Design Report for Chikwina Service Lines

W O R L D V I S I O N W O R L D V I S I O N DESIGN REPORT FOR CHIKWINA-MPAMBA WATER SUPPLY SCHEME FEEDER LINES

2012W . E M T O N G A

Chikwina-Mpamba Water Supply Scheme Design Report for Service Lines

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EXECUTIVE SUMMARY

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World Vision Malawi through Chikwina-Mpamba Area Development Programme is providing water to rural communities in its catchment area and ensures that people have convenient access to water in sufficient quantity and adequate quality for basic use. In view of the above objective World Vision Malawi carried out design works for Chikwina- Mpamba Water Supply Scheme. The first design assignment covered the assessment of the existing scheme which did not include service lines. This assignment is aimed at designing service lines to demand points across the scheme. Due consideration has been given to the fact that part of the projected population demand does not exist today but is expected to occur in future. Generally scheme components that can easily be upgraded in future are left to be implemented when the demand arises due to uncertainties in predicting where and when exactly the demand will occur otherwise there may be creation of dead ends that may prove to cause more problems than solving them

Project Objectives

The main objective of the project is to carry out hydraulic analysis for service lines and design the pipelines. According to the terms of reference the assignment has the following specific objectives:-

i. To survey areas from the distribution main to communities and to determine specific feeder line connection points to the main line.

ii. To carry out detailed hydraulic analysis and modeling for all feeder lines and specify safe working pipepressures including that for valves and other accessories.

iii. To produce a design report and associated working drawings and bills of quantities.

Service Lines Design

The assignemet came up with and designed the following service lines;-i. Service Line to Kayuni Upper.ii. Service Line to Kayuni Village Headquarters.iii. Service Line to Mapund and Matias Nkhata.iv. Service Line to Zawanji

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v. Service Line to Choma vi. Service Line to Kalongavii. Service Line to Muyombeviii. Service Line to Chalewaix. Service line to Kapoti Westx. Service Line to Kapoti Eastxi. Service Line to Chivuti (From Chikwina Market going northwards)xii. Service Line to Chivuti (From Chikwina Market going eastwards)xiii. Service Line to Jumboxiv. Service Line to Wadenyaxv. Service Line to Luwazi

Some communities are located very close to the road from Chikwina to Mpamba where the distribution main is located. They do not need special service lines. Connections may be connected directly to the distribution main without disturbing the hydraulic arrangement of the scheme

Recommendations

The recommendations may be summarized as follows;

Install pipelines following the recommendations indicated in chapter six.

Some places are located in isolated areas and have altitudes which are almost the same as the service tanks or are above them. These places can only be served by using high heads. High heads can only be generated by using a bypass in case of storage tank no 2 and shifting the position of the break pressure tanks upwards. This arrangement requires installation of high class pipes particularly in the valley sides

Use of Existing pipes

There are various sizes classes of pipes already in stock. Even though the exact inventory is not known, it was generally observed that some pipes may still be used based on the following conditions:-

1) Pipes can be installed where the design prescribes the same pipe size and class.

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2) Where such situations cannot match it is advisable to use bigger pipes where the classes prescribed are the same.

3) Where there is a mismatch between pipe classes, it is advisable to use a higher class as long as the sizes are the same or higher.

Generally the pipes prescribed for feeder lines are smaller than 110. Introducing bigger pipes compared to the prescribed size reduces hydraulic losses further and therefore it is hydraulically an advantage. However, it becomes an over design since the carrying capacity installed is higher than the minimum requirement. In terms of economics it implies that the system is no longer economical. However, since the costs were already incurred this may be considered to be water under a bridge.

In conclusion, the actual number of pipes that may be utilized in the scheme is dependent on the approval of the resident engineer since the current condition of the pipes in stock will also matter when installing these pipes. It is also wealth noting that the storage conditions of these pipes may have introduced fatigue and other issues which may change the hydraulic conductivity, physical strength as well as other characteristics of the pipes.

Table of ContentsEXECUTIVE SUMMARY..................................................................................................3Project Objectives........................................................................................................3Service Lines Design....................................................................................................3Recommendations.......................................................................................................4Use of Existing pipes....................................................................................................5Table of Contents.........................................................................................................6List of Figures..............................................................................................................9CHAPTER ONE: INTRODUCTION...........................................................................101.1 Background Information..................................................................................10

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1.2 Project Objectives............................................................................................101.3 Approach to the Assignment............................................................................111.3 Aims and Structure of the Report....................................................................12CHAPTER TWO: DESCRIPTION OF THE SERVICE LINES...........................................132.1 General Description of the Area.......................................................................132.2 Structure of the Distribution Area....................................................................142.3 Water Supply Area Boundary...........................................................................15

2.4 The Main Distribution Line............................................................................17CHAPTER THREE DESIGN OF SERVICE LINES..........................................................18

3.1 Tap Locations...............................................................................................213.2 Design of Taps and Communal Water Points................................................223.3 Details of Service Lines................................................................................223.3.1 Line to Upper Kayuni................................................................................233.3.2 Line to Kayuni Head Quarters...................................................................24

3.3.3 Line to Mapunda and MatiasNkhata Villages................................................253.3.4 Line From tank No 2 to the edge of the eastern mountains.........................27

3.3.5 Branch to Choma......................................................................................283.3.6 Branch to Kalonga Village and Chikwina Community Day Secondary School

313.3.7 Branch to Chikwina Health Centre and Muyombe Village.........................313.3.8 Branch to Chalewa Village........................................................................323.3.9 Service Line to Kapoti Village (West)........................................................323.3.10 Service Line to Kapoti East.......................................................................333.3.11 Chivuti Line (From Chikwina Market going northwards)............................333.3.12 Chivuti Line (From Chikwina Market going eastwards)..............................333.3.13 Jumbo Line................................................................................................343.3.14 Service Line to Wadenya..........................................................................343.3.15 Service Line to Lwazi Mission....................................................................34

CHAPTER FOUR: GENERAL DESIGN CRITERIA AND CONSIDERATIONS...................364.1 Design period...............................................................................................364.2 Per Capita Demand......................................................................................364.3 Design Population........................................................................................364.4 Design Flow..................................................................................................374.5 Distribution of Demand along the Pipelines.................................................374.6 Alignment of Pipelines..................................................................................384.7 Pipe Materials...............................................................................................384.8 Pipe Class.....................................................................................................394.9 Valves and Fittings.......................................................................................394.10 Thrust Blocks............................................................................................40

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4.11 Aprons, Washing Slabs and Drainage.......................................................414.12 Structural design of Break Pressure Tanks................................................41

4.13 Joints and Connections.................................................................................41CHAPTER FIVE REVIEW OF DESIGN FOR DISTRIBUTUIN MAINS.............................425.1 Line between Tank No 2 and Tank No 3...........................................................42

5.2 Line between Tank No 4 and Mpamba.........................................................435.3 Incorporation of Mavwivwi Water Supply Scheme into ChikwinaMpamba Water Supply Scheme............................................................................................43

CHAPTER SIX: RECOMMENDATIONS......................................................................456.1 General............................................................................................................456.2 Project Management........................................................................................456.3 Environmental Management of the catchment area........................................466.4 The Distribution Main.......................................................................................466.5 Service Line to Kayuni Upper...........................................................................466.6 Service Line to Kayuni.....................................................................................466.7 Service Line to Mapunda and Matiasi Nkhata..................................................476.8 Service Line to Zawanji....................................................................................476.9 Service Line to Choma.....................................................................................476.10 Service Line to Kalonga................................................................................476.11 Service Line to Muyombe.............................................................................486.12 Service Line to Chalewa...............................................................................486.13 Service Line to Kapoti West..........................................................................486.14 Service Line to Kapoti East...........................................................................486.15 Service Line to Chivuti (From Chikwina Market northwards)........................486.16 Service Line to Chivuti (From Chikwina Market eastwards)..........................496.17 Service Line to Jumbo...................................................................................496.18 Service Line to Wadenya..............................................................................496.19 Service Line to Luwazi..................................................................................496.20 Other Service Lines......................................................................................496.21 Use of pipes in stock....................................................................................50

List of Figures

Figure 1: Map of the Supply Area...............................................................................19Figure 2: Satellite Image of Supply Area.1.................................................................20Figure 3: Service Line to Kayuni Upper......................................................................27Figure 4: Service line to Kayuni village HQs part 1.....................................................28Figure 5: Service Line to Kayuni Village -part 2..........................................................28Figure 6: Line to Mapund and Matias Nkhata part 1...................................................29

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Figure 7: Line to Mapunda and Matias Nkhata part 2.................................................30Figure 8: Satellite Image showing line to Zawanji part 1............................................31Figure 9: Satellite Image showing Zawanji Line part 2...............................................32Figure 10: Satellite Image showing Zawanji Line part 3.............................................32Figure 18: Some of the fittings that require installation of thrust blocks....................40

CHAPTER ONE: INTRODUCTION

1.1 Background Information

World Vision Malawi through Chikwina-Mpamba Area Development Programme is providing water to rural communities in its catchment area and ensures that people have convenient access to water in sufficient quantity and adequate quality for basic use. In view of the above objective World Vision Malawi carried out design works for Chikwina- Mpamba Water Supply Scheme. However, the design did not include service lines that transport water from distribution mains to communities or tap locations. World Vision Malawi therefore contracted W. E. Mtonga to carry out design works for service lines.

1.2 Project Objectives

The main objective of the assignment is toidentify water demand points from the development patterns of the supply area and to design feeder lines from the distribution mains and reservoirs to carry adequate flows of water at sustainable pressures to reach intended beneficiaries. The design was carried out through simulation of a hydraulic model of the distribution system as a whole and individual service line to the target area through skeletonizing process.

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According to the terms of reference the assignment has the following specific objectives:-iv. To survey areas from the distribution main to communities and to

determine specific feeder line connection points to the main line.v. To carry out detailed hydraulic analysis and modeling for all feeder

lines and specify safe working pipepressures including that for valves and other accessories.

vi. To produce a design report and associated working drawings and bills of quantities.

1.3 Approach to the Assignment

In order to carry out the assignment the following methodology was employed:-

a) Maps of scale 1:50000 indicating important features in the project area were collected.

b) Desk study of the project area was conducted and a plan for further investigations was established.

c) Spot visit to some points within the distribution area was conducted.d) Demographic data was collectede) Settlement patterns were established through map study and physical

checks in the fieldf) Land use patterns were established.g) General relief for the project area was establishedh) Physical barriers were established.i) Pipeline routes were established targeting major demand pointsj) Detailed topographic survey was conducted along all feeder lines.k) Details of the main components of feeder lines were established

including fittings and other appurtenants. l) Hydraulic analysis was conducted.m) Detailed design for the scheme was undertaken using 2011 as base

year.n) Detailed drawings were compiledo) Report was compiled

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1.3 Aims and Structure of the Report

The report is aimed is aimed at indicating field observations that guided the routing of feeder lines to reach the intended water consumers and the ultimate design for feeder lines.

The report is divided into five chapters with each chapter tackling items under the heading. The following are the chapters:-

1. Chapter 1 gives the introduction, general background and objectives of the consultancy.

2. Chapter 2 describes the service (feeder) lines with respect to location of people and other constraints.

3. Chapter 3 gives the detailed account for design of the feeder lines4. Chapter 4 gives an account of the challenges encountered during

survey works and the design process.5. Chapter 5 gives conclusion and recommendations for the design.

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CHAPTER TWO: DESCRIPTION OF THE SERVICE LINES

2.1 General Description of the Area

ChikwinaMpamba Gravity Fed Water supply Scheme is located in Traditional Authority Timbiri and Sub Traditional Authority Mnyaluwanga areas in Nkhata-Bay District. The area is located between easting 844200 and 844450 and between northing 617000 and 620500.coversapproximately 1 251.98km2

Other details are best described using table 1.0 below.

Topic Current dataTotal Programme Area [km²] 1 251.98km2

Physical Environment and Important Landmarks (e.g., Lakes, Hills, Rivers)

Chikwina/Mpamba Program is located about 10km to the west of Lake Malawi. The topography varies from moderate to steep slope, with shallow and stony soils (lithosols). The area is cut by a number of rivers which make the cultivation of rice viable. Cassava is also grown.

Two major types of vegetation are found in Chikwina/Mpamba Program and these are the Semi evergreen forest found towards the upland and are characterised by Brachystagiaspiciformis; and the perennially wet grassland which is found along the rivers and dambos in the area.

Climate Chikwina/Mpamba Area Development Program shares the Warm Tropical Climate that is characteristic of Nkhata Bay District.

Average Temperature in Cold Season and in Hot Season

The area has an annual average temperature of over 32 degrees Celsius which is experienced in the month of October and an annual minimum temperature of slightly over 20 degrees Celsius which is experienced in the months of June and July.

Annual Rainfall in mm and/or Rainfall Profile The area receives an annual rainfall of about 2000 mm most of which is distributed within the area’s typical rainy season which occurs between October and March. The highest monthly average of about 380 mm is usually experienced in March while the lowest monthly average of 5mm is usually experienced in September.

Infrastructure (Telephone, Electricity, Quality of Roads etc.) .

Roads: There are two major roads. The area is dissected by a tarmac road from Mzuzu to Nkhata Bay District. Another Road runs from the Tarmac road and exits the ADP at its Northern end. This road and all other roads are mostly gravel and seasonal

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Telephone: Most people have access to cheap mobile phones that are communicating through phone networks being offered by two mobile phone service providers, Zain and TNM. Currently TNM network covers the largest part of the ADP.

Electricity: there are Gridlines that have been tapped along the Nkhata Bay Mzuzu road. Another grid passes at the Northern end of the area (Chikwina).

Water source: the major source of water in the area is the borehole. A gravity fed piped water system funded by World Vision is currently under construction

Hospital: There are two Health Centres, one owned by the Government and offering free services (Mpamba) and another owned by a mission offering paying services (Luwazi)

Table 1: Description of Chikwina-Mpamba Area

2.2 Structure of the Distribution Area

The following factors were considered in determining the distribution area;-i. Topographic considerationsii. Populationiii. Political Boundaries

Generally, the distribution area is located along the ridge that runs south-wards from Chikwina towards Mpamba. There are hills of Kaning’ina on the western side of the supply area. There are also hills on the eastern side of the water supply area. The western hilly area falls within the protected area of Kaning’ina Forest Reserve and therefore the area is not inhabited. The eastern hilly side is also not inhabited. Figure 2 below shows a satellite image of the supply area. The image shows three distinct characteristics. The eastern deep green area is hilly. Similarly is the western deep green area. The lighter green area in the middle is the ridge that can also be referred to as supply area. From the image it can be seen that the area is narrow in the north and wider in the south. Communities are concentrated along this ridge.Few isolated communities are located across streams in the dissected hilly areas. Far up north is Nkhata village located closer to Manyenyezi River Valley. Far south west is Lwazi Mission.

2.3 Water Supply Area Boundary

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Figure 1 shows a map of the supply area. It is marked by a boundary line for Kaning’ina Forest Reserve to the west. In the north the boundary falls in the boarder for TA Nyaluwanga. The eastern side is marked by the edge of mountains. In the south the boundary lies along M12 Road from Mzuzu to Nkhata-Bay. Figure 2 is a satellite image adopted from Google Earth indicating the supply area.

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Figure 1: Map of the Supply Area

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Intakes

Main Tank

SchemeBoundary

Tank No 2

Tank No 3

Tank No 4

Tank constructed by Africare-Mavwivwi


Figure 2: Satellite Image of Supply Area.1

The scheme boundary roughly follows where the deep green colour ends.

2.4 The Main Distribution Line

The main distribution line passes through four tanks downstream of the 1ststorage tank to Mpamba Market Centre. It has a total length of 32.225Km. The line passes on the side of the road all the way through from Chikwina to Mpamba. The line passes through Chikwina Trading Centre as a major consumer before connecting to Mpamba down south.

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CHAPTER THREE DESIGN OF SERVICE LINES

The major objective of designing and installing service lines is to link tap locations to the distribution main. The design is aimed at distributing the total demand that was applied in the design of the transmission and distribution mains to individual segments of the target communities for service. Due consideration is given to the fact that some of the demand does not exist at present. This demand comprises all future projections up to the design period. The prediction of demand allocation is based on current development trends. This implies that service lines are designed to cater for future development in addition to satisfying current demands. With this in mind almost all service lines end with end caps indicating that there is room for expansion except where head cannot suffice or there other limitations due cost constraints

The design flow for service lines was determined in the following stepwise fashion;-i. Estimate the average daily demand.ii. Estimate the maximum daily demand.iii. Estimate the maximum hourly demand

Design flows are arrived at by incorporating factors which indicate how the demand shoots over the average daily demand at peak times. According to the Design Manual Peak Flow is the flow to one tap. It should be 2 times the calculated 16hr flow for a branch with one tap. For branches with less than 5 taps a peak factor of 2 is applied. A peak factor of 1.5 is applied to branches with taps between 5 and 9. For branches with 10 taps and above a peak factor of 1 is applies

Besides carrying enough flow the service lines were designed to operate within an acceptable range of pressures. If the pressure is too low, system may not operate satisfactorily to the consumers requirements while if the pressures are too high the fittings may leak. In this case the service lines were designed to operate at a minimum pressure of 10m head at the tap and a maximum service pressure of 45m head.

The other design criteria were floe velocity. Generally low flow velocities need to be avoided because they encourage stagnation. High flow velocities also need to be avoided as they influence pressure surges. Generally flow velocities between 0.5m and 1.5m are considered a good. However it should be mentioned that sometimes

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the site situation demands that water should be distributed uphill while there is limited available head. This scenario necessitates increasing pipe diameter to reduce hydraulic losses as much as possible so that the available head is utilized in delivering flow to the required destination. The increase in diameter reduces flow velocity. In this case it is acceptable to reduce flow velocity to as low as 0.2m/s. However velocities lower than 0.2m/s are not acceptable. In like manner there may be steep slopes which force water to flow at very high heads. In this case the pipe diameter is reduced to increase hydraulic losses or to apply breaks. The reduction in pipe diameter increases flow velocity. The velocity may be increased to 2m/s but values greater than 2m/s are not acceptable.

The routing and alignment of service lines considered the following factors amongst others;-

i. Right of wayii. Constructabilityiii. Future demandiv. Access for future maintenancev. Separation from other utilities particularly within the proximity of trading

centres.vi. Subsurface conflicts.vii. Materials for construction including technology availabilityviii. Pipeline operationsix. Protection from damage from both human beings as well as natural disasters.x. Long term integrityxi. Compliance with legislation affecting the environment, water quality

One would conclude that the ideal route would be a straight line from the tap to the nearest point on the distribution main. However, this has been altered in some cases due to physiographic, environmental, design and construction constraints. In some cases more than one taps are located within the same locality. As a result the most cost effective way of designing a service line is to connect all taps including future projected ones from a certain locality to one service line. Typical of gravity fed water supply systems service lines are branched. Thus all taps and communal water points are connected to the service lines through branched systems.

Generally service lines were routed along the sides of the existing walkways for people and roads. These walkways follow ridges in most cases. Due consideration

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was given to minimizing pipe length. Numerous river crossings were avoided to minimize costs.

The service lines were designed with end caps at the end of the line indicating the possibility of accommodating new demands that were projected over the design horizon. Thus in the current set up taps are located to points where houses are located but the service line does not end at the tap. It ends at a point convenient for future development. Generally it is not economical to extend the service line to an environment where there are no people because that creates a dead end where water will stagnate during the period when there is no settlement but at the same time there is a possibility that people may settle elsewhere due to shift in factors that influence settlement.

The design of service lines utilized two models for predicting flow characteristics in the pipelines. The first model uses Hazen Williams Formula for predicting frictional and form losses. This formula is as follows;-

H L=1.177∗1013 x Q1.852 xL

C1.85 x D4.865 where;-

HL is head loss in metres per kilometer Q is the flow in cubic metres per second L is length which in this case is 1Km C is constant based on material characteristics D is pipe diameter in metres

The second approach uses the Darcy- Weisbach formula in which head loss is evaluated as follows:-

H f=fxlx V 2

2xgxDwhere;-

Hf is head loss on account of surface resistance in metres. f is the frictional factor. V is flow velocity in metres per second. G is acceleration due to gravity in m/s/s D is the pipe diameter in metres.

The second formula is changed to be in parameters that are known i.e. in terms of design flow. Thus the formula changes incorporates the relation between flow and flow velocity as follows;-

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V=QAwhere,

V is flow velocity as explained above. Q is flow in cubic metres per second A is the cross-sectional area of the pipe in square metres.

It is also known that area A=πx D2

4 thus head loss due to surface resistance or

friction is given by the formula;-

H f=8 xfxLxQ 2

π2 xgx D5 where Hf,f,L,Q,g and D are as explained above

Please note that the frictional factor f is a function of Reynolds number which is also a function of flow velocity i.e. whether the flow is laminar, turbulent or is in transition between the two. In water networks flows are generally turbulent and therefore f is simplified.

The two approaches are similar but differ in precision due to the fact that the Hazen Williams formula does not consider flow regimes and as results the margin of error becomes big for certain flows. The second model was favoured in limiting flow of velocity especially the lower limits.

3.1 Tap Locations

The criteria for determining tap locations are based on settlement patterns but with due consideration of the following principles;-

i. Each tap shall serve not more than 120 people.ii. Consumers shall move not more than 500m to access safe water.

Generally settlements patterns are guided by the following factorsi. Political and administrative boundariesii. Topographical set up of the area.iii. Access to social amenitiesiv. Natural physical features such as rivers, mountains, ridges etc that demarcate

the settlements

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The first step in identifying tap locations is to determine where people are living at present. This was observed from topographic maps, census maps, aerial photographs and satellite images of the supply area. The information was verified through field visit. All locations of human settlements were automatically assigned taps as follows;-

i. The number of taps in the area was based on village design population.ii. At the design stage each 110 people were allocated to each tap. This left 10%

of the taps unallocated. The excess will be used to fill the number of requests which will be received immediately after commissioning the project.

iii. Allocation of taps to an area with large population concentration considered possibilities of sharing a tap but limiting the number of consumers to 120 people per tap.

iv. Smaller concentrations were allowed to share a single tap but the moving distance was limited to 500m.

v. Schools, health centres, and other institutions were automatically allocated one tap to each institution.

vi. Taps were located to places such that they are not too close to rivers, dambos, graveyards or environmentally hazardous points.

3.2 Design of Taps and Communal Water Points

The consultant is aware that taps and communal points are constructed on request from the consumers. The actual location is decided by the community. The design of the tap or communal water point considered technical aspects that need to be followed when accepting a request from consumers. In this case consideration must be given to the fact that each tap is to connect to the nearest service line and hence must be located where it is technically feasible to connect without disturbing the design flow regimes for the service lines. Big angled junctions need to be avoided to reduce hydraulic losses.

3.3 Details of Service Lines

3.3.1 Line to Upper Kayuni

This is the first line that connects to the uppermost part of the distribution area. Generally this line is targeting two communities located on the upper part of Kayuni village. It was observed during field work that some new communities were being

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established within the proximity of this line. These communities were targeting agricultural landthat is available in the mountainous area. Figure 3 shows a satellite image of the area. It is also indicating the route through which the proposed pipeline passes.

It is estimated that 20% of the people from Kayuni Village will utilize this line. The current population for the whole village is estimated to be 528 people and 20% turns out to be 106 people.

The total length of the line is 705.85m. It has a design flow of 0.45l/s.

This line is going uphill. The elevation of the target village is higher than the level of the tank. As a result the diameter of the service line was increased as much as possible to make sure that water is able to reach a certain point closer to where people are living. However, it was noted that water can only reach chainage 366.77m from the origin of the line. In this regard people will still have to move some distance in order to collect the water. However, the distance is less than 500m which means this design meets government standards for this community.

Figure 3: Service Line to Kayuni Upper

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3.3.2 Line to Kayuni Head Quarters

This line branches off the distribution main just outside the main tank. It runs down to communities located closer to the stream before crossing to Kayini Village Headquarters. At the headquarters the line still passes ongoing eastwards to link to the communities located closer to the stream. This stream demarcates Kayuni Village from Chalewa Village.

The line is 2.3Km. The line will use 40mm PVC class 10 pipes throughout. It was designed to serve 60% of Kayuni Population and some communities located to the east just across the stream.

Generally this area across the stream is located at an altitude that is almost the same as that of the service tank. Therefore this line was only extended to places closer to the river.

Figure 4: Service line to Kayuni village HQs part 1

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Figure 5: Service Line to Kayuni Village -part 23.3.3 Line to Mapunda and MatiasNkhata Villages

This line branches from the distribution main at a road junction between Chikwina-Mzuzu Road and the road going nothwards, not far from the DECO camp for road construction. The road was at one time under construction and was tipped to link Nkhata Bay and Usiska. However, the project failed.The line runs nothwards for about 2km before turning westwards. The line has branches to Mapunda and part of Choma before reaching Matias Village. It has a design flow of 1.62l/s. It is 3.5Km long. There are two pipe diameters prescribed for this line. The first portion is 50mm PVC class 10 to be laid between chainage 0 and 1+663.47m. The second portion is 40mm PVC class 10 to be laid between 1+663.47m and 3+541.97m

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Figure 6: Line to Mapund and MatiasNkhata part 1

Figure 7: Line to Mapunda and MatiasNkhata part 23.3.4 Line From tank No 2 to the edge of the eastern mountains

This line starts off from the second tank and runs northwards down the mountains. It has two main branches that are treated separately. The main line passes through

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part of Chama Village, Kalonga Village before and end cap at Zawanji near the edge of the mountain.

The line is design to supply water to the following villages;-a. Chomab. Kalongac. Mjutud. Zawanji

Zawanji is a newly introduced village born out of Kalonga. Therefore the population projections for Kalonga cover Zawanji as well.

It has a design flow of 2.17l/s. It is 2.54Km. Two pipe diameters have been prescribed for this line. The first portion is 63mm PVC Class 10 from chainage 0+00m to 674.86m. The second portion is 50mm PVc class 10 from chainage 674.86m to 2+546.56m.

The line targets communities that are located down the valley. As a result the pipeline sustains a lot of head. The total static head down stream is beyond 120m requiring installation of class 16 pipes. This is not economical. Instead a break pressure tank is introduced at chainage 1+608.36m. This break pressure tank enables use of class 10 pipes throughout the line.

3.3.5 Branch to Choma

This branch takes off from the main line at chainage 641.33m and reduced level 1063.18. This line targets Choma Village and some few other communities located in Manyenyzi Valley. The design flow for the line is 1.8l/s. It starts off at static head of 48.8m. The total length of the line is 2.026Km.

Two classes of PVC pipes have been prescribed for the line. This first portion is 40mm PVC class 10 from chainage 0+00m to 0+792.33m. 40mm PVC class 12 pipes should be installed between chainage 0+792.33m and 1+438.43m. A break pressure tank (BPT) should be installed at chainage 1+438.43m. 40mm PVC class 10 pipes should

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be installed again from chainage 1+438.43m to the end of the line at 2+026.57m. There is an end cap at the end of the line to allow for extension to the exact locations where water connections are needed.

Figure 8: Satellite Image showing line to Zawanji part 1

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Figure 10: Satellite Image showing Zawanji Line part 3

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Figure 9: Satellite Image showing Zawanji Line part 2


3.3.6 Branch to Kalonga Village and Chikwina Community Day Secondary School

This line branches off from the Zawanji Line about 600m north of Chikwina Community Day Secondary School. The line has design flow of 1.24l/s. It targets Kalonga Village plus other communities located closer to the mountains in the eastern side. The line is 1.117Km.

Two clsses of pipes have been prescribed for the line. The first portion is 40mm PVC class 10 from chainage 0+00m to 0+665.52m. From this point 40mm PVC class 12 pipes should be laid up to chainage 0+853.88. The pipe diameter is the reduced to 32mm after losing flows to the school and communities around it. 32mm PVC class 12 pipes should be laid from chainage0+853.88m to chainage 0+894.24m. A break pressure tank is introduced at chainage 0+894.24m. 32mm PVC class 10 pipes should be laid from the break pressure tank to the end of the line at chainage 1+117.15m.

3.3.7 Branch to Chikwina Health Centre and Muyombe Village

This line branches off from the distribution main at the health centre. It goes in the western direction going uphill before turning northwards and down the mountains again. It was observed that the communities of Chalewa Village are located at altitudes which are close to or above the level of Tank No 2. As a result it is not possible to supply these communities from Tank No 2. Effectively the tank is a pressure breaking device. Therefore, the option was to eliminate the effect of Tank No 2 and utilize the upper header tank to provide head.

Using the upper tank can only happen with the use of a bypass. This changes the working pressures at the junction to 71m with a static head of 93m.

Even though the design flow is very small the diameter of the pipe was enlarged to reduce head losses as much as possible so that at least water can reach the premises of the target villages particularly Chalewa. Therefore 90mm PVC class 10 pipes are recommended from chainage0+0.00m to 0+878.20m where a branch to Chalewa takes off. From this point the line goes downwards towards Muyombe Village. Therefore the diameter is reduced to 40mm. All this section should be laid with class 10 pipes up to the end of the line.

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3.3.8 Branch to Chalewa Village

This branch has a design flow of 0.75l/s. It goes upwards to Chalewa Village. The location of Chalewa is almost the same as that for Tank No 1. The small difference in head that exists is consumed by head losses before the water can reach the exact location of the village. The same issue affectes some few communities for Mjutu as water has to pass through Chalewa before coming to this point. In this design water can only reach chainage 653.00m from the branch. At this point there is a working head of 10.55m. It should be pointed out once again that this scenario can only be achieved by changing the operation from use of Tank No 2 to a bypass which enables utilization of head from Tank No 1

Even though the design flow for the line is small a bigger diameter of 63mm is recommended from the junction to the end of the line at chainage 0+653.00m. Class 10 PVC pipes are recommended. A bigger diameter is recommended to reduce the losses as much as possible but at the same time ensuring that flow velocity does not fall below 0.2m/s.

3.3.9 Service Line to Kapoti Village (West)

Kapoti Village has two major communities that are demarcated by a narrow valley. One community is located to the west while the other is located to the east. This then means that there are two separate service lines serving the two communities but originating from the same premises at Chikwina Primary School Ground. For the sake of this design only one line takes off from the distribution man to Kapoti West. There is a branch to Kapoti East at chainage 112.75m.

The line has a design flow of 1.0l/s. The flow is reduced to 0.5l/s at chainage 0+112.75m. 40mm PVC class 12 pipes are prescribed for the section between chainage 0+0.00m and 0+112.75m. The pipe diameter should be reduced to 32mm of the same class 12 for the rest of the line up to chainage 0+433.69m

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3.3.10 Service Line to Kapoti East

This line takes off at chainage 0+112.75m of the Kapoti West Line. At the takeoff point the line has a static head of 91.40m and a working head of 67.40m. Therefore it is recommended to lay 40mm PVC class 12 pipes from chainage 0+00m to chainage 0+359.81m. A break pressure tank is introduced at this chainage. From this point 40mm PVC class 10 pipes are recommended up to the end of the line at chainage0+598.18m.

3.3.11 Chivuti Line (From Chikwina Market going northwards)

This line is designed to serve part of Chivuti Village. It has a desgn flow of 0.71l/s. In terms of pipe selection the critical situation arises when a bypass is opened as static head increases indicating the difference in head between the level of Tank No 1 and the junction or take off point for this line. Using this scenario as the design criteria it is noted that the takeoff point is at a static head of 95.30m with a working head of 64.00m.

Therefore it is recommended to lay 32mm PVC class 12 pipes throughout this line from chainage 0+0.00 to 0+420.67m.

3.3.12 Chivuti Line (From Chikwina Market going eastwards)

This line takes off at Chikwina Market targeting a community to the east of the market. Since the takeoff point is very close to that going northwards the same pressure head prevails. This applies to both static head as well as working head.

This line is designed for a design flow of 0.51l/s. It is therefore recommended to lay 32mm PVC class 12 pipes throughout this line.

3.3.13 Jumbo Line

This is another small line branching from after Tank No 3 targeting the interior of Jubo Village. It is designed for a total flow of 0.6l/s. It is 385m long. At the takeoff point

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there is a working head of 30.57m and a static head of 37.51m. It is therefore recommended to lay 32mm PVC class 10 pipes throughout the pipeline from chainage 0+0.00m to 0+385m.

3.3.14 Service Line to Wadenya

This line is designed to serve two villages namely Wadenya and Chipaike. Most parts of Chipauke are located within the vicinity of the road to Mpaba. The line goes eastwards down the mountains. There is a steep slope thus hydraulic head increases sharply from the junction going eastwards.

The line is design for a total flow of 1.08l/s. It is 470.17m long. It takes off with a working head of 64.81m and static head of 77.83m Therefore it is recommended to lay 50mm PVC class 10 pipes from chainage 0+0.00m to chainage 0+96.18m. It is further recommended to lay 50mm PVC class 12 from chainage 0+96.18m to chainage 0+262.09m. A break pressure tank should be constructed at chainage 0+262.09m. It is recommended to lay 40mm PVC class 10 pipes from the BP tank to the end of the line

3.3.15 Service Line to Lwazi Mission

This is one of the longest service lines for the scheme. It targets communities for two group village headmen with villages located along the road to Luwazi Mission. The villages falling along the way are as follows;-KamtamboChideruKapalapataKangoThumbaGoneka.These villages constitute a total demand of 5.8l/s

The mission is located at a distance of 4.7Km from the junction. The elevation is far much higher than the position of the break pressure tank prescribed in the design of the distribution main. If the break pressure tank is to be maintained water will not

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reach the intended destination. Therefore the only option is to shift the break pressure tank to a convenient point that can enable water to a least reach the vicinity of the target area. However, it should be mentioned that shifting the position of the break pressure tank implies use of pipes of higher class than what was prescribed before particularly for locations closer to the river valley. Class 16 pipes are generally expensive. There use is therefore limited to a small portion so that water can just reach the vicinity of the area.

Since the pipeline is going uphill from the river valley, a bigger pipe diameter is prescribed to reduce head loss as much as possible. In this case 160mm PVC has been prescribed throughout the length of this line. Class 16 pipes are recommended from chainage 0.00m to 163.45m. Class 12 pipes are recommended from chainage 0+163.45m to chainage 0+ 441.4m. Class 10 pipes are recommended for the rest of the line up to chainage 3+929.91m

CHAPTER FOUR: GENERAL DESIGN CRITERIA AND CONSIDERATIONS

This chapter has been reproduced from the report for the Design of Chikwina-Mpamba Water Supply Scheme. Most of the facts apply to the design of service lines. Facts that do not apply to this assignment have been removed.

4.1 Design period

According to terms of reference the design period is 20 years. This period is acceptable and was adopted in the assessment of the existing infrastructure and design of facilities that are not constructed yet. It is convenient due to the fact that a very long design period increases the risk of departure from the

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forecast since certain factors change as time passes. The pipelines are also subject to upgrading when the demand outweighs the available capacity.

4.2 Per Capita Demand

Generally the Malawi Government recommends 36l as per capita demand per day for rural piped water. Where there is shortage of water the Malawi Government recommends 27lcd. The 1981 Centre for Social Research report on rural piped water indicated that the actual average consumption was about 14lcd.There is plenty of water in this scheme. It is possible even to connect people with in-house connections. The only limiting factor is local topography for some few areas that are either above the level of the service reservoir or the difference in height is so small that the whole head is lost in frictional losses and other local losses.

4.3 Design Population

The current population is based on the data sourced from National Statistical Office. The data was collected during the 2008 population census. The current population figures are forecast based on the growth trends that were observed during that census.Generally, population growth in rural areas follows a geometric trend due to availability of land and other resources that sustain human activities. Geometric increase in population is given by the following formula;-Pn=Po x (1+r )nwherePo=Total population∈n yearsPo=Initial populationr =Growth rate in percentagen =number of years in the projection period

It was observed that new villages have been created in the supply area. These villages have been born out of the existing population. There has not been any introduction of new population. Therefore population projections are not affected. The original boundaries have not been modified. There new villages are only subsets of the original boundaries.

4.4 Design FlowPage 33


The demand was calculated from the per capita demand of 36lcd for the projected population over 20 years from 2011 which was adopted as base year. It was also based on the number of taps that can be supplied with a maximum of 120 people per tap. All the service lines were designed by incorporating peak factors as explained earlier. In this case the design has been conservative to ensure that peak demands are accommodated.

4.5 Distribution of Demand along the Pipelines

The general characteristics of Chikwina- Mpamba Water Supply Scheme are as follows;-

There is one source located at a point with high elevation that enables water to reach all the target population.There is one main line connecting all reservoirs and Mpamba Trading Centre.All branches are joined to one main like a tall tree with a big main stem and smaller branches.There are no storage tanks on the branch lines.An additional source is Mavwivwi water Supply system which joins the main scheme through a reservoir located close to Thanula Village. It only requires proper linking of the reservoir to the distribution main. This provides extra capacity that can be utilized even beyond Mpamba.There are few localized and isolated areas within the supply area that are either far away from the main line or their elevations are limiting mode of supply. There is need to review the design so that water can conveniently reach the areas.

4.6 Alignment of Pipelines

The general criterion is to align pipelines as follows:-i. Where possible lines should be sited on ridges.ii. Where possible minimize the length of piping.iii. Where possible lines should be located close to roads.

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iv. Avoid numerous river crossings as these crossings demand use of Galvanized Iron (GI) or Galvanized Steel (GS)( pipes or other related materials which are expensive.

In this scheme roads from the source to the target communities are generally absent. Since the flow is by gravity the terrain of the area and proximity of the target communities dictated the alignment of lines. In some cases the existing physical features prohibited accessibility and as such the proposed lines were relocated to proper routes.

4.7 Pipe Materials

The selection of pipe materials was based on cost, durability and site conditions. The most common types for a well-covered environment are PVC and HDPE. PVC is generally used for diameters of 32mm and upwards while HDPE is used for lower diameters. Even though larger diameters of HDPE are available elsewhere, they are not common in Malawi. All stream crossings will use Galvanized Steel pipes. Rocky surfaces will also utilize GS pipes. In this case all prescribed pipes are PVC because the design has been limited to pipes larger or equal to 32mm. It is hoped that the communities themselves will arrange for connections which may either be stand pipes within compounds or communal water points

4.8 Pipe Class

Class of pipes was determined from static head and working pressures. Generally PVC and HDPE have the following classes:-

Class 6 for pressures up to 60m h Class 10 for pressures up to 100m h. Class 12 for pressures up to 120m h Class 16 for pressures up to 160m h.

4.9 Valves and Fittings

In general all PVC pipes are jointed using a rubber-ring located at one end of each pipe. The end without a rubber-ring is carefully inserted into the end with a rubber-ring. Where the PVC pipe is jointed to a GI pipe like in case of stream crossings, an appropriate size of couplings may be used.

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HDPE pipes are jointed using couplings of appropriate sizes determined by the pipe size.

Y fittings will be installed at all places where there are branches. The size of the fittings will be dictated by the diameter of the branch. Please refer to the profiles for specifications of each fitting.

Sluice Valves will be located in each line just after the branch. Air valves will be installed on all high spots to prevent air-locks. Wash-out valves and drains will be provided on all lower spots to ensure that water is flushed out during maintenance.

Gate valves will be installed to all smaller lines immediately after branches to ensure that they are isolated when need arises. In like manner gate valves or stopcocks will be installed just before taps.A section of about 5m to the stand pipe including the stand pipe itself will utilize GI pipes. The GI pipes will be fitted to HDPE using couplings of appropriate size. Bends, elbows and bib taps will be of GI.Isolation valves have been proposed in section which are more than 2.5Km

Adaptors or reducers will be installed where a smaller pipe is joined to a larger pipe.

4.10 Thrust Blocks

Thrust blocks have been proposed for all valves (but not gate valves), bends, tees and reducers. The general requirement is that thrust blocks must be adequate to resist the maximum expected pressure.

Figure 18 below shows some of the fittings that require installation of thrust blocks in the distribution system.

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Figure 11: Some of the fittings that require installation of thrust blocks

4.11 Aprons, Washing Slabs and Drainage

It is proposed to construct aprons and washing slabs at each tap to ensure that tap premises are kept clean and without mud. It is equally proposed to construct brick wall drains so that all water wastes can be discharged into soak pits. However this is at the discretion of the community.

4.12 Structural design of Break Pressure Tanks

The design of Break Pressure Tanks considered the following amongst others.The maximum water flow.Geology of the areaMaterials for constructionStability of the structureWater tightness

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4.13 Joints and Connections

Where a bigger water line branches off from the main line equal or unequal tees will be installed with sizes dependent on pipe sizes. Alternatively Y’s may be used following the same designation of equal or unequal Y. Where a connection is needed for a kiosk or a stand pipe at a yard, a turbot will be installed by applying a suddle with ferule.

CHAPTER FIVE REVIEW OF DESIGN FOR DISTRIBUTUIN MAINS

It was discussed in the design of the service line from the health centre to Muyombe and Chalewa that water cannot reach the sites particularly Chalewa without changing the operational set up of storage tank no 2. In like manner it was noted that water cannot reach Luwazi Mission with the designed break pressure tank in place. The break pressure tanks effectively mean that water cannot reach any place equal or higher than their locations. For the system to serve its intended purpose, the design for the distribution mains need to be reviewed. This affects the line between Tank No 2 and Tank No 3. It also affects the line between Tank No 4 and Mpamba.

5.1 Line between Tank No 2 and Tank No 3The demand pattern is the same. Therefore pipe sizing will not change but the classes of the pipes need to be changed to cope with the pressure from Tank No 1. Analysis reveals that the section lower than Chikwina Market supply water to places located lower than the respective junctions. This means that introducing a break pressure tank in this portion does not hamper the supply as long as the BP tank is

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located upper than the location of the third tank to enable water to flow into this tank. This scenario is achieved by the following arrangement.

Lay200mm PVC class 10 pipes between chainages 9+515.00m and 15+515m.

Lay 200mm PVC class 12 pipes between chainages 15+515m and 16+415m. Install break preasure tank at chainage 16+415m. Lay 160mm PVC class 10 pipes between chainages 16+415m and 17+495m

The operational arrangement is difficult as the operator has to judge when water is not in balance in a certain locality. Tank No 2 is needed in the operations in order to balance the large demand from Kalonga, Choma and part of Chivuti.

The other option of minimizing operation problems is to install another storage reservoir within the premises of Chalewa Village particularly at the highest spot. The tank should be linked to the transmission main from where water can go directly to this subset of the supply area.

5.2 Line between Tank No 4 and Mpamba

Once again the demand pattern has not changed from the original design. Therefore pipe sizing remains the same. But pipe classes need to be changed to accommodate high pressures created by shifting the break pressure tank upwards.

In this section the operational set up remains the same. The water will flow by itself. The new arrangement should be as follows:-

Lay 200mm PVC class 10 pipes between chainages 20+825m and 23+855m Install break pressure tank at chainage 23+855m. Lay 200mm PVC class 10 pipes between chainages 23+855m and 25+685m. Lay 160mm PVC class 10 pipes between chainages 23+855m and 27+215m. Lay 160mm PVC class 12 pipes between chainages 27+215m and 27+845m. Lay 160mm PVC class 16 pipes between chainages 27+845m and 28+985m Lay 160mm PVC class 12 pipes between chainages 28+985m +29+255m Lay 160mm PVC class 16 pipes between chainages 29+255m and 32+225m

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5.3 Incorporation of Mavwivwi Water Supply Scheme into ChikwinaMpamba Water Supply Scheme

Site observations revealed that Mavwivwi Water Supply Scheme can easily be incorporated into Chikwina-Mpamba Water Supply Scheme. There is a tank at a sharp bend before reaching Thanula Village from Chikwina. This tank is in good condition and is wealthy utilizing once the distribution pipeline is installed around that area. So far the arrangement is very simple. There is need to connect the tank to the new distribution system. The existing outlet shall be left unchanged. A new outlet will be installed for the main distribution pipeline to Mpamba. A bypass line is needed in case of a problem with the tank or with water quality from either of the two sources.

Interviews with residents of Thanula revealed that the water source for Mavwivwi Water Supply Scheme has plenty of water all the year round apart from water quality problems which are faced during the rainy season. They indicated that turbidity is a problem.

From the statement it can be noted that there is need to relook at the design of the intake structure so that it can effectively exclude all floating debris. Stability of the structure needs to be ascertained as well. It is hoped that the review of the design will consider specific yield for further planning.

In summary Mavwivwi is a good system for incorporation into Chikwina-Mpamba. It has a good potential to improve the lives of people even beyond the present boundaries. The problems of water quality can be handled by reviewing the design of the intake structures. If this cannot be adequate a sedimentation tank or a simple filtration tank may be introduced before the water can be blend with the one from Chikwina-Mpamba.

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CHAPTER SIX: RECOMMENDATIONS

6.1 General

The general issues outlined in the Design report for Chikwina-Mpamba water Supply Scheme still apply to this report. Actually the task of this exercise is to complete what was left before.

This project is huge and requires commitment of a lot of resources in a careful manner if it is to be implemented successfully. It has good potential for expansion into areas that are outside the impact area of World Vision Malawi. As a result there is need for involvement of various stakeholders including the Malawi Government to put resources together and to come up with an optimal design of the scheme that can effectively supply safe water to all potential beneficiaries including those located outside the influence of World Vision.

There are many recommendations of the assessment and design of the scheme. They have been put under headings to emphasize the important fact of the headings themselves.

6.2 Project Management

The success of any project is based on assembling an efficient project team that peaks up responsibility to run the affairs of the project from the start to the end i.e. in a complete project cycle. The team must have adequate expertise to carry out all necessary tasks. It was pleasing to note that an

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engineer has been appointed to be project manager for the project. It is hoped that problems of management and technical capacity that existed before will be sorted out soon

6.3 Environmental Management of the catchment area.

It was pleasing to note that the catchment area is already a protected zone. It is well covered with natural trees and grass. It is highly recommended to keep this area protected and to avoid human encroachment. It is also recommended to engage in practices that can improve the existing set up for example by planting indigenous species where necessary.

The incorporation of Mavwivwi Water Supply Scheme means that there is need to look at modalities of protecting this catchment area as well. The problems with water quality can be further reduced if the catchment area is well protected.

6.4 The Distribution Main

For effective supply of water to all the isolated high places, there is need to replace some low class pipes in two distribution mains with high class pipes to sustain high pressures created by bypassing tank No 2 and relocation of the break pressure tank in the distribution main between tank No 4 and Tank No 5. There is need to further review the design to check the impact of incorporating Mavwivwi Water Storage Tank into the whole system particularly with regard to water supply to Luwazi.

6.5 Service Line to Kayuni Upper

The following are the recommendations for this service line. Lay 40mm PVC class 10 pipes from chainage 0+0.00m to chainage

0+366mPage 42


6.6 Service Line to Kayuni

The following are the recommendations for this service line Lay 40mm PVC class 10 pipes from chainage 0+00m to chainage

2+301m.

6.7 Service Line to Mapunda and Matiasi Nkhata

The following are the recommendations for this service line. Lay 63mm PVC class 10 from chainage 0+00m to chainage 0+748m. Lay 50mm PVC class 10 from chainage 0+748m to 1+631m. Lay 40mm PVC class 10 from chainage 1+631m to 3+541m.

6.8 Service Line to Zawanji

The following are the recommendations for this line Lay 63mm PVC class 10 pipes from chainage 0+0.00m to chainage

0+641m. Lay 50mm PVC class 10 pipes from chainage 0+641m to chainage

1+608m. Install a break pressure tank at chainage 1+608m Lay 50mm PVC class 10 from chainage 1+608m to chainage 2+546m.

6.9 Service Line to Choma

The following are the recommendations for this service line;- Lay 40mm PVC class 10 pipes from chainage 0+0.00m to chainage

0+805m Lay 40mm PVC class 12 pipes from chainage 0+805m to chainage

1+438m. Install a break pressure tank at chainage 1+438m. Lay 40mm PVC class 10 pipes from chainage 1+438m to chainage

2+026m.

6.10 Service Line to Kalonga

The following are the recommendations for this service line.Page 43


Lay 40mm PVC class 10 pipes from chainage 0+00m to 0+665.52m. Lay 40mm PVC class 12 pipes from chainage 0+665m to chainage

0+853.88. Lay 32mm PVC class 12 pipes from chainage 0+853.88m to chainage

0+894.24m. Install a break pressure tankchainage 0+894.24m. Lay 32mm PVC class 10 pipes from the break pressure tank to the end

of the line at chainage 1+117.15m.

6.11 Service Line to Muyombe

The following are the recommendations for this service line;- Lay 90mm PVC class 10 pipes from chainage 0+0.00m to 0+878.20m. Lay 40mm PVC class 10 from chainage 0+878m to the end of the line

at chainage1+403m.

6.12 Service Line to Chalewa

The following are the recommendations for this service line;- Lay 63mm PVC class 10 pipes from chainage 0+0.00m to the end of

the line at chainage 0+975m.

6.13 Service Line to Kapoti West

The following are the recommendations for this service line;-

Lay 40mm PVC class 12 pipes from chainage 0+0.00m to chainage 0+433m.

6.14 Service Line to Kapoti East

The following are the recommendations for this service line Lay 40mm PVC class 12 pipes from chainage 0+0.00m to chainage

0+359m. Install a break pressure tank at chainage 0+359m

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Lay 40mm PVC class 10 pipes from chainage 0+359m to the end of the line at chainage 0+598m

6.15 Service Line to Chivuti (From Chikwina Market northwards)

The following are recommended for this service line;-

Lay 32mm PVC class 12 pipes from chainage 0+0.00m to chainage 0+420m.

6.16 Service Line to Chivuti (From Chikwina Market eastwards)

The following are recommended for this service line;- Lay 32mm PVC class 12 from chainage 0+0.00m to chainage 0+97m.

6.17 Service Line to Jumbo

The following are recommended for Jumbo Service Line. Lay 32mm PVC class 10 pipes throughout the pipeline from chainage

0+0.00m to 0+385m.

6.18 Service Line to Wadenya

The following are recommended for Wadenya Service Line;- Lay 50mm PVC class 10 pipes from chainage 0+0.00m to chainage

0+96m. Lay 50mm PVC class 12 from chainage 0+96m to chainage 0+262m. Install a break pressure tank at chainage 0+262m. Lay 40mm PVC class 10 pipes from the BP tank to the end of the line

at chainage 0+470m.

6.19 Service Line to Luwazi

The following are recommended for Luwazi Service Line;- Lay 160mm PVC class 16 pipes between chainages 0+0.00m and

0+163. m Lay 160mm PVC class 12 pipes between chainages 0+163m and

0+441m.

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Lay 160mm PVC class 10 pipes between chainages 0+441m and 3+929 m

6.20 Other Service Lines

Generally most communities are located within the premises of the road. Connecting these communities to the water supply system requires relatively short lengths of pipework with a small change in head. The impacts of these connections on the hydraulic system are negligible apart from the fact that they equally draw water from the main. Therefore these lines have been considered as service connections that do not require special modeling but have demand allocations.

6.21 Use of pipes in stock

There are various sizes classes of pipes already in stock. Even though the exact inventory is not known, it was generally observed that some pipes may still be used based on the following conditions:-

4) Pipes can be installed where the design prescribes the same pipe size and class.

5) Where such situations cannot match it is advisable to use bigger pipes where the classes prescribed are the same.

6) Where there is a mismatch between pipe classes, it is advisable to use a higher class as long as the sizes are the same or higher.

Generally the pipes prescribed for feeder lines are smaller than 110. Introducing bigger pipes compared to the prescribed size reduces hydraulic losses further and therefore it is hydraulically an advantage. However, it becomes an over design since the carrying capacity installed is higher than the minimum requirement. In terms of economics it implies that the system is no longer economical. However, since the costs were already incurred this may be considered to be water under a bridge.

In conclusion, the actual number of pipes that may be utilized in the scheme is dependent on the approval of the resident engineer since the current

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condition of the pipes in stock will also matter when installing these pipes. It is also wealth noting that the storage conditions of these pipes may have introduced fatigue and other issues which may change the hydraulic conductivity, physical strength as well as other characteristics of the pipes.

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Documents

Design Report for Chikwina Service Lines