If a licensed interpreter appointed under section 20-153 is not able to provide effective communication with a deaf or hard of hearing person, the appointing authority shall obtain another licensed interpreter. An oral interpreter shall be provided upon request of a deaf or hard of hearing person who chooses not to communicate in sign language. If an interpreter is unable to render a satisfactory interpretation, the appointing authority shall then obtain an intermediary interpreter to assist the appointed interpreter. The appointing authority shall ensure that any interpreter is properly situated so as to permit effective communication with the deaf or hard of hearing person and full participation of the deaf or hard of hearing person in the proceeding.