Easements at least twenty feet in width centered along rear or side lot lines shall be provided where necessary for sanitary sewers, water mains and storm sewers. Easements at least ten feet in width centered along rear or side lot lines shall be provided wherever necessary for gas mains and electric lines, unless otherwise requested by the respective utility company. Easements shall also be provided as required by the Planning and Zoning Commission along every water course, drainage channel or stream within a subdivision. All plats shall contain a restriction requiring that no structures, plantings, etc. will be permitted in the easement area.