You can sue the fire department and the trailer park for negligence.Negligence on the part of the fire department is the failure to exercise due care (that degree of care that a reasonable fire department would have exercised under the same or similar circumstances to prevent foreseeable harm).Negligence on the part of the trailer park is the failure to exercise due care (that degree of care that a reasonable trailer park would have exercised under the same or similar circumstances to prevent foreseeable harm) ( having a hydrant).You would file one lawsuit naming both the fire department and trailer park as defendants.  Your damages (monetary compensation you are seeking in your lawsuit) would be the value of what you lost in the fire.