Scottish Road Network Landslides Study - University of Glasgow

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2.4 CURRENT INSPECTION AND MAINTENANCE ARRANGEMENTS 22 BACKGROUND The current term contracts for the management and maintenance of the Scottish trunk road network require that embankments and cuttings are inspected (Section 2.7 of Schedule 7 Part 1 to the Contract: Embankments and Cuttings). Guidance on inspections and on failure modes and their identification together with procedures for remedial works are given in HA48/93 Maintenance of Road Earthworks and Drainage (DMRB 4.1.3). HA48/93 has recently been superseded by HD41/03 Maintenance of Highway Geotechnical Assets (DMRB 4.1.3), which has replaced HA48/93 for use on the trunk road network in England. HD41/03 is heavily slanted towards the Highways Agency’s organisational procedures and system of geotechnical checking, but the principles are suitable to be applied where appropriate to the trunk road network in Scotland. Having been the conforming standard at the time of letting the current term maintenance contract, HA48/93 remains active for use on the trunk road network in Scotland. The Operating Companies are required to carry out detailed inspections of all embankments and cuttings to check for any indication of instability. Evidence of instability is reported using Form A and remedial works proposed on Form B of Appendix A of HA48/93. Although the actual requirement is for the Operating Companies to inspect embankments and cuttings, Form A includes for the reporting of instability in both those two categories and additionally in natural slopes. Notwithstanding this, the HA48/93 itself is focussed upon cuttings and embankments with only a brief note (paragraph 3.3) on the potential for the reactivation of slab slides (a variant upon that illustrated in Figure 2.1(c)) by the excavation of a cut slope or by loading with an embankment. Inspections are required to be carried out (Section 1.6 of the Schedule 7 Part 1 to the Contract: Detailed Inspection Requirements) at intervals of one year and no later than 14 days after the anniversary of the previous inspection. Further, in the North West Unit area, for example, additional earthwork monitoring requirements are specified. These are as follows: A83 Rest and be thankful (west of Arrochar): three monthly inspection and levelling survey of the road surface. A83 Loch Shira (east of Inverary): six monthly inspections. A83 Artilligan Sea Wall (south of Ardrishaig): two weekly inspections of sea wall and rock protection. A84 Doctor’s Corner (Loch Lubnaig): visual inspection of previous slip area. The possible need for additional inspection requirements in the light of a recent report on rock slope stability along the A83 is also highlighted. As part of their routine maintenance operations the Operating Companies are required to remove debris from behind netting, repair and replace netting, remove debris in rock traps and from behind rock fences. Other maintenance activities are to be the subject of an Order following the submission of Forms A and B in HA48/93. For the Scottish trunk road network schemes, the geotechnical process is subject to Geotechnical Certification as operated by the Scottish Executive and its Independent Geotechnical Checker. A high degree of comfort is therefore assured that all aspects of
23 BACKGROUND earthworks stability have been properly addressed in design and construction. At the end of the maintenance period responsibility for inspection passes to the Scottish Executive and the relevant Operating Company. 2.5 POTENTIAL THIRD PARTY ISSUES The landslides which occurred during August 2004, see Section 2, all occurred either directly or indirectly as a result of rainfall and consequential debris flows on land outwith the trunk road boundary. Many of the other landslides which have occurred in Scotland have also been instigated on land outwith the road boundary. This raises questions as to how such land can be accessed and controlled in order that future events can either be prevented, minimised or managed. In addition, the responsibilities of the third parties who own or control such land need to be clarified in relation to such occurrences. With regard to trunk roads a number of powers are available to the Scottish Ministers as roads authority to assist in such matters under the Roads (Scotland) Act 1984 (House of Commons, 1984). Such powers are also available for use by local roads authorities for roads under their control. The various sections of the Act which are of relevance are as follows: Section 30 - this section provides for works to be carried out by the roads authority in order to protect the road against hazards of nature, including landslide. Section 104(1)(a) authorises the roads authority to acquire land, either on a compulsory or voluntary basis, for the protection of a public road. Section 109 provides, by reference to Schedule 5, distance limits for acquiring land compulsorily, but in terms of Section 109(3) those distance limits do not apply for purposes connected with the protection of a public road. The roads authority therefore has the power to acquire land to construct a barrier or carry out other works to protect a road from landslide even although that barrier or work might be remote from the road itself. Section 31 makes provision for drainage of a public road including preventing surface water from falling on to the road. Section 32 authorises the roads authority to make contributions towards drainage works or flood prevention operations which may be desirable for the protection of a public road. Section 93 imposes an obligation on the roads authority to take steps to obviate any danger on land beside or near to a road. Section 95 deals with the deposit of mud or other materials from vehicles on to roads. Section 99 requires the owner and occupier of any land to prevent any flow of water or other matters from that land on to the road. Section 102 deals with the ploughing of unenclosed land adjoining a public road It is worth considering what the potential liability of third parties such as owners and occupiers of land adjoining a road is in relation to landslides and what might be the impact on land values and the economy in general.
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Page 5 and 6: MINISTERIAL FOREWORD The landslide
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Page 13 and 14: 1 INTRODUCTION TO LANDSLIDE HAZARDS
Page 15 and 16: 11 INTRODUCTION Section 6 describes
Page 17 and 18: 13 BACKGROUND However, Varnes (1978
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77 CONTRIBUTORY FACTORS 5.3 FACTORS
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A84 South of Strathyre (8km) HIGH H
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HIGH HAZARD AREAS AND EARLY OPPORTU
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8 DEBRIS FLOW MANAGEMENT AND MITIGA
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8.2.3 United Kingdom MANAGEMENT AND
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MANAGEMENT AND MITIGATION OPTIONS D
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MANAGEMENT AND MITIGATION OPTIONS a
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MANAGEMENT AND MITIGATION OPTIONS N
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MANAGEMENT AND MITIGATION OPTIONS r
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MANAGEMENT AND MITIGATION OPTIONS F
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9 SUMMARY AND RECOMMENDATIONS FOR D
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SUMMARY AND RECOMMENDATIONS The ini
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SUMMARY AND RECOMMENDATIONS extensi
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115 REFERENCES Chan, R. K. S. 2000.
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117 REFERENCES Moore, R., Lee, E. M
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APPENDIX - PROJECT WORKSHOP AGENDA
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Scottish Road Network Landslides Study - University of Glasgow

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