Assumptions Used in the Analysis

1998 was the first year that EPA collected information from the commercial hazardous waste treatment sector. EPA has taken steps to adjust for possible double counting of some disposal or other releases in TRI now that EPA collects information from this sector. The potential for double counting arises because some manufacturing facilities report transfers of chemicals to other facilities that may then report the disposal or other release of these chemicals. TRI facilities transfer off- site chemicals in waste to other facilities for disposal or other release. These other facilities can dispose of the wastes in on-site underground injection wells, landfills, disposal surface impoundments, in land treatment facilities, and other types of land disposal or, if metals are sent to a wastewater treatment facility, they may be discharged to surface waters. These other facilities generally are treatment, storage and disposal (TSD) facilities regulated under the federal Resource Conservation and Recovery Act (RCRA). As mentioned above, such facilities are in one of the industries required to report to TRI for the first time in the 1998 reporting year.

To avoid counting the transfers to the TSD facilities that are also reported to TRI as on-site disposal or other releases by the TSD facilities, off-site transfers for disposal or other releases to these TSD facilities have been omitted from tables that compare or summarize on-site and off-site disposal or other releases nationally or at the state level. Only the on-site disposal or other releases from the TSD facilities have been included. The tables contain a note at the bottom of the table if transfers were omitted for that particular table. In general, these transfers were omitted if the data were being analyzed from a national or state perspective. 1

In addition to the double counting adjustment described above, EPA reclassified reporting for metals and metal compounds in this analysis in an effort to correct facility reporting errors. EPA requires the transfer of metals and metal compounds for further waste management be reported as either a transfer to recycling or a transfer to disposal or other releases (due to the fact that metal has no heat value and thus can not be combusted for energy recovery and can not be treated because it can not be destroyed). Two new disposal codes were added to the TRI reporting form in 1997 to provide more accurate reporting, codes M41 (solidification/stabilization metals and metal compounds) and M62 (wastewater treatment (excluding POTWs) metals and metal compounds). Since 1997, a number of facilities have incorrectly reported the waste management of metals and metal compounds. These chemicals were incorrectly reported under codes M40 or M61, as being treated. In order to account for this error and to compare reporting for these transfers prior to 1997, EPA has included metals and metal compounds that were reported in the waste treatment categories with codes M40 or M61 in the corresponding categories for metals and metal compounds (M42 and M62) instead.

1Conducting this exercise required that EPA match amounts transferred to TSD facilities with amounts reported by these TSD facilities by using the reported RCRA ID number. In some cases, these RCRA ID numbers were not reported correctly by the facility so there are some quantities that cannot be matched and, therefore, these quantities could not be omitted from the analysis.

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