(1)    If an existing private on-site wastewater treatment system either is not located in soil meeting the siting standards or is not constructed in accordance with design standards promulgated under s. 145.02, the owner of the private on-site wastewater treatment system may petition the department for a variance to the siting or design standards.

   (2)   The department shall establish procedures for the review and evaluation of existing private on-site wastewater treatment systems which do not comply with siting or design standards.

   (3)   Upon receipt of a petition for a variance, the department shall require the owner of the private on-site wastewater treatment system to submit information necessary to evaluate the request for a variance. If the department determines that the existing private on-site wastewater treatment system is not a failing private on-site wastewater treatment system, and continued use of the existing private on-site wastewater treatment system will not pose a threat of contamination of waters of the state, then the department may issue a variance to allow continued use of the existing private on-site wastewater treatment system. The department shall rescind the variance if the existing private on-site wastewater treatment system becomes a failing private on-site wastewater treatment system or contaminates waters of the state.