ABSTRACT
The ERWAT DD5A Regional Outfall Sewer traverses an area alongside the Blesbokspruit; an internationally proclaimed Ramsar wetland site. This paper describes analysis methods, design, risk studies, construction control and post-construction monitoring of the pipeline in accordance with an Environmental Management Plan, to ensure compliance with strict controls imposed by Authorities.
Deep percussion holes to bedrock, combined with a risk analysis of spillage were used to predict the reliability of the system.
Multi-point piezometers installed in and beneath a geotextile enclosed bedding layer, enabled monitoring and testing of ground water to be undertaken.
Laboratory testing of locally available materials which did not satisfy conventional specifications, combined with finite element analyses simulating envisaged construction sequences, enabled low cost materials to be specified with confidence. Those portions of the line installed at depths up to 10m, required detailed analysis and design to ensure safety of workpersons during pipeline installation.
