TABLE OF CONTENT TITLE PAGE CERTIFICATION TABLE OF CONTENTS PAGE ACKNOWLEDGEMENT i LIST OF FIQURES ii SUMMARY a 1.0 MY EDUCATION TRAINING INTRODUCTION 1 1.1 Industrial training 1 1.2 Final year project 2 1.2. 1 Design of counterfort earth retaining wall 2 1.2. 2 Preliminary design 2 1.2. 3 Bearing pressure analysis 3 1.2. 4 Stability analysis 5 1.2. 4.1 Check for overturning 5 1.2. 4.2 Check for sliding 5 1.2. 5 Final design and detailing 5 2.0 WORKING EXPERIENCE WITH ANBEEZ SERVICES LTD THE PROJECT AREA 7 2.1 Location 7 2.1 Climate 7 2.3 Regional Geology 7 2.4 Vegetation 8 2.5 Population 8 2.6 Socio-economy 8 2.7 Topography 9 2.8 Rainfall 9 2.9 Access 9 3.0 EXISTING WATER SUPPLY SITUATION IN THE AREA 14 3.1 Water Sources 14 (a)
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TABLE OF CONTENT
TITLE PAGE
CERTIFICATION
TABLE OF CONTENTS PAGE ACKNOWLEDGEMENT i LIST OF FIQURES ii
SUMMARYa
1.0 MY EDUCATION TRAINING INTRODUCTION 1
1.1 Industrial training 1
1.2 Final year project 2
1.2.1 Design of counterfort earth retaining wall 2
1.2.2 Preliminary design 2
1.2.3 Bearing pressure analysis 3
1.2.4 Stability analysis 5
1.2.4.1 Check for overturning 5
1.2.4.2 Check for sliding 5
1.2.5 Final design and detailing 5
2.0 WORKING EXPERIENCE WITH ANBEEZ SERVICES LTDTHE PROJECT AREA
3.0 EXISTING WATER SUPPLY SITUATION IN THE AREA 14
3.1 Water Sources 14
3.1.1 Rain Water 14
3.1.2 Surface Water 14
3.1.3 Ground Water 14
3.2 Water Uses 14
3.3 Water Source Contamination 15
4.0 PLANNING AND DESIGN - DATA COLLECTION 164.1 General 16
(a)
4.2 Methodology 16
4.2.1 Population Data 16
4.2.2 Water Quality Data 18
4.2.3 Meteorological And Hydrological Data 19
4.2.4 Surveying and Mapping 20
5.0 POPULATION ESTIMATION AND WATER REQUIREMENTS 21
5.1 General 21
5.2 Design Period 21
5.3 Population Estimation 21
5.4 Determination of Water Demand 22
6.0 WATER SUPPLY SYSTEMS – SELECTION AND DESIGN 23
6.1 Treatment Selection and Design 23
6.2 Quality Consideration and Choice of Source 23
6.3 Treatment Process 23
7.0 DESIGN SYNTHESIS OF WATER SUPPLY SYSTEMS 24
7.1 General 24
7.2 Development of Engineering Design of the Water Supply System 27
7.3 Design Criteria and Calculations 33
7.3.1 Selection and sizing of Pumping Equipment 34
7.3.2 Pump Controls and Instrumentation 3
6.7.1 Aluminium Sulphate 33
8.0 CHEMICAL DOSING SYSTEM 38
8.1 Aluminium Sulphate 38
8.2 HTH Powder Sulphate 38
8.3 Lime 38
8.4 Chemical Dosages 38
9.0 ELECTRICAL POWER REQUIREMENTS 39
10.0 CONCLUSIONS AND RECOMMENDATIONS 41
(b)
EXECUTIVE SUMMARY
In the process of executing this design project, the Consultant, carried out extensive field investigations and topographical surveys culminating in the final synthesis and design of the Etono Ikun Biakpan Water Scheme Project.
The highlights of this design report are as follows:
(a) Project Area
The project area consists of four major population centres, namely Etono-1,
Ikun, Biakpan and Etono-2. The total population of the area is projected from
1991 National Census to be 25,000 at present and this is expected to grow to
59,000 by 2034 (25 year’s time) at a growth rate of 2.8% per annum.
(b) Economy of the Area
The economy of the area is agrarian in nature, with yam farms, rubber
production, palm oil production and fishing. There are no industrial activities
in the area. Commercial activities exist but lack of good roads restricts
activities to a few months in the year.
(c) Access to Project Area
Access to the area is difficult due to the condition of the roads. There are two
main routes. One is from Akpet Central through an asphalted road up to
Okurike village on the eastern bank of the Cross River. From Okurike, the
Cross River has to be crossed by boat operated by the local people. The other
route is circuitous via Ikot Ekpene-Uyo-Bende-Ohafia and is the only route
through which motor traffic can get into the area.
(d) Existing Water Supply Facilities
There are presently no operational water supply facilities in the area.
However, a 25m3 overhead tank as found at Etono-1 but the associated
borehole(s) was not in use as at the time of site investigations on this project.
(e) Water Demand
The four towns served by the project are classified as semi-urban areas.
Accordingly a water consumption rate of 60 litres/capita/day as used in
estimating the water demand for the area in according with the National Water
Supply and Sanitation Policy as set out by the Federal Ministry of Water
Resources in 2000. Projected calculations indicate that present day (2009)
water demand for the area stands at about 1800m3/day and this is expected to
increase to 3500m3/day in 2034 (25 years’ time).
(f) Water Sources
(a)
Surface water was identified as the best option for sourcing of water for the
project. Two rivers, Cross River and Obana River, were chosen as sources of
raw water.
(g) Treatment Process
In consideration of the quality of water found, the following treatment process
The population of the project area was found to be concentrated in two axes
with Etono-1 and Ikun situated close to the bank of Cross River while Biakpan
and Etono-2 are close together at about 15 km away from Cross River. This
informed the decision to locate two separate water supply schemes of
capacities 2000m3/day for Etono-1 and Ikun, and 1500m3/day for Biakpan
and Etono-2. These are located near Etono-1 and Biakpan respectively. The
plants were designed on the basis of 12 hour operation
(i) Power Supply
There is no public power supply in the area; as such, the plants shall operate
using diesel generator sets. Three generator sets are to be provided, two
(200KVA and 100KVA) in Etono-1 and one (100KVA) in Biakpan plant.
(b)
2.0 THE PROJECT AREA
2.1 Location
The Biakpan, Ikun, Etono Mini Water Scheme in Biase Local Government Area of
Cross River State is proposed to supply potable water to the aforementioned
communities within the Local Government Area. The Towns of Etono 1 and Ikun are
communities located close to the bank of Cross River while Biakpan with its
neighbouring community of Etono 2 are located about twelve kilometres away from
the Cross River bank. The project area lies approximately between longitudes E7.925
to E8.033 and latitudes N5.580 and E5.650 as shown in Figure 2.3.
2.2 Climate
The project area has the typical tropical humid climate characterised by distinct wet
and dry seasons. These distinct climate seasons are created by the regular movements
of a zone of surface discontinuity between the Maritime – Atlantic air masses and dry
– Sahara air masses. The rainy season in the project area begins about February and
continues throughout October.
2.3 Regional Geology
The Cross River State is covered by the following geomorphical units: lower delta
plain, alluvial plain of the cross river, coastal plains, escarpment and hills – Obudu
and Oban hills.
The main geological formations in the project area are (FDLAR, 1985):
a) The coastal beach: This is primarily sand occurring in the southernmost part of
Akwa Ibom, along Ibeno and James town areas. The coastal sands are located
within the lower Delta plain.
b) The mangrove swamps: They occur along the network of creeks along the
coast in the vicinity of the estuary of Cross River, Imo and Qua Iboe River.
c) The river alluvium: This is located within the river plains – along the Cross
River, Qua Iboe and Imo River estuaries.
d) The coastal plain sands: Between the Cross & Imo Rivers where the coastal
plain exists, the underlying geological material consists of the coastal plain
sands. These tertiary sand deposits have different textures which range from
coarse to fine sands.
(1)
e) Sandstone and Shales: These occur immediately north of the coastal plain
sands, at certain locations, the sandstone and shales are underlain by massive
deposits of limestone which are exploited by the cement industry.
f) The acid crystalline rocks: These occur extensively mainly in the northern part
of the Cross River State. The rocks are essentially metamorphic and igneous,
composed of granite,
g) Gneisses, schists, quartz, quartzites, undifferentiated basalt etc. Outcrops of
these rocks are very common in Akamkpa Local Government Area of Cross
River State.
2.4 Vegetation
The original vegetation of the project area has been greatly modified by human
activities. The vegetation zones from south – north in the project area are in the order:
mangrove, deltaic swamp forest, moist evergreen forest, and sub-mountainous forest
in the high Obudu plateau. Biakpan and the other communities in the project area lie
within the moist evergreen forest in the middle western part of the state with
evergreen vegetation.
2.5 Population
The population distribution of the area ranged from sparse to dense among the villages and scattered settlements. Most households are made up of a man, a wife and many children. Most of the inhabitants are Christians, although a few traditional worshippers were observed.
From the interview granted by one of the village elders he said their population is about 35,000 people. Data obtained from the national Population Commission indicate that the population of the area was about 18000 in 1991. This figure when projected using a population growth rate of 2.8% (as recommended by an official of the Population Commission) shows a present (2009) population of about 30,000 people. However, the project area, like most parts of the South South Zone of Nigeria, normally experience unprecedented migration of people into it during festive periods like Christmas, Easter, New Yam festivities etc.
Population growth rate of the project area is assumed to be typical of that in any other
Nigerian rural community. It should, however, be noted that population growth will
increase immediately when the water scheme is completed and this trend is expected
to continue for some time before it stabilizes to follow the normal pattern.
2.6 Socio-economy
The principal occupation of the people in these areas is farming. The primary crops
farmed are crops such as yams, cassava, beans, melon, plantain and vegetables. There
(2)
is rubber plantation in this area too. Timbering is another activity that is taking place
in the nearby forest which generates a lot of economic activities.
Harvesting of palm nuts and subsequent production of palm oil is also prevalent in the area. There are some traders who trade on mostly food items. However, movement of people and goods is seriously impeded due to the absence of good motorable roads. As a matter of fact, the road between Etono 1 and Biakpan is impassable during the rainy season.
2.7 Topography
Topography of the project area is essentially undulating terrain with poor natural drainage system. Seasonal rivulets and small streams constitute the dendritic drainage pattern of the area, interconnecting pockets of swampy areas that generally drain into Cross River that eventually empties into south-eastern corner of the Atlantic Ocean.
2.8 Rainfall
Rainfall plays an important part in any water supply assessment and evaluation. In the project area, there is adequate rainfall throughout the year. The annual maximum rainfall in the area records as high as 1800mm. This provides a constant runoff to the stream channels, keeping then actively surcharged. There is however a great variability in monthly rainfall having its peaks between the months of July and September.
2.9 Access
Access to the project area is in poor condition. The access roads are neither tarred nor graded and also very rugged. The four main communities of Etono 1, Ikun, Biakpan and Etono 2 can be accessed through either Akpet Central off the Calabar–Ikom highway or through Ikot Ekpene – Odoro Ikpe – Bende – Ohafia – Asaga then to Biakpan or Ikun. It is to be noted that this latter route goes through neighbouring states of Akwa Ibom and Abia and is the only route through which vehicular traffic can access the area by land.
The road from Akpet Central is tarred but terminates at Okurike Village on the eastern bank of Cross River. To get to Etono-1 on the western bank requires crossing by local river transport. Thus, movement of construction materials through this route to the project area would prove difficult. This leaves only the alternative option of access through a labyrinthine route for the movement of construction materials and equipment through Ohafia in Abia State as stated earlier.
(3)
(4)
Fig. 2.2: Map of Biase Local Government Area of Cross River State
(5)
Figure 2.3: Project Area Layout Map
(6)
3.0 EXISTING WATER SOURCES AND SUPPLY SITUATION IN THE AREA
3.1 WATER SOURCES
The existing water supply sources for the inhabitants of the project area comprises
mainly of rain, streams and ground water.
3.1.1 Rain Water
As a common practice in the southern and coastal areas, there is a great reliance on
rainwater sources, firstly because there is an abundance of rain in its due season, and
secondly the rains spread nearly throughout the year. This provides a source for rain
water harvesting using drums, plastic containers and basins. The rain water source
helps to reduce the labour in trekking in search for water from the streams and rivers.
3.1.2 Surface Water
Other sources of dependable water are the streams and rivers in the area. Fortunately
the people of Etono and Ikun get their surface water source from Cross River and
other locations in the community. But unfortunately, the existing water sources are
fetched by trekking long distances to and from the streams with consequent loss of
time that is needed for other activities. Moreover, the amount of water taken to the
house is grossly inadequate for home uses.
The streams are slow moving thereby harbouring pathogenic organisms that constitute
source of all sorts of diseases which are causing a lot of health hazard to the people
living in these communities.
3.1.3 Ground Water:
There had been government intervention water projects in the area at Etono
(motorised borehole with elevated tank) and hand-operated borehole pumps at
Biakpan but these have long ceased to work. This means that the inhabitants have
reverted to traditional sources of water which are mainly based on ground water.
3.2 Water Uses
Essentially, the communities make use of the available water for domestic activities
such as drinking, cooking, bathing, washing, etc while agriculturally it is being used
for irrigation farming, processing of cassava and palm oil among other things. The
amount of water used for agricultural purpose in the area is very low since most of the
(7)
agricultural activities depend on rain fed irrigation. Water is needed mostly in the
domestic gardens. Despite the fact that these people reside in areas with high amount
of rainfall, the potential for high water use is hampered by lack of adequate storage.
3.3 Water Source Contamination
A major concern in the area which may affect water quality is the risk posed by open
defecation on river and stream banks. Runoffs from precipitation on their way to the
stream channel do carry along these faeces into the stream thus contaminating it. The
practice poses a serious health risk to the people, although many of them may not be
aware of this danger.
Another source of contamination of surface water is the practice of fermentation of
cassava and other agricultural products in the rivers and streams.
Groundwater, though not very viable in the area due to the geologic form is also open
to faecal contamination
(8)
4.0 PLANNING AND DESIGN DATA COLLECTION AND FIELD INVESTIGATIONS
4.1 GENERAL
The success of any water supply scheme depends on the use of reliable existing data
over a length of time. The collection of data is complemented by investigations
carried out during such an exercise. A good field investigation does not only help in
making the best choice of the source of water for the scheme but it also ensures that
the design of such a scheme is built on a strong database to prove the required
stability, durability and efficiency.
4.2 METHODOLOGY
Thorough and conscientious field investigation and data collection were carried out to
provide suitable database for designing a technically feasible scheme. In the course of
collecting data for use in this project data were collected using, personal interview,
documentary, and observation methods. These methods though rigorous, helped to
ease the data collection process and ensured the accuracy of the data collected. The
data collected include:
(i) Population data(ii) Rainfall data(iii) Metrological data(iv) Hydrological data(v) Geological data
4.2.1 Population Data
The 1991 Census population data for the major communities of Etono-1, Ikun,
Biakpan and Etono-2 were obtained from the Calabar office of the National
Population Commission. The 2006 census figures were said to be unavailable since
they were not yet officially released. The official of the Population Commission
recommended that a population growth rate of 2.8% should be used for population
projection calculations for the area.
The population data for the whole of Biase Local Government Area was collected are
shown in Fig. 4.1. The relevant figures for the project communities were then
extracted and used for calculating population projections as shown in Fig. 4.2
(9)
Fig. 4.1: 1991 Census Figures for Biase Local Government Area
TOTAL 17,964 29,529 33,902 38,921 44,685 51,302 58,898Data Source: National Population Commission/1991 Census FiguresPopulation Growth Index is 2.8% as recommended by NPC official.
Fig. 4.2: Projected Population Figures for Project Communities
4.2.2 Water Quality Sampling Data
Water samples were taken from identified surface water sources on Cross River and
Obana Stream and sent for laboratory analysis at the Enugu State Water Corporation
Water Analysis Laboratory. A detailed chemical analysis of the water sample
covering the three perspectives of physical, chemical and bacteriological aspects was
carried out and the results are given below Tables 4.3 and 4.4.
(11)
Fig 4.3: Laboratory Test Results for Water Sample from Cross River
(12)
Fig 4.4: Laboratory Test Results for Water Sample from Obana River
(13)
4.2.3 Meteorological and Hydrological Data
4.2.3.1 Rainfall data
The major centres for rainfall data are those at Umudike and the Nimet Office in
Calabar.
The mean monthly Rainfall data and number of rainy days for the
area is given in table 4.5 below. This forms the basis for
establishing the hydrological potential of streams and rivers in the
In this process the storage tank is to allow for initial equalisation of flow through the
treatment plant to be met before going into coagulation and flocculation units.
20
The coagulation will help to increase flocs density, which through the process of
flocculation with appropriate velocity gradient selected will enhance flocs density
settled in the sedimentation tank.
The sedimentation process is designed to allow for a reasonable retention time for
settling to take place, from where clarified flow will pass to rapid sand filtration unit.
The filtration unit will ensure that short circuit flocs do not pass into the clear water
tank.
Subject to the final water quality parameters analysed, there is need to incorporate
aeration unit in the treatment layout
As a means of dealing with the bacteriological aspect of water, a filtration unit will be
adopted, the sizing of which will based on the throughput flows and filter system
design criteria.
Disinfection of the filtered water will be needed to protect treated water from harmful
bacteria.
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7.0 DESIGN SYNTHESIS OF WATER SUPPLY SYSTEMS
7.1 General
Analysis of data gathered from site has revealed several features of the project area
which must be considered in the synthesis of the engineering design of this project.
The following are some of the important funding:
(a) The main population centres in the project area are Etono-1, Ikun, Biakpan
and Etono 2 and area spread geographically over a wide area except for
Biakpan and Etono 2 which are adjoining each other. The other towns of Ikun
and Etono-1 are separated by considerable distances as shown in Table 7.1
below:
From ToRoad
Distance Km
Direct Distance
(km)
Biakpan Ikun 17.5 8.0
Biakpan Etono-1 10.5 12.5
Etono-1 Ikun 8.5 6.2
Biakpan Etono 2 0.8 0.8
Fig 7.1 – Geographical Spread of Project Towns
(b) The roads linking the various communities in the project area are just ordinary
earth roads that are in very poor state. The 10.5 km road between Etono-1 and
Biakpan can be particularly bad during the rainy season when it becomes
impassable to vehicular traffic. Sections of this road are also prone to heavy
flooding during the rainy season.
The road between Etono and Ikun appears to be not as bad as the Biakpan –
Etono road.
(c) Both Ikun and Etono-1 are located closer to the bank of Cross River and have
depended on the river for sourcing of water for domestic use for ages.
Biakpan and Etono-2 are however located a considerable distance away from
the Cross River. They presently depend mainly on streams and rain water for
their needs. Some of the streams are seasonal but one of them, Obana River,
is perennial and is the main source of water for the people during the dry
season.
22
(d) Cross River is prone to annual flooding during the rainy season which lasts
from early May to early December. Site measurements and observations
indicate that the fluctuation in the level of the river ranges from about 5m to
13m above sea level – about 8m amplitude. This is illustrated in Fig 7.2
below which shows the ground profile along the road from Etono-1 to Etono
Beach. The water level (at its lowest) shown in this drawing was taken in the
month of February 2009 and the local people affirmed that was the lowest
level and would remain so until the rains come again when the level would
rise again. At the low water level, people can wade across to the other side of
the river. Sand bars abound all over the river bed at this period and the water
course is constrained to meander among them. Fortunately, it was found
that the water course runs by the river bank at Etono-1 Beach where the
bank is firm in a clayey formation - a situation which is considered ideal
for the siting of a raw water intake structure since the problems of
sanding/silting problems would be minimized.
Fig. 7.2: Longitudinal Profile of Road to Etono Beach
Illustrating Flood Level Variations on Cross River
23
(e) It was found out from satellite pictures that a high ground exists close to the
Ikun junction on Etono-1/Biakpan road. Subsequent field topographical survey
confirmed this fact. Similarly, a high ground was located about 1.5km south
of Biakpan between Obana River and Biakpan town which could serve as the
site of a water treatment plant.
7.2 Development of Engineering Design of the Water Supply System
From the results of analysis of data obtained from site investigations/and topographic
survey, the following conclusion have been drawn:
(i) The geological formation of the project area does not offer conducive environment for sustained ground water exploitation for water supply purposes.
(ii) Cross River offers a veritable alternative source of surface water for water supply purposes to the project area. However, since the river is subject to great variations in flood levels during the rainy season the design of intake structures for water abstraction would require careful attention to ensure that such structures are accessible and functional all year round.
(iii) Biakpan and Etono-2 communities are located a considerable distance away from the Cross River and higher elevation and it would require pumping facilities and over 12.5 km of pipeline to transport treated water. From the Cross River bank to Biakpan and Etono-2.
(iv) Obana River, which is perennial, was identified about three kilometres south of Biakpan as being capable of meeting the design water demands of both Biakpan and Etono-2 which is approximately 1500 m3/day (see Table 5.2). Laboratory tests have indicated relatively high turbidity and bacteriological count compared with results of samples from Cross River, a result which is consistent with the slow flowing nature of the river as observed on site in the month of February. The adoption of Obana River as water source would greatly reduce the operational costs of pumping water all the way from Cross River.
(v) A convenient hill lies between Obana River and Biakpan in which to locate a water treatment plant. The level difference between hilltop and Biakpan is about 30m and is adequate head to supply water by gravity to the consumers below without the need for elevated tank in the towns.
(vi) Public power supply is not available in the project area and the plant would operate solely on generators.
24
(vii) Access to the project area by road is only possible through Ohafia in Abia State. Therefore, the arrangements for bringing construction materials to site must be given proper consideration by contractors.
Detailed scrutiny of the above findings and subsequent calculations have led to the consideration of the following alternative configurations for siting water treatment plants under this project, thus:
Alternative 1
In Alternative 1, only one water treatment plant will be constructed to supply water to all the four communities benefitting from this project. This plant with a total design capacity of 3500m3/day (25-year period) will be sited along Etono-1-Ikun Rd some 2.2 km away from Etono-1 and will comprise of the following main components:
River Intake Works on bank of Cross River in the vicinity of Etono Beach. Raw water will be abstracted and pumped to the Water Treatment Plant.
250mm diameter Raw Water Transmission Line from the Intake Works to the Water Treatment Pant
Water Treatment Plant comprising of the following main components:(i) Aerator(ii) Flocculation/Clarifier(iii) Rapid Gravity Sand Filter(iv) Pump House(v) Underground Storage Tank(vi) Chemical Building(vii) Administration Building(viii) Staff Houses(ix) Gate House(x) Generator House
Power Supply Facilities consisting of two generator houses; one at the River Intake Works and the other at the Water Treatment Plant.
150mm dia Clear Water Rising Mains to Etono-1 (approx. 2.1 km long)
150mm dia Clear Water Rising Mains to Ikun (approx. 6.5 km long)
150mm dia Clear Water Rising Mains to Biakpan and Etono-2 (approx 11 km long)
Four (4 No) Overhead Storage/Distribution Tanks, one in each of the project towns of Etono-1, Ikun, Biakpan and Etono-2.
It should be noted that this alternative requires pumping of treated water from the water treatment plant through the rising mains to the overhead tanks in each project town.
25
Alternative 2
Under this alternative, two separate water treatment plants are to be implemented; one near Etono-1 at the same location as in Alternative 1 as described above and the other at Biakpan.
The main advantages of this alternative include:
(a) Elimination of capital cost of providing pumping facilities including associated pipeline to transport water from Cross River to Biakpan and Etono-2.
(b) Elimination of maintenance and running costs of pumping equipment and pipeline referred to in (a) above. This aspect also includes elimination of possible vandalisation of the pipeline that would run through thick forest vegetation and poorly maintained road.
(c) The effects of breakdowns during operation will only affect a section of the project area.
The main components of the water supply facilities shall be as follows:
Alternative 2a
A water supply system shall be sited in the same locations as described i Alternative 1 but with a reduced capacity of 2000 m3/day. This plant shall supply water to Etono-1 and Ikun communities, and consists of the following components:
(i) River Intake Works about 2.2 km from the bank of Cross River from which raw water will be pumped to the water treatment plant.
(ii) 200mm dia Raw Water Pipeline 2.2 km long from the River intake works to the water treatment plant.
(iii) Water Treatment Plant of capacity 2000 m3/day with components as in the water treatment plant described in Alternative 1 above.
(iv) 100m3 Elevated Tank 9m high shall be provided to serve as storage/distribution tank to Etono-1 and Ikun by gravity. Thus, there will be no need for overhead tanks in those communities.
(v) 150 dia gravity pipeline to Etono-1 about 2.2km long
(vi) 150 dia gravity pipeline to Ikun x 6.5 km long.
(vii) Power Supply Facilities consisting of two generator houses; one at the River Intake Works and the other at the Water Treatment Plant
Alternative 2b
A second water supply facility of 1500m3/day capacity shall be built at Biakpan to supply water to Biakpan and Etono-2 communities. It consists of a River Intake Works on the bank of Obana River and a water treatment plant located about midway between Obana River and Biakpan Town.
The components of this plant are as in Alternative 2a except that there will no overhead distribution tank at the water treatment plant since the elevation at the plant has enough head to supply water by gravity to Biakpan and Etono-2. However, a
26
service water overhead tank of 25m3 capacity will be required for process, office and residential needs.
Thus, the main components of this system are as follows:
150mm dia Raw Water Transmission about 1.2km long Water Treatment Plant consisting of
o Aeratoro Flocculation/Clarifiero Rapid Gravity Sand Filtero Pump Houseo Service Water Elevated Tanko Underground Tanko One Generator House located at the Water Treatment Plant. Unlike the
plant at Etono, only one generator house is recommended with power extended to the River Intake Works via overhead power cables.
o Chemical Buildingo Administration Buildingo Staff House
150mm dia Gravity Distribution pipeline to Biakpan with a 100mm dia branch pipeline about 600m long to Etono-2.
S/N ComponentElevation
(m) asl1. Cross River Intake Works 3.002. Water Treatment Plant 31.0003. Etono 1 22.0004. Ikun 26.5005. Biakpan 28.8006. Etono-2 25.200
Fig 7.3: Relative Levels of Locations in Project Area
After due consideration of the various conditions and factors, it was decided that
Alternative 2 in which two separate plants are to be built offers the best option for
construction, operation and maintenance. The process diagrams for the two plants to
be located at Etono-1 and Biakpan are shown indigos 7.3 and 7.4.
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28
29
7.3 Design Criteria and Calculations
From the population and water demand data shown in Fig. 5.2, we have constructed
Tables 7.5 and 7.6 to obtain the design data for the two designated water supply
systems, namely Etono1 Plant and Biakpan Plant. These tables reveal that the present
water demand for Etono-1 Plant is about 1000m3/day and is expected to double to
2000m3/day in 2034 (25 year’s time). For the Biakpan Plant, the corresponding
demands are about 800m3/day in 2009 and 1500m3/day in 2034.
A design period of 25 years is to be adopted for this project; hence all subsequent
calculations shall use the water demand of 2000m3/day for the Etono-1 Plant while
1500m3/day shall be used for the Biakpan Plant.
S/No Town YEAR 2009 2014 2019 2024 2029 2034
1 Etono 1 Population 6,818 7,828 8,987 10,318 11,846 13,600 Water Demand
(m3/day)409 470 539 619 711 816
2 Ikun Population 10,034 11,520 13,225 15,184 17,432 20,013