Significant industrial users shall submit a minimum of semi-annual reports (on dates specified by the City) indicating flows and the nature and concentration of pollutants in the discharge. The specific standards or the City itself may require these reports to be filed more frequently. Other users may be required to submit reports as directed by the City. City Code, 1976/83, art. 25, §7(b)(2)(1st par.) Ord. 91-775