30 Tex. Admin. Code § 116.174
The executive director may grant authority to a permit applicant to use prior emission reductions and emission reductions granted to the applicant by another entity (either public or private) in accordance with § 116.170 of this title (relating to Applicability for Reduction Credits) if the commission determines that the prior emission reductions have, in fact, occurred and, when considered with other emission reductions that may be required by the permit as well as contaminants that will be emitted by the new source, will result in compliance with § 116.150 of this title (relating to New Major Source or Major Modification in Ozone Nonattainment Areas), § 116.151 of this title (relating to New Major Source or Major Modification in Nonattainment Areas Other Than Ozone), § 116.160 of this title (relating to Prevention of Significant Deterioration Requirements), and § 116.162 of this title (relating to Evaluation of Air Quality Impacts), as applicable, in the area where the new source is to be located. Prior as well as future emission reductions to be used as an offset shall be made conditions for granting authority to construct the proposed new source and shall be enforced.
30 Tex. Admin. Code § 116.174