Woodbrook Landfill Coastal Protection And Cliff Stabilisation - PowerPoint PPT Presentation

Woodbrook Landfill Coastal Protection And Cliff Stabilisation Preferred Emerging Solution

Woodbrook Landfill • Historic Landfill along 300m of coastline • Eroding coastline 0.3m/year • Oversteep cliff • Landfill material is falling from the cliff face onto the beach at Woodbrook 09/05/2018 Woodbrook landfill Rev A 2

Coastal Protection - Need • Ongoing erosion – 0.3m/year • Cliff instability – Over-steep Cliff • Historic Landfill Site • Prevention of historic landfill material entering the sea 09/05/2018 Woodbrook landfill Rev A 3

Woodbrook Landfill • Coastal Protection – Reduce ongoing Cliff Erosion • Cliff Stabilisation – Prevent Cliff Failure 09/05/2018 Woodbrook landfill Rev A 4

Landfill Site • Historic – pre 1968 • Mostly builder’s rubble • Top 2m to full height • Contaminant Levels Low • Tier 2 Assessment • Remedial Measures Appraisal 09/05/2018 Woodbrook landfill Rev A 5

Landfill Site – Recent Assessments • Tier 2 Risk Assessment - FT • Appraisal of Remedial Measures - FT – Construction materials and some ACM – Risk from leachate is low – Leave material on site – Prevent further loss of material into sea • Coastal Protection Measures - MWP – Reinforced concrete seawall – Sheet piling – Full height revetment – Revetment to cliff toe with cliff stabilisation • Preliminary Design – Revetment options 09/05/2018 Woodbrook landfill Rev A 6

Preliminary Design • Full Height Revetment • Revetment to cliff toe and regrade face of upper cliff to stable slope • Sediment sampling and Analysis • Preferred design – Revetment to cliff toe and regrade face of upper cliff is feasible 09/05/2018 Woodbrook landfill Rev A 7

Preliminary Design 09/05/2018 Woodbrook landfill Rev A 8

Preliminary Design • Key Quantities – Primary Armour:9,000m3 – Underlayer:4,500m3 – Mattressing: 600m2 – Cliff regrading: 5,500m3 09/05/2018 Woodbrook landfill Rev A 9

Preliminary Design • Programme – 4 to 6 months • Source of materials – Primary armour • Access to Site – By Road 09/05/2018 Woodbrook landfill Rev A 10

Assessments • Conservation architecture • Archaeology • AA screening • Coastal Processes 09/05/2018 Woodbrook landfill Rev A 11

Conservation Architecture • Railway Bridge Abutments • Historic Railway Seawall • The abutments are within the footprint of the proposed works • The abutments will be lost whether or not the works proceed. 09/05/2018 Woodbrook landfill Rev A 12

Archaeology • Railway structures • Historic forest • Avoid if possible • Preserve by record if not • Monitor construction works 09/05/2018 Woodbrook landfill Rev A 13

AA Screening • Assesses potential impacts on SAC/SPA • No significant adverse impact 09/05/2018 Woodbrook landfill Rev A 14

Coastal Processes • Extreme water levels – 2%AEP • Extreme wave conditions – depth limited • Shingle and cobbles on upper shore • Sand on lower shore • Sediment transport analysis • Potential impacts: – Lack of material for sediment budget – 4% – Increased erosion immediately north - localised 09/05/2018 Woodbrook landfill Rev A 15

Woodbrook Landfill Coastal Protection And Cliff Stabilisation Preferred Emerging Solution