Under §112(g) of the 1990 CAAA, a preconstruction review is required upon construction, reconstruction, or
modification of a "major source". However, following national EPA guidance, the DAQ is not implementing
case-by-case MACT for modified major sources - only for those major sources that will be constructed or
reconstructed. For purposes of Section 112(g) sources must submit a pre-application construction permit
application (typically, through 45CSR13) proposing source-specific MACT.
Section 112(g)(2) provides that the program does not take effect until "after the effective date of a permit
program under Title V in any state..." After this date, a "major source" in the state may not construct,
reconstruct or modify its facility unless EPA or the state determines that MACT will be met. This
determination will be made on a case-by-case basis if EPA has not yet issued an applicable standard. The
EPA-approved effective date for West Virginia's Title V program was December 15, 1995. Section 2 of 45CSR34
provides the Director of the DAQ with the authority to establish the applicable requirements.
Unlike the pre-1990 NESHAPs, MACT standards do not focus on a single HAP. Rather, the standards will control
source emissions of a number of HAPs, as is the case with CAA New Source Performance Standards (NSPS) and
Clean Water Act "effluent guidelines."
The chart , "Case-by-Case Maximum Achievable Control Technology (MACT) Applicability Determination",
contains information which may be used as an aid in determining the applicability of case-by-case MACT. If a
source is subject to case-by-case MACT requirements, these must be addressed before construction begins,
typically though the NSR (45CSR13) Preconstruction Permits program.