Construction Risk in Coastal Engineering

Contents

Illustrations XXV

1. Introduction 1

1.1. The need to manage risks in coastal engineering construction, 1

1.2. Scope of coastal engineering works and materials, 3

1.2.1. Harbour breakwaters, 4

1.2.2. Coastal defence works, 4

1.2.3. Marine jetties and dolphins, 6

1.2.4. Navigational dredging works, 7

1.2.5. Intakes and outfalls, 7

1.3. Benefits and aims of risk management, 7

1.4. Objectives, readership, structure and use of this manual, 8

1.4.1. Objectives of the manual, 8

1.4.2. Readership of the manual, 10

1.4.3. Structure and use of the manual, 11

Part A 15

2. Protocol 17

2.1. General duties, 19

2.1.1. Duties of clients, 19

2.1.2. Duties of the designer, 20

2.1.3. Duties of the contractor, 22

2.2. Duties relating to different facets of the project process, 22

2.2.1. Project concept or inception, 22

2.2.2. Project programme, 24

2.2.3. Project design development, 25

2.2.4. Pre-qualification of contractors, 26

2.2.5. Preparation of tender documents, 27

2.2.6. Tender period, 31

2.2.7. Award of contract, 32

2.2.8. Construction period, 33

2.2.9. Post-construction, 34

Part B 35

3. Risk identification, modelling and management 37

3.1. Introduction, 37

3.2. The benefits of systematic risk management in coastal engineering, 39

3.3. Risk management at various stages of project development and implementation, 41

3.3.1. Design stage (client driven), 41

3.3.2. Pre-procurement stage (client driven), 43

3.3.3. Tender stage (contractor driven), 43

3.3.4. Construction (client and contractor driven), 43

3.4. Risk management procedure, 44

3.5. Risk definitions, 44

3.5.1. Risk, 44

3.5.2. Hazard, 47

3.5.3. Uncertainty, 48

3.6. Risk assessment approaches, 50

3.6.1. STEP 1 – Strategic business assessments, 51

3.6.2. STEP 2 – Identify the objectives of the risk assessment and the level of detail to be adopted, 52

3.6.3. STEP 3 – Identify hazards and risks, 52

3.6.4. STEP 4 – Consider the ownership of the risks, 53

3.6.5. STEP 5 – Assess the likelihood and consequences of these risks, 54

3.6.6. STEP 6 – Identify control/mitigation measures, 54

3.6.7. STEP 7 – Assess the residual risks including new risks that are created by the mitigation measures, 55

3.6.8. STEP 8 – Estimate the cost of mitigation measures, 55

3.6.9. STEP 9 – Estimate the net benefit of the measure, 57

3.6.10. STEP 10 – Select and implement beneficial mitigation actions, 57

3.6.11. STEP 11 – Monitor and review the process/feedback into the cycle, 57

3.7. Simple risk management tools, 58

3.7.1. Risk workshop, 59

3.7.2. Influence diagrams and rich pictures, 59

3.7.3. Likelihood-consequence tables, 60

3.7.4. Flow diagrams, 63

3.7.5. Decision/event tree, 64

3.7.6. Recording risk control strategies, 64

3.7.7. Risk calendar, 65

3.7.8. Sensitivity analysis, 65

3.7.9. Monte Carlo methods, 66

3.8. Evaluation of risks by contractors at tender stage, 69

3.9. Budgets and contingencies, 74

3.10. More complex tools (computational risk models), 77

3.10.1. Cost risk techniques, 77

3.10.2. Schedule risk techniques, 83

3.10.3. Scenario modelling, 88

3.10.4. Real-time modelling, 89

4. The uncertain sea 91

4.1. The basic parameters, 93

4.1.1. Wind climate, 93

4.1.2. Wave climate, 95

4.1.3. Tidal currents, 106

4.1.4. Water levels, 107

4.1.5. Joint probability of waves and water levels, 110

4.2. Methods of estimating site conditions, 111

4.2.1. Estimation of wind data, 111

4.2.2. Estimation of wave conditions at the site, 111

4.2.3. Estimation of water levels, 115

4.2.4. Estimation of currents, 121

4.3. Real time forecasting, 123

5. Coastal construction methods and risks 131

5.1. Coastal construction plant, operability levels and availability, 131

5.1.1. Plant types, 131

5.1.2. Plant operability, 142

5.1.3. Availability of staff, plant and facilities, 156

5.2. Temporary stability of works, 156

5.3. Construction tolerances, 166

5.4. Safety of the public and site personnel, 170

5.5. Sea bed and beach profile changes, 171

5.6. Uncertainty of ground conditions, 173

5.7. Uncertainty of condition of existing structures, 175

5.8. Reliability of materials’ supply, 177

5.9. Timing of works, 178

5.10. Access, 185

5.11. Variability of quantities, 187

5.12. Infilling of excavations and dispersal of spoil heaps, 192

6. Safety, health and the environment 193

6.1. Health and safety, 193

6.2. Safety legislation in the coastal environment, 194

6.2.1. Acts, 194

6.2.2. Regulations, 196

6.3. Safety enforcement in the coastal environment, 198

6.4. Current problems with health and safety in coastal engineering, 202

6.5. Common safety hazards in coastal engineering, 203

6.5.1. Working over/adjacent to water, 204

6.5.2. Cofferdams, 205

6.5.3. Earth moving plant, 205

6.5.4. Sea outfalls, 205

6.5.5. Diving, 205

6.5.6. Explosives underwater, 206

6.6. Safety risk assessment and integration with other risk assessments, 206

6.7. Environmental risks, 207

6.7.1. Noise, 207

6.7.2. Traffic, 209

6.7.3. Dredging and disposal, fisheries and compensation. 209

7. Insurance 219

7.1. Introduction, 219

7.1.1. Limitations of insurance as an option for covering a risk, 219

7.1.2. Glossary, 221

7.2. Risk management, 221

7.2.1. Evaluation of the risk, 222

7.2.2. Limits of Liability, 225

7.2.3. Levels of excess, 226

7.2.4. Division of risk – client or contractor, 227

7.3. Types of cover available, 229

7.3.1. Contractor’s All Risks & Erection All Risks, 230

7.3.2. Decennial Liability, 233

7.3.3. Marine Insurance, 234

7.4. Limitation of liability for vessels, 244

7.5. Specific problems in relation to coastal construction, 245

7.6. Use of specialists, 248

7.6.1. Specialists for identifying risks, 248

7.6.2. Specialists for identifying risks in respect of exclusions under a policy, 249

7.6.3. Loss Adjusters and Average Adjusters, 250

7.7. Advice to Underwriters, 251

7.7.1. Advice to Underwriters of changing risk during period of policy, 251

7.7.2. Advice to Underwriters of claims, 251

8. Procurement 263

8.1. Introduction – the objectives of a procurement strategy, 263

8.2. The client in coastal engineering, 266

8.2.1. The nature of the client, 266

8.2.2. Size and experience of the client, 267

8.3. Project Funding in Coastal Engineering, 269

8.3.1. The public sector, 269

8.3.2. Choice of an appropriate procurement strategy, 272

8.4. Selecting a procurement strategy, 276

8.5. Methods of Procurement – The Well Established Options, 277

8.5.1. Traditional, 277

8.5.2. Design and build, 278

8.5.3. Construction management,281

8.5.4. Management contracting, 282

8.6. A Procurement Strategy for Coastal Engineering, 283

8.6.1. The contract strategy, 284

8.6.2. Pre-qualification of tenderers, 296

8.6.3. Bid review, 298

8.6.4. Tender review, 298

8.7. Problems of Risk Perception, 299

8.8. Suggested Improvements in Risk Allocation within Tender Documents, 308

8.9. The Impact of Risk, 310

8.10. Procurement Strategies for the Future, 311

8.10.1. Project partnering, 316

8.10.2. Refine and build, 317

8.11. Conclusion, 319

Part C 321

9. Specific risks – introduction 323

9.1. Introduction, 323

9.2. Risk Identification, 323

9.2.1. Common ‘general’ risks, 324

9.2.2. Common risks related to structure types, 324

9.3. Risk evaluation, 325

9.4. Possible Risk Control Strategies, 325

9.4.1. Remove, 326

9.4.2. Reduce, 326

9.4.3. Transfer, 326

9.4.4.. Share, 327

9.4.5. Accept, 327

9.4.6. Insure, 328

9.5. Risk monitoring and review, 329

10. Rock works 335

10.1. Introduction, 335

10.2. Client’s project objectives, 335

10.3. Rock work types, 336

10.4. Rock sourcing – obtaining rock that complies with the specification, 338

10.5. Rock delivery, 341

10.5.1. Road delivery, 342

10.5.2. Rail delivery, 342

10.5.3. Sea delivery, 344

10.6. Rock placing, 354

10.6.1. General rock placing and buildability, 354

10.6.2. Availability of plant, 356

10.6.3. Stone variability and void ratio, 356

10.6.4. Ability to achieve rock profile, 358

10.6.5. Experience and flexibility of the client’s representative on site, 358

10.6.6. Variations in the formation line, 360

10.6.7. Stability of the incompleted works, 360

10.6.8. Settlement, 362

10.6.9. Wastage due to breakages, 362

10.6.10. Core material loss, 364

10.6.11. Barge beaching risks, 364

10.6.12. Damage to vessels, 366

10.6.13. Public safety, 366

10.6.14. Exchange rate risk, 366

11. Concrete armour units 371

11.1. Introduction, 371

11.2. Client’s project objectives, 374

11.3. Forming units, 374

11.3.1. Obtaining consent to use the unit, 3 74

11.3.2. Availability of moulds and inadequate numbers, 374

11.3.3. Land availability for unit production, 374

11.3.4. Cracking, 376

11.3.5. Transporting units, 376

11.4. Placing of units, 378

11.4.1. Achieving the placing specification, 378

11.4.2. Sea state, 378

11.4.3. Plant availability, 380

11.4.4. Public safety, 380

11.4.5. Timing of the works, 380

11.4.6. Stability of the incompleted works, 380

12. Concrete seawalls and revetments 387

12.1. Introduction, 387

12.2. Client’s project objectives, 387

12.3. Sea state, 390

12.4. Public safety, 390

12.5. Water levels, 390

12.6. Variation in existing structures, 392

12.7. Variation in beach levels, 392

12.8. Ground investigation, 392

12.9. Timing of the works, 394

12.10. Congestion, 394

13. Caisson works 399

13.1. Introduction, 399

13.2. Client’s project objectives, 399

13.3. Timing of the works, 400

13.4. Transportation of the caisson to position – waves, wind, water levels and currents, 400

13.5. Bed preparation, 402

13.6. Positioning, 402

13.7. Temporary instability of caisson, 402

13.8. Availability of temporary facilities, 404

13.9. Plant availability, 404

14. Coastal piling works 409

14.1. Introduction, 409

14.2. Client’s project objectives, 409

14.3. Sea state, 410

14.4. Ground conditions, 412

14.5. Plant availability, 412

14.6. Timing of the works, 412

15. Outfall and intake projects 417

15.1. Introduction, 417

15.2. Client’s Project objectives, 420

15.3. Timing of the works, 420

15.4. Materials, 422

15.5. Sea State, 422

15.6. Water levels, 424

15.7. Currents, 424

15.8. Considerations affecting dredged trench, 424

15.9. Plant and plant availability, 426

15.10.. Integrity of pipes during installation, 428

15.11.. Launch site, 428

15.12.. Diffuser Installation by drilling through sea bed, 430

15.13.. Public safety, 430

15.14.. Ground Investigation, 430

15.15.. Fishery aspects, 430

16. Navigational dredging works 435

16.1. Introduction, 435

16.2. Client’s project objectives, 436

16.3. General issues, 438

16.3.1. Timing of the works, 438

16.3.2. Weather and sea state, 438

16.3.3. Inadequate or inaccurate ground investigation, 438

16.3.4. Siltation and measurement, 440

16.3.5. Turbidity, 440

16.3.6. Fishery aspects, 440

16.3.7. Debris, 442

16.3.8. Side slopes, 442

16.3.9. Ordnance, 442

16.4. Dredging vessels, 444

16.4.1. Backhoe and grab dredging vessels, 444

16.4.2. Bucket chain dredging vessels, 446

16.4.3. Cutter suction dredging vessel, 447

16.4.4. Trailing suction hopper dredging vessels, 448

17. Beach nourishment 453

17.1. Introduction, 453

17.2. Client’s project objectives, 453

17.3. General Risks, 454

17.3.1. Timing of the works, 454

17.3.2. Material sourcing, specification and availability, 454

17.3.3. Disruption due to fishery aspects, 456

17.4. Delivery By Sea, 458

17.4.1. Sea State, 458

17.4.2. Water levels, 460

17.4.3. Currents, 462

17.4.4. Measurement, 462

17.4.5. Availability of plant and materials, 466

17.4.6. Restrictions on working hours, 466

17.4.7. Public safety, 468

17.4.8. Access availability, 470

17.5. Delivery by land, 472

17.5.1. Public safety, 472

17.5.2. Access availability, 472

18. References 477

Appendix 481

Index 491