Opinion ID: 544587
Heading Depth: 4
Heading Rank: 5

Heading: K090 and K091

Text: 57 In 1980, EPA proposed to amend the characteristic of extraction procedure toxicity to apply to hexavalent chromium instead of total chromium, see 45 Fed.Reg. 72,029 (1980), based on EPA's recognition that trivalent chromium is not a health hazard, see id. at 72,030. Petitioners claim that EPA, having raised the trivalent/hexavalent chromium issue in 1980 and 1981, arbitrarily and capriciously ignored the issue completely when it made the listing decision in the 1988 Rule. The petitioners claim, in addition, that EPA violated RCRA Sec. 3001(a) and 40 C.F.R. Sec. 261.11(a)(3) by listing ferroalloy dusts and sludges on the basis of the presence of total chromium when the record indicates that these materials contain nearly exclusively trivalent chromium. They also argue that relevant chromium does not exhibit the toxicity EPA sought to regulate. See Final Brief of Consolidated Petitioners at 65-66. They also note that sixteen other wastes listed because of the presence of chromium were listed on the basis of hexavalent chromium, not total chromium, and that EPA's action here is therefore not consistent with this regulatory precedent, in violation of 40 C.F.R. Sec. 261.11(a)(3)(x). See id. at 66. Moreover, they claim that there is no evidence in the record that chromium has the potential to migrate even if the ferrochromium and ferrochromium silicon materials are improperly managed. 58 EPA summarizes petitioners' claims as posing the issue whether the ferroalloy wastes have the potential to leach significant concentrations of Cr(VI). Because EPA relies on data not cited in the 1988 Rule to respond to AMC's challenges concerning EPA's classification based on total chromium, see Brief for the Respondent at 47-48 (citing Ferro Ass'n Supp. Comments at 19, 27, reprinted in J.A. 434, 442), we must remand for further explanation. However, we deny the petitioners' petition concerning the volume of ferroalloy wastes. They contend that EPA improperly failed to consider the decline in the amount of K090 and K091 generated nationwide since 1980 due to economic conditions. That challenge is based on post-1980 data and may be raised in a petition for new rulemaking.