Easements at least 12 feet in width along rear lot lines and 10 feet in width centered along the side lot lines shall be provided where necessary for sanitary sewers, gas mains, water mains, electric lines, and Village sewers. Easements shall also be provided as required by the Village Planning Commission or Village Engineer along every watercourse, drainage channel, detention or retention basin or stream within a subdivision. Such easement shall be exclusive of the width of the watercourse, drainage channel or stream. An easement of this type shall be provided for on each side of such facility, or on one side if conditions dictate and if approved by the Village Engineer.