A responsible person shall be liable to the city for all cleanup costs incurred by the city, including, but not limited to, fees payable by the city to any public or private agency for assistance pursuant to any 28E agreement, local ordinance or emergency request of the city, for chemical damage, for contamination of equipment, and for the use of consumable materials, but shall not be liable for those losses, burdens or costs normally associated with response to fire emergencies which do not involve hazardous conditions. If charges for such cleanup costs are not paid within thirty (30) days after invoice, the city may proceed to obtain payment by all legal means. A public or private agency providing assistance to the city pursuant to any 28E agreement, local ordinance or emergency request of the city may directly bill the responsible party for the fees for assistance provided in regard to cleanup of a hazardous substance. The responsible party shall be responsible for the payment of such fees to same extent as if the fees were billed by the city to the responsible party. (2000 Code § 36.05)