Annual Outfall 10 Diffuser Inspection

A contract has been awarded for the Annual Inspection of the Outfall 10 Diffuser for four years from 2019 - 2022. The inspection must be carried out between 1 April and 31 July each year. The location of the outfall diffuser (Outfall 10), which discharges low level radioactive liquid effluent, is approximately 0.25 N.M from the Dounreay Site. Water depth is 25m below Chart Datum in a tidal range of 3.5m. The diffuser structure is ~ 10metres long x 8 metres wide x 3 metres in height. The inspection will include: 1. Carry out an 'as found' visual survey of the Outfall 10 Diffuser, the (9 off) Duckbill valves numbered 4 - 12 and (3 off) blank flanges numbered 1 - 3. 2. Clean marine growth from the duckbill valves and blank flanges. 3. Clean marine growth from the interior of the chamber and the outer parapet. 4. a) Check duckbills, nuts and bolts for integrity and security. A decision as to whether any other duckbills require to be replaced will be made at the time of inspection. b) Replacement split rings will be provided by DSRL. 5. Carry out an inspection of the outer chamber and concrete plinth, taking particular note of the condition of the south east corner. 6. Clean all areas of the chamber and base as directed. 7. After inspection carry out any repairs that may be required. 8. Record on DVD all areas of work carried out including commentary of work being carried out. This will include identification of the duckbill valves 4 -12, blank flanges 1-3 and the four corners of the parapet as a minimum. 9. Any other work required would be discussed on the day and a forward plan identified. This may include a visual check only on the condition of the old risers to verify that they are not diffusing if time allows. 10. Provide a Report to DSRL which includes: • A description of all works carried out. • A daily Dive Log. • A summary of the inspection which includes recommendations for subsequent surveys. 11. The provision of a Safe System of Work which includes Method Statement, Risk Assessment and Local Rules. 12. Pre dive and equipment check lists should also be provided by the Contractor.