preliminary engineering design report water … · 5.2 wastewater treatment works ... 8 cost...

128 Beyers Naudé Dr. Cnr. Mendelssohn Rd. Roosevelt Park, 2195 Johannesburg, Gauteng

PO Box 48550 Roosevelt Park, 2129 Johannesburg Gauteng

Tel: 011 888 1425 Fax: 011 888 1075 [email protected] www.scip.co.za

ISO 9001:2008 Certified A member of CESA Directors: JD Booyens;

NM Mjodi; C Meyer; P Booyens. Reg. No. 1996/15526/07 Vat No. 4010168278

JOHANNESBURG EMALAHLENI

Our ref: 972/001

PRELIMINARY ENGINEERING DESIGN REPORT WATER AND SANITATION

DEVELOPMENT OF FORT WEST PHASE 2

IPW-PRT2011/08/0107

Date: 21 June 2012 Client: Gauteng Department of Local Government and Housing. Contact: Mr. P Booyens Tel: 011 888 1425 Email: [email protected]

mailto:[email protected]

PRELIMINARY ENGINEERING DESIGN REPORT: WATER & SANITATION. FORT WEST PHASE 2

EXECUTIVE SUMMARY

The Preliminary Feasibility Report completed under IPW-PRT2011/08/0107 indicated that 181 ha of land identified for developments in the west of Pretoria, just north of lotus gardens, is suitable for the development of approximately 3500 residential units.

The proposed development falls across two reservoir zones, namely Lotus Gardens and Pretoria West HL reservoir zones. Furthermore, within the Lotus Gardens reservoir zone, part of the development falls in the PRV sub zone as well. A 250mm diameter main waterline is required to supply the northwestern part of the proposed development, from the Lotus Gardens reservoir. The southeastern section of the development will be fed by a 315mm pipeline from the Pretoria West HL reservoir. The total cost for new bulk water infrastructure is estimated to be R3,325,540.00 and the internal network will be approximately R14,494,500.00 The existing 225mm diameter sewer line is not sufficient to service Fort West Phase 2. Both Phase 1 and Phase 2 will require upgrading the bulk sewer pipeline. Therefore, collaboration should be done between the two developments. The total estimated cost for bulk sewer upgrade is R10,346,000.00 and the internal network will be approximately R20,936,500.00


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CONTENTS

1 INTRODUCTION ....................................................................................................... 3

1.1 Project Description........................................................................................... 3

1.2 Locality ............................................................................................................. 3

2 SCOPE OF THE REPORT .......................................................................................... 3

3 TOWN PLANNING STATUS ...................................................................................... 3

4 BULK WATER ........................................................................................................... 5

4.1 Existing Reservoirs .......................................................................................... 5

4.2 Existing Pipelines ............................................................................................. 5

4.3 Residential Water Demand .............................................................................. 5

4.4 Proposed Bulk Pipelines .................................................................................. 6

5 SANITATION ............................................................................................................. 7

5.1 Generated Sewer .............................................................................................. 7

5.2 Wastewater Treatment Works (wwtw) ............................................................. 7

5.3 New Main Outfall Sewers ................................................................................. 7

6 LEVEL OF SERVICE: INTERNAL SERVICE ............................................................... 8

6.1 Type of Development and Appropriate Level of Service .................................. 8

6.2 Water Supply: Design Standards ..................................................................... 8

6.3 Sanitation: Design Standards ........................................................................... 9

7 SERVICE CONTRIBUTIONS .................................................................................... 10

8 COST ESTIMATE .................................................................................................... 10


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LIST OF FIGURES

Figure1: Preliminary Town Planning Layout 2

LIST OF TABLES

Table1: Calculated Water Demands 4

Table 2: Cost Estimate – Bulk Infrastructure 8

Table 3: Cost Estimate – Internal Networks 8

ANNEXURES

ANNEXURE A Locality Plan

ANNEXURE B GLS Water and Sewer Master Plans

ANNEXURE C Existing and Proposed Water Network

ANNEXURE D Existing and Proposed Outfall Sewers Network

ANNEXURE E Standard Water Details

ANNEXURE F Standard Sewer Details

PRELIMINARY ENGINEERING DESIGN REPORT: WATER AND SEWER. FORT WEST PHASE 2

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1 INTRODUCTION

SCIP (Pty) Ltd was appointed by Gauteng Department of Local Government and Housing for the water and sanitation preliminary engineering design report for Fort West Phase 2 (Farm Fort 464 IQ). This development falls within the jurisdiction of the City of Tshwane.

1.1 PROJECT DESCRIPTION

The project is referred to as the development of Fort West Phase 2 in the west of Pretoria, north of Lotus Gardens. The area forms part of the City of Tshwane Spatial Development Framework, and is located in region 3 of City of Tshwane. The SDF earmarked this area as residential development zone with supporting services.

1.2 LOCALITY

The proposed areas of development are located west of Pretoria CBD, north of the N4- Hartbeespoort dam direction bordering Lotus Gardens to the north, and Danville to the west. The locality plan is attached in Annexure A.

2 SCOPE OF THE REPORT

The report addresses the full scope of work required for the preliminary design of the water and sanitation for the Fort West Phase 2 development. Differentiation is made between the internal reticulation service (that is to be financed by the DOLG&H) and the link and bulk service (to be financed by the Municipal Infrastructure Grants).

3 TOWN PLANNING STATUS

A feasibility study was conducted indicating possible land use per block as described by the city of Tshwane’s SDF. The potential housing developments in Fort West will consist of a few parks, some heritage areas and 3221 households. The heritage areas consist of the former West Fort Leprosy hospital and associated buildings (kitchen complex, theatre, stores etc.). These buildings are in an ill state of repair and are illegally occupied.


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Proposed town planning layouts for this development have been completed and submitted for application of township establishment. The town planning layout is indicated in Figure 1, below.

Figure 1: Preliminary Town Planning Layout (Fort West Phase2)


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4 BULK WATER

4.1 EXISTING RESERVOIRS

The proposed development falls across two reservoir zones, namely Lotus Gardens and Pretoria West HL reservoir zones. Furthermore, within the Lotus Gardens reservoir zone, part of the development falls in the Lotus Gardens PRV sub zone.

The northwestern part of the proposed development will be serviced from the Lotus Gardens reservoir and the southeastern section will be serviced by the Pretoria West HL reservoir. The capacity analysis done by GLS Consulting, shows that these reservoirs will be sufficient to supply the development – see Annexure B for the sewer and water master plan.

4.2 EXISTING PIPELINES

The existing Lotus Gardens development is serviced by the Lotus Gardens and Pretoria West HL reservoirs. The western part of the Lotus Gardens development is fed by two parallel pipelines that run from the Lotus Gardens reservoir. These pipelines are 350mm and 400mm in diameter, with a pressure reducing valve (PRV) situated on the 400mm pipeline. The eastern part of the Lotus Gardens development is fed by a 350mm pipeline from the Pretoria West HL reservoir. The existing and proposed bulk water lines are shown in Annexure C (Existing and Proposed Water Network).

4.3 RESIDENTIAL WATER DEMAND

The average annual daily demand (AADD) is used to determine the size of the bulk pipelines for the new development. The AADD was calculated using the CoT Guidelines for the Design and Construction of Water and Sanitation Systems, as well as the Guidelines for Human Settlement Planning and Design (“The Red Book”). The following AADDs were used in the calculations:

Land Use AADD Unit

Residential Type 1 0.75 kl/erf/day

Residential Type 2 0.8 kl/unit/day

Residential Type 3 0.6 kl/unit/day

Parks (size ≤ 2ha) 15 kl/day

Parks (2ha<size≤10ha) 12.5 kl/day


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Table 1, below, show the calculated water demands for Fort West Phase 2. It is important to note that the heritage areas were not included in this calculation. Table 1: Calculated Water Demands

Land Use Units/ha ha Dwelling

Units Total AADD

(kl/d)

Residential Type 1 - n/a 272 204.00

Residential Type 2 40 4.60 184 147.20

Residential Type 3 80 34.56 2765 1658.88

8 Parks (size varies) 13.57 - 186.80

Total 3221 2197 The AADD is calculated as 2197 kl/d. The AADD that falls within the Lotus Gardens reservoir zone is approximately 1000 kl/d. The Lotus gardens reservoir has enough capacity to accommodate Fort West Phase 2, however, Fort West Phase 1 is also in the planning stage. Phase 1 will definitely push the water demand too high for the reservoir, and a second Lotus Gardens reservoir will be required.

4.4 PROPOSED BULK PIPELINES

The analysis done by GLS Consulting, shows that the following bulk pipelines are required to accommodate Fort West Phase 2:

• A 250mm diameter pipeline supplying water from the Lotus Gardens reservoir, running from west to east. This pipeline will connect to the 400mm existing pipeline, after the PRV.

• A 315mm diameter pipeline (which reduces to 250mm), supplying water from the Pretoria West HL reservoir.

For more detail on these pipelines, see Annexure B (GLS Water and Sewer Master Plans) and

Annexure C (Existing and Proposed Water Network).

It is recommended that a 24-hour onsite pressure test should be conducted before any design is finalized. This is done to ensure that the required pressure is in range with the standard residential pressures required, and to determine if any pressure reducing valves are needed (the master planning only deals with theoretical pressures).


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5 SANITATION

5.1 GENERATED SEWER

The peak daily dry weather flow (PDDWF) for the proposed development area is calculated as 1974kl/d. However, a flow of 13.74Ml/d (159l/s) was used for the design of the bulk sewage system. This design flow is the instantaneous peak wet weather flow (IPWWF) as calculated by GLS Consulting, and it includes future developments upstream of Fort West Phase 2.

5.2 WASTEWATER TREATMENT WORKS (WWTW)

The generated sewer flows will be accommodated at the Daspoort WWTW and excessive flow would be accommodated at the Rooiwal 2 WWTW. Currently Rooiwal is being upgraded and refurbished, to accommodate overflow from the Daspoort WWTW. In the GLS Master Plan no changes or recommendations were made with regard to the wastewater treatment works.

5.3 NEW MAIN OUTFALL SEWERS

A new main gravity line is proposed for the development which will start at a diameter of 450mm and will increase to 525m - see Annexure B (GLS Water and Sewer Master Plans) and Annexure D (Existing and Proposed Outfall Sewers Network). It is important to note that the bulk sewer line should be upgraded (enlarged to 525mm diameter) up to the point where it connects to the existing 825mm diameter pipeline.


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6 LEVEL OF SERVICE: INTERNAL SERVICE

6.1 TYPE OF DEVELOPMENT AND APPROPRIATE LEVEL OF SERVICE

Fort West represents a subsidized integrated housing development consisting of smaller sized Residential 1 erven as well as larger Residential 2 and 3 erven. In terms of the CoT Guidelines for the Design and Construction of Water and Sanitation Systems it is proposed that each property be provided with a full-pressure unrestricted conventional water house connection. It is also proposed that each individual erf be provided with full waterborne sanitation. This will consist of a 100mm diameter house connection which is connected to the sewer lines at a distance of 500mm inside the erf boundary and not less than 1m from the side boundary at the lowest point of the boundary.

6.2 WATER SUPPLY: DESIGN STANDARDS

An internal distribution network with individual connection points is proposed with underground pipes laid in road reserves. Water meters will be installed for each individual property. The standard water details applicable to projects in the supply area of City of Tshwane are indicated in Annexure E. These details are the standard required details of the City of Tshwane. The following will be considered during the detail design of the water reticulation network:

• Hydraulic design of the pipeline network will be done to achieve a minimum head of 25 m under peak demand and a maximum head of 60m.

• Fire demand: Group 1, low risk with 8m residual head at peak flow.

• Velocities in pipes will generally not exceed the following under peak demand:

o 3,5 m/sec for pipe diameters smaller than 150 mm, and

o 2.5 m/sec for pipe diameters bigger than 200 mm.

• Isolating valves will be provided to isolate any section of pipeline:

o using no more than 4 valves; and

o the total length of main included in an isolated section will not exceed a nominal 600 m; and

o no more than 60 dwellings will be isolated at a given time (low costing housing development).

• Fire Hydrant spacing to be 240m on 75mm diameter and larger pipes.


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• The minimum pipe size in the network will be 75mm diameter.

• Pipe material to be used will be Class 12 uPVC/mPVC, SABS 966 approved.

• Trenching, bedding and backfilling shall conform to SANS 1200 LB and SANS 1200 DB and to class B bedding, backfilled to 93% of Mod. AASHTO density.

• House connections will consists of 40mm diameter class 12 HDPE pipes, reducing to 25mm diameter.

6.3 SANITATION: DESIGN STANDARDS

An internal reticulation network with connection points to each property is proposed with underground pipes laid in mid block servitudes or road reserves. The standard sewer and manhole details to be used for this project are indicated in Annexure F. These details are the standard required details from the CoT. The following guidelines will be used in the detail design of the sewer network:

• Hydraulic design of the sewers will be done with the following minimum pipe slopes: 1 : 80 at head 1 : 80 for 160mm dia pipe 1 : 120 for 200mm dia pipe 1 : 1600 for 250mm dia pipe 1 : 200 for 300mm dia pipe

• Minimum velocity of flow in a rising main should be 0.75m/s at 70% full

• Inspection manholes will be placed at convenient positions.

• Maximum manhole spacing shall not be more than 80 meters.

• Minimum manhole diameter will be 1250 mm constructed of dolomitic type aggregate.

• Heavy duty manhole cover slabs with an opening of 750 mm will be used in road reserves together with a frame and cover of nominal diameter 560 mm.

• Medium duty manhole cover slabs with an opening of 750 mm together with a frame and cover of nominal diameter 560mm will be used in all other locations besides road reserves.

• Manholes shall protrude above ground level by not less than 150mm.

• Minimum pipe size for the rising main sewers will be 160 mm diameter (NB) and 110 mm diameter for house connections.


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• Pipe material will be specified as 400KPa PVC with slip on couplings.

• Trenching, bedding and backfilling shall conform to SANS 1200 LB and SANS 1200 DB, backfilling compaction to 90% Mod AASHTO density in servitudes and 93% in road reserves.

• Sewer reticulation will be tested in accordance with the relevant requirements of SANS 1200.

7 SERVICE CONTRIBUTIONS

Service contributions are usually not applicable to subsidized housing developments and Fort West Phase 2 will therefore be eligible to be excluded from services contributions.

8 COST ESTIMATE

The tables below show the cost estimate for the water and sewage systems for Fort West Phase 2. Table 2: Cost Estimate – Bulk Infrastructure

Item Description

Amount Length (m) Diameter (mm)

Bulk Water Pipeline W1 30 160 R 37,000.00 W2 1215 250 R 1,088,360.00 W3 215 200 R 166,740.00 W4 900 160 R 478,000.00 W5 845 315 R 1,098,440.00 W6 493 250 R 457,000.00

Total (Bulk Water) R 3,325,540.00 Outfall Sewer

S1 1142 450 R 3,426,000.00 S2 1730 525 R 6,920,000.00

Total (Outfall Sewer) R 10,346,000.00 Table 3: Cost Estimate – Internal Networks

Item Description Amount 1 Water Network (3221@ R4500/erf) R 14,494,500.00 2 Sewer Network (3221 @ R6500/erf) R 20,936,500.00

Total R 35,431,000.00


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The cost estimates are based on 2011 construction costs and exclude professional fees and VAT. We trust that you find this report in order and should you have any queries please feel free to contact us. Sincerely,

______________ P Booyens SCIP Engineering Group

preliminary engineering design report water … · 5.2 wastewater treatment works ... 8 cost...

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