Nejeni Construction and Project Management (Pty) Ltd

Delft

Delft Advanced Pressure Management System
Client City of Cape Town
Location Delft, Cape Flats
Scope Of Work Design and construct the Delft Advanced Pressure Management System
Schedule 2010

Project Detail

General Information

Table 2.1 Contractual Dates

Tender Advertised 21 August 2009
Site Clarification Meeting 1 September 2009
Closing date of Tender 17 September 2009
Appointment 20 January 2010
Dummy Shut down 8 April 2010
Construction Start Date 29 April 2010
Certificate of Practical Completion 1 July 2010
Date of Commissioning 4 August 2010
Certificate of Completion of Works 19 August 2010

Brink and Heath were appointed in 20 January 2010 through a tender process by the City of Cape Town to do design and construct the Delft Advanced Pressure Management System.

Delft is situated on the Cape Flats area, east of the airport and west of the R300. The northern boundary is Stellenbosch Arterial Rd and the southern boundary is the N1.

The area is mainly low-cost housing, usually characterised by high levels of leakage and low levels of payment.

A 200 mm PRV at the Mulberry 500 mm supply was installed in a previous contract and the tender document assumed that PRV installations would happen in two phases at the 800 mm Tambotie supply. Phase 1 (this contract would be to install a 300 mm PRV on the 600 branch and phase 2 (a subsequent contract) would be to install a PRV on the 400 mm branch.

Statistical Information

Source

Population

SI

Number of households

SI

Average number of persons per household

SI

Number of properties on SAP

31 193

GLS

Number of properties on GIS

GLS

Total number of properties

GLS

AADD (all properties)

8 909

GLS

Total Input volume

UFP

Billed consumption

8 909

GLS

Number of residential connections

21 155

GLS

AADD (residential) 8 399
Number of cluster housing & flats

1 817

GLS

AADD (cluster housing & flats)

26

GLS

Number of other connections

8 215

GLS

Number of Large users > 20 kl/d 6

GLS

AADD of all large users

254

GLS

Number of 24 hour operations

?

GLS

AADD of 24 hour operations

?

GLS

Total length of pipe

172 000

GLS

Current average operating pressures (no PRVs) @ AADD 61

GLS

Number of supplies

3
Supply 1 Tambotie

BW

Supply 2 Mulberry

BW

Supply 3

BW

Emergency supplies Delft Main Road

Retic

Actual Installations

The main components of the works included:

  • The construction of PRV installation at Tambotie consisting of two 200mm ø PRVs including a divisional valve on the 800mm ø main.
  • The completion of the 200mm ø PRV installation at Mulberry consisting repairs to the chamber and the installation of a pilot valve, bios chamber and controller.

Figure 2.1 Location of Tambotie PRV

Figure 2.1 Location of Mulberry PRV

Savings

Critical Point Pressure Analysis

The pressures at the critical points, Gatwich and Bloch critical points, before and after setting the PRVs on a fixed outlet pressure are shown in Figure 8.2 and Figure 8.3 below:

Figure 8.2: Pressures at Gatwich before and after settings the PRVs

Figure 8.3: Pressures at Bloch critical point before and after settings the PRVs

It was found that the reason for the lower pressures at Bloch St was that a critical valve had been left shut. On opening this valve the pressures improved dramatically as shown in Figure 8.3

Schematic