Nejeni Construction and Project Management (Pty) Ltd

Bishop Lavis

Bishop Lavis Pressure Management Project
Client City of Cape Town
Scope Of Work Design, construction and commissioning of advanced pressure management solution

Project Detail

General Information

PROJECT AND PROJECT TEAM

Client contract number Contract Number: 74Q 2011/12
Project name: Bishop Lavis Pressure Management Project
Project description: Design, construction and commissioning of advanced pressure management solution for Bishop Lavis.
The Project involved the construction of 2 PRV installations for Bishop Lavis and 2 for Bonteheuwel, 1 for Nooitgedacht and 1 for the additional area, Montana.
Client / Local authority: City of Cape Town
Main Contractor Brink and Heath Civils (Pty) Ltd
Technical design (Sub-Consultants to
Main Contractor)
Mechanical and Civil Works: UFP Consulting
Structural Works: De Villiers Sheard
Specialist Contractor Nejeni Construction

The Project

Previous to the pressure management of Bishop Lavis, Bonteheuwel, Nooitgedacht and Montana the areas experienced pressures between 7 and 9 bars and were not completely discrete zones. No comprehensive feasibility study was undertaken prior to the tender. However, based on the experience in other areas in Cape Town, it was assumed that the water supply system experienced high levels of leakage due to high pressures, poor internal plumbing (Retreat in particular), frequent burst pipes and aging water infrastructure. In this regard, the City of Cape Town requested tenders for the design, construction and commissioning of a sustainable pressure management solution for Bishop Lavis, Bonteheuwel, and Nooitgedacht. Montana was added as a Variation Order.

The pressure management solution involved the construction pressure management installations on the two main feeds to Bishop Lavis, the two main feeds to Bonteheuwel, the main feed to Nooitgedacht and the main feed to Montana. All other supplies to these areas were shut in the course of the project. (now Divisional Valves or DVs).

Statistical Information

Thornton

Bishop Lavis

Nooitgedacht

Bonteheuwel

Montana

Pipe length (m)

22 122

43 395

5 145

56 265

2530

Area (ha)

184

262

40

356

24

AADD

1 113

2 384

494

3 941

153

AADD NRW

1 374

3 405

706

5 630

218

Units

2 210

3 811

568

7 465

142

Meters

1 103

3 733

406

7 280

139

Stands

1 508

3 778

422

7 490

143

Actual Installations

The Works

The contract involved the construction of pressure management installations at the following locations:

Bishop Lavis

  • Wayside Road and Valhala Drive
  • John Ramsay and Modderdam Roads

Bonteheuwel

  • Vanguard Drive and Jackalsvlei Road
  • Valhalla Drive and Jackalsvlei Road

Nooitgedacht

  • Heilbot and Modderdam Roads

Montana

  • Valhalla Drive and Jackalsvlei Road

 

Supply Main and PRV Details

Zone PRV Location Supply Main PRV Size
Nominal Material OD Tee (inlet) Tee (outlet) PRV supply Current Future
Nooitgedacht Heilbot 225 AC 262 250 250 250 100 150
Bishop Lavis John Ramsay 315 PVC 315 250 250 250 150 200
Bishop Lavis Wayside 300 AC 363 250 250 250 150 200
Bonteheuwel Valhalla 300 AC 363 250 250 250 200 200
Bonteheuwel Vanguard 300 AC 363 250 250 250 200 200
Montana Valhalla 225 AC 262 250 250 250 150 150

Savings

Figure 6-1: Bishop Lavis Pressure Logging Results at PRV and Critical Point

Figure 6-2: Bonteheuwel Pressure Logging Results at PRV and Critical Point

Figure 6-3: Nooitgedacht Pressure Logging Results at PRV and Critical Point

Figure 6-4: Montana Pressure Logging Results at PRV and Critical Point.

The Flow logging results for Bishop Lavis, Bonteheuwel, Nooitgedacht and Montana are included in Figure 6-5, Figure 6-6, Figure 6-7, and Figure 6-8 respectively.

Note that all of the PRVs had already been set and were decommissioned for a period to calculate the savings

Figure 6-5: Bishop Lavis Flow Loggings before and after pressure management

Figure 6-6: Bonteheuwel Flow Loggings before and after pressure management

Figure 6-7: Nooitgedacht Flow Loggings before and after pressure management

Figure 6-8: Montana Flow Loggings before and after pressure management

 

The changes in the Minimum Nigh Flow (MNF) and the average flow into the pressure management zones and the water savings in litres per second and m3 per hour are shown in Table 6-1 below:

Table 6-1: Zonal savings

Bishop Lavis

Bonteheuwel

Nooitgedacht

Montana

Upstream Pressure P Max

P Min

P Ave

Downstream Pressure P Max

P Min

P Ave

78.0

38.0

53.2

90.0

46.0

62.4

68.0

32.0

48.0

81.0

41.0

56.1

Critical Point Pressure P Max

P Min

P Ave

91.0

44.0

62.4

71.0

32.0

50.5

75.0

33.0

49.3

Flow Q Max

Q Min

Q Ave

195.0

24.0

91.8

444.0

30.0

185.2

42.0

8.4

21.6

162.0

15.0

73.3

Zone P Ave

26.6

62.4

49.3

52.7

Savings

 

Reduction in MNF

Water savings/d

Water savings/annum

Rand savings/d*

-9.0

216.0

78 840

2 052

-42.0

1008.0

367 920

9 576

-4.0

96.0

35 040

912

-10.5

252.0

91 980

2 394

Rand savings/annum*

748 980

3 495 240

332 880

873 810

FINAL REPORT/S AND OTHER STATISTICAL ANALYSIS CAN OBTAINED VIA THE CONSULTANTS