Residential uses, and appurtenant accessory uses and structures, when authorized in the underlying zoning district; provided, the land owner signs and records in the deed and mortgage records of Curry County a hold harmless agreement, avigation and hazard easement and noise easement, and submits same to the airport sponsor and city planning department; and also provided, that the area is beyond where the 20:1 approach penetrates the horizontal surface at elevation 608 feet.