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COMBINED SEWER OVERFLOWS (CSOs)

COMBINED SEWER OVERFLOWS (CSOs). POST PROJECT APPRAISAL. CSO PPA – Objectives / Aims To survey a Representative Sample of CSOs constructed / commissioned within AMP3 To quantify Progress, Compliance and Success within the current AMP Period To seek Policy, Protocol and Guidance

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COMBINED SEWER OVERFLOWS (CSOs)

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  1. COMBINED SEWER OVERFLOWS (CSOs) POST PROJECT APPRAISAL

  2. CSO PPA – Objectives / Aims To survey a Representative Sample of CSOs constructed / commissioned within AMP3 To quantify Progress, Compliance and Success within the current AMP Period To seek Policy, Protocol and Guidance for use in the next AMP Period OVER 200 CSOs INSPECTED IN PAST 18 MONTHS

  3. CSO PPA - Scope Chamber Identification / Location / Project Logistics CSO Chambers Type / Design Guide Compliance / Location / Current Responsibility Chamber Access General, Vehicular, Personnel Access / Screen Removal & Maintenance CSO / Screen Performance Operation of Relief / Premature Operation / Self Cleansing Operation / Maintenance Operator Awareness / Maintenance Routine Receiving Watercourse Location of Outfall / Condition of Receiving Watercourse Individual Site Specific Inspection Reports Project End Report

  4. CSO PPA – Outputs / Deliverables Generic Findings - Feedback to Design Process - Update Design Guidance Site-Specific Findings - Site-Specific Action Plans - Add to “Snagging Lists” All Findings - Roll Out / Workshop Use Findings to identify where additional OP-EX is required within current AMP period Use Findings to identify where additional CAP-EX will be required during next AMP period

  5. FINDINGS

  6. CSO Chambers - Location

  7. CSO Chambers - Location

  8. CSO Chambers - Location

  9. CSO Chambers - Location

  10. CSO Chambers – Responsibility for Site

  11. CSO Chamber Access – General

  12. CSO Chamber Access – Vehicular

  13. CSO Chamber Access – Personnel

  14. CSO Chamber Access – Personnel

  15. CSO Chamber Access – Screen

  16. CSO Chamber Access – Screen

  17. CSO Chamber Access – Screen

  18. CSO Screen – Installation Issues

  19. CSO Screen – Installation Issues

  20. CSO Screen – Installation Issues

  21. CSO Screen – Installation Issues

  22. CSO Screen – Installation Issues

  23. CSO – Condition

  24. CSO Screen – Condition

  25. CSO Screen – Condition

  26. CSO Screen – Condition

  27. CSO Screen – Condition

  28. CSO Screen – Condition

  29. CSO Screen – Condition

  30. CSO Chamber – Outfall Condition

  31. CSO – Condition of Receiving Watercourse

  32. RESULTS

  33. CSO PPA – Type / Design Compliance 59% of the CSOs inspected are standard (WaPUG) Side Weir Overflows 70% of these CSOs comply with contemporary design guidance in most major respects

  34. CSO PPA – Chamber Location 25% of the CSOs inspected are located in highways / carriageways 46% are located in other public spaces or private ground owned by others 29% are located within land owned by the relevant Water Company

  35. CSO PPA – Site Responsibility 34% of the CSOs inspected were found to be still under the control of the construction contractor on the day of the inspection

  36. CSO PPA – Access 81% of the CSOs inspected have vehicle access within 10 m of the chamber 32% of the CSOs have personnel access to both sides (Continuation & Spill) of the CSO 46% of the CSOs require special tools (of a type not normally carried by Operatives) to effect full entry

  37. CSO PPA – Access (Cont) 46% of the CSOs inspected have full plan area access above the screen Summary: Restricted access to either the chamber, the screen, or both, at 55% of the CSOs inspected, may restrict the level of maintenance carried out

  38. CSO PPA – Screen Type 35% of the CSOs inspected have powered screens, 62% have non-powered screens, and 3% have no screens Of the CSOs with non-powered screens, 12% have self-cleansing screens, whilst 88% have static screens 37% of static screens have spray-bar cleansing systems

  39. CSO PPA – Screen Installation / Condition The screens at 52% of the CSOs inspected can be described as fully and correctly installed The screens at 95% of theCSOs inspected can be described as being in ‘good’ condition mechanically / structurally

  40. CSO PPA – Chamber / Screen Performance The performance of 43% of the CSO / screen combinations inspected have been found to be ‘acceptable’ The performance of 45% of the CSO / screen combinations inspected have been found to be ‘average’ The performance of 12% of the CSO / screen combinations inspected have been found to be ‘unacceptable’

  41. CSO PPA – Operation / Maintenance Operatives present on the day of inspection at 28% of the CSOs were fully aware of the operation of the overflow, and had received appropriate training Routine, planned preventative maintenance, which was in general being adhered to, was found at 62% of the CSOs

  42. CSO PPA – Receiving Watercourse Evidence of Sewage Related Debris (SRD) was found in the receiving watercourse or adjacent to the outfall structure at 50% of the CSOs inspected

  43. WORKSHOP

  44. CSO PPA – Leading Issues LOCATION / ACCESS HAND-OVER POST- PROJECT EQUIPMENT SELECTION / STANDARDISATION INSTALLATION & COMMISSIONING OPERATION & MAINTENANCE

  45. KEY QUESTION WaPUG Guide – “Design of CSOs to Incorporate Screens” (Page 6) - This Guide does not seek to give advice on the selection, design, installation or operation of screens (Page 15) - Other aspects … such as access, venting, ancillary equipment, ladders and safety chains, and the design, installation, operation & maintenance of M & E plant and equipment are beyond the scope of this Guide IN LIGHT OF THE FINDINGS / RESULTS PRESENTED, WOULD ‘PARALLEL’ GUIDANCE COVERING SUCH ISSUES BE USEFUL ?

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