When construction commences it is necessary to be responsive to the geological and geotechnical conditions encountered and not to adhere to those assumed at the design stage. Therefore the in-situ conditions should be carefully inspected throughout the construction process. Also, care should be taken that the construction activities do not have a deleterious effect on drainage.
The planned drainage systems for a project can only be finalized during the work’s execution, when the local geotechnical conditions are fully understood. Thus, it is important that an adequate specification is produced for the anticipated
type of drainage system and for suitable materials, so that the implementation teams are able to deliver the best solutions.
The many phases which constitute the construction of a road are sometimes delayed, and this can be drainage related, due to:
• Alteration in design flows;
• Obstruction of the surface and underground water flow path, due to earth moving and material placement;
• Possible surface and underground water contamination, due to earth moving, machine cleaning and associated incidents;
• Increase in the soil’s compaction in the areas where there is flow to or from an aquifer; and
• Alteration in the hydrological regime, as a consequence of the disturbed soil caused by the construction of the road structure.
Thus, it is necessary to plan the phases of project to adopt preventative measures so that there is:
• Adequate design flow, taking into account the future plans of the drainage area (land use) as well as current needs;
• Optimization of the programming of the earthworks and drainage activities, taking into account the season in which they are to be performed;
• Adoption of a plan to control erosion and soil sedimentation; and
• A work phasing plan, so that the heavy trucks and machinery do not cross the water courses, and do not affect the infiltration and recharge of the aquifer.
Normally, the supplier is obliged to demonstrate the way in which he establishes, maintains and implements a Quality Management System (QMS) to control the construction. In Europe, this quality management system must comply with the requirements of the ISO 9001:2000 standard as well as with any national or European legislation that might be relevant. The system must account for regulations applicable to quality assurance as well as for the QMS and should be based on a Quality Plan assembled for the construction project that contains the procedures, inspection and testing plans, work instructions, audit plan, training and information plan, as well as other plans containing the different specialist activities involved in the project.
