About Loading Tool Data

The Loading Tool contains information for industrial and municipal point source dischargers. While the Loading Tool includes discharges for more than 60,000 facilities, it is not a complete inventory of all discharges permitted under the Clean Water Act.

Although the Clean Water Act requires all point source dischargers to obtain a NPDES permit and monitor their wastewater, not all facility, permit, or discharge monitoring data are uploaded into ICIS-NPDES. For example, non-major facilities were not required to submit permit or DMR data to EPA prior to December 21, 2016 (phase 1 implementation of the NPDES eReporting Rule).

There are also differences between the states on sharing facility level data with EPA’s ICIS-NPDES database for general permit covered facilities (e.g., oil and gas extraction facilities, construction stormwater sites). EPA and states issue general permits to increase the efficiency of the permit program as multiple similar facilities can be regulated under one permit.

Use the State Statistics and Loadings Search to download state statistics and loadings for each year for individual permits.

The Loading Tool only calculates loads for permit types that correspond to NPDES permit coverage: NPDES Individual Permit (NPD) and General Permit Covered Facility (GPC). All other permit types are excluded.

Other types of Clean Water Act releases that are not available in the Loading Tool include:

• Wastewater releases from industrial facilities that are connected to a publicly-owned treatment works (POTW) sewerage system (e.g., indirect discharges), regulated through the CWA Pretreatment Program;
• Biosolids monitoring data, regulated through the CWA Biosolids Program;
• Discharges related to wet-weather events, such as stormwater from municipal separate storm sewer systems (MS4s), stormwater from industrial facilities, discharges from construction activities, combined sewer overflows, sanitary sewer overflows, and concentrated animal feeding operations (CAFOs).

The Loading Tool includes thousands of pollutant parameters, including specific chemicals (e.g., phenol), bulk parameters (e.g., biochemical oxygen demand), temperature, and wastewater flow. However, these pollutants do not account for all pollutants discharged to U.S. waters.

• ICIS-NPDES only includes information about discharges of pollutants that a facility is required by permit to monitor; facilities are not required to monitor or report all pollutants they actually discharge.
• Discharge data are entered into ICIS-NPDES using a variety of measurement units. The Loading Tool can only calculate mass discharges for pollutants that are measured either as mass quantities or concentrations. Therefore, some pollutants, such as toxicity parameters measured as percent, are excluded from loading calculations. Further, the Loading Tool cannot calculate a load for concentration measurements if a corresponding wastewater flow measurement is not provided.
• DMR data are recorded in ICIS-NPDES in a variety of measurement units. EPA uses conversion factors to calculate loads (e.g., 2.205 pounds/kilogram). These pollutant loads are not rounded to avoid reporting insignificant figures. This allows users to replicate the calculated pollutant loads from the reported DMR data. 

The Loading Tool matches facilities to receiving watersheds based on a facility's latitude and longitude coordinates and watershed spatial data in the Natural Resources Conservation Service's Watershed Boundary Dataset. The Loading Tool cannot establish a match between a facility and a watershed if either:

• The facility does not have latitude or longitude coordinates; or
• There are no spatial data for the receiving watershed.

The Loading Tool uses names from the USGS Geographic Names Information System (GNIS). The GNIS is closely integrated with the Watershed Boundary Dataset (WBD), which makes these data more useful for plotting on maps and for watershed modeling and other research. Not all water bodies receiving wastewater discharges have names in the GNIS and the not all names in the GNIS match the names that facilities provide in their NPDES permit application.

See Watershed Data for further information about how the Loading Tool matches DMR facilities to receiving watersheds.

DMR data may be entered into the ICIS-NPDES database manually, which can lead to data-entry errors. The database supporting this online tool uses data extracts from ICIS-NPDES with regular error correction updates from EPA's Integrated Error Correction Process. The Integrated Error Correction Process allows EPA to track and incorporate into the Loading Tool database error corrections submitted by the public. EPA also works with states to identify any error corrections that they make to their data outside of the Integrated Error Correction Process.

Some facilities have intermittent discharges and may have one or more outfalls that don't discharge for one or more months. ICIS-NPDES has ways of identifying when there is no discharge at a particular outfall for an entire monitoring period. In such cases, the Loading Tool does not calculate pollutant loads for these outfalls during these monitoring periods.

EPA also developed a methodology with the states to estimate intermittent discharges that occurring within a monitoring period (e.g., there is a discharge from the outfall but it only occurs two days out of the monthly monitoring period). Specifically, the Loading Tool uses three ICIS-NPDES "Duration of Discharge" codes for identifying these intermittent dischargers: 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, there is a limitation with ICIS-NPDES data in that not all NPDES permits require permittees to submit Duration of Discharge codes when there are intermittent discharges that occur within a monitoring period. Consequently, the tool may overestimate pollutant discharges for these intermittent dischargers that do not report the Duration of Discharge codes. NPDES permittees with intermittent discharges are encouraged to engage with their permit writers to add one of the Duration of Discharge codes to their DMR. NPDES permittees may also contact EPA if the Duration of Discharge codes are not yet in their DMR.

TRI reporting is limited to industrial facilities (i.e., POTWs do not report to TRI) and not all industry sectors report to TRI. Additionally, small establishments (less than 10 employees) are not required to report, nor are facilities that don't meet the reporting thresholds. Thus, facilities reporting to TRI may be a subset of an industry. See the Basics of TRI Reporting and Factors to Consider When Using TRI Data for more information.

TRI reporting focuses on toxic pollutant discharges and does not include common wastewater pollutants like Total Suspended Solids and Biochemical Oxygen Demand, which can be important factors when assessing the potential impact to surface waters. Additionally, the TRI Program does not require additional monitoring, so reported releases are often, in part, based on estimates instead of measurements, and due to TRI guidance, may differ greatly from DMR data, especially at facilities with large wastewater flows. Finally, certain chemicals (e.g., polycyclic aromatic compounds (PACs), dioxin and dioxin-like compounds, metal compounds) are reported as a class, not as individual compounds. Because the individual compounds in most classes have widely varying toxic effects, the potential toxicity of chemical releases may be inaccurately estimated.

TRI reporting does require facilities to report the names of the surface water bodies and POTWs that receive their wastewater discharges. See Sections 5.3 and 6.1 in TRI Form R. However, these reported names are not standardized or indexed to USGS's NHD or EPA's Federal Registry Service (FRS).

See Watershed Data for further information about how the Loading Tool matches TRI facilities to receiving watersheds.

The TRI Program conducts a number of activities every year to ensure the quality of TRI data reported to EPA. These activities range from providing extensive reporting guidance, intelligent reporting software, and training to facilities prior to the reporting deadline as well as data validation and analysis after the data are received. See TRI Data Quality Program Information for more information on these activities.