Civil Engineering November 2022 | Vol 30 No 10

I n view of the 2010 FIFA World Cup, SANRAL proposed the construction of the Nelspruit Northern Ring Road (NNRR) under the Concession Contract. As part of the NNRR planning and design, the Karino Interchange was developed with the objective to replace the former at-grade intersection between the N4 and the R538. The intersection was under pressure to handle the high traffic volumes experi- enced on both the N4 and R538, especially in peak hours. The turning traffic alone in the afternoon peak hour increased from 383 vehicles in 2008 to 975 vehicles in 2014 – a 155% increase. Due to high traffic volumes on the N4 Toll Road it had become increasingly difficult for vehicles to enter the N4. At night, in misty conditions and rainfall, the sight distance was further compromised. Consequently, the speed limit for this section of the N4 was reduced to 80 km/h. The intersection became notorious for the number and severity of accidents over the years. The Mbombela Local Authority requested that the interchange be imple- mented due to the high number of com- muters travelling between Kanyamazane and Mbombela, as well as the considerable economic development that is anticipated will take place along this corridor in the future. PROJECT DESCRIPTION In essence the project entailed the upgrading of the intersection between the N4 and the R538 (D636) which is the major access to the Kruger Mpumalanga International Airport, Kanyamazane and Witrivier (White River). The contract period was 24 months, with a three-month mobilisation period. Due to several events, the construction duration was extended, and practical completion of the project was scheduled for 17 May 2022. The project generally included: Q Q Widening the existing N4 to a four-lane undivided dual carriageway facility between km 62 950 and km 66 250. Q Q Upgrading the existing Karino Intersection to a level separated, par- tial clover quad interchange consisting of three ramps and one loop. Q Q Realigning the existing R104 (Link Road) to join up with the new inter- change, eliminating the dangerous at- grade intersection at Crocodile Valley. Q Q Structural work including the following: Q Q The existing river bridge B1519 on the N4, crossing the Karino Spruit, was widened, including the addition of two cells, increasing hydrological capacity Q Q The existing steel river bridge (B138) over the Crocodile River was repaired and upgraded to provide alternative access to the Karino Citrus packing facility Q Q A new overpass bridge B0491 was constructed, providing grade sepa- ration between the D636 and the N4 Q Q A new agricultural underpass (C586) was constructed. ASPECTS OF MERIT From a technical standpoint, the project boasts several impressive infrastructure components including bridges, multi-lane highways, mechanically stabilised earth retaining walls, and large lateral support structures. Additionally, implementation of the project in challenging topography and challenging geotechnical condi- tions required innovative engineering design and close collaboration among all role-players. From a social and economic perspec- tive, the project created employment for 374 people in the short term and has contributed towards infrastructure devel- opment of the area and the country.  SANRAL SA I CE 2022 Nat i onal Awards Category: Techn i cal Excellence FINALIST Technical Excellence category (Sponsored by SKI Civil and Structural Engineers) KEY PLAYERS Client: Trans African Concessions (TRAC) Consultant: SNA Civil and Structural Engineers Contractor: Raubex Construction Grade separated interchange at Karino 20 November 2022  Civil Engineering The existing intersection became notorious for vehicle accidents The upgraded interchange