(a) An industrial user (IU) is a significant industrial user (SIU) if they meet one or all of the criteria as defined in the WSSC Plumbing and Fuel Gas Code (WSSC Chapter 14.25), Chapter 8, and the Code of Federal Regulations (40 CFR 403.3).

(b) Four criteria are used to determine investigation and compliance monitoring frequencies for SIUs. These criteria are:

(c) Comprehensive facility investigations are conducted annually on all SIUs. The investigations focus on all processes generating waste, associated chemical usage and storage, pretreatment operations, and spill and/or slug control plans (where applicable). The results are recorded on the “Industrial Investigation Reports,” which include general administrative information such as contact name, addresses, account number, number of employees, work hours, inspection dates, and investigation results.

(d) In addition to an annual inspection, follow-up investigations are also conducted. Follow-up investigations generally focus on verifying IU activities regarding completion or progress on a corrective measure, and take place within 14 days of a final compliance date. These investigations are recorded on “Follow-Up Industrial Investigation Reports,” which briefly describe the reason for the investigation and the observations pertinent to specific areas of interest or concern.

(e) Compliance monitoring is scheduled annually or semiannually, without advance notice to the IU. This method of scheduling provides the Industrial Investigator flexibility to plan compliance monitoring based on information obtained during previous inspections, and also allows the consolidation of resources to a geographic region for purposes of scheduling monitoring and investigation activities (e.g., monitoring several SIUs located in the same industrial park).

(f) Routine monitoring of SIUs includes collecting samples for all parameters regulated in the IU’s discharge authorization permit and annual monitoring for all parameters subject to local limitations. Flow measurements or estimations are recorded for the duration of all sampling trips.

(g) Follow-up compliance monitoring generally consists of monitoring for all regulated parameters, but may consist of monitoring only for those parameters for which the IU was found to be in violation. Follow-up compliance monitoring is conducted within 30 days after the final compliance date.

(h) Sample collection methods and frequencies are as follows:

(i) Minimum inspection and monitoring frequencies are assigned as follows:

(j) Increases in investigation and compliance monitoring frequencies are determined based on the IU’s compliance status. Violations are generally addressed with increased compliance monitoring. The degree to which frequencies are increased is determined by the IU’s compliance history and current management practices as observed by the Industrial Investigator. (Industrial discharge control program enforcement response plan § I(A), dated April 22, 2013)