9 Construction of earthworks
At this point in the process the team should have developed the design and specification for the works, but these documents alone will not deliver a successful earthworks project; achievement of this goal depends greatly on the practical experience of the construction team, and in particular the earthworks manager and earthworks foreman.
The construction team should plan the earthworks construction to optimize the use of the fill materials available, prepare a mass haul diagram to ensure that the proposals can fit with other aspects of the construction works, and programme activities such as haul roads and drainage to ensure that the fill material does not deteriorate during the works. The construction team should take account of the recommendations in Clauses 5 to 8.
NOTE These activities rely on experience of earthworks, the ground conditions at the site, and the climatic conditions of the area. Without this experience, there is a considerable risk of potentially good material being rendered unsuitable and the project running into major difficulties.
The following subclauses provide some general comments on these aspects of earthworks and how the works should be undertaken.
These comments should not however replace the construction team's practical experience.
9.2 Organization of earthmoving operations and construction practice
Earthmoving operations by their nature present considerable risk; safe systems of work and good working practices should be adopted to minimize that risk. Provision should also be made for emergency response in event of a major instability.
9.3 Planning of the earthmoving operations
The earthworks planning process should be ongoing from project conception through the design and construction phases of the project. The advice of staff with practical experience of earthmoving operations should be taken into account at all stages of that process.
Earthworks planning should take account of factors which can have a major impact on the programming of earthmoving operations such as:
- contractual constraints;
- environmental constraints;
- agricultural constraints;
- constraints imposed by the presence of adjacent infrastructure;
- site investigation data;
- control of settlement and temporary stability of slopes and embankments;
- the discovery of archaeological remains;
- the presence of protected species or habitats.
Land acquisition should be planned not only to allow for construction of the permanent works but to take account of land required for temporary road or rail diversions, site compounds, welfare facilities, tips and borrow pits, delivery and storage areas, haul roads and turning areas, hard standings for craneage, services, runoff and pollution control, watercourse and temporary utility diversions.
Road and railway projects are characterized by being linear worksites accessible from both ends and with few intermediate access points: whilst the provision of access points for work activity, along the site might not be necessary, additional access points for use in an emergency should be planned.
Earthmoving operations should be planned to be constructed in such a way as to minimize risk to site personnel and the public. Planning should allow for the safe movement of vehicles and personnel. Traffic flow should follow a logical pattern in which conflict between vehicles and between vehicles and personnel is avoided. Traffic flow patterns should minimize the need for reversing, and one-way flow patterns are often useful in this respect. Appropriate signing and traffic control measures should be devised and realistic speed limits should be set.
An appropriate network of well-maintained access and haul roads, and passing and turning points should be planned and sufficient land for these should be acquired during the land acquisition phase.
Particular attention should be paid to loading, tipping and spreading areas. Pedestrians should be kept separate from traffic routes and safe systems of work devised to allow supervisory staff, banksmen, etc. to work safely and effectively. Site rules should be drawn up to reflect these objectives.
Any use of explosives for rock excavation should be undertaken in accordance with BS 5607.
9.4 Earthmoving plant and equipment
All earthmoving plant and equipment used should conform to the requirements of BS EN 474 (all parts) or BS EN 500-4. It should be maintained in a serviceable condition in accordance with the manufacturer's recommendations.
NOTE Plant and equipment not conforming to these standards can present increased risks due to deficiencies such as poor operator visibility.
Plant and equipment should be selected on the basis of suitability for the planned operations and the expected site conditions.
Environmental considerations should also be taken into account. Excavating, hauling and compaction equipment should all be sized to be compatible with each other; large plant requires fewer movements so reducing the overall number of vehicle movements.
Use should be made of remotely operated fittings, such as visibility aids, self sheeters, hydraulic doors and interchangeable tools, on wagons and plant to enhance safety by reducing operator input away from the safety of the cab.
Plant and equipment should not be used in inappropriate situations, e.g. road compaction plant should not be used for earthworks compaction.
Plant inspections should be done on a regular basis and all hired plant should be included in the process prompted by receipt of the delivery ticket on site.
9.5 Operator fitness
Only operators who have demonstrated their competence, and are authorized to do so, should be allowed to operate earthmoving plant and equipment. It is recommended that a competence assessment scheme such as that run by the CPA (www.cpa.uk.net) should be adhered to on site.
Operators should be subject to occupational health checks to confirm their fitness for work. Such checks should be no less stringent than for road going vehicle operators.
A drug and alcohol policy should be implemented on site which should reflect laws for driving on the highway or better.
9.6 Site interfaces and demarcation
The site boundaries should be physically established before earthmoving operations begin. Permanent or temporary fencing or walls should be erected as appropriate. Barriers that are more robust should be used where the site is adjacent to live road or rail traffic.
The number of crossing points over public highways, bridleways, farm roads, etc. should be minimized. Traffic at crossing points should be appropriately controlled and lit as necessary.
Temporary demarcation of site traffic routes, working areas, haul road boundaries, underground and overhead service locations, drainage or settlement ponds and sterile or contaminated areas, etc. should be provided as appropriate.
Wheel washes should be provided at site exit points. Road cleaning equipment should be deployed to prevent surface contamination of roads and footpaths affected by the works. The use of concrete or bituminous surfaced areas or temporary matting at exit points and crossings can reduce the carry over of contamination.
The runoff of contaminated water from the site should be controlled by the use of drainage channels along with settlement and other treatment facilities; contamination can arise from suspended soil particles in the runoff as well as from spillage of fuel, lubricants and chemicals used on site.
Water spraying vehicles should be deployed to control environmental dust nuisance.
Gates, entrance security checkpoints, etc. should be located to prevent site traffic obstructing existing roads or footpaths. Parking areas for delivery vehicles and employee vehicles should be provided. Materials delivery vehicles should be subject to similar traffic management procedures as site vehicles.
Co-operation and co-ordination between adjacent projects should be encouraged through the planning and management of works that occur near or on mutual site boundaries.