C.R.S. § 25-16-309

(1) Nothing in this part 3 shall absolve any person from obligations under any other law or regulation, including any requirement to obtain permits or approvals for work performed under a voluntary clean-up plan. (2) If the United States environmental protection agency indicates that it is investigating a site which is the subject of an approved voluntary clean-up plan or no action petition, the department shall actively pursue a determination by the United States environmental protection agency that the property not be addressed under the federal act or, in the case of property being addressed through a voluntary clean-up plan, that no further federal action be taken with respect to the property at least until the voluntary clean-up plan is completely implemented.