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 (WPCB), Environmental Services Program (ESP) and regional office staff. 

The primary purpose for this guidance is to describe the procedures for addressing sanitary sewer overflows (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.  Any discharges from these locations are required to be reported to the department as bypasses because the water has not been fully treated.

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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

Per permit Standard Conditions Section B 3. as revised November 1, 2013

If the SSO reaches waters of the state or it may pose an imminent or substantial endangerment to the health of welfare of persons, the permittee shall notify the department within 24 hours and follow-up with a final report within five days.  The preferred method to report will be electronically through the department’s website.  Telephone and faxed 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 five-day final report are still acceptable and can be sent to the regional office.

If the wastewater does not reach waters of the state and is not expected to pose an imminent or substantial endangerment to the health of welfare of persons, SSOs and bypasses can be reported with the next discharge monitoring report (DMR).  SSOs such as this occur typically during wet weather events.

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 an 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 SSOs.  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. This would be for the uncommon situation where a series of service lines are connected to a common main and the main has not been conveyed to an operating authority.  Those individuals will be responsible for any water quality impacts associated from discharges from those lines, the laterals and the main.  If the small common main line (such as a mobile home park without its own treatment plant) connects to a permitted collection system (which would be the continuing authority), the operator of the permitted system should not be considered responsible unless the cause of the discharge originates from their system (e.g., a grease blockage).  For these situations the department would pursue a remedy with the owner of the small common main if there is a violation of WQS and not take enforcement action on the larger system (if the problem was not caused by their main line).  The department would report the situation to the larger system so that they may follow-up with the smaller system through their local ordinances, contracts or other agreements.  Under certain circumstances, the department may take enforcement action with the larger system if the issue violated an MS4 requirement.

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, e.g., some small municipalities, subdivisions, mobile home parks, and industrial parks, 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.  A release from any part of the collection system would constitute a discharge without an MSOP, and could cause violations of 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 an MSOP 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, unless the issue is caused by the homeowner’s service line.  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.  Public access areas include urban areas, parks, 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 appropriate regional office or the Spill Line on off hours or weekends and state holidays.   

Leaving voice mails or e-mailing a form does not 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

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 Part I, Standard Conditions, Section B of your MSOP. 

For the purpose of this report, an 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.

If the SSO reaches waters of the state or it may pose an imminent or substantial endangerment to the health of welfare of persons, they are required to be reported within 24-hours on-line, orally, or by fax (voice mail messages and e-mails 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 the appropriate regional office.

If the wastewater does not reach waters of the state and is not expected to pose an imminent or substantial endangerment to the health of welfare of persons, reports shall be provided with the permittee’s or owner’s next discharge monitoring report.

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 allowed under the Missouri Clean Water Law; any such discharges would be subject to MSOP requirements.  Additionally, the owners of the property may be in violation of local ordinances or other requirements in relation to community MS4 programs.

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9.4 Public Notice

The department's public information office will be notified by the SSO 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 that 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, or operator error, etc. The public should be notified of all dry weather discharges 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 affected 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 – response 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 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 rivers 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 number, 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: EER staff will contact MDC of fishkills
  1. Gather Equipment:       
    • Another person (if possible).
    • Departmental ID.
    • Maps (road and topo/aerial).
    • Spill response kit (sampling equipment-cubies, DO meter, gloves, etc.).
    • 4WD vehicle, if available.
    • Phone.
    • Coolers.
    • Boots/waders.
    • Camera.
    • Video camera (if possible).
    • Copy of name/numbers of people you may need to contact.
    • GPS unit.

On Site Activities:

Sample Locations:

Sample Parameters:

*Also refer to Compliance 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 (LOW) or notice of violation (NOV).  The department’s CC&P policy shall be followed in accordance with Chapter 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.

In general, wet weather investigations and compliance actions are much less common than dry weather. However, any wet weather bypass that causes a violation of water quality standards, general or specific criteria, or otherwise creates a significant environmental or health violation will be investigated and will result in an NOV.  Chronic wet weather discharges and reporting issues are primarily addressed through the SSO inspection protocol.

Dry Weather SSO/Bypass Compliance Actions

There are many factors that must be considered when determining if an LOW or NOV is appropriate following a dry weather SSO/bypass investigation.  The following chart provides guidance for most situations, but is not all inclusive – difficult or unusual situations should be discussed with WPCB enforcement staff before decisions are made.  Additional guidance is provided following the chart.

Dry weather SSO Investigation Findings

No violation cited







Violation of water quality standards (WQS) general or specific criteria (w/ no fishkill)



Consult with Enforcement

>50,000 gallons discharged (investigation required)




Failure to report within 24 hours and/or 5 days




Failure to provide timely or appropriate clean up




Operation and maintenance Issue




Inadequate capacity




Service line discharge caused by permittee’s main line issue




Service line discharge (not caused by permittee’s main line) that does not cause WQS violations {note we would not typically respond to these}

√ discuss MS4 with city




Service line discharge (not caused by permittee’s main line) with WQS violations



√ to homeowner


Discharge leaves permittee’s property of origin but does not reach waters of the state (most discharges from manholes or lift stations would be off property)


√ if we investigated



Discharge reaches waters of the state but no public or environment threat (not to WBC stream, cold water fishery or public beach,etc) and no WQS violation




Discharge reaches losing stream, sinkhole, DW source, WBC stream or public use area(potential for adverse impact on public health or env.) but no WQS violation



Consult with enforcement


CAFO discharges held in secondary containment




CAFO discharges



Yes, if WQS violations

2nd time any of the above LOW issues are found same at the same location within 12 months of LOW



Probably, consult with Enforcement

Multiple (2 or more) LOW issues seen during same event




Multiple violations seen during same event, some LOW level and some NOV level




Multiple minor SSOs which do not individually warrant investigation

√ review during SSO inspections




Multiple O&M, capacity or reporting violations, which have previously received LOWs, for any locations




Facility currently in enforcement*





History of noncompliance*





Catastrophic Event with Governor-issued Disaster waiver






Additional Guidance:

Cost Recovery
Early in the investigation of an SSO or bypass, staff should establish a job code to track time for use in the cost recovery processes. A job code should be established for SSOs or bypasses where department staff conduct an inspection and determine the event warrants issuance of an NOV.  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 and 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 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.