For the purpose of this subchapter, the following definitions apply, in addition to the definitions contained in 15-6-135, MCA:

(1) "Apportionment" means the identification of the extent to which multi-purpose property, facilities, machinery, devices or equipment are used for pollution control purposes.

(2) "DEQ" means the Montana department of environmental quality.

(3) "DOR" means the Montana department of revenue.

(4) "Substantial compliance" means either full compliance with all applicable rules, laws, orders, or permit conditions, or noncompliance with such requirements, provided that incidents of noncompliance are isolated or casual, do not involve continuous acts or patterns of noncompliance, and do not result in the initiation by DEQ of an administrative or judicial enforcement action.   For purposes of this definition, issuance by DEQ of a citation or a notice of violation, without an accompanying compliance or penalty order, does not constitute the initiation of an enforcement action.