1. Approaches to CSO Control Adrienne Nemura, P.E. Limno-Tech, Inc.

2. Approaches to CSO Control 2 Items to Be Covered Approaches for evaluation of controls Calculation of 85 percent capture Example Demonstration approach Types of CSO controls

3. Approaches to CSO Control 3 Approaches The overall objective of CSO control should be to meet WQ standards and protect designated uses. The evaluation of alternatives should be conducted in a framework that enables a reasonable assessment of controls, costs, and benefits related to the objectives. The evaluation may be less extensive for small CSO communities. Development and implementation of a LTCP represents a WQ-based control approach.

4. Approaches to CSO Control 4 Approaches Presumption approach Demonstration approach Watershed approach Combination of Presumption and Demonstration approaches

5. Approaches to CSO Control 5 Presumption Approach Relies on performance criteria. Options are: Average of 4 overflows per year (with discretion to add 2 additional overflows) Elimination or capture for treatment of 85% of the volume of combined sewage in CSS during precipitation events on an "average annual basis.” Elimination or capture for treatment of 85% of the mass of pollutants in CSS during precipitation events on an average annual basis. Still need post-construction compliance monitoring!

6. Approaches to CSO Control 6 85 Percent Capture: Calculation Methods Use model calculations Requires continuous simulation over annual average period Can be used in planning and determining post- construction compliance Use metered data Requires continuous metering at key locations and collection of data Generally used in post-construction

7. Approaches to CSO Control 7 Model Calculation Method Volume of combined sewage collected in the CSS during precipitation events – runoff + sanitary sewage, or dry weather flow (DWF) Runoff – Modeled or calculated flow entering the CSS during precipitation events DWF – Metered or apportioned sanitary sewage in CSS during precipitation events

8. Approaches to CSO Control 8 Calculation of 85 Percent Capture “ During precipitation events” considered to be period of rainfall producing runoff + period for CSS to drain Period for CSS to drain can be calculated as: Observed time for runoff to pass through CSS (approximately 6 to 12 hours) Time until DWF returns to normal (time until it reaches ~105 to 110% of DWF)

9. Dry-Weather Flow in CSS 9

10. Runoff During Precipitation Events 10

11. Volume of Combined Sewage Collected in the CSS During Precipitation Events Continued for 365 days 11

12. Approaches to CSO Control 12 Demonstration Approach Permittee must demonstrate that: Planned control program is adequate to meet WQ standards. Remaining CSO discharges will not preclude attainment of WQ standards (TMDL may be needed if non-CSO sources are extensive). Planned control program will provide the maximum pollution reduction benefits reasonably attainable. Planned control program is designed to allow cost- effective expansion or retrofitting if needed.

13. Approaches to CSO Control 13 Evaluating Conditions at Different Locations E. Coli – number of days exceeding 126#/100ml 0 10 20 30 40 50 60 70 Knox BrJade IsOak PointClove Br No Control Alt A Alt B

14. Approaches to CSO Control 14 Demonstrating Whether WQ Standards Will be Attained E. Coli Geomean (#/100ml) April – October 0 50 100 150 200 250 Knox BrJade IsOak PointClove Br No Control Alt A Alt B WQS=126

15. Approaches to CSO Control 15 Combination of Presumption and Demonstration Approaches Selective use of both can be justified for different receiving waters, same CSS Post-construction compliance monitoring required for both Meeting 85% volume criteria roughly matches 4 overflows per year and the “knee of the curve” inflection point for cost- effective CSO control in some situations

16. Approaches to CSO Control 16 Types of CSO Controls O&M practices —Ensure effective sewer system performance Collection system controls —Improve the collection system Storage facilities —Add additional storage Treatment technologies —Add conveyance, treatment processes and capacity Low Impact Development —Control timing and volume of storm water and reduce wastewater volume

17. Approaches to CSO Control 17 Factors Influencing Selection of Given Technology Condition of sewer system Wet weather flow characteristics (e.g., peak flow rate, flow volume, conc., frequency & duration of events) Hydraulic and pollutant loading to a facility Climate Implementation requirements Maintenance requirements

18. Approaches to CSO Control 18 NMC and LTCP Distinction is not always clear Overlap can occur with Maximizing storage in CSS (NMC-2) Maximizing flow to POTW (NMC-4) Control of solids and floatables (NMC-6) Pollution prevention (NMC-7) Monitoring to characterize impacts and the efficacy of CSO controls (NMC-9)

19. Approaches to CSO Control 19 O&M Practices Sewer inspection and testing Manual vs. remote Sewer cleaning Hydraulic, mechanical, chemical Pollution prevention Source control Water quality monitoring and public notification To minimize exposure Note: Many elements of NMC are source controls

20. Sewer Inspection & Testing: Smoke Testing to Identify Inflow Points Approaches to CSO Control 20

21. Sewer Cleaning: Hydraulic Cleaning Technique Approaches to CSO ControlApproaches in CSO Control 21

22. Pollution Prevention: Storm Drain Stenciling Approaches to CSO Control 22

23. WQ Monitoring & Notification: Warning Sign Approaches to CSO Control 23

24. Approaches to CSO Control 24 Collection System Controls Maximizing flow to the treatment plant Monitoring & real-time control Inflow reduction Sewer separation Sewer rehabilitation Service lateral rehabilitation Manhole rehabilitation

25. Monitoring & Real-Time Control Approaches to CSO ControlApproaches to CSO Control 25

26. Inflow Reduction: Eliminate Illegal Downspouts Approaches to CSO Control 26

27. Sewer Separation Approaches to CSO Control 27

28. Sewer Rehabilitation: Sewer Lining Approaches to CSO Control 28

29. Manhole Rehabilitation Approaches to CSO Control 29

30. Approaches to CSO Control 30 Storage Facilities In-line storage—oversized conduits and regulators; in-line tanks; parallel relief sewers Possibility of basement backups and street flooding Off-line storage—retention basins/tunnels to store wet weather flow for subsequent treatment On-site storage / flow equalization—storage at WWTP to manage excess wet weather flow

31. In-Line Storage: Inflatable Dam Approaches to CSO Control 31

32. Off-Line Storage: Deep Tunnel Approaches to CSO Control 32

33. On-Site Storage: Flow Equalization Basin Approaches to CSO Control 33

34. Approaches to CSO Control 34 Treatment Technologies Supplemental treatment Plant modifications Disinfection Vortex separators Floatables control

35. Supplemental Treatment: Primary Clarifier Approaches to CSO Control 35

36. Disinfection Approaches to CSO Control 36

37. Vortex Separator Approaches to CSO Control 37

38. Floatables Control: Netting Approaches to CSO Control 38

39. Approaches to CSO Control 39 Low Impact Development Porous pavement Green roofs Bioretention Water conservation

40. Porous Pavement Approaches to CSO Control 40

41. Green Roofs Approaches to CSO Control 41

42. Bioretention Approaches to CSO Control 42

43. Approaches to CSO Control 43 Recent Innovations The majority of recent technological innovations related to CSO control have enhanced existing practices, rather than developing new technologies. Improved information management supports the selection of appropriate technologies and their cost-effective application.

44. Approaches to CSO Control 44 Most Widely Used CSO Controls RankLTCP Control Activity 1Sewer separation 2Sewer rehabilitation 3Retention basins 4Disinfection 5Primary sedimentation 6Storage tunnels and conduits 7Upgraded WWTP capacity 8Outfall elimination

45. Approaches to CSO Control 45 More on Sewer Separation Some states like Maine and Vermont strongly encourage complete separation for small CSO communities. Separation can be expensive and disruptive, but one advantage is that the discharge of sanitary sewage is eliminated. One disadvantage is the generation of more (probably untreated) urban storm water discharge.

46. Approaches to CSO Control 46 CSO Technology References Report to Congress on Impacts and Control of CSOs and SSOs http://www.epa.gov/npdes/pubs/csossoRTC2004_AppendixL.pdf EPA Municipal Support Division Fact Sheets www.epa.gov/owm/mtb/mtbfact.htm Rouge River National Wet Weather Demonstration Project (MI) www.wcdoe.org/rougeriver/ Columbus Water Works National Demonstration Program (GA) www.cwwga.org/NationalPrograms/Index.htm