Section 62.14403 - What happens if I modify an existing HMIWI?(a) If you commenced modification (defined in 40 CFR 62.14490 ) of an existing HMIWI after April 6, 2010, you are subject to 40 CFR part 60, subpart Ec (40 CFR 60.50c through 60.58c ), as amended, and you are not subject to this subpart, except as provided in paragraph (b) of this section.(b) If you made physical or operational changes to your existing HMIWI solely for the purpose of complying with this subpart, these changes are not considered a modification and you are not subject to 40 CFR part 60, subpart Ec (40 CFR 60.50c through 60.58c ), as amended. You remain subject to this subpart. 78 FR 28067 , May 13, 2013