Nejeni Construction and Project Management (Pty) Ltd

Crossroads Project

Crossroads Project
Client City of Cape Town
Location Crossroads , Cape Flats
Scope Of Work Pressure management implementation
Schedule 2011

Project Detail

General Information

Nejeni’s current directors and other employees were afforded the opportunity to work with the appointed contractor, Brink & Heath Civils.
The potential for pressure management implementation in Crossroads areas was originally investigated by the City of Cape Town in a Feasibility Study dated November 2009.

Crossroads is situated on the Cape Flats area and comprise of approximately 4,673 properties on the SAP system. According to the 2001 census updated in 2007 there are 4,376 formal and 4,087 informal households. The area is mainly low-cost housing, usually characterised by high levels of leakage and low levels of payment.

Almost 50% of the households are therefore informal.

Statistical Information

Summary of Presmac analysis from Feasibility Study

Option

Fixed outlet PRV

Time modulated PRV

Current inflow (m³/yr)

1,266,077

1,266,077

Predicted inflow (m³/yr)

1,078,737

1,063,075

Predicted reduced losses (m³/yr)

194,280

203,002

Predicted reduced consumption (m³/yr)

39,327

41,413

Predicted reduced inflow (m³/yr)

233,607

244,415

Net saving (Rand)*

2,311,521

2,321,943

Payback period (months)

9.0

9.5

@ R9.50 average historical cost of water. Loss of income with reference to reduced consumption is not considered due to low payment levels.

System characteristics

Item

Description

Number of properties (SAP, CCT, 2009)

4 673

Number of connections (SAP 2009 plus estimate for informal – 160 taps)

4 833

Length of water mains (CCT, 2008)

23.5 km

Population (2007 figures based on Census 2001)

34,074

Supply points

200 mm from Mahobe Dr (150 meter)
300 mm from Lansdowne Rd (200 meter)

Actual Installations

The locality of the PRV installation on the supply at the corner of New Eisleben and Lansdowne Road

The installation was constructed off-line and parallel to the main 300mm AC pipeline supplying into Crossroads at the corner of New Eisleben and Lansdowne Road. The inlet to the works is on the 300 steel main that crosses Lansdowne Road. The existing valve upstream of the existing meter becomes the divisional valve (for by-passing the PRV during maintenance) when the PRV is operating.

Savings

Logging Results

Logging results indicating the pressure reduction are included in Figure 6-1. Pressures at Pauli Street and Klipfontein Road (Critical Point) have been reduced from an average of 60m to 35 and from 55m to 30m respectively. The minimum pressure recorded at the critical point is 22.7m which is 1.3m below the stipulated minimum. This reduction in pressure has resulted in a reduction in water demand in Crossroads. The reduction in excess pressure has the added benefit of extending the life of the reticulation infrastructure as well as domestic plumbing infrastructure.

(Note that the pressure logger at Klipfontein was not functioning during the “before” period.)

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