Construction World December 2015

C

Professional Services

Highly Commended

Construction of the Northern Areas Sewer – Phase II

64

AECOM was appointed in 2009 by the City of Cape Town (CCT) for the professional services related to the design of the new Northern Areas Sewer – Phase II (NAS2), and the subsequent tender compilation and contract administration. The existing Northern Areas Sewer (NAS) is a major collector sewer currently serving an area of 4 100 ha of the northern suburbs of Cape Town. Project information • Company entering: AECOM • Project start date: 7 May 2013 • Project end date: 20 October 2015 • Client: City of Cape Town • Main contractor: CSV Construction • Principal agent: AECOM • Project manager: AECOM • Consulting engineer: AECOM • Subcontractor: Wepex • Project value: R160 708 688,14 (including VAT, 10% contingencies and escalation)

The NAS starts just east of Jan van Riebeeck Drive and follows the Elsieskraal River up to Jan Smuts Drive where it turns south along Jan Smuts Drive up to the Langa Pump Station. The total length of the NAS is approximately 8,7 km. The NAS was originally commissioned in 1951 and is over 60 years old. Since 1994 it was reported that the NAS does not have sufficient capacity to service the existing catchment area. To this extent a portion of the NAS (from the start just east of Jan van Riebeeck Drive to a position just west of Jakes Gerwel Drive, i.e. a total length of approximately 3,8 km) was replaced in 2000/2001. This project entailed the replacement of the remaining 4,9 km portion of the original NAS, downstream of Jakes Gerwel Drive up to the Langa Pump Station.

AECOM conducted an updated estimate of the expected future flows in the NAS (in terms of the required capacity) based on a design life of at least 50 years. The predic- tions took into account all future develop- ment plans in the catchment, including the plans to develop Wingfield, Acacia Park, the Conradie Hosipital Site and the Old Mutual Golf Course site. In addition, densification was taken into account based on the CCT’s Densification Strategy. Based on these assumptions, it was esti- mated that the maximum flow that the NAS2 would need to accommodate during future peak wet weather flow conditions would be approximately 3 000 ℓ/s. This is significantly higher than the current capacity of the existing sewer which is in the order of 600 ℓ/s CSV Construction was appointed for the construction of the NAS2 in May 2013.

2 15 BEST PR O JECTS

CONSTRUCTION WORLD DECEMBER 2015