Tree trimmings, building and manufacturing wastes, grasses, weeds, leaves and rocks shall not be allowed to accumulate upon any premises in the city so as to create a menace to health, a fire hazard or an unsightly appearance; and shall be removed at the expense of the person responsible for the accumulation. Under no condition may tree trimmings, grasses, weeds, leaves, or building and manufacturing wastes be burned within the city unless they are burned by authority personnel acting in line of duty. (Prior code § 9-6)