly Minimum
MIN YM Yearly Minimum
TTL AA Allowed Load
TTL AD Annual Total
TTL AL Annual Mass Loading
TTL BF Cumulative Total
TTL DK Discharge Per Day Total
TTL DN Discharged
TTL ET Event Total
TTL LE Pounds Per Event
TTL MP Monthly Total
TTL MY Monthly Loading
TTL QT Quarterly Total
TTL ST Semi-Annual Total
TTL TA Total Amount Applied
TTL TB Total
TTL TC Season To Date Total
TTL WT Weekly Total
TTL YA Year-To-Date Total

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.

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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