• Novice
  • Aware
  • Competent


This topic covers:


The following are highlights from "CMOM" - "Capacity Assurance, Management, Operations and Maintenance", the USEPA's Proposed SSO Rule under PL 92-500, The Clean Water Act.

CMOM is a comprehensive program constituting a proposed regulatory rule for "proper operation and maintenance" of the wastewater system as required under the Clean Water Act, with a particular focus on the collection system.

The rule updates long-standing NPDES permit regulations by focusing on collection system capacity, management practices, and operations and maintenance procedures.

If properly applied, it can result in cost savings when compared to conventional approaches.

Built around six required elements, the CMOM plan can be viewed as essentially an internal manual for the system's capacity assurance, system management, and maintenance. Many of the required elements are founded on Best Practices of asset management.

The nation's Clean Water Act prohibits "sanitary sewer overflows". A sanitary sewer overflow (SSO) is a release of untreated sewage from a sanitary sewer system, and constitutes an "unauthorized discharge" in violation of the Clean Water Act.

SSO discharges can occur at locations throughout the sewer system including basements, streets, through manholes, and pumping stations.

SSOs happen when flow in the sewer system exceeds the system's hydraulic capacity. They are often associated with:

  • Wet weather events, when rainfall-induced inflow and infiltration ("I/I") increase wastewater flows beyond the design capacity of the sewer system
  • When the dry weather design capacity is exceeded due to growth or has deteriorated due to inadequate maintenance (including renewal).

SSOs, by themselves or in combination with other pollutant sources, can affect the quality and uses of surface waters. SSOs present a potential threat to public health because of bacteria, viruses, pathogens and other pollutants contained in the wastewater.

USEPA has drafted a rule to clarify what is necessary to avoid SSOs.USEPA has filed a Federal Register notice to provide guidance, policies, and proposed regulations to clarify, and add new requirements, to the National Pollutant Discharge Elimination System ("NPDES") permit requirements for municipal sewer collection systems and SSOs.

The notice includes proposed modifications to NPDES permit requirements for collection systems, and is intended to clarify the application of existing NPDES standard permit conditions for SSOs.

The clarification offers "plain-English" regulatory interpretation of the existing requirements in ยง122.41 and 42, "proper operation and maintenance", and "duty to mitigate". (In accord with the request of the Municipal Caucus of the Federal Advisory Subcommittee, this clarifying language may serve as an "affirmative defense" in excusing violations.)

The proposed "Capacity, Management, Operations and Maintenance" or "CMOM" rule also presents new requirements for planning, analysis, prioritization, and audits.

The crux of the rule was developed from wastewater industry Best Practices. CMOM defines "proper" operations and maintenance ("O&M") and collection system management (122.41(e); 122.42(e))

CMOM - the Big Picture

CMOM is itself a subcomponent of the federal rules that administer PL 92-500, the Clean Water Act.

First passed in 1972, then substantially amended in 1986, the Clean Water Act affects virtually every aspect of water resource management - both public sector and private - from wastewater to stormwater.

While the Act is not new, rulemaking (how to administer the Act) has occupied much of its 30-year history. Many of these rules are now firmly in place; their ramifications are now reaching the agendas of our municipal agencies.

To understand where CMOM fits into the management of urban sewer systems, it is essential to understand the bigger picture.

There are three categories of sewer systems, depending upon how the sewerage system was initiated:

  • Sanitary sewer systems, which are installed today in some form in any urban area. These systems can serve an entire region (e.g., City and County of Los Angeles) or the newer portions of cities served by combined sewers. Sanitary sewers are to be regulated by CMOM.
  • Separate storm sewer systems, which collect and convey stormwater to stormwater treatment facilities or watercourses or, in those municipalities with combined sewers, to the combined sewer system. Storm sewer systems are regulated by another set of rules promulgated by the USEPA.
  • Combined sewer systems, receiving both sanitary sewage and stormwater runoff. Combined sewer systems were used in cities from last quarter of the 19th century to the 1960s, and most of the older eastern cities and a few western cities of the United States have combined sewers in the lower portions of their systems. Examples are Washington, DC, St. Louis, MO and San Francisco, CA. Combined systems are regulated under the "nine minimum controls" program of the USEPA.

Rulemaking about each type of system under the Clean Water Act has been substantially driven by legal initiatives from environmental groups, and has caused or will cause the owners of the sewer system to undertake comprehensive investigations of their systems.

The investigations include inspection, cleaning, identification of rehabilitation and relief needs, and preparation of CIPs (capital improvement programs) to fund the improvements over multi-year periods.

What is CMOM?

CMOM is a comprehensive program constituting the existing regulatory requirement for "proper operation and maintenance" (CFR 122.42(e)).

If properly applied, CMOM can result in cost savings when compared to conventional approaches.

The CMOM plan can be viewed as essentially an internal manual for the system's capacity assurance, system management, and maintenance.

Systematic documentation avoids the pitfalls of "mortal databases" - those talented employees with it "all in their head" who will not be around forever.

CMOM is an acronym for "Capacity, Management, Operations, and Maintenance":

  • "Capacity" deals with adequate installed pipe size, the requirement to maintain effective system capacity, and to minimize inflow and infiltration (I/I)
  • "Management" means coordinating measures to assure that the system of assets performs as designed over time
  • "Operations" means running pump stations, diverting flow, etc.
  • "Maintenance" means inspection and repair, refurbishment or replacement as necessary to sustain system performance - rodding, jetting, caulking/grouting, root removal, and the like.

Purpose of SSO Rule

Nationally, collection systems represent a $1.8 trillion public investment in infrastructure.

Many systems have deferred maintenance, resulting in system deterioration and reduced capacity, and therefore:

  • SSOs - a violation of the Clean Water Act
  • excess treatment costs for dilute flows
  • basement backups
  • customer complaints
  • emergency repairs.

CMOM's focus is on proper system management, not merely on the design storm or the number of SSO events per year.

Proper management will eliminate overflows except those truly "unavoidable" (due largely to wet weather flow).

Timing of Rule

The Draft Rule was proposed in early 2001. Formal comments on the draft have been received and the rule has been advertised in the Federal Register.

However, Final Rule adoption is stalled in Congress.

Once adopted, the rule will move to the States for adoption (which will require approximately 1 year after approval by Congress).

CMOM program will be due on NPDES permit renewal cycle (5 years).

While the rule is currently stalled in Congress, we note that many "compliance orders" and "consent decrees" rendered by USEPA since 2003 for SSO violations have incorporated many aspects of CMOM into the mandated corrective requirements.

The rule can be tracked at the USEPA SSO Rulemaking website at www.epa.gov/owm/sso.htm.

Why is CMOM important?

CMOM programs generally incorporate many of the "best practice" operation and maintenance (O&M) activities that are routinely implemented by conscientious operators of collection systems.

The objective of CMOM is to optimize sewer system performance by taking full advantage of ongoing O&M, and placing it in the context of structured planning and implementation activities, with an emphasis on prioritization of problem areas.

The current performance of many collection systems is poor, with widespread SSOs. Collection systems corrode, erode, collapse, clog and ultimately deteriorate and fail in the absence of proper CMOM.

CMOM programs are needed to protect and safeguard this infrastructure. They help to ensure that the labor, equipment, and materials required to maintain the integrity of collection systems are made available so that the systems can efficiently collect, transport and treat sanitary sewage.

In the case of capacity-related SSOs, system-wide analysis must be undertaken to diagnose and target problem areas.

Note that, while the primary focus of the rule is the collection system, capacity issues that are traced to treatment plants are included within the embrace of CMOM. Both capital and maintenance investments may be needed to correct capacity deficiencies.

USEPA's proposed rule on SSOs includes a general NPDES permit condition requiring permittees to properly manage, operate and maintain, at all times, all parts of [their] collection system.

All NPDES permit holders will therefore be required to develop and implement CMOM programs "appropriate and applicable" to their system.

Why Act Now?

CMOM principles are, in reality, established "Best Practices" in asset management.

It is a comprehensive program that incorporates performance measures and targeted, measurable Levels of Service.

Deployment of the program:

  • improves customer service and reduces complaints
  • improves system performance and long-term "Asset Management"
  • provides comprehensive documentation for internal use by new staff and among departments
  • supports budget requests for effective operations and maintenance
  • improves efficiency that may result in savings or redirection of resources toward backlog maintenance.

What's New With CMOM?

CMOM is not just another plan, or even just documentation, it is a program of system-wide management action.

Most of CMOM consists of what a well-managed agency should be doing already - but there are some new elements such as:

  • establishing legal authorities for controlling flows and setting design standards
  • executing a system evaluation and capacity assurance plan if peak flows contribute to SSOs.

Other provisions of note:

  • constructed overflows will be phased out under the proposed rule
  • a written "Overflow Response Plan" must be adopted with specific criteria for notification of interested parties (e.g, drinking water purveyors) and for the public, for defined events
  • annual SSO reports must be made available to the public.

CMOM - The Affirmative Defense

The emphasis of CMOM is on demonstrating that the organization has taken all feasible actions to avoid SSOs, both maintenance related, and non-maintenance related.

A CMOM Program will be "...one of the first pieces considered when USEPA looks at taking enforcement action." (An "affirmative defense" against enforcement actions).

CMOM Program Components

A good CMOM program will strike a balance between O&M activities and management activities.

O&M activities are viewed as central to collection system performance.

Management activities are complementary as they provide:

  • System-wide planning and prioritization for O&M activities
  • An implementation schedule for more capital intensive renewal efforts.

Taken together, these CMOM components provide a solid platform for safe, efficient and economical operation of collection systems over the long term.

It should be noted that many of these clarified elements are not new, but detail better what is meant by the terms "proper O&M" and "duty to mitigate" as contained in the Clean Water Act.


Every O&M program should be built on routine maintenance, inspection and assessment. Routine, preventive, and predictive maintenance is important in the identification and repair of problems before they are elevated to emergencies.

O&M programs should also include regular line cleaning and inspections to check for root, insect, rodent, and odor problems.

The current physical condition of the collection system should be assessed through investigation of the structural integrity and capacity of the collection system and treatment facilities.

This is typically accomplished through manhole inspections, internal TV inspections, and smoke and dye testing.

New sewers and new system connections need to be properly designed, installed, tested, and inspected to ensure that additional flows are within the system capacity.


Planning activities are necessary to ensure that limited municipal dollars generate the maximum benefit in terms of collection system performance.

When managing a collection system, it is important to assure that the system maintains adequate capacity to carry all levels of flow, and that treatment facilities can effectively treat those flows, to comply with permit requirements.

Planning activities include:

  • Identifying and prioritizing structural and hydraulic deficiencies
  • Developing and implementing short- and long-term rehabilitation plans to address them
  • Surveying the peak flows from municipal satellite collection systems (collection systems located outside the municipal boundary of the wastewater treatment authority), which are discharging to the collection system for the receiving wastewater treatment plant. For those satellite systems that contribute significantly to peak flow conditions, corrective measures should be imposed through service agreements to keep satellite systems from exceeding peak flow allocations
  • Designing a comprehensive emergency overflow response plan that includes a strategy for addressing potential system failures and procedures for mitigating overflows and reporting SSOs to the proper State and/or local health agencies.

Implementation procedures are the means for coordinating the O&M and planning components of a good CMOM program. The major activities required include:

  • Development and maintenance of a system to analyze and manage information (not necessarily computer-based) for compiling and accessing information relevant to the CMOM program, including:
    • Maintaining a map of the collection system (an atlas of design drawings may suffice)
    • Prioritizing CMOM activities
    • A procedure to identify and illustrate trends in overflow occurrences
    • A system to track work orders.
  • Documentation of collection system performance measures
  • Evaluation of system components determined to lack adequate hydraulic capacity
  • Development and enforcement of sewer-use ordinances, which require all sewer system elements to be properly designed, constructed, inspected, and maintained. It is also important to use legal agreements to manage wastewater flows received from satellite collection systems
  • Public notification in such a manner that persons can take actions to avoid exposure to overflows
  • An education program including employee training, such as an operator safety program, and outreach to the public about wastewater treatment and its impact on water resources.

CMOM - The Five Performance Standards

A CMOM program must meet 5 performance standards:

1. Properly manage, operate and maintain all parts of collection system.

2. Provide adequate capacity.

3. Mitigate the impact of sanitary sewer overflows.

4. Provide notification to parties who may be exposed to an SSO.

5. Document the CMOM program and make documents available to the public upon request.

CMOM Management Program - Meeting Performance Standards

CMOM requires the implementation of six elements in order to meet "General Standards" defined in the rule:

1. Set written program goals.

2. Identify who in your organization is responsible for performing specific program activities.

3. Establish legal authority.

4. Develop appropriate activities (e.g. track system performance).

5. Develop design and performance provisions.

6. Track program implementation and effectiveness.

The Six CMOM Program Elements - An Overview

Each CMOM program must contain six "Program Elements". A brief description of each of the six elements follows.

Written Program Summary (which must reflect all six elements)

  • Written and measurable goals - utility driven, responsive to CMOM
  • Organization structure and responsibility - with emphasis on identifying responsible staff, lines of authority, reporting
  • Legal Authority - ordinances and agreements for:
    • Flow
    • Design/installation and inspection
    • Pre-treatment
    • Agreements with satellites (public and private-but public satellite will be newly regulated)
  • Measures and Activities:
    • Provide adequate facilities and equipment to support system
    • Maintain collection system map
    • Manage and use information to prioritize CMOM activities and identify trends in overflow occurrences
    • Execute routine preventive maintenance
    • Assess current capacity, identify capacity deficiencies, and assure adequate capacity for growth
    • Identify and prioritize peak flow capacity deficiencies and implement rehabilitative actions for each deficiency
    • Train staff in CMOM program
    • Maintain equipment and parts inventories
  • Design and Performance Provisions:
    • Standards for installation of new and major rehabilitation/replacement projects
    • Procedures for inspecting and testing installation of sewer components
  • Tracking Collection System Performance
    • Measure effectiveness of CMOM program using written performance indicators
  • Communications:
    • Public education as well as public notification and involvement
    • Incorporates "Communications" piece of "Overflow Response Plan"
    • Incorporates "Record Keeping and Reporting" provisions - especially provisions for public notice
    • Generally provides for public input in strategy preparation (use existing public input process).

System Evaluation and Capacity Assurance Plan

  • Utilize Sewer System Evaluation Survey ("SSES") logs, flow monitoring, and overflow trend analysis to identify peak flow problem areas
  • Optimize corrective actions (use small-basin analysis), review alternatives, and prioritize
  • Include steps to ensure that adequate future capacity is maintained in areas not fully built out

Overflow Response Plan

  • Procedures to promote a rapid response and 'mitigate' impact of any overflow
  • Coordinate with interested parties such as drinking water authorities and health departments
  • Prepare plan for criteria for public notification (e.g., yellow tape is adequate for small spills, up to recreational waters closures)
  • Train staff to mobilize quickly and investigate reports

CMOM Program Audits

  • Baseline audit is the first step in the CMOM process
  • Identify gaps between program elements that may be in place already, CMOM requirements, and your program goals
  • Iterative process to track implementation and next steps
  • Internal audit (can be done by a consultant), unless progress is unsatisfactory

previous home next
Emergency Response Plans   Asset Maintenance