Nothing in this chapter shall be construed to prohibit local governments or private enterprise from the construction or operation of approved sanitary landfills, or of any other heretofore or hereafter approved solid waste disposal system, it being the intent of this chapter that its provisions shall be supplementary to, and not restrictive of, any previously authorized solid waste disposal system, facility, or operation, nor of any other such system, facility or operation that may be authorized in the future. Nor shall this chapter be interpreted as granting any regulatory authority to the department that is not otherwise granted in other statutes.