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2004 Combined Sewer Overflow Statistically-Valid Noncompliance Rate Study

Combined sewer overflows (CSOscombined sewer overflows) and SSOs (sanitary sewer overflows (SSOs) are significant environmental compliance problems. SSOs and CSOs pose a significant threat to public health and the environment because they carrydue to high concentrations of bacteria from fecal contamination, as well as other disease-causing pathogens and viruses. The Combined Sewer Overflow Statistically-Valid Noncompliance Rate Study was undertaken by the EPA in 2002, to determine the rate of compliance for the more than 900 combined sewer systems (CSS) across the United States. It was repeated in 2004 to determine compliance trends. The following are the results of that second study and what EPA has determined about trends.

The Combined Sewer Overflow Statistically-Valid Noncompliance Rate Study was undertaken by the EPA in 2002, to determine the rate of compliance for the more than 900 combined sewer systems (CSS) across the United States. This study was repeated in 2004 to determine trends in compliance over time. The 2004 results show that, while progress has been made in compliance with required controls, there is still work to be done. EPA’s Office of Enforcement and Compliance Assurance (OECA) and Office of Water are continuing their efforts to reduce combined sewer overflows. Given the scope and serious impact of overflows on public health and the environment, OECA has made CSOs a National “Wet Weather” Enforcement and Compliance Assurance Priority since 1998.

Combined sewer systems are designed to collect rainwater runoff, domestic sewage and industrial wastewater in the same pipe. During periods of heavy rainfall or snow melt, the wastewater volume in a combined sewer systemCSO can exceed the capacity of the system or its treatment plant. When the capacity is exceeded, the excess wastewater flows into nearby streams, rivers or other water bodies. These combined sewer overflows can contain not only storm water, but also untreated human and industrial waste, toxic materials and debris. Exposure to contaminated sewage can increase the risks of contracting serious stomach ailments.

There are approximately 836 permits in the United States for combined sewer systems in the United States. The study showed that:

Affected communities are located in 32 states and the District of Columbia, and serve approximately 46 million people, primarily in the Northeast and Midwest.
Annual discharges from CSOs are estimated to be 850 billion gallons (based on EPA modeling).

Given the scope and serious impact of overflows on public health and the environment, EPA’s Office of Enforcement and Compliance Assurance (OECA) addresses CSOs as a national priority. CSOs have been a part of the National “Wet Weather” Enforcement and Compliance Assurance Priority since OECA’s 1998-1999 annual work planning cycle. CSOs were selected in1998 because, though efforts to control these problems had been underway for several years, many areas still needed compliance assistance, compliance monitoring, and/or enforcement. EPA, with strong support from States and other stakeholders, renewed CSOs and SSOs as continued Clean Water Act/Wet Weather enforcement priorities for 2005-2007, based on: 1) significant environmental impact to human health and the environment from overflows; 2) widespread noncompliance with EPA’s 1994 CSO Control Policy; and 3) the need for a nationally consistent approach to address noncompliance. Detailed information about this priority is available at http://www.epa.gov/compliance/data/planning/priorities/cwacso.html.
CSOs, and SSOs, which separate domestic sewage from rainwater runoff, were included as national priorities in 1998 because, though efforts to control oeverflow problems had been underway for several years, many areas still needed compliance assistance, compliance monitoring, and/or enforcement. EPA, with strong support from states and other stakeholders, chose to continue CSOs and SSOs as Clean Water Act/Wet Weather enforcement priorities for 2005-2007, based on: 1) significant environmental impact to human health and the environment from overflows; 2) widespread noncompliance with EPA’s 1994 CSO Control Policy; and 3) the need for a nationally consistent approach to address noncompliance.

EPA, often in partnership with states, has reached important settlements with numerous municipalities and local governments across the country to address CSO and /SSO violations that impacting many of our nation’s watersheds. (EPA to date has entered into approximately 35 CSO judicial orders, 25 SSO judicial orders, 60 CSO administrative orders, and 95 SSO administrative orders.)

Results of the Study:

The 2004 CSO Statistically-Valid Rate Sstudy looked at facilities’systems’ compliance with the requirements for Nine Minimum Controls (NMCs) and Long Term Control Plans (LTCPs) requirements over . The 2002 CSO study looked at systems’ compliance with the Nine Minimum Controls only because EPA felt that implementation of the LTCPs was premature at that time. The statistically-valid noncompliance rate approach relies on a method of estimating the compliance rate for the entire population of combined sewer systems from a moderate-sized sample of just over 200 inspections.

Nine Minimum Controls

Overall NMC Compliance Rate looks at the controls required in a permit or order, usually issued by the state (i.e., there could be fewer than nine controls required of a given facility). Rates are at the 90% confidence level.
• 47% (± 4.8%) or less than half, of systems had a 100% compliance rate with required NMCs;
• 78% (± 4%) of systems had a compliance rate of 70% or greater for required controls.

The majority of combined systems are not in compliance with the nine minimum controls, though they were supposed to be in compliance by 1997.

 

Compliance Rate for Adequate Documentation of Individual Controls ranged from 69% to 83%; for the controls of solid and floatable materials, and elimination of dry-weather CSOs respectively.

Compliance Rate for Implementation of Controls ranged from 69% to 86% for the controls of solid and floatable materials, and implementation of pollution prevention programs and control of dry-weather CSOs respectively.

Some specific controls need additional focus. In particular, the 14% of systems that are still experiencing dry weather overflows need to be investigated by EPA and the states.

 

Comparison to 2002 NMC Rates (note: the 2002 combined sewer system universe was 954 facilities; in 2004, it was 881)

• The overall NMC Compliance Rate for 2002 was 45.6%, which is not statistically different than the 2004 rate of 47%;
• The percent of systems with no NMC requirements in their permits dropped from 7.4% in 2002 to 2.4% in 2004;
• The percent of facilities required to document and implement at least one of the NMCs increased from 45.6% in 2002 to 61.4% in 2004.

Given these results, EPAdetermined that more work is needed. However, the increase in the percentage of systems with NMC requirements in their permits and the increase in requirements for those with permits are good indicators of progress within the state and EPA permitting program.

 

2004 Long Term Control Plan Rates
• Systems with an LTCP required in a permit or enforcement order - 78.5% (± 4%)
• Of the systems required to have a LTCP, 85% (± 3.5%) had developed one.
• Of the facilities that had developed a plan, 70.5% (± 4.3%) had started to implement it.

EPA is encouraged that almost 80% of combined sewer systems are required to have a Long Term Control Plan and that most of these systems have begun to both develop and implement the plan.

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