EPAs CSO Policy

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EPAs CSO Policy

• Environmental Law I
• Fall 2005

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Whats Combined in a Combined Sewer System?

• Sanitary waste
• Pretreated industrial waste
• Stormwater collecting in sewers

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Where the Combined Sewers Are
750 out of 20,000 systems nationwide
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How a CSO Happens
Feeder lines
Trunk or Interceptor
Sewer Plant
CSOs
River
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Where the Bflo CSOs are . . .
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A view from the river
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Primary Legal Handle for CSOs

• CSOs are subject to NPDES permit program
  (including water quality based standards)

• CSOs are not subject to secondary treatment
  requirements for POTWs
• Primary screen out solids, disinfect
• Secondary digest the sewage (activated sludge,
  e.g.)

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Problems in CSO regulation

• Most CSO fixes are extremely expensive
• Unfunded mandates (a political and a legal
  problem)
• Unfunded Mandates Act
• Federalism/10th Amendment
• Lapse of federal sewer grants and replacement
  with revolving loan fund
• Passing burden to urban ratepayers

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Current Solution EPAsCombined Sewer Overflow
Policy(33 USC sec. 1342(q))

• Phased implementation considering a communitys
  financial capability
• Guidance, not binding
• Flexible and site-specific
• Try to force localities and states to engage in
  coordinated planning

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Short-Term/Long-Term Strategy

• Short term (within 2 years) adopt the Nine
  Minimum Controls and document it

• Develop a long-term plan based on adequate
  understanding of the sewer system and water body,
  local financial ability

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Nine Minimum Controls (pt. 1)

• Assure proper operation, regular maintenance
• Maximize system storage capacity
• Maximize flow to the POTW for treatment
• No CSOs in dry weather

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Nine Minimum Steps, pt. 2

• Control solids and floatables in CSOs
• Use pollution prevention
• Give public notice of CSO occurrences, impacts
• Monitor to characterize CSO impacts, efficacy of
  controls

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Long Term Control Plan (1)

• Characterization, monitoring, modeling of the CSS
• for a range of storm events
• N, location, frequency of overflows
• volume, mass, concentration of pollutants
  discharged
• impacts on designated uses of receiving waters

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Characterizing the sewer system

• Examine complete rainfall record for area
• Evaluate flow variations in river
• Correlate CSOs to receiving water conditions
• Document overflows in relation to sensitive areas
  and pollution sources (can you move or relocate
  outfall?)

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Monitoring of CSOs

• Should be comprehensive and representative
• Should include frequency, duration, flow rate,
  volume, pollutant concentration in CSOs
• Also should include impact of CSOs on receiving
  waters

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Uses of Modeling

• EPA supports the proper and effective use of
  models, where appropriate
• Sophistication of the model should relate to the
  complexity of the system and the information
  needed
• Continuous simulation models using historical
  rainfall data are best

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Consideration of alternatives

• Zero overflows per year
• 1 to 3 overflows/yr
• 4-7 overflows/yr
• 8-12 overflows/yr

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Presumption vs. Demonstration

• If it meets any of the following criteria, the
  controls are presumed adequate otherwise, you
  have to prove it

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• No more than 4-6 overflows per year, on average
• System-wide average capture during storm events
  of 85 of the flow volume
• Removes at least the mass of pollutants causing
  impairments

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Cost-Performance Curves Finding the Knee of the
Curve
Cost
Pct Captured
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What if too much stormwater gets to the treatment
plant?

• Bypasses--40 CFR 122.41(m)
• Unavoidable to prevent loss of life, personal
  injury, or severe property damage
• No feasible alternative
• Notice is given

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Buffalos Long-Term Study
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Automated monitoring (Hydrolab Datasonde 4) All
10 sites, sample every 15 minutes
Analyze for conventional parameters (DO,
turbidity, pH, temperature, conductivity)
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Some control options

• Complete separation
• Storage (e.g., deep tunnel or retention basin)
• Input reduction
• Screen flotables

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The land use dimension
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An Alternative Approach to CSOs

• Mr. FloatieMascot of People Opposing Outfall
  Pollution (P.O.O.P.), Vancouver, B.C.