S3 Excavation

S3 Excavation

S3.1 Breaking the Surface

S3.1.1 Care must be taken when cutting surface layers to avoid undue damage to the running surface or to the bond between the surface course and binder course materials. Cutting by machine, e.g. road saw, coring equipment or planer, is preferred. All loose materials shall be removed to ensure that the trench edge is in a safe and stable condition.

S3.1.2 When excavating in modular construction, the existing modules shall be lifted carefully, and stored for re-use. Where pre-existing damage has resulted in fragmentation or breakage of modules made out of natural materials the fragments shall be removed and stored, unless agreed otherwise with the Authority.

S3.1.3 The Authority shall be informed of any material, natural material, cobbles or setts encountered that may be of historical or archaeological interest and shall be afforded the opportunity to inspect the material prior to it being excavated.

S3.1.4 Modules shall be reinstated in accordance with Appendix A12.

S3.1.5 The shape and line of larger trenches and their reinstatement should have regard wherever possible to the aesthetic appearance.

S3.2 Excavation

S3.2.1 All excavations in the road shall be carried out in a manner that avoids undue damage.

S3.2.2 The trench width shall be such that adequate access is available for compaction of the surround to apparatus.

S3.2.3 The trench walls shall be even and vertical with no undercutting of the running surface. If undercutting occurs and compaction is impossible, measures shall be taken to fill any voids as soon as practicable or immediately after trench support has been provided.

S3.2.4 Excavations shall be protected, as far as is reasonably practicable, from the ingress of water, and water running into them shall be drained or pumped to an approved disposal point. Any drainage sumps shall be sited so as to prevent damage to the excavation.

S3.3 Excavated Material

S3.3.1 All excavated materials that are to be re-used shall be protected from excessive drying or wetting during storage. Additionally, these materials shall be excavated, stored, handled and laid so as to avoid contamination and loss of fines.

S3.3.2 Excavated material unsuitable for re-use shall be removed from site as soon as practicable. Excavated material retained on site shall be stockpiled within the confines of site barriers, at a safe distance from the trench edge and prevented, so far as is practicable, from entering any drainage system or water course.

S3.4 Side Support

S3.4.1 The sides of all excavations in soft or loose ground shall, ordinarily, be provided with a side support system. The support system shall be properly designed and installed to restrain lateral movement of the sidewalls, and should be installed without delay.

S3.4.2 Supports shall be progressively withdrawn as backfilling and compaction progresses, and all voids carefully filled.

S3.5 Drainage

S3.5.1 The Undertaker shall take all reasonably practicable measures to prevent the permanent disturbance of artificial or natural drainage systems/paths. Where disturbance does occur it shall be notified immediately to the owners of the system and any landowners who are affected. Disturbed systems shall be restored to the requirements of the owner; see Section S11.4.

S3.5.2 For any works site where the Authority is aware of a history of flooding or drainage problems it should inform the Undertaker in advance. In such situations the Undertaker and the Authority should liaise closely to identify a suitable method of working.

S.3.5.3 If site conditions indicate to the Undertaker that the use of some sub-base materials may be detrimental to drainage, advice on the selection of suitable materials should be sought from the Authority.

S3.5.4 See also Section S11.4 for other water-related matters.

S3.6 Shallow or Aborted Excavations

S3.6.1 No shallow or aborted excavation shall be permitted to undermine the integrity of the remaining road structure. Any excavation terminated at an incomplete stage or depth for whatever reason shall, depending on the layer at which the excavation was terminated, be reinstated in accordance with the following requirements:

1) Where reinstatement can be achieved by laying a thicker surface course in accordance with the thickness requirements of Appendix A2 and, in the case of small excavations and narrow trenches, in accordance with Section S6.4.10, no further excavation is required.

2) In all other cases, the binder course shall be excavated to allow a binder course layer to be reinstated in accordance with Appendix A2. Where the existing depth of excavation is greater than 100 mm and the additional depth is less than the minimum layer thickness of Base material a thicker binder course may be laid.

3) In deeper excavations, no further excavation shall be required. Reinstatement shall be carried out in accordance with the relevant requirements of Sections S5 to S9 inclusive, as appropriate.

S3.7 Trenchless Pipelaying

S3.7.1 Moleploughing uses a ploughing machine to pull a flexible pipe or cable below ground. It is employed in unmade ground and may be used in the verges of roads. The moleplough creates a slit in the surface of the ground, which should not require reinstating provided that the surface profile is restored in accordance with Section S9. However, where connections are made to apparatus installed by moleploughing techniques, excavations shall be carried out and reinstated in accordance with this Specification.

S3.7.2 Soil Displacement moling and other trenchless methods do not create an excavation and, when carried out in a proper manner, do not require reinstatement. However, reinstatement shall be carried out in accordance with this Specification at the launch and receive pits and at any intermediate excavations where connections are made to apparatus installed by soil displacement moling and other trenchless techniques.

S3.7.3 Where, as a result of the use of trenchless methods for the installation of apparatus under a road, the Authority has reasonable cause to believe that damage may have been caused to the structure of the road, the Investigatory Works Procedure described in the RAUC (S) Code of Practice for Inspections should be commenced as if the defect was associated with a reinstatement defect for the purposes of that Code. Any remedial work agreed between the Authority and the Undertaker, if carried out by the Undertaker, shall be in accordance with this Specification at the Undertaker's expense.

S3.7.4 If the agreed remedial work is carried out by the Authority at the Undertaker's expense the provisions of this Specification shall not apply.

S3.7.5 In the absence of agreement between the Authority and the Undertaker, liability for any damage shall be determined in accordance with section 141 of the Act (Liability for damage or loss caused).