TRI Water Pollution Search Development
The Toxics Release Inventory (TRI) Water Pollution Search interface allows users to perform analyses on TRI water releases within the Water Pollutant Loading Tool. These analyses include calculating total weighed pound equivalent (TWPE) and ranking discharges by industry, watershed, and pollutant. Users can also compare wastewater discharge data reported on DMRs under the NPDES permit program and water releases reported under the Toxics Release Inventory (TRI) at a national, regional, or state level.
The database tables in the Water Pollutant Loading Tool provide the input to the TRI queries.
On this page:
TRI Water Release Methodology
The DMR_LOADINGS_TRI_RELEASES table contains annual direct and indirect pollutant releases for each unique calendar year, TRI Facility ID, and TRI chemical name. The Loading Tool creates the DMR_LOADINGS_TRI_RELEASES table using the reported TRI water release data and the following additional calculation steps:
Publicly Owned Treatment Works (POTW) Removals for Indirect Releases
For facilities that reported transfers of chemicals to POTWs (indirect releases), the Loading Tool adjusts the reported pollutant loads to account for pollutant removal at the POTW prior to discharge to the receiving stream. POTW removal rates are specific for each pollutant.
The pounds of facilities’ waste released to the surface water after POTW removal is estimated using the following equation:
- Indirect Release (pound/year) = [Transfer to POTW (pound/year)] × [1 - POTW Removal Rate (%)]
Toxic Weighting Factors (TWFs)
To identify potential impacts on human health and the environment, TWFs are used to estimate toxic equivalent mass discharge. The Loading Tool uses the REF_TRI_CHEM_TWFS table, which lists TWFs by CAS number, to calculate TWPE for chemical discharges. If the table does not list a TWF for a specific parameter, then pollutant discharges for the chemical are not included in TWPE estimates.
In some cases, the Loading Tool calculates industry-specific TWFs for certain chemical compound categories reported in TRI. These TWFs are not used to calculate TWPE for chemical discharges in ICIS-NPDES. Specific TRI TWFs were created from available information about the composition of the compound category. These chemicals include:
- Dioxin and dioxin-like compounds;
- Polycyclic aromatic compounds;
- Creosote.
EPA’s 2009 Technical Support Document for the Annual Review of Existing Effluent Guidelines and Identification of Potential New Point Source Categories (EPA 821-R-09-007) describes the development of these TWFs in detail.
TRI Water Releases for Metals
Facilities report metal compounds to TRI on a single reporting form for each parent metal and do not specify the individual compound(s) released. If the facility is required to report for a metal and its compounds, the facility may report both the metal and metal compound on a single form. For metal compound reporting, the release quantities are based on the mass of the parent metal, only. To calculate loads and TWPEs for metal compounds, the Loading Tool combines the loads for the metal and metal compounds and uses the TWF for the parent metal.
Point Source Categories
The DMR_LOADINGS_PSC_TRI_XWALK table links unique TRI Facility IDs and TRI Chemical IDs to industrial point source categories. The point source category crosswalk assigns records to existing point source categories based on NAICS codes from the TRI dataset.
These crosswalk tables are available on the Water Pollutant Loading Tool Resources page.