Texas Natural Resource Conservation Commission Austin Texas Interoffice From: Bill Zeis, Attorney, Legal Division To: Lawrence Pewitt, P.E., Director, Permits Program Date: August 2, 1985 Subject: Legal Opinion - Amoco Oil Permit 2384A, Fluid Catalytic Cracking Unit (FCCU) No. 1 This is in response to your request for a legal opinion on whether a proposed increase in hourly emissions from Amoco's FCCU No. 1 is a "modification" under the Texas Clean Air Act (TCAA) and therefore subject to Regulation VI review. Amoco proposes to stay within their annual allowable for sulfur dioxide emissions. First, TCAA Section 1.03(a) defines a "modification" as "any...change in the method of operation of a stationary source which increases the amount of any air pollutant emitted by such source into the atmosphere..." (emphasis added). The Legal Division interprets this to include any increase in mass emission rate over any time period for which an emission rate was specified in either 1) the construction or operation permit or 2) the representations in the construction or operating permit applications. Second, the increase will only be a "modification" if it is "significant," since Section 1.03(a) specifically excludes insignificant emissions from the definition of "modification." If the increase in emission rate is insignificant, a permit amendment will still be required under Regulation VI, Rule 116.5 now 116.116(a).