Idea Transcript
ANOTHER HOPE CHILDREN’S MINISTRIES WATER SUPPLY SYSTEM PROJECT
SURVEY, DESIGN AND DOCUMENTATION OF ANOTHER HOPE CHILDREN MINISTRIES WATER SUPPLY SYSTEM KKONA VILLAGE WAKISO DISTRICT
DESIGN REPORT FEB. 2013
BY
BUSSEBWE ENGINEERING SERVICES LTD
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TABLE OF CONTENTS
WATER SUPPLY COMPONENTS ................................................................................................................................... PUMPED WATER SCHEME COMPONENTS ................................................................................................................ COST ESTIMATION .........................................................................................................................................................
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TITLE: DESIGN OF WATER SUPPLY SYSTEM FOR KKONA VILLAGE IN WAKISO DISTRICT Project Area Location Another Hope Children Ministries is located at Kkona Village is located in Wakiso District. The area is generally a flat area with the highest point of 60m which is about 1000m from the proposed pumping area. Climate The climate of Wakiso District where Kkoona Village is located can be described as hot and wet being near the equator. The rainfall patterns are heavily influenced by Lake Victoria. The climate of Wakiso District is tropical in nature, being modified by relief and Lake Victoria. The rainfall pattern is bimodal having two seasons with dry spells between July and August, and January to February. The months of March, April and May receive very heavy and well distributed rains of up to 2,000 mm. The second heavy rains occur in the months of September to December .The annual average rainfall range received is 1,125-2,250 mm and the monthly mean rainfall is 140mm with 230-270 rainy days per year. Evaporation over Lake Victoria range 3-5 mm per day making an average of 120mm per month and 1460mm per year. The mean annual vapour pressure is 20.5 millibars. The probability of receiving mean annual rainfall of 1500mm in Wakiso District in nine out of ten years is 10% and that of 1750mm in four years out of five is 20%. The average annual maximum temperature is 25o C with a mean annual minimum of 17.5o C. Sunshine on the District has an average of 6.1 hours per day with a mean radiation of 450cal/cm2/day. Some Islands have permanent flowing streams draining all Island watersheds into Lake Victoria. (Source: Wakiso District Situation Analysis Report 2010). Existing Infrastructure Power supply The Village does have no existing power supply line from the National Grid. Existing Water Supply All residents rely mainly on rainwater harvesting for collection of water for domestic use. Tanks were provided by the Anotherl Hope Children Ministries. The major problem with the water used in Kkoona Village is that it is not adequate as the supply depends on availability of rain fall and proper roof catchments which are not adequately sustainable. There exists a broken down shallow well 1Km away from the Children Ministries Home which is not functional. Population and Institutional Growth Design Period and Growth Rates for Kkona Village The project design horizon has been put at 15 years and 2013 has been used as the design base year when the project is expected to be commissioned. Based on the population forecast established from Wakiso District Population Office Kkona Village is expected to have a population of 800 people by 2028 and having a current population of 300 people. Population Projection A constant growth rate formula has been used to estimate the projected populations: Pn = Po (l + r) n …………………………………… (1) Where Po = Present (Known) population, Pn = Probable population n years later r = a constant growth rate (6.5% for Wakiso District) n = period of n years Water Demand The water supply scheme is based on only one type of service (domestic use). It is anticipated that in future, some of the residents will request to have yard taps. The following consumption patterns have therefore been assumed. Table 1: (Water Service Levels) Connection Type Population Served Stand pipes 98% Yard taps 2%
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WATER SUPPLY COMPONENTS General Design Data The criteria used for the various elements of the system operating conditions are given in the table below. Table 2: (System Operating Conditions) OPERATING CONDITION
DESIGN CRETERIA
Average Day Demand
The Design Demand is based on the Average Day Demand
Maximum Day Demand
The Design Demand is based on 1.2 times the Average Day Demand. Maximum Day Demand ratio is based on the changes in water use due to weather or any other activity like washing.
Reservoir
Transmission main to have capacity to deliver Maximum Day Demand over 6 hours pumping period. Reservoir capacity is required to cover peak hour fluctuations and designed for the Maximum Day Demand.
Peak Hour Demand
The Design Demand is based on 2.0 times the Average Day.
Distribution Network
Distribution network mains designed for maximum static pressure of 60m minimum residual pressures of 10 m in all areas.
Transmission Main
For the various anticipated levels of service and water usage in Kkona Village, the Unit Water Demands given in Table 3 have been adopted. Unit Water Demand The Wakiso District Water Office had estimated unit demands of 20/c/d for stand pipes and 40l/c/d for yard posts as adequate for this Landing Site. Table 3: (Water Demand) TYPE OF USE DEMAND Assumptions Domestic Yard tap
40 l/c/d
Assumes pit latrine or pour flush type of sanitation Assumes population limit their consumption to drinking water Demand does not change over design horizon
House Connection
50 l/c/d
Demand assumes limited household plumbing (flush or pour flush toilet, shower, sink) Demand does not change over design horizon
Water Demand The estimated average daily water demand is 40m3/day by year 2028. Pipes The types of pipes have been selected based on cost, ease of laying and suitability for ground conditions. Efforts were made to standardize pipe pressure ratings to avoid confusion during construction supervision. The selected option for simulation is using Hazen-Williams Formula. PUMPED WATER SCHEME COMPONENTS Intake The source of water for this landing site shall be groundwater from a well constructed shallow well. The well shall be atleast 10m deep well lined with filtration materials, clay seal and concrete capping.
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Pump Since the intake is at a low altitude compared to the community to be supplied, the water will be pumped from the source to a storage reservoir. The water will be pumped a diesel pump installed and protected in a pump house. Treatment The raw water shall be filtered using a 2 stage Pressure filtration process. There will be one set of primary pressure filters followed by secondary Pressure filters for polishing purposes. This will reduce the suspended solids significantly to acceptable water quality standards. Online dosing of disinfectant shall be carried out. Chlorine dosing is recommended for purposes of disinfection in water treatment and also killing residual micro-organisms remaining in the network. This serves to disinfect any contamination in the water and pipe network. A dose of 5 mg/l using HTH chlorine and dosing carried out online after the filtration units. Transmission This will connect the source, treatment units and the storage reservoir. It is also the pumping main since water will be pumped to a reservoir located on Water Tower that is 4m above ground the Lake level. The transmission pipe from the Lake to the reservoir will be 900 m long and will have a pipe of HDPE OD50mm PN6. Design of Pumps Pumps were selected after calculating the hydraulic losses and static lift to the Reservoir. The static lift includes 22m to the top of the tank. This is added to the pipe hydraulic losses to give the total required pumping head. Hydraulic losses have been calculated using a selected option for simulation using Hazen-William Formula in the analysis of the transmission main. The details of Hazen -William’s Formula are in the appendix for head loss calculations. Specification for pump shall be: Table 3: (Pump Specification) Capacity
120 liters / minute
Head
40m
Power
Diesel Pump
Delivery and Suction pipes 2” Diameter Storage The clear water tank shall be made of plastic (uPVC from Crestank or Equivalent Installed on a fenced concrete slab).The reservoir capacity has been sized by taking 100% of the maximum days supply and approximating to 40m3 The size of the tank was determined based on the following two factors: Balancing of variations in water demand during the day and peak hours. No emergency storage has been included in case of system breakdown. Distribution The distribution network was optimized using the Microsoft Excel Software; a spreadsheet was prepared for simulation. The selected option for simulation using Hazen-William Formula in the analysis of the water supply distribution network. The formula is as follows: Q = K*C*A*R^0.63*S^0.54 Where: Q = Discharge in the section (m3/s) C = Hazen Williams roughness coefficient (unit less) 150 for uPVC, 140 for HDPE A = Flow area m2 S = Friction slope (m /m) K = Constant (0.85 for SI) R = Hydraulic radius (m) D = 4R Where: R = Hydraulic radius (m) D = Diameter (m) Extended period simulations have been carried out to analyze the proposed piping systems response to varying demand schedules. The following parameters were used in the simulation: Maximum day factor 1.2, Peak Hour Factor 2.0 Maximum Pressure 60 m, Minimum Pressure 10 m Details of the hydraulic analysis of the distribution network are in attached Appendix
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Table 3: Distribution Pipe Networks No. Outside Pipe Diameter Internal (mm) (mm) 1 50 44.2 2 40 35.4 3 25 21.4 TOTAL
diameter Length of pipe (m) 1000 1000 600 2600
The simulation using the distribution network model was carried out using internal diameters for plastic pipes. Water shall flow by gravity in the distribution network from the reservoir tank. The water shall flow in a branched distribution system. COST ESTIMATION Proposed Project Implementation The project will be implemented in a single phase It will involve construction a floating intake, installation of solar pumps, construction of the transmission mains, treatment unit installation, storage tank construction, and distribution network and stand taps. Estimated Investment Costs The table below shows an estimated breakdown of the Capital Investment cost for the Another Hope Children Ministries Water Supply System at Kkoona Village. The total Cost of the entire project will be Ug. Shs.139, 150,000 (One Hundred Thirty Nine Millions One Hundred Fifty Thousands Shillings)
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BILLS OF QUANTITY FOR CONSTRUCTION OF KKONA VILLAGE WATER SUPPLY SYSTEM IN WAKISO DISTRICT S/N Description Unit Qyt Rate Amount ($) Preliminaries 1 Reconnaissance survey of the Entire System
LS
1
Specified Requirements
200
200
0
0
2 Water Sample Testing by NWSC
LS
1
200
200
3 Construction of Intake works including shallow well construction and planting grass, fencing with barbed wires and treated eucalyptus poles plus gate
LS
1
3,400
3,400
4 Construction of Pump House as per drawings including all finishes to completion
LS
1
3,800
3,800
5 Pipe laying including all trenching, covering for main transmission an all distribution works plus all fittings 6 Construction of Concrete Water Tower (Tank Stan) which can support 40m3 of water with Steel railings to include all metallic works, welding and finishing
LS
1
17,400
17,400
LS
1
5,800
5,800
7 Supply and installation of 20m3 uPVC tank including all fitting and pipe works
LS
2
4,400
8,800
8 Supply and install a Non-Electric Liquid Chlorine dispenser operated chemical dozer. Delivery ranging from 10l/hr to 2.5m3/hr complete with solution tank (HDPE or Fibre Glass) to 200 liter Capacity. Dozer and Solution tank to be installed 1m above ground Level
LS
1
2,000
2,000
9 Supply and install diesel pump capacity of 120l/minute on 80m Head with suction depth of 20m using 50mm delivery and suction pipes
LS
1
13,800
13,800
10 Allow for de-watering of works
LS
1
100
100
11 Provision for hoarding of site
LS
1
160
160
Total
55,660
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ANNEXURE 2: HEADLOSS CALCULATION Head loss from lake to Reservoir Q =K* C*A*R^0.63*S^0.54 C= Hazen Williams Coefficient S= Friction slope (m/m) A= Flow area (m2) K= 0.85 R= D/4 D= Diameter in M Q= C= A=
1.1l/s 140 0.00153
D= 0.0442 R= 0.01105 Velocity V (m/s) = R^0.63 =
0.0011 for HDPE
m3/s 1.10412
OD50mm PN6 0.71995
0.05852
0.54 =
S^ 0.10338 1.85185 S= 0.01496 Length of transmission main (m) = 400 Total frictional head loss along raw water transmission main (m) = 0.01496*400 Total static head including Tank height Required residual head to foster flow into tank Total Pumping head
6.0 22 2. 30
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ANNEXURE 3: PUMP SELECTION
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9
10
Cover
Overlow pipe GI1.5" Inlet pipe GI 1.5"
uPVC Tank (20,000l)
Wash out pipe GI pipe 1.5" Outlet pipe GI 1.5"
100mm Ref. slab on 300mm compacted H/core and 23omm brick plinth wall resting on 300mm class 20 fdn concrete
SECTION A-A 150
Ground level
230
230
230
1155
1155 3300
150
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