Project:   Northern Areas Sewer Phase II

 

Location:  5.2 km of major collecting sewer pipeline running from Vanguard Drive, along Jan Smuts Drive in Pinelands to the
                  Langa Pumpstation at the N2.

 

Scope:  The Contract entails the second phase of the replacement of the original NAS (constructed in 1951) using 
              concrete pipes with a sacrificial layer, including construction of the associated manholes.  
              The selection of the NAS to be replaced starts just west of Vanguard Drive and follows the Elsieskraal River Canal 
              up to Stella Road where it turns south traversing through the Thornton residential area up to Viking Road,it then
              turns in a westerly direction along Viking Road up to Jan Smuts Drive, and then turns in a southern direction
              along Jan Smuts Drive up to the Langa Pumpstation just north of the N2 National Road.

              The total length of the NAS Phase 2 is approximately 5.2km and the sewer diameter and associated pipeline lengths 
              are as follows:

 

              The depth of installation of the NAS Phase 2 typically varies between 4m and 7m. In terms of bedding preparation, 
              trench excavation will be to a depth of up to 8m. In terms of deep trench excavations in
specific areas of
              limited working space, shoring will be required to provide safe working conditions on
site. It should be noted that a 
              high water table will be encountered on site.

 

              In addition to the construction of the new outfall sewer, manholes will be constructed at approximately 90m intervals,
              and also at changes to the vertical and horizontal alignment of the sewer, to allow for
access for operation and
              maintenance.
              The manholes typically comprise of an in-situ cast concrete
chamber (with benching) constructed to be below 
              ground level, and provided with an access chimney 
constructed using precast concrete manhole rings.

              Furthermore, the existing 525mm diameter Kensington Sewer which currently discharges into the existing NAS at the
              Langa Pump Station, will be re-routed for approximately 60m using a 600mm
diameter concrete pipeline to discharge
              directly into the wet well of the Langa Pump Station. 
              This rerouting
will also include the construction of an in-situ cast concrete screening chamber.

                Considering that large volumes of soil and construction materials may have to be transported to and from site, provision
              is made in the Contract for reinstating some internal roads in the Thornton
residential area that may be
             damaged due to construction traffic.

 
              Construction of the sewer at major road and railway crossings shall be carried out by means of pipe jacking. The
              total number of pipe jacks envisaged on the Contract are nine varying in diameters from
810mm to 1675mm, and
              the length varying from approximately 22m to 84m.

 

 

Project Value:  R 146 million

 

Duration: 18 months

 

Extent of Participation: A total of 9 pipe jacks and a 1.7km section of Cured In Place (CIPP) is subcontracted, the balance of work by CSV.

 

Recent Articles relating to NAS Project (please click on the links below to read the articles):

Slick, Silent & State of the Art - Plant Equipment & Hire - September 2014 (vol 38, no 9, p 28)

Lateral Thinking - The Civil Engineering Contractor - October 2014 (vol 49, no 10, p. 22)

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