The permitting provisions of the CSO Control Policy apply to all combined sewer systems that overflow as a result of stormwater flow from precipitation events, which includes stormwater runoff, snow melt runoff, and surface runoff and drainage. Dry weather flow is the flow in a combined sewer system that results from domestic sewage, groundwater infiltration, commercial and industrial wastewaters, and any other non-precipitation related flows (e.g., tidal infiltration). Discharges from combined sewer systems during dry weather are prohibited by the CWA, CSO Control Policy, and the KPDES permit.
CSO outfalls are point sources subject to KPDES permit requirements including both technology-based and water quality-based requirements of the CWA. Information about CSO outfalls is included on Part G of Form A as part of the KPDES permit application for POTWs.
Nine Minimum Controls
Permittees with CSOs are required by Section II.B of the CSO Control Policy to immediately implement the Nine Minimum Controls (NMC). The activities used for the NMC are particularly applicable for combined sewer systems because the types, concentrations, and quantities of pollutants expected from CSO discharges are highly variable for each precipitation event. The Combined Sewer Overflows Guidance for Nine Minimum Controls [U.S. EPA, May 1995, EPA 832-B-95-003] provides examples of activities that may be used to address each control measure and guidance to evaluate and document implementation of the NMC, which are:
- Proper operation and regular maintenance programs for the sewer system and the CSO outfalls
- Maximum use of the collection system for storage
- Review and modification of pretreatment requirements to assure CSO impacts are minimized
- Maximization of flow to the POTW for treatment
- Prohibition of CSOs during dry weather
- Control of solid and floatable materials in CSOs
- Pollution prevention
- Public notification to ensure that the public receives adequate notification of CSO occurrences and CSO impacts
- Monitoring to effectively characterize CSO impacts and efficacy of CSO controls
- Combined sewer systems in Kentucky have all submitted a NMC Compliance Report documenting implementation of the NMC, including proposed schedules for completing any minor construction activities.
Long Term Control Plans
Permittees with CSOs are required by Section II.C of the CSO Control Policy to develop and implement long term CSO control plans (LTCP) that will ultimately result in compliance of CSO discharges with the requirements of the CWA. LTCPs consider the site-specific nature of CSOs and evaluate the cost-effectiveness and performance of a range of control options/strategies. Implementation of CSO controls may be phased based on the relative importance of and adverse impacts upon water quality standards and designated uses, as well as the permittee's financial capability and its previous efforts to control CSOs. The Combined Sewer Overflows Guidance for Long-Term Control Plan [U.S. EPA, September 1995, EPA 832-B-95-002] provides guidance to assist permittees with CSOs in developing technically feasible, affordable, and comprehensive LTCPs consistent with the objectives of the CSO Control Policy.
Combined sewer systems in Kentucky have all either submitted and are implementing an approved LTCP, or have separated their combined sewers and eliminated all CSO outfalls instead of submitting an LTCP.
Monitoring and Reporting
Permittees with CSOs should have a comprehensive, representative monitoring program that measures the appropriate frequency, duration, flow rate, volume or pollutant concentrations of CSO discharges in order to characterize CSO discharges and their water quality impacts. The monitoring program helps evaluate CSO controls alternatives during develop of the LTCP; evaluate impacts of CSOs on receiving waters to verify compliance with water quality standards and protection of designated uses; determine the effectiveness of NMC and CSO controls and that the CSO controls are constructed, operated, and maintained as designed in the LTCP; and determine compliance with permit limits.
The KPDES permit requires permittees with CSOs to submit a comprehensive monitoring plan prior to completion of LTCP implementation that documents the locations, methods, and frequency of monitoring and sampling of the combined sewer system, and describes the criteria and calculations that will be used to evaluate the performance of the combined sewer system and overall success of the LTCP in meeting the requirements of the CSO Control Policy and the KPDES permit.
Discharge Monitoring Reports
KPDES permits for combined sewer systems include effluent limitations and monitoring requirements for the combined sewer system and for each permitted CSO outfall with monitoring results reported on Discharge Monitoring Reports similar to other outfalls at the POTW. During implementation of the LTCP, the permit includes system-wide precipitation along with volume, duration, and number of occurrences of CSO discharges as a result of precipitation for each permitted CSO. Additional pollutant-specific and performance criteria monitoring and reporting requirements may be applied as appropriate.
Dry Weather Overflows
Dry weather overflows from CSO outfalls are prohibited and are reported to DOW, along with other non-compliance of the combined sewer system, in accordance with 401 KAR 5:065.
CSO Annual Reports
While some CSO discharge information is reported on DMRs, the KPDES permit requires additional information including compliance with NMC, progress of implementation of LTCP CSO controls, and annual summaries of monitoring results and combined sewer system performance to be provided in CSO Annual Reports. Submission of a CSO Annual Report is a requirement of the KPDES permit for permittees with CSOs. Annual reports cover an entire calendar year (January – December) and must be submitted to DOW by March 1 of the following year. The CSO Annual Report Template is available and due March 1 of the following year. All entries in the reports must be filled out completely or the report will be considered deficient. Failure to submit the report by the deadline may result in enforcement actions.
CSO Annual Reports may be submitted as a single .pdf file through the ePortal. Instructions on how to create an account and use the portal can be found in the eDocument Module User Guide.
These CSO Annual Reports are separate from progress reports that may be required to be submitted to the Division of Enforcement by enforcement orders, although some information may be similar and can be used in both types of reports.