Division of Environmental Quality

Operations Manual

Chapter 9 - SSO Policies and Procedures (Revised 06/12)

9.1 Purpose | 9.2 Terminology | 9.3 Facilities to Report | 9.4 Public Notice | 9.5 DNR On-Site Response |
9.6 DNR Response
| 9.7 Sampling | 9.8 Compliance Process | 9.9 DNR Data | 9.10 E-Report System

9.1 Purpose

This is guidance for use by Water Pollution Control Branch, or WPCB, staff, Environmental Services Program, or ESP, and Regional Office staff. 

The primary purpose for this guidance is to describe the procedures for addressing SSOs and bypasses by department staff.

This guidance complies with regulations and includes policies not covered by regulations. 

Other guidance or processes
There are other department and EPA guidance or enforcement documents covering:

Constructed bypass structures at plants, such as at peak flow clarifiers for use during wet weather, are not allowed by state law.  These issues are not addressed by these policies.

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9.2 Terminology 

Federal terms
In Federal documents, a bypass is limited to discharges that occur at a wastewater treatment plant, i.e. major mechanical or biological treatment devices are bypassed by the incoming wastewater at the headworks, from a treatment unit or from pumps and piping within the plant.  This can be referred to as a problem “inside the fence” or on the property of the treatment plant. Untreated or partially treated water is discharged.  See 40 CFR 122.41(m)(i).

Missouri terms
In Missouri regulations, bypasses are discharges of untreated or partially treated wastewater any place in a collection or treatment system, i.e. they are not limited to the plant.  See 10 CSR 20-2.010

Both Federal and Missouri
In both Federal usage and in Missouri, the term Sanitary Sewer Overflow (SSO) has the same definition – discharges from sewer pipes, manholes, lift station pumps or other places in the sewer system before the wastewater enters the wastewater treatment plant.  Can be referred to as “outside the fence.”

Terms for this guide
To be the most specific, this document uses the following EPA terms:

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9.3 Facilities to Report

For dry weather SSOs and bypasses
The permittee shall notify the department within 24 hours and follow-up with a final report within 5 days.  The preferred method to report will be electronically through the department’s website.  Telephone reports will still be accepted and they must be made to the regional office or, after business hours, to the Spill Line.  The preferred method to transmit the final report will also be the electronic reporting system.  Written reports for the 5-day final report are still acceptable and can be sent to the Regional Office.

Wet weather SSOs and bypasses
According to 10 CSR 20-7.015(9)(E)2, for POTWs, wet weather SSOs and bypasses can be reported with the next discharge monitoring report, or DMR.  However, reporting via the DMR applies only if those reported discharges do not violate permit effluent limitations or permit conditions.  Permit Standard Conditions, Part I, does not allow for discharges that could result in potential endangerment to health or the environment. 

Since the burden of proof that there is no endangerment is on the permittee and since the likelihood is low that discharges could meet effluent limits, staff should recommend that all bypasses be reported within 24 hours. 

Reporting wet weather SSOs within 24 hours can only be recommended to POTWs not required.  Requirements can only be made if it can be established that there is a WQS violation.

Waters of the State of Missouri

Basement backups and Private Service Lines
Sewer utilities should record any instances of basement backups, discharges from lateral lines or cleanouts.  These records should be reviewed by department staff as part of any inspection. (Sanitary Sewer Overflow Policy Implementation 04/04/07). 

Sewer utilities are not required to submit a SSO report for basement backups unless the water is pumped out of the structure and is released to the environment.    If the sewer utility is aware a homeowner is pumping wastewater out of the basement, they are encouraged to report the event to the department and the local health department.

Discharges from private service lines, laterals or cleanouts do not have to be reported by the sewer utility.  However, the department does encourage the reporting of these releases to ensure that appropriate coordination is made with the local health department or, if necessary, to provide a response to the incident.

If a sewer utility initially reports an SSO that is later found to be the fault of a private service line, the final report should make note of this fact.  In general, the department will not address problems associated with private service line issues in any analysis of a systems SSO’s.  An exception may occur if excess inflow problems have been identified due to downspouts or foundation drains. 

Property owners are all responsible for problems associated with a common line where there is no continuing authority in-place.  Those individuals will be responsible for any water quality impacts associated from discharges from those lines.  If the line connects to a permitted collection system, the operator of that system should not be considered responsible unless the cause of the discharge originates from their system (e.g., a grease blockage).  Ultimately, the larger operating authority should have the common line conveyed to them for future operation and maintenance responsibilities.  Transfer of the private line is encouraged but is solely a matter between the property owners and the continuing authority.

Solids and residuals on the ground from a bypass or overflow should be promptly cleaned up and properly disposed.  Solids that occur from a line or manhole that serve more than a single family residence are subject to the Solid Waste Law and regulations.  These materials should ultimately be disposed of at a permitted sanitary landfill.  Materials from a private lateral serving only a residence   would not be subject to the Solid Waste requirements but should still be properly managed.  The responsible party should notify the Missouri Department of Health and Senior Services and coordinate any cleanup actions with that agency.

Satellite Sewer Systems
Since SSOs are a potential threat to human health and the environment, department staff will require satellite systems to report to the department.  

Satellite communities are municipalities that act as the operating continuing authority for their sanitary sewer collection systems, but do not have a wastewater treatment plant and do not have an MSOP.  An example would be cities in the east and south parts of Jackson County, such as Belton, Grandview and Lee’s Summit that have sewers that deliver the wastewater to the Little Blue Valley Sewer District’s treatment plant or the city of Holts Summit that contributes to Jefferson City’s system.

Usually, much of the department’s authority for regulating a collection system is based in the conditions of the MSOP (NPDES permit) held by the wastewater treatment plant.  However, in the case of satellite communities, the permit is held by another community or regional treatment facility, and the authority of that NPDES permit may not extend to all parts of the tributary collection system.  Releases from a collection system would constitute a discharge without a MSOP or violations of effluent regulations or water quality standards.

Gray Water
Gray water is wastewater from kitchen sinks, dishwashers, clothes washers and similar household sources.  Gray water is sometimes discharged directly outside a home and does not enter a sewer.  Since the wastewater did not enter a sewer system, it cannot be a sewer overflow.  Gray water discharges are discharges without a permit and the responsibility of the discharger and not the owner or operator of the sewer system.  The department will address these unpermitted discharges.

Discharges onto Private Property
Reporting of SSOs is required regardless if the discharge is confined to private property, including property of the sewer system.

The permittee or sewer owner/operator is responsible for cleanup regardless of the ownership of the contaminated property.  This applies to outside contamination and does not apply to damages in basements. The permittee or sewer owner/operator must coordinate any access issues with the property owner. 

The sewer owner/operator will determine the level of cleanup needed based on public access to the site and based on public health threats.  Access is assumed an issue in urban areas and public use areas such as parks or beaches and other sites where the public could be exposed to contamination.  Clean up will include, but not be limited to, removal of solids, vacuuming up free liquids and liming the ground.   Since lime can impact water quality, in some locations other methods should be employed.

How Facilities Should Report
As soon as possible, but no later than 24 hours of the release, facilities are required to report by methods approved by the department.  The preferred method to report will be e-reporting.  Telephone reports will still be taken by the Regional Office or the Spill Line on off hours or weekends and state holidays.   

Leaving voice mails, Emailing, or faxing a form does not satisfy the 24-hour reporting requirements. Written notification alone is not sufficient to satisfy the 24-hour reporting requirements.

Although e-reporting is the preferred method, sewer operators phoning in must speak to a department staffer.  The data required in the attached e-reports screen shot can be used by the facility staff to guide them in making a call.

Guidance for Permittees
The guidance sheet next is designed to be sent to permittees by department staff.  Staff may mail, email or fax the guidance to local officials, wastewater system staff or operators.  Reporting forms that follow should be attached when sending the guidance to facilities.

Guide for Wastewater Facilities Reporting SSOs and Bypasses

Reporting of all sanitary sewer overflows (SSOs) and treatment plant bypasses are required by Missouri Clean Water Commission regulation 10 CSR 20-7.015(9)(E) and your Missouri State Operating Permit [MSOP, also known as the National Pollutant Discharge Elimination System (NPDES) permit].  Failure to notify the Department may result in civil or criminal penalties for noncompliance.  Please refer to the Noncompliance Notification section of Part I Standard Conditions included as part of your MSOP. 

For the purpose of this report, a SSO or a Plant Bypass is defined as the diversion of wastewater from any portion of the wastewater collection system or wastewater treatment facility regardless if it reaches waters of the state.

During wet or dry weather, all SSOs from the collection system or bypasses at the plant are required to be reported within 24-hours on-line or orally (voice mail messages, Emails, or faxes do not satisfy this requirement) to the Missouri Department of Natural Resources.

Online reporting is preferred.  The e-reporting system is available at the department’s website.  Telephone reports will still be taken at the following phone numbers: 

Kansas City Regional Office 816-251-0700
Northeast Regional Office 660-385-8000
St. Louis Regional Office 314-416-2960
Southeast Regional Office 573-840-9750
Southwest Regional Office 417-891-4300
Weekends, holidays and after 5 p.m. DNR’s 24-hour Spill Line at 573-634-2436

Within five calendar days a final report is required.  It can be submitted online or in writing to a regional office.

Public Owned Treatment Works, or POTWs, that have a wet weather bypass at the plant may only need to report the discharge on their Discharge Monitoring Reports, or DMRs, according to 10 CSR 20-7.015(9)(E)2.   However, such reported discharges must not violate permit effluent limitations or permit standard conditions.  Permit Standard Conditions, Part I, does not allow for discharges that could result in potential endangerment to health or the environment.  Since there is a strong potential for endangerment and the likelihood is low that discharges could meet effluent limits, the department strongly recommends reporting all SSOs and bypasses.

Reporting required
SSOs from satellite sewer systems (communities or companies with sewer systems but without a treatment plant) should be reported by the satellite system to the regional office as described above.  Also, the satellite system should report to the receiving plant operator.

Reporting not required
Flows from combined sewers at permitted outfalls are not required to be reported as overflows.  But the sewer system must follow CSO requirements.

Basement backups are not required to be reported, unless the wastewater leaves the structure.  Basement backups should be tracked by the sewer system operator and the information made available to the department during inspections.

Discharges of gray water from homes or businesses are not required to be reported as SSOs by the local sewer owner/operator.  However, such discharges are not legal for the owners of the property and may be in violation of ordinances or other requirements in relation to community MS4 programs. Gray water discharges from regulated facilities are subject to MSOP requirements.

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9.4 Public Notice

The department's Public Information Office will be notified by the e-reporting system.

Guidance for Permittees about notifying the public
Next is an example of a sheet that may be sent to permittees or satellite sewer systems or other entities responsible for sewage spills

Sanitary Sewer Overflows
Plant Bypasses



Sewage discharges contaminate the environment with bacteria and other pollutants and can threaten public health. The Missouri Department of Natural Resources advises holders of wastewater discharge permits (Missouri State Operating Permits) or other owners/operators of sewer systems that it is their responsibility to inform the public of all sewage releases, other than their authorized discharge.  Overflows from collection systems or at wastewater treatment plants can occur during either dry or wet weather conditions

Dry Weather Discharges
Dry weather overflows occur when failures prevent the sewer system from transporting or treating wastewater. Failures can be due to line blockages, power outages, equipment malfunction, operator error, etc. The public should be notified of all dry weather discharges immediately when they occur by the most expedient method available.

If the sewage stays on private property, affected property owners can be notified by a visit, phone call, door hanger, or otherwise, in that order of preference.

If the sewage leaves private property, some form of public notification is recommended. Public notification may take the form of a news release to television, radio and newspaper outlets in the affected area, or a similar notification effort. Further, signs should be posted as soon as possible but at least within 12 hours anywhere the public has access to any waters that are affected by the discharge. The signs must contain an appropriate warning about health risks; such as, “WARNING! This water has been contaminated with sewage. Avoid contact!” Common posting points include beaches, parks, play grounds, low water crossings, or anywhere the public can reasonably be expected to have access to, or contact with, the affected water. Posting should remain in place until bacterial testing shows the water to be safe. (All permit holders who may be subject to posting should identify posting locations in advance and have signs already prepared.)

Wet Weather Discharges
Wet weather discharges occur when infiltration and inflow into a sewer system exceeds the system’s ability to transport or treat the flow. As a result, untreated wastewater, mixed with the infiltration and inflow, can flow from the system at various locations. Large discharged volumes or discharges of long duration have the potential to contaminate a drinking water supply or expose the public to health risks. The public should be notified of all wet weather discharges.  If there are possibilities of public contact with the effected water, posting on site should be done as described for dry weather discharges. Otherwise general notices are sufficient.

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9.5 DNR On-Site Response


In most cases, staff must consider a combination of factors to determine the level and type of response to undertake.

Required – conduct an on-site response.
Discretionary – respond at Regional Office discretion.  Coordinate with enforcement or management.
Unlikely – for this event DNR staff likely do not need to conduct an on-site response, unless other factors demonstrate a need for it.  Remember to consider the combination of all factors.

If no on-site response is planned, assure the discharge report or information has been forwarded to the appropriate party (owner, city, sewer district or local health department) and require they advise the Regional Office of the outcome in a timely fashion.

Condition Respond? Notes
Less than 1,000 gallons Unlikely Small overflows can still cause violation of WQS – be sure to look at all factors
1,000 to 50,000 gallons Discretionary  
>50,000 gallons Required An exception to the required response can be made for larger bodies of water such as the Missouri and Mississippi Rivers since dilution is a consideration.  
Discharge contained on facility property Unlikely  
Off facility property, did not enter Waters of State Discretionary Most discharges from manholes or lift stations would be considered off-property
Did not impact whole body contact waters – no public health threat Discretionary An example would be a discharge that entered and remained in a dry creek bed.
Likely an impact to a drinking water source or losing stream, sinkhole, etc.   Required An exception to the required response can be made for larger bodies of water that are drinking water sources such as the Missouri and Mississippi River since dilution is a consideration. 
Discharge reaches a cold water fishery Discretionary Consider the volume of discharge and the size of the stream
Discharge reaches outstanding state resource waters Required Refer to outstanding state resource waters in 10 CSR 20-7.031, Tables D and E.
Discharge into a public use or accessible area, such as a park or beach Required  
Discharge entered waters of the state with whole body contact use in quantities that could affect water quality Required

This is usually a consideration during the recreational season. 

An exception to the required response can be made for larger bodies of water such as the Missouri and Mississippi River since dilution is a consideration. 

Originating at a CAFO Required Discretionary if all of the discharge is held in secondary containment.
Causing a fish kill Required

Response required if department staff know that the fishkill is caused by a SSO or bypass.

If not an SSO or Bypass, coordinate with MDC to verify that the cause is natural (low dissolved oxygen in hot weather or cool weather turnover).

Ongoing Release Discretionary
  • On-going and impacts not known and/or repair of problem, containment, cleanup, etc. are uncertain – it is more likely that the RO should respond.
  • On-going, but it is a small release, there are likely no impacts to WOS or health, the operator has people and equipment on site, and it’s likely the SSO will be stopped soon – more likely that RO would not respond.
  • Terminated and contained discharge – more likely that RO would not respond.
Timelines of report Discretionary

Did facility report as soon as possible or wait until near the 24-hour time limit?

Likely respond if delayed.

Incomplete, contradictory, or questionable “24-hour” report Discretionary Before responding, it is recommended to call the facility to clarify information in the report.
Facility currently an enforcement case Discretionary Staff must coordinate with enforcement to determine whether or not an on-site response is required.
Facility history of non-compliance Discretionary Usually it is recommended that staff respond

Overriding considerations

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9.6 DNR Response

Staff Preparation to go into the field.

In Office Activities:

  1. Gather pertinent information:   
    • Responsible Party - Name, title, Phone #, location, details of what happened and when.
    • Citizen (complainant) - Name of water body, location, suspected source, magnitude of fish kill (if one), types of dead fish, appearance and odor of water. 
  2. Notify the following:
    • Supervisor or next in chain of command and regional director.
      • The supervisor may request a job code at this time to track event response costs
    • EER in Jefferson City (spill line), and Public information staff will receive notification from the E-reporting system.  At Regional Office staff or management discretion, EER, Public information staff, or upper management should be called.  This would be for high profile situations as to media interest, elected officials’ interest, public health threats or much impact to the environment.
    • Local health department if public health issue.
Note icon.

Note: EER staff will contact MDC of fishkills

  1.  Gather Equipment:       

On Site Activities:

Sample Locations:

              Sample Parameters:

*Also refer to Compliance Manual and Operations Manual.

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9.7 Sampling

When Sampling Should Be Done
Wet weather – Typically no sampling is recommended.  There may be circumstances where department staff can use their discretion to require sampling by the responsible party.

Dry weather – Usually sampling is recommended.  However, it should be conducted by department staff for certain circumstances.

Sampling recommendations or requiring sampling will be at the discretion of the department staff responding to the event.

Who Should Sample
Department staff may request the facility staff take samples and have them tested. 

At the discretion of department staff, regional office staff takes and tests samples based on issues such as these.

Sample Locations and Test Parameters

Sample Locations:

Sample Parameters:

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9.8 SSO/Bypass Compliance Process

Note icon.

Note:  Staff should also refer to the Compliance Manual.

CC&P may involve the issuance of a Letter of Warning, or LOW, or Notice of Violation, or NOV.  The department’s CC&P policy shall be followed in accordance with Section 3 of the Compliance Manual

Wet Weather SSO/Bypass Compliance Actions:
A wet weather event is the discharge of wastewater from the sanitary sewer collection system or the treatment plant that is the direct result of a storm event.

Any wet weather by-pass that causes a violation of Water Quality Standards, general or specific criteria, will result in additional actions as indicated in the Compliance Actions section below. 

Compliance Actions:


The following violations are subject to issuance of a Letter of Warning (LOW) if the overflow/bypass does not result in a violation of Water Quality Standards, general or specific criteria:

  1. The overflow/bypass is caused by failure to implement standard operation and maintenance procedures.
  2. The overflow is due to inadequate system capacity to handle dry weather flow and the owner or operator disputes this conclusion.  If the owner or operator disputes this conclusion the Regional Office shall require submission of an engineering evaluation.
  3. Failure to report the SSO/bypass in a timely manner.

Generally, if the overflow/bypass results in an on-site investigation as documented by the Department, an LOW will be issued for any violation not requiring a NOV.  However, the regional office has discretion to not issue LOWs for situations beyond the control of the facility that do not cause environmental harm or violation of Water Quality Standards General or Specific Criteria and in which they have acted responsibly in reporting and correcting the incident. 


The following violations are subject to issuance of a Notice of Violation:


An enforcement action request will be written to refer the case to Water Protection Program enforcement for these circumstances:

  1. Has a required response specified in rule or guidance.  This includes overflows that cause fishkills and overflows from CAFOs that are not contained in secondary structures.
  2. In all other cases, the issuance of Enforcement Action Request will be left to the discretion of the Regional Office Directors after consideration of all pertinent factors or consultation with Water Protection Program Enforcement staff.





Significant health and/or environment threat








Required response per law








Dry weather – violation of water quality standards




Wet weather – violation of water quality standards




Failure to operate and maintain properly

If previously informed






Capacity issues

If previously informed






Failed to report in a timely manner

If stream impacted





If on-site investigation was done

At RO discretion



Cost Recovery
Early in the investigation of a SSO or bypass, staff should establish a job code to track time for use in cost recovery processes. This would be for SSOs or bypasses where there is a possibility that the amount of staff time would be significant.  See Section 9.3 of the Compliance Manual for more information.

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9.9 DNR Data

Where Is Bypass Information Kept
The e-reporting system is  functional and all SSO/bypass data will be stored there. Phoned-in reports will be entered into the system by regional office staff.

The SSO/Bypass reporting system is part of the Missouri Clean Water Information System on the DNR webpage at http://dnr.mo.gov/mosso.

Previously, regional offices keep information in facility files and some offices used  separate databases to track and store information.  There was no common format or database in use, therefore searches for information from before the third quarter of 2011 are available in these various records.

What Is Done With Bypass Data
This information can be reviewed during SSO inspections or enforcement actions.  This information can be used to direct a system to areas that need improvement – such as finding the manholes or watersheds that have the most problems. Examples of issues for which information can be sorted:

9.10 E-Report System

The department has developed an electronic reporting application that also serves as a database to store SSO and bypass information.  DNR users can access the application through the department’s SSO Bypass Event System webpage.  Facilities must log in to the Citizen’s Application Gateway to gain access to the application .  Instructional videos are available as a link in the application or on the Sanitary Sewer Overflow Bypass System Help webpage.

Wastewater systems are encouraged to use this application rather than calling or mailing in reports (both the “24-hour” report and the “5-day” final written report). Wastewater system staff can still phone or write in and DNR staff in the regional offices will enter the data in the e-reporting application.

Currently, the e-reporting application cannot accept reports from satellite systems.  The application draws facility information from the MOCWIS permitted facility data.  Satellite sewer systems do not have a Missouri State Operating Permit (NPDES permit) because they do not discharge wastewater to the environment; they discharge to another system that is permitted.  Future plans are to improve the e-reporting application to be usable by satellites.    

Reports that summarize SSO and Bypass information are available on the department’s rePortal.