The discharge, directly or indirectly, into any opening, or into any gutter leading into any sewer, receiving basin or drain, within or leading into the parkway system, of any sewage, oil, gas or vapor, industrial waste, or any substance which may form a deposit tending to choke the same, or any volatile liquid which will emit a flammable vapor, or any stream or hot water above 100 degrees Fahrenheit, is prohibited.