Construction World January 2015

PROJECT PROFILE

Preparing the deck formwork north overpass.

Low perspective of south overpass.

Both structures included abutments at either end with three sets of intermediate piers between. The south overpass was cast as a continuous deck in three stages along its length, whilst the north overpass was cast in four stages split transversely into individual spans. Environmental impact consideration Where possible existing road materials were recycled for re-use in the project. On the N9 and the N1, the base course layer was milled, supplemented with crushed material and stabilized with cement to form a new sub-base layer. New pavement layer materials were sourced from six local borrow pits and one commercial source in Colesberg. The borrow pits have been satisfactorily rehabilitated in terms of environmental management plans which were in place prior to the commence- ment of the project. The interchange precinct now contains many features which enhance aesthetics and address environmental issues. The fill and cut slopes of the roadworks and the areas affected by construction were rehabilitated with the use of imported topsoil and hydros- eeding. The seed composition was identified by a specialist from the University of Free State who determined the vegetation types classification as Upper Eastern Karoo. The site was also assessed by environ- mental, heritage, paleontological and botan- ical specialists prior and during construction. Health and safety Following the recommendations of an expert appointed to minimise noise levels, the inter- change precinct was further enhanced by the construction of earth berms to reduce audial impacts, particularly of heavy vehicles, on residents adjacent to the roads. In addition flood protection berms were designed and

achieving a simultaneous completion date. This project was governed by rigid quality control standards, which resulted in quality acceptance testing for all road and concrete materials. During this process more than 8 000 quality tests were carried out on the road layers and pavement structure and more than 7 000 quality tests were carried out on all the concrete structures. Risk management Risks that were successfully managed and overcome included the following: The comprehensive stakeholder consul- tation process resulted in a three month delay in the interchange construction but was resolved to the satisfaction of all concerned. While the N9 rehabilitation started on time, it was soon discovered that the roadbed adjacent to the route was saturated due to exceptionally high rainfall experienced in the area. The saturated in-situ materials were unable to drain due to impervious underlying layers and had to be removed and replaced with suitable rock fill from various sources such as widened cuttings and blasting from borrow pits. Ultimately 40 000 m 3 of rock fill, which required urgent sourcing and procure- ment, was placed to enable the project to proceed. This resulted in the programme being extended by almost six months. Hard rock materials such as crushed stone base course, surfacing aggregate, crusher dust and concrete stone were to be supplied from a separately operated source about 45 km south of Colesberg. However the dolerite stone from this source failed the durability requirements and the contractor proposed an alternative in Colesberg. This alternative source was tested and approved, with significant cost savings due to its prox- imity to the site. Had this alternative not been successful, the probable resultant delays may have had a significant negative cost impact on the outcome of the project.

constructed in the interchange area to control storm water runoff, which in the recent past had flooded the Engen access road and prop- erty and the entrance road to Colesberg. The project was built under trafficked conditions and this was achieved by accom- modating two-way traffic initially using one way stop-go passing lanes, and later using a two way bypass through some sacrificial widening. This latter innovation enabled road users to experience less inconvenience by not having to stop and wait for oncoming traffic to pass through the deviation. In the case of the N1 upgrade and the construction of the N1/N9 interchange, the N1 north and south carriageways were deviated so that the interchange could be built without disruption to traffic flow on the route. The N9 and the N1/N9 interchange precincts were maintained during the construction period by the contractor to ensure that the road surface was in a satisfac- tory condition from a safety aspect while new construction continued simultaneously. Cost and quality The project was completed within the approved amended budget and the amended time. Basil Read, in joint venture with Newport Construction, commenced construc- tion in March 2011 and the contract was completed in April 2014 at a combined value of just over R400-million for the interchange and the N9 rehabilitation. The N1/N9 interchange portion of the works was delayed by three months due to administrative issues relating to access to the Colesberg Engen 1-Stop, which is situated right in the heart of the planned interchange. As a result the project was phased so that the N9 portion of the works com- menced as originally planned, with the N1/N9 interchange portion of the works commencing three months later targeting and

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CONSTRUCTION WORLD JANUARY 2015