Loading Tool Data Corrections


EPA conducted DMR data quality reviews and identified several wastewater flows and pollutant measurements that exceeded the reasonable range. EPA reviewed these data and developed the following corrections, which are applied to DMR values before calculating pollutant loadings. This page describes the types of autocorrections applied to DMR data and includes CSV files of the corrected DMR data. 

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Corrections to DMR Data (by year)

Note: These CSV files are updated weekly as part of the Loading Tool data refresh. As creation of these files is automated, the file sizes below are approximate.

DMR Data Corrections: Data Element Descriptions
Element Description
EXTERNAL_PERMIT_NMBR A nine-character code used to uniquely identify a permitted NPDES facility (NPDES ID).
DMR_YEAR The calendar year of the pollutant discharge.
PERM_FEATURE_NMBR A four-character code in ICIS-NPDES that identifies the point of discharge (e.g., outfall) for a facility. A NPDES permit may have multiple points of discharge.
MONITORING_LOCATION_CODE A single-character code in ICIS-NPDES that indicates the sampling location for each pollutant measurement. The Loading Tool only includes locations for effluent sampling points. These include: 
  • 1 -- Effluent gross discharge
  • 2 -- Effluent net discharge
  • A -- After disinfection
  • B -- Before disinfection, and
  • SC -- See Comments.
LIMIT_SET_DESIGNATOR A single-character code in ICIS-NDPES that groups limits that are set on a similar basis (e.g., monthly, annual, or seasonal limits). A limit set designator code is provided for each DMR measurement and limit.
LIMIT_SEASON_ID A 1-digit code to indicate one of four subdivisions of the year.
MONITORING_PERIOD_END_DATE The end date (MM/DD/YYYY) of the monitoring period for the discharge.
PARAMETER_DESC The description or parameter name that corresponds to the parameter code.
PARAMETER_CODE A five-character code in ICIS-NDPES that identifies the regulated pollutant parameter in a NPDES permit and specifies both the pollutant name and pollutant form (e.g., dissolved or suspended).
DATA_FIELD The ICIS-NPDES measurement field (e.g., quantity or concentration field) corresponding to the correction.
OLD_VALUE The original DMR value, from ICIS-NPDES.
NEW_VALUE The corrected value, in the Loading Tool.
CORR_DESC The description of the Correction Type Code. See Types of DMR Value Autocorrections for more information about corrections made by the Loading Tool.
CORRECTION_TYPE_CODE The code used to classify the type of correction. See Types of DMR Value Autocorrections for more information about corrections made by the Loading Tool.
REVIEW_CYCLE The general review cycle or date during which the data was reviewed and updated. Not Applicable (NA) indicates an automated correction. "Annual Review" refers to EPA's Effluent Guidelines Program review of industrial effluent discharges.

Types of DMR Value Autocorrections

Autocorrect flow for month to month variability (AUTOFLOW_1)
The Loading Tool applies a correction factor to flows greater than 1,000 MGD having month to month variability of one or more orders of magnitude. Section 3.1.2 of the Technical Users Background Document describes the procedure and provides an example.
Autocorrect flow for variation in design vs. actual (AUTOFLOW_2)
The Loading Tool applies a correction factor to flows greater than 1,000 MGD where the reported flow is one or more orders of magnitude larger than the actual average flow or design flow. Section 3.1.2 of the Technical Users Background Document describes the procedure and provides an example.
Autocorrect flow exceeding 5,000 MGD (AUTOFLOW_3)
The Loading Tool applies a correction factor to flows greater 5,000 MGD by dividing these values by 1,000,000. This error correction assumes that the intention was to report a DMR value with the unit of gallons per day but that the value actually reported was in million gallons per day.
Autocorrect flow in Ohio exceeding 1,000 MGD (AUTO_OH_FLOW)
The Loading Tool applies a correction factor for NPDES permits in Ohio (i.e., NPDES IDs that begin with “OH”) where the flows are greater than 1,000 MGD. The Loading Tool will divide these values by 1,000,000. See Section 3.4 of EPA’s Technical Support Document for the Annual Review of Existing Effluent Guidelines and Identification of Potential New Point Source Categories (EPA-821-R-09-007, October 2009).
Autocorrect dioxin exceeding 0.001 mg/L (AUTO_ALL_DIOXIN)
The Loading Tool applies a correction factor for all dioxin concentration values greater than 0.001 mg/L by 1,000,000 for all dioxin parameters. This pollutant is never reported on DMRs with values above 0.001 mg/L.
Autocorrect mercury exceeding 1 mg/L (AUTO_ALL_MERC)
The Loading Tool applies a correction factor for all mercury concentration values greater than 1 mg/L by 1,000,000 for all mercury parameters. This pollutant is never reported on DMRs with values above 1 mg/L.
Autocorrect Duration of Discharge (AUTO_NMBR_DAYS)
EPA developed a methodology to estimate intermittent discharges that occur within a monitoring period (e.g., there is a discharge from the outfall that only occurs two days out of the monthly monitoring period). Specifically, the Loading Tool uses three ICIS-NPDES Duration of Discharge parameter codes for identifying intermittent discharges: 50037, 82517, and 81381. The Loading Tool will automatically adjust the pollutant loading calculation such that the calculation only estimates pollutant discharges for the time when the outfall is discharging (e.g., two days in the month instead of the entire month).
However, not all NPDES permits require permittees to submit Duration of Discharge data when they have intermittent discharges occurring within a monitoring period. Consequently, the Loading Tool may overestimate pollutant discharges for intermittent dischargers that do not report these Duration of Discharge codes.
This correction reflects adjustments to the duration of discharge for the purpose of calculating pollutant loadings, as reported to EPA by permittees that had intermittent discharges but were not required to submit Duration of Discharge information. NPDES permittees with intermittent discharges are encouraged to engage with their permit writers to add one of these Duration of Discharge codes to their DMR. NPDES permittees may also Contact Us if these Duration of Discharge codes are not yet in their DMR.

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