Weaverley Housing Coop Design Report.pdf

8/9/2019 Weaverley Housing Coop Design Report.pdf

1/21

WEAVERLEY HOUSING COOPERATIVE

WEAVERLEY HOUSING COOPERATIVE

INFRASTRUCTURE DESIGN PARAMETERS

FOR RESIDENTIAL DEVELOPMENT

D NDE CIVIL PROJECTS

CONSULTING ENGINEERS

Civil &Structural Engineering Consulting

P.O Box 6851HarareTel. 04-771484Cel. 0773 282 522

FEBRUARY 2015


2/21

2

WEAVERLEY COOPERATIVE HOUSING

INFRASTRUCTURE DESIGN

PARAMETERS FOR RESIDENTIAL DEVELOPMENT

CONTENTS LIST

Page

1. INTRODUCTION 4

1.1 General 4

1.2 Town Planning 5

1.2.1 Town Planning Development 5

1.2.2 Survey & S.G Co-ordinated Plans 5

2. SITE DESCRIPTION 6

2.1 Location 6

2.2 Topography 6

2.3 Geology 6

3. PARAMETERS OF DESIGN 7

3.1 Design References 7

4. CIVIL ENGINEERING SERVICES : RETICULATION 8

4.1 Local Roads 8

4.1.1 General 8

4.1.2 Road Cross Section 8

4.1.3 Horizontal Alignment 9

4.1.4 Vertical Alignment 104.2 Local Stormwater Control 11


3/21

3

4.2.1 General 11

4.2.2 Design 11

4.2.3 Materials 12

4.2.4 Ancillary Stormwater Control 12

4.2.5 Sub Surface Drainage 13

4.3 Sewer Reticulation 13

4.3.1 Sewer Reticulation 13

4.3.2 Sewer Reticulation Design 13

4.3.3 Computer Analysis 14

4.3.4 Pipeline Layout and Gradients 15

4.3.5 Material Specifications 15

4.4 Water Reticulation 16

4.4.1 Water Demand 16

4.4.2 Water Reticulation Designs Development 16

4.4.3 Design Parameters 16

4.4.4 Computer Analysis 18

4.4.5 Pipe Materials Specification 18


4/21

4

1. INTRODUCTION

1.1 General

Dande Civils was appointed by Waverley Cooperative for the design of their

infrastructure services for 271 stands for residential purpose. This design report

forms part of the Consultants’ appointment and covers the strategy for the

planning, designing and construction of the of the infrastructure services.

Weaverley cooperative intend to develop the site with the installation of Civil

reticulation, for the 271 stands , with associated bulk and link infrastructure on

behalf of Kadoma Municipality.

The development principles to be adopted by the development team of Town

Planners, Engineers and Architects is to develop a township with ‘green’ areas,

adopt green engineering principles and appropriate engineering technologies

as is practical.

Engineering Reticulation Services will therefore be as follows;

Civil Engineering

- Kerbed and surfaced roads

- Stormwater control primarily in the roads, then channelled to

open channels as topography dictates

- Waterborne sewerage reticulation

- Individual metered water supply to each stand.

- Fire protection for the development within the water reticulationnetwork.


5/21

5

1.2 Town Planning

1.2.1 Town Planning Development

The original Town Planning from the own plan developed by the

Regional Office of the Department of Physical Planning was used. This

town plan was the layout used for the initial civil design.

1.2.2 Survey & S.G Coordinated Plans

Topographical Survey

Detail ‘on site’ topographical survey is required for detailed

design of,

• Sewer reticulation

• Roads reticulation

SG Coordinated Plans & Site Pegging

SG Plan

• The SG coordination plan is dependent upon the Town Planning

• The coordinated Town Plan was received by Dande Civils for

detail design in January 2015.


6/21

6

2. SITE DESCRIPTION

2.1. Location

The proposed housing development is located on portions of Subdivision A of

Plot 3 of Railway Farm 9 situate in the district of Kadoma and is situated in

Kadoma.

2.2 Topography

The site generally slopes down towards stand number 3666

2.3 Geology

Attached is a preliminary site assessment of the insitu soils – Appendix 1.

Material is generally SG5-SG9 material with a few areas with SG3


7/21

7

3. PARAMETERS OF DESIGN

3.1 Design References

CIVIL

ZIMBABWE

Ministry of Local Government & Housing for Water, Sewerage, Road

& S/W BCHOD : 1981

- Design Approach to Water and Sewerage Problems Relative to Urban

(predominantly High Density) and Rural Communities in

Zimbabwe.

SOUTH AFRICA

- Guidelines for the provision of Engineering Services&

Amenities in residential township Development – South Africa

(Red Book)


8/21

8

4 CIVIL ENGINEERING SERVICES : RETICULATION

4.1. Local Roads

4.1.1 General

The road reticulation system within the Township is developed on the following

principles :-

- To provide all weather access to stands – Class 5a/5b

- To provide linkage to the distribution roads by vehicle or bus – Class 4

- All Class 5 and Class 4 roads to be designed to transport Stormwater within

the township and to avoid potential Stormwater damage to properties.

Design speed on the roads is to be limited to 40 km/hr by the use of traffic calming

measures mini traffic circles or speed bumps. However, and where possible, the design

stopping / site distance is to be designed for a traffic speed of 60km to ensure additional

safety within the local streets for pedestrian movement.

Adjacent all local streets and the bus route, one side only , paved footways are to be

installed providing all weather pedestrian movement facility.

Roads geometric and pavement design has been undertaken with criteria from the

Guidelines for the Provision of Engineering Services in Residential Township issued by the

National Housing Board SA.

4.1.2 Road Cross-Sections

Class 4 Road- Local bus route

18m Road Reserve

- Road carriageway offset to allow for Electrical HT Servitude

- Carriageway 6m wide with 2½ % crossfall

- Edging support of pre cast concrete mountable kerb on low side and pre cast

concrete edging on high side

- 900mm wide footway on low side (Acts with the road as an additional paved

S/W channel in the event of substantial storm water discharge.

- Road reserves to be compacted to grades to assist S/W control and stand

access as detailed on the typical road section detail drawing.

- Reserves to be top soiled and grass seeded to avoid erosion and

provide a visually pleasing finish to the reserves.

- Classification


9/21


10/21

10

10m for class 5a to 4

15m for class 4 to class 3

4.1.4 Vertical Alignment

Road Gradient

Class 4 Max gradient 10% Class 5

Max gradient 12%

In certain short sections of roads these grades will need to be exceeded to ensure

stormwater control and avoidance of erosion to reserves, as the dictates of the topography

and design in minimizing cut/fill requirements.

Vertical Curves

Class 4 : Verified curve length 40 m min

2% change of grade – no curve required

Class 5 : Vertical Curve Length 20 m min

3% change of grade – no curve required

Access junction between roads -an allowance of up to 5% change of grade with no

vertical curve can be implemented as a valley between road crossfall and vertical

alignment of the adjoining road ensuring minimum cut/fill and avoiding potential

ponding of stormwater discharge from the road junction.

Pavement Design

Road Class 4 : Category UB 0.05≥3 E80s : Class E1

Road Class 5a/5b : Category UC/UD < 0.2 E80s : Class ER / EO

Roads to be designed with allowance for const ruction traffic use.

General CBR Min 10 (3 < 7 in vlei areas)

Roads to be granular material with pre mix surfacing

Footways to be granular material with 60mmblock paving surfacing and

cement stabilized base.


11/21

11

Bus bays to be 80mm block paving and cement stabilized base.

Design will be based on the catalogue of designs in the Red Book Section 6

Appendix 5 to suit the relevant road category and traffic E80 Class as

designated above and to be based on granular bases in moderate to dry

region Figure 5A.

Note: For Class 5b roads E/O compaction of G5 material to obtain a CBR of >60 will be

used for the road base material to limit the import of G4 / or crusher run base material.

4.2 Local Storm-water Control

4.2.1 General

As noted in Section 4.1 the local residential access roads are to be utilized as far as

possible to transmit localized Storm-water discharge to U/G pipe system or side

drains.

The pipe system, side drains or direct discharge from the roads via kerb chute outlets

will transfer the storm-water discharge into the three existing drainage channels on the

northern side of the development area of 271 stands.

Local design storm intensity will be for 1:5 storm discharge with 1: 10 year storm

surcharge onto the roads.

The roads and road reserves will also act as the major S/W discharge conduit for

storms up to 1:50 year intensity.

4.2.2 Design

Storm-water discharge design will be based on the Rational formula : Q =

AIC m³/sec360

Intensity will vary to suit the time of concentration (Tc) based on :

- the return storm intensity

- Topography

- Vegetations / Ground coverage

- Paved areas


12/21

12

- Channelized Flow

- Mean annual Rainfall of 900mm / annum

4.2.3 Materials /Installation

- Inlets to U/G pipework will be via kerb inlets or gulley inlets with concrete inlet

chambers and brick manhole chambers

- Concrete inlet channels will be used to increase the capacity of the standard

2m long Kerb inlets with end inlet to the KI to cater for the additional flow.

- Concrete chute outlets (precast and insitu) will be used on kerbed roads to

discharge to open drainage systems

- Pipework will be precast concrete pipes with spigot and socket flexible joints

equivalent to Class C pipework with Class B bedding – full granular surround andbedding factor 1.8.

- Cover under roads to be 1m to soffit but with concrete surround, 750 mm to soffit

will be acceptable provided a minimum of 450 mm cover to the pipe is available

when the road pavement is being constructed.

- Open drains will be designed to suit the required flows with concrete or stone lining

to avoid erosion where required.

- Manholes are to be brick manholes with full depth benching to ensure

constant velocity transfer through the manholes. The shape of the manhole is

dependent upon pipe sizing, number of inlets and turning requirements Covers to

be cost iron, or cast iron frame with concrete infill in open areas.

4.2.4 Ancillary Stormwater Contro l

To assist Stormwater discharge certain stands will be deemed Stormwater servitudes

to assist the control of major Stormwater run-off and avoid damage to houses if theywere to be constructed in that location.

These areas generally occur :

- At the bottom of steep roads when the flow ‘cannot’ change direction due to

velocities or horizontal alignment requirements of the Town Planning Layout

- Transfer of pipework or open drains to avoid bends and major direction

changes

- Areas that will be damaged with flood discharge

The open areas will generally be graded to form a central shallow V drain which may or


13/21

13

may not have the invert lined dependent upon stormwater discharge velocities.

However, as drain lining can also act as paved walkways I is considered that lining of the

invert should be undertaken

4.2.5 Sub Surface Drainage

- Due to the topography and the type of soil ground water is not expected in

many areas. However, areas where ground water may be encountered are :

- Potential perched water tables at the intersection of the granite sills and

granite ‘whale backs’

In these areas single aggregate stone bedding will be used to ensure protection to

underground pipework and open concrete lined drains and underground fin drains

will be installed adjacent roads to protect the road pavement.

4.3 Sewer Reticulation

4.3.1 Sewer Capacity

The Design Approach to Water and Sewerage Problems Relative to Urban

(Predominantly High Density) and Rural Communities in Zimbabwe and Guidelines

for the Provision of Engineering Services and Amenities in Townships Development-

South Africa identify typical water consumption rates in urban centers as:

Item Description Return to Sewer Design Guideline

1 Medium Income 70% Water Demand +

15% for S/W ingress.

850liters/stand/day

Zimbabwe Guidelines

4.3.2 Sewer Reticulation Design

The designs developed for sewer reticulation are based on data containedabove. Designs have taken into account the following.

- The proposed phasing of the development.

- The availability of materials and cost

- Contributing figures for sewage based upon water consumption figures

- Projected population figures

- Proposed types of housing units

- Pumping Station requirements

- Ease of maintenance


14/21

14

Sewerage reticulation is mid-block where the plan and terrain permits it. The

sewer lines are located at 1.0 meter from the stand (plot) boundary.

The minimum pipe size is 110 millimeters in diameter. (O/D UPVC)

Sewage velocities have been designed to be high enough to transport solids,

but not so high that scouring of pipes would occur. Minimum velocities for

design have been achieved at the daily peak, which is not less than 0.6 m/s

with pipe flow 0.5D.

Peak flow factors have been limited to 5.25 x dry weather flow which is the

requirement to meet the blue standard of reticulation design as per Zimbabwe

regulations.

Stand connections are to be Y-connections, capped and attached to markers

to indicate their location. Each connection shall be located at the lower end of

the stand. If convenient erf connection will be made directly to the sewer line

M.H.

The design for connections has been based on 1:60 fall from any point on the

stand GL. +450mm (min) to give a minimum connection depth to the main

161mm dia sewer line.

Manholes have been located at a maximum spacing of 80m for 110mm

diameter pipes and 90m for pipes of 225mm diameter and above. Manholes

locations for larger diameter pipes have been designed to accommodate the

maintenance equipment available to the maintaining authority.

4.3.3 Computer Analysis

The sewer reticulation will be analyzed by Autocad CIVIL 3D software

package that carries out the pipe line hydraulic calculations for design flow

and maximum flow. The software out data is listed below:

• Longitudinal sections of sewer line annotated automatically with pipe

specifications, diameter and bedding specifications.

• Hydraulic information also placed automatically on longitudinal section.

• Manholes are numbered and sorted in branch order.

•

Pipes are numbered and sorted.• Manhole / pipe topology automatically determined


15/21

15

• Pipe length calculated and totaled.

• Ground and invert levels determined at special chainages such as pipe or

road crossings.

• Manhole invert

• Pipe grades

• Drop manholes

• Pipe earthworks excavation quantities for all branches in the network,

pipeline layout and gradients

4.3.4 Pipeline Layout and Gradients

The sewers are laid with a minimum cover of 750mm depth between stands and

900mm Min cover elsewhere.

Road crossing are to be 1.25m depth to soffit to allow for road construction to be

undertaken without damage to any installed sewers.

Diameter (mm) Gradients

Maximum Minimum

160 1:10 1:120

200 1:16 1:150

250 1:24 1:200

315 1:30 1:300

400 1:40 1:350

675 1:70 1:600

Note : 1 in 80 is the minimum grade at the start of a sewer run

4.3.5 Material Specification

The pipeline material to be used is uPVC pipes sewer class 34 with flexible spigot

and socket joints for all sewer reticulation. Pipework above ground on pipe bridge

sections will be Mild Steel coated and painted as specified with Viking Johnson

Coupling Joints to allow for expansion.

Manholes are to be pre-cast concrete rings 1m dia unless noted on the drawings.


16/21

16

4.4 Water Reticulation

4.4.1 Water Demand

Item Description Water Demand Design Guideline

1 Medium Income 1000liters/stand/day South African

Guidelines

2 Schools - Day 20liters/ pupil/day Zimbabwe Guidelines

3 Shops 20 liters / Employee Zimbabwe Guidelines

4 Bars 300 liters / Stand Zimbabwe Guidelines

5 Offices 20 liters / Employee Zimbabwe Guidelines

6 Dry services industry 10 000 -15 000 liters

/Ha

Zimbabwe Guidelines

4.4.2 Water Reticulation Designs Developed

The designs developed for water reticulation are based on data contained in

the above documentation.

Designs have taken into account the following :-

Phase 1

- 271 Units + associated infrastructure

- Balanced reticulation with the 271 reticulation of units for

Phase 1 inclusive of supply line from reservoirs

- Peak flows @ 1.8 to 3 peak hourly factors

- Average Flow + Fire Flow from 1no. Hydrant to be used for final pipe

sizing.

4.4.3 Design Parameters

Item Description Design Guideline

1 Water Demand per stand 400m2 stand.

Medium density – 1000liters per day

South Africa Guidelines

2 Peak hourly factor 3 Zimbabwe Guidelines

3 Minimum Residual pressures at supply points 15m to

20m

Maximum Static pressure 60m

Zimbabwe Guidelines


17/21

17

4 Design Velocity between 0.5m/s to 2m/s Zimbabwe Guidelines

5 Cover over pipelines

Stand connection 450mm

In gardens 750mm

Under roads 1250mm

Zimbabwe Guidelines

6 Fire Flow

Low Risk area. One hydrant to Discharge at any one

time.

Hydrants at 240m coverage / spacing

Flow Rate 15liters per second.

Flow Time 1 hour.

Minimum Diameter of reticulation with Fire main

75mm diameter.

Adjacent to Institutional centers - additional Fire

Hydrant

South Africa Guidelines

Zimbabwe Guidelines

7 Institu tional Demand

Schools – Boarding 80 liters / Boarding pupil

Schools - Day 20 liters /Day pupil

Hospitals-200 - 400 liters /Bed

Primary Healthcare Centre- 10 liters /Out patient

Hotels 300 – 500 liters /Bed

Hostels/Rest Camps 200 - 300 liters/ Bed

Commerce or Administration

Shops 20 liters / Employee

Bars 300 liters / Stand

Zimbabwe Guidelines

Zimbabwe Guidelines


18/21

18

Offices 20 liters / Employee

Industry

These will vary considerably according

to processes used.

Dry services industry 10 000 -15 000 liters /Ha

Wet Industrial to be individually

assessed.

Zimbabwe Guidelines

8 Peak Demand Zoned Areas

Between min 1.8 max 3.5

SA Guidelines

4.4.4 Computer Analysis

The water reticulation system is analyzed by Epanet software package

that carries out a static analysis and a time simulation of the network.

The software out data is listed below:

Hydraulic results for each water pipe include:

• Diameter Chosen (mm)

•

Flow (l/s)• Velocity (m/s)

• Calculated Darcy friction factor

• Calculated equivalent Hazen Williams friction factor

• Friction loss in meters per 100 meters

Hydraulic results for each node include:

• Energy level (m)

• Pressure (m)

4.4.5 Pipe Materials Specifications

The pipeline material will be

• uPVC pipes Class 9 with spigot and socket joints for all water reticulation

pipelines


19/21

19

• HDPE Type 4 pipes with compression fittings for stand connections.

• Joints connections for tees and valve connections to be CI with

spigot and socket joints. Alternative flange joints to be used where

directed specifically on valve connections

• Valves to be CI to water works quality to SABS 665 , with

connections to suit uPVC pipework.

• Bends to be

uPVC pressure bends up to 450 .with spigot and socket joints

450 / 900 bends or where noted on the pipework schedule to be CI with

joints to suit spigot and socket uPVC pipework..

• All bends, tees etc required thrust block as specified on the drawings.


20/21

TITLE : WEAVERLEY COOPERATIVE HOUSING DEVELOPMENT

Project Team : Dande Civils

Client : Weaverley Cooperative

Client Project No : ………..

Status of Report : Final

Morad Report No : 1

Date of this Issue : 10 February 2015

For Dande Civils issuing

Written & by

Compiled

M.Benhura (Bsc) Civil

Hons

Initials & Surname Signature Date

Peer – reviewed

byM Kaendeza (Pr.Eng)

Initials & Surname Signature Date


21/21

APPENDIX 1: INSITU SOILS

Documents

Weaverley Housing Coop Design Report.pdf