Title: EPAs CSO Policy
1EPAs CSO Policy
- Environmental Law I
- Fall 2005
2Whats Combined in a Combined Sewer System?
- Sanitary waste
- Pretreated industrial waste
- Stormwater collecting in sewers
3Where the Combined Sewers Are
750 out of 20,000 systems nationwide
4How a CSO Happens
Feeder lines
Trunk or Interceptor
Sewer Plant
CSOs
River
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7Where the Bflo CSOs are . . .
8A view from the river
9Primary 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.)
10Problems 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
11Current 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
12 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
13Nine 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
14Nine 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
15Long 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
16Characterizing 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?)
17Monitoring 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
18Uses 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
19Consideration of alternatives
- Zero overflows per year
- 1 to 3 overflows/yr
- 4-7 overflows/yr
- 8-12 overflows/yr
20Presumption vs. Demonstration
- If it meets any of the following criteria, the
controls are presumed adequate otherwise, you
have to prove it
21- 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
22Cost-Performance Curves Finding the Knee of the
Curve
Cost
Pct Captured
23What 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
24Buffalos Long-Term Study
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26Automated monitoring (Hydrolab Datasonde 4) All
10 sites, sample every 15 minutes
Analyze for conventional parameters (DO,
turbidity, pH, temperature, conductivity)
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30Some control options
- Complete separation
- Storage (e.g., deep tunnel or retention basin)
- Input reduction
- Screen flotables
31The land use dimension
32An Alternative Approach to CSOs
- Mr. FloatieMascot of People Opposing Outfall
Pollution (P.O.O.P.), Vancouver, B.C.