Frequent Questions

Data sources and basis of estimate codes for estimating releases and other waste management activities

For TRI reporting, EPA has identified four basic methods that a facility may use to develop the estimates for releases and other waste management activities: monitoring data, mass balance calculations, emission factors, and other approaches such as engineering calculations. The best method for calculating the quantities of each release and other waste management activity will depend on the facility’s site-specific knowledge and available data sources. What potential data sources are available for each basis of estimate type?

Potential monitoring data sources can include stack monitoring data, outfall monitoring data, air permits, industrial hygiene monitoring data, National Pollution Discharge Elimination System (NPDES) permits, publicly owned treatment works (POTW) pretreatment standards, effluent limitations, Resource Conservation and Recovery Act (RCRA) permit data, hazardous waste analysis, pH for acids, and continuous emission monitoring. The basis of estimate code used in Section 5 or 6 of the TRI Form R for monitoring data is either M1 or M2, depending on whether the estimate was based on continuous monitoring data (M1) or periodic or random data or measurements (M2).

Potential data sources for mass balance calculations can include supply records, a hazardous material inventory, an air emissions inventory, pollution prevention reports, hazardous waste manifests, and spill event records. The applicable basis of estimate code for mass balance calculations is C.

Potential emission factors can include AP-42 emission factors, other EPA emission factors, published facility or trade association chemical-specific emission factors, site-specific emission factors relating release quantity to through-put or equipment type (e.g., air emission factors), or other site-specific emission factors developed specifically for a situation or process on site that takes into account the actual field conditions at the location. The applicable basis of estimate code is either E1 or E2, depending on whether the estimate was based on published emission factors (E1) or site-specific emission factors (E2).

Other potential data sources can include engineering calculations, best engineering judgment, volatilization rates, Raoult’s Law, Henry’s Law, and solubilities. The applicable basis of estimate code for these types of other approaches is O.

The potential sources and factors provided above are only examples. A facility can use any source of information so long as the source is consistent with §313(g)(2): "the owner or operator of a facility may use readily available data (including monitoring data) collected pursuant to other provisions of law, or, where such data are not readily available, reasonable estimates of the amounts involved."

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