Water Network Design: Beit El Chaar, Lebanon

NOTRE DAME UNIVERSITY
Faculty of Engineering
Department of Civil & Environmental Engineering
CEN 463 – SPRING 2019
Water and waste water networks
WATER NETWORKS DESIGN
BEIT EL CHAAR
PREPARED BY
Alain Tannous
Antoine Aoun
Charbel Salloum
Joy Hamouche
Mario Chamoun
Mario Fares
SUBMITTED TO:
Maya Atieh, PhD.
May 8, 2019
1. Abstract
In the water and waste water network course, it was required to choose a Lebanese city and
design its water distribution network, storm water system and wastewater network. Beit el Chaar
was picked and the study began. The municipality was visited, the necessary data was collected
and the design phase started. First, the population was projected to 50 years ahead to design
accordingly, then, the demand of the city was calculated to be 7207500 L/day. Then, a storage tank
was designed to satisfy the need of the city. After that, EPAnet was used to design the water
distribution network. The map was divided into 6 loops that cover the demand of the whole city,
and the software resulted in the diameters of the pipes, flows and velocities in the links and
pressures at the nodes. The results were overall satisfactory although some problems were faced
in keeping the pressures within the limits. After that, a storm network was designed by hand
calculation using the Rational method taking into consideration the peak runoff that can occur.
Then, similarly, a waste water network was also designed by hand calculations making sure that
the diameters of the pipes are within the allowed limits, as well as the velocities in the pipes.
Finally, a brief non-professional cost estimate was provided to have an idea about the project cost
as a whole.
2
Contents
1.
Abstract ............................................................................................................................... 2
2.
Introduction ......................................................................................................................... 5
3.
Location .............................................................................................................................. 7
3.1
Geography, topography and climate .............................................................................. 7
3.2
Land use, zones and areas. ............................................................................................ 8
4.
Population growth and projection......................................................................................... 9
5.
Water demand and fire requirements .................................................................................. 11
6.
Design flow ....................................................................................................................... 12
7.
Water storage tank design .................................................................................................. 14
8.
Water distribution network................................................................................................. 17
9.
Design of water distribution network using EPAnet ........................................................... 18
10.
Storm Water System....................................................................................................... 21
11.
Waste Water System ...................................................................................................... 25
12.
Cost estimate .................................................................................................................. 29
13.
Conclusion ..................................................................................................................... 30
14.
References...................................................................................................................... 31
List of Tables
Table 1. Zones and surface areas ................................................................................................. 8
Table 2. Population data in Beit el Chaar .................................................................................... 9
Table 3. Distribution of population in Beit el Chaar .................................................................. 10
Table 4. Water demands for each zone ...................................................................................... 11
Table 5.Variation of water demand throughout the day ............................................................. 13
Table 6. Operational and equalizing storage results ................................................................... 15
Table 7. Drainage areas and properties ...................................................................................... 23
Table 8. Computation of slopes ................................................................................................. 23
Table 9. Maximum and minimum factors for average daily flow ............................................... 26
Table 10. Distribution of Q to the manholes and calculation of slopes, diameters and velocities 27
Table 11. Check for minimum factor for average daily flow...................................................... 28
Table 12. Cost estimate ............................................................................................................. 29
3
List of Figures
Figure 1. Location of Beit El Chaar on the Lebanese map ........................................................... 7
Figure 2. Distribution of zones in Beit el Chaar ........................................................................... 8
Figure 3. Variation of population per year ................................................................................... 9
Figure 4. Hourly demand as percent of average ......................................................................... 13
Figure 5. Variation of hourly supply and demand versus time ................................................... 16
Figure 6. Galvanized steel pipes ................................................................................................ 18
Figure 7. EPAnet Pipe Network Layout .................................................................................... 19
Figure 8. EPAnet results: velocity in pipes and pressure at nodes .............................................. 19
Figure 9. EPAnet Table indicating the Velocity and Flow Results in the pipes .......................... 20
Figure 10. EPAnet Table indicating the Pressure and Head Results at the junctions .................. 20
Figure 11. Drainage areas and storm water manholes ................................................................ 21
Figure 12. Rainfall intensity vs duration.................................................................................... 22
Figure 13. Location of manholes throughout the main street ..................................................... 25
4
2. Introduction
When someone says water networks, this means that water distribution network,
stormwater drainage system and waste water system are being referred to. First, a definition of
each will be stated to clarify the aim of this study.
•
A water distribution network is also known as a water supply system, which provides people
with the necessary quality amount of water, to be used for many purposes and satisfy their
basic needs.
•
A stormwater drainage system is a system that tends to maneuver and manage the water runoff
that occurs due to excess of rainfall.
•
A waste water system is a system that is responsible for collecting and disposing of water that
goes down the sinks, toilets and drains.
In Lebanon, water networks are poorly designed in many areas especially in rural ones that
are away from the cities, and if present, they lack maintenance and sometimes need replacement.
People are recently suffering from water shortage crisis although rainfall is attaining its yearly
averages. The main reason behind that is our damaged and poorly designed networks that lead to
water leakage, or that fail to provide the needed amount of water. Our responsibilities as engineers
is to contribute as much as possible in solving this water network problem, even if it is a small
contribution. Hence, a project was provided in the waste and waste water networks course that
required to pick a local municipality, collect the needed data, make logical assumptions if the data
is absent, and then design a water distribution system, a stormwater system and a wastewater
system for the chosen municipality. The design will be performed by hand calculations and using
the EPAnet software.
First, a local municipality will be chosen, visited and studied. Data about its area,
topography, soil types, climate, land use (residential, commercial, industrial…), population and
water usage will be collected. Then, the population will be projected to 50 years in order to design
accordingly. The water demand will then be calculated, taking into account the water fire demands.
After that, the variation of this demand across the year, and throughout the day and hours will be
checked.
5
Second, water resources (inlets) and the location of outlets on the map will be identified.
Thus, the map will be divided into loops to make sure that the nodes are located at the inlets and
outlets, and that all the areas of the city are covered and can benefit from the water distribution
system. EPAnet software will be used to draw the loops and run the analysis accordingly. The
outcome of the software will result in the flow in each pipe, the diameter of the pipes, velocities,
heads and pressures.
In addition, a water storage tank will be designed in order to provide the necessary
operational and equalizing volume to satisfy the needs of the city. Its location will be decided on
throughout the report.
Then, a stormwater drainage system will be designed to cover a part of the studied area.
The rational method will be used and hence the diameters of the storm network pipes will be
calculated by hand.
Once done, a wastewater system will also be designed by hand calculations to come up
with a diameter and a velocity of the flow.
At the end, a brief cost analysis will be provided based on research only (no experience in
this field), in order to have an idea how much this project will cost as a whole.
6
3. Location
3.1 Geography, topography and climate
Beit El Chaar - Mazraat El Hdaira is a Lebanese village situated in Matn - Mount Lebanon.
The municipality is a member of Federation of “Matn El Chamali El Sahili Wal Awsat”
municipalities. It is located a little north east of Beirut’s airport (17 km away). It is surrounded by
Dik El Mehdi from the north, Mazraat Yachou’ from the east, Mtaileb from the South and Mazraat
El Hdaira from the west. This municipality’s altitude ranges between 210 m above sea level at the
extreme west and 400 m at the extreme east. It has a mountainous topography similar to all the
areas that are located on the west side of Mount Lebanon.
Figure 1. Location of Beit El Chaar on the Lebanese map
The average temperature in Beit El Chaar is moderate, varying between 9°C in winters
and 28°C in summers, in average.
7
3.2 Land use, zones and areas.
Beit El Chaar is mostly a residential area, with a public park that occupies around 1.5% of
the total municipality area. Although there are some small commercial shops on the ground floor
of some buildings along the main roads, they can be assumed as residential apartments because
they are mostly family size companies (2 to 3 persons at most). Hence, what is important is that
Beit El Chaar does not include any schools, universities, hospitals, sports academies or industrial
areas of any kind. The total area of Beit el Chaar covers around 0.63 km2 in surface, divided into
5 main zones, whose data was collected from the municipality. These zones vary in size, shapes
and elevations, but they are all residential areas in general, and are detailed in table 1 and illustrated
in figure 2. The sum of all the areas in table 1 results in a total of 628580 m2, equivalent to 0.62858
km2.
Table 1. Zones and surface areas
Zone
Surface area (m2)
A
68093
A1
62251
B
414705
B1
47358
B2
36173
Figure 2. Distribution of zones in Beit el Chaar
8
4. Population growth and projection
Population statistics in Beit el Chaar were last taken in 2015, and no accurate number is
recent. The population was projected 50 years starting 2015, which is the year when the last data
was collected. The population growth between 1995 and 2015, detailed in table 2, was provided
by the municipality.
Table 2. Population data in Beit el Chaar
Year
Population
1995
4500
2000
5300
2005
5600
2010
6600
2015
7500
8000
7500
y = 146x - 286830
R² = 0.976
Population
7000
6500
6000
Actual growth
5500
Linear growth
5000
4500
4000
1990
1995
2000
2005
2010
2015
Year
Figure 3. Variation of population per year
9
2020
Plotting the population versus the year, it is shown in figure 3 that a linear trendline is the
best fit line that suits this population growth, because the R-squared value is close enough to 1.
Hence, an arithmetic growth will be taken into consideration to estimate that population 50 years
from 2015, in 2065.
From figure 3, the slope of the best fit line was obtained to be 146, which is karith. So, to
estimate the population at the 50th postcensal year (2065), the following calculation was done:
𝑦" = 𝑦$ + &𝑡" − 𝑡$ )𝑘+,-./
𝑘+,-./ = slope of linear trendline = 146
𝑦0123 = 7500 + (2065 – 2015)×146 = 14800 persons.
These people are distributed randomly in Beit el Chaar and no precise data is available
regarding the distribution of population. Hence, the population will be distributed according to
the percentage of area covered by each zone. Table 3 indicates the distribution of people in Beit
el Chaar by the year 2065.
Table 3. Distribution of population in Beit el Chaar
Zone
Surface area (m2)
Portion of area (%)
Population
A
68093
10.83%
1603
A1
62251
9.90%
1466
B
414705
65.97%
9764
B1
47358
7.53%
1115
B2
36173
5.75%
852
Total
628580
100%
14800
A sample calculation is detailed below:
For zone A, the percent of area covered by zone A is:
68093
628580
Population in zone A: 14800 × 0.1083 = 1603 persons
10
= 0.1083 = 10.83%
5. Water demand and fire requirements
No accurate data is available regarding the average residential water demands in Beit el
Chaar, so it was assumed that each person consumes 160 liters per day. Plus, as mentioned before,
in zone B, there is around 1.5% of the total area of the municipality covered by a public garden,
which is around 9500 m2. It is known that gardens need at least 1 inch of water per week, which
is equivalent to around 0.623 gallons per week for each square foot.
Water needed for the 9500 m2 garden:
9500 m2 = 102257.1 ft2
0.623 gal × 102257.1 ft2 = 63706 gallons for the total area per week.
63706 gal/week × 3.78541 L/gal = 241153 L/week
241153 L/week ×
< >??@
A B+CD
= 34500 L/d
Table 4 will represent the amount of water demands for each zone, assuming that the average
residential water demand is 160 Lpcd.
Table 4. Water demands for each zone
Zone
Population
Average water demand (L/d)
Demand per zone (L/d)
A
1603
160
256521
A1
1466
160
234513
B
9764
160
1562286
34500
34500
Garden
B1
1115
160
178408
B2
852
160
136272
Total
14800
2402500
11
Fire requirements:
The collected information stated that there are around 340 buildings in Beit el Chaar,
majority reinforced concrete. However, it is not possible to design for a fire that attacks all the
city. This is why 12 buildings will be considered, 2 stories each, with an area of 400 m2 per floor.
Total area = 12 × 2 × 400 = 9600 m2 = 103333.5 ft2
Referring to Table 4.13 in the textbook named Water Supply and Wastewater Removal, 3rd ed, and
having an area between 97701 ft2 and 112700 ft2, the required fire flow for type I noncombustible
buildings is 3500 gpm for 3 hours. This is equivalent to:
E+F
H
"-G
3500 "-G × 3.78541 E+F × 60 /IJ, × 3 hours = 2385000 L
6. Design flow
v Considering peak daily demands:
Qpeak daily = kQavg + Qfire = 1.8×2402500 + 2385000 = 6709500 L/d
v Considering peak hourly demand:
Qpeak hourly = kQavg = 3×2402500 = 7207500 L/d
Since the peak hourly demand is greater than the peak daily demand that includes the fire
requirements, Qdemand = 7207500 L/d will be considered when designing.
Qdemand =
A01A311
0K
= 300312.5 L/h
In order to account for the variation of water demand throughout the day, logical
assumptions have to be made. That is why it will be referred to table 6.13 in the same textbook,
which provides a real-life situation example where the demands in the morning and at night are
maximum, and minimum after midnight. This example provides the hourly demands as percent of
the average, for each hour of the day. These values are provided in table 5 and will be used in the
design. In addition, a graph shown in figure 4 illustrates the variation pf this percentage throughout
the day.
12
Table 5.Variation of water demand throughout the day
Time
Hourly
demand as
percent of
average (%)
Time
Hourly
demand as
percent of
average (%)
12 am - 1
1-2
2-3
3- 4
4-5
5-6
6 -7
7-8
8-9
9 - 10
10 - 11
11 - 12 pm
47.9
45.4
44.1
42.1
41.3
42.4
43.2
76.2
108.9
117.8
123.6
126.7
12 pm - 1
1-2
2-3
3- 4
4-5
5-6
6 -7
7-8
8-9
9 - 10
10 - 11
11 - 12 am
132.4
135.2
133.4
132.4
133
139.5
153.3
195.5
174.4
105.8
53.8
51.7
250
Percent of average demand (%)
200
Actual
demand
Average
demand
150
100
50
0
12:00 AM
4:00 AM
8:00 AM
12:00 PM
4:00 PM
8:00 PM
Time
Figure 4. Hourly demand as percent of average
13
12:00 AM
7. Water storage tank design
We are all aware that there are significant variations in water demands at different time
periods of the day. The equalizing and operating storage, which is the quantity of water required
to meet the peak demands in a community, will depend on these variations. Thus, in order to design
the volume of a water storage tank, the average demand of 300312.5 L/h will be used, and
depending on the hourly demand as percent of average, it will be known how much water should
be provided hourly. However, the supply on the other hand should also be considered. In the
design, it will be assumed that a continuous pumping into the storage tank throughout the 24 hours
of the day is provided, in a way that the total supply equals the total demand of 7207500 L/d. Note
that the numerical or tabular method will be used to calculate the operational and equalizing
storage,
As calculated before, the total volume of 7207500 L/d accounts for the fire requirements.
However, in case the inflow to the reservoir is shut off due to equipment failure, pipeline breaks,
power failure, pumping failure, contamination or due to maintenance, an emergency reserve
storage, that sustains the community needs in case any of these problems takes place, should be
considered. This emergency storage is generally not more than 25% of the total storage.
Considering an unknown dead storage to be used as well, the 25% of the total storage will roughly
be equivalent to 30% of the equalizing and operational storage. Thus, the storage tank will be
designed accordingly.
A sample calculation of the results detailed in table 6 is explained below:
Qdaily demand = 7207500 L/d
Qhourly demand =
A01A311
0K
= 300312.5 L/h = Hourly supply (continuous)
At 2 a.m., the demand consists of 44.1% of the average demand (300312.5 L/h)
Q2-3 = 300312.5 × 0.441 = 132438 L/h
The total operational and equalizing storage will be equal to the summation of all positive
“supply – demand” or all negative “supply – demand”
14
Table 6. Operational and equalizing storage results
Time
Hourly
demand as
percent of
average
Hourly
demand
(L/h)
Hourly Supply
(L/h)
Supply - demand
(L/h)
12 am - 1
1-2
2-3
3- 4
4-5
5-6
6-7
7-8
8-9
9 - 10
10 - 11
11 - 12 pm
12 pm - 1
1-2
2-3
3- 4
4-5
5-6
6-7
7-8
8-9
9 - 10
10 - 11
11 - 12 am
47.9
45.4
44.1
42.1
41.3
42.4
43.2
76.2
108.9
117.8
123.6
126.7
132.4
135.2
133.4
132.4
133
139.5
153.3
195.5
174.4
105.8
53.8
51.7
143850
136342
132438
126432
124029
127333
129735
228838
327040
353768
371186
380496
397614
406023
400617
397614
399416
418936
460379
587111
523745
317731
161568
155262
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
300312.5
156463
163971
167875
173881
176283
172980
170578
71474
-26728
-53456
-70874
-80183
-97301
-105710
-100304
-97301
-99103
-118623
-160067
-286798
-223433
-17418
138744
145051
Total
7207500
Summation of
positive values
1537300
Summation of
negative values
-1537300
Equalizing and operational storage = 1537300 L
15
Figure 5 illustrates the variation of the hourly demand versus the provided hourly supply.
The graph looks exactly like the one in figure 4 simply because the 100% of the average demand
is equal to the continuous provided supply. By looking at these graphs, it is noticed that the tank
is emptying between 8 a.m. and 9 p.m., when the demand is greater than the supply, and filling
between 9 p.m. and 8 a.m. when the demand is less than the supply.
700000
Flow rate (L/h)
600000
500000
Hourly
demand
400000
Continuous
supply
300000
200000
100000
0
12:00 AM
4:00 AM
8:00 AM
12:00 PM
4:00 PM
8:00 PM
12:00 AM
Time
Figure 5. Variation of hourly supply and demand versus time
As discussed before, the emergency reserve storage will be assumed to be 30% of the equalizing
and operational storage:
Emergency storage = 1537300 × 0.3 = 461200 L
Hence, the total volume of the storage tank will be:
1,537,300 + 461,200 + a dead storage assumed to be 500,000 L = 2498300 L
16
8. Water distribution network
Requirements:
•
Satisfied quality and quantity standards
•
To enable reliable operation during irregular situations (fires…)
•
To be economically and financially viable, ensuring income for operation, maintenance
and extension.
•
To be flexible with respect to the future extensions.
Water sources:
Beit El Chaar has no internal source of water. Water is supplied from two springs located
in the nearest village of Mazraat Yachouh which are Nabeh El Manboukh and Nabeh El Aasal.
But, due to lack of data availability, the supplied flow rates are not recorded to be able to compare
them to the demand flow rates. Hence, the supply flow rates will not be included in the design and
it will be assumed that enough water is provided to account for the maximum demands.
Water Reservoirs:
There are no available water tanks in Beit El Chaar, this is why a reservoir tank was
designed in the previous section, to be built directly outside the border of the city, in cooperation
with Mazraat Yachouh municipality, to take advantage of the highest possible elevation (450 m).
Pipes:
Galvanized steel pipes are pipes that have been dipped in a protective zinc coating to
prevent corrosion and rust. Galvanized piping was commonly installed in homes built before 1960.
When it was invented, galvanized pipe was an alternative to lead pipe for water supply lines. Most
galvanized steel pipes remain functional for about 40 to 50 years. Galvanized steel pipes are more
flame resistant than PVC and are stronger than aluminum. So galvanized steel pipes will be used
in the project since it satisfies all the requirements.
17
Figure 6. Galvanized steel pipes
9. Design of water distribution network using EPAnet
EPAnet Definition and usage:
EPAnet is a computer program that performs extended period simulation of hydraulic and
water quality behavior within pressurized pipe networks. A network can consist of pipes, junctions,
pumps, storage tanks and reservoirs.
Advantages:
•
Survey data can be read into program (using excel)
•
All Calculations are done internally and quickly
•
Summary outputs tables and graphs
•
Unlimited network size and complexity (Looped systems…)
•
Error Checking
18
Figure 7. EPAnet Pipe Network Layout
Figure 8. EPAnet results: velocity in pipes and pressure at nodes
19
Figure 9. EPAnet Table indicating the Velocity and Flow Results in the pipes
Figure 10. EPAnet Table indicating the Pressure and Head Results at the junctions
20
Discussion of Results:
Six loops were designed to provide the necessary water for Beit el Chaar. The velocity in
the pipes must range between 0.6 m/s and 1.8 m/s. Pressure in pipes must range between 40 to 60
psi and 90 to 110 psi. However, velocities are maintained between the given ranges while pressure
is not as shown in figures 8 and 9.
To solve this issue, there are two ways to decrease the pressure at the nodes:
•
Decrease the amount of water flow, which cannot happen because we need to satisfy
people’s demands, and this demand cannot be reduced further.
•
Increase the diameter of the pipes. However, this increase will cause the velocity to drop
below the limits and might cause deposition of silt in the pipes.
10. Storm Water System
In order to design the draining system for the storm water, the lower half of the area of
Beit el Chaar will be considered as shown in figure 11. This area will be divided into 4 smaller
ones and each one will lead to a manhole.
Figure 11. Drainage areas and storm water manholes
21
In order to use the rational method, some parameters need to be determined
1. A Runoff coefficient of C=0.5 will be used for all areas as stated in the City of Lebanon
Specifications for Storm Water Drainage and Retention.
2. The rainfall intensity will be determined from figure 12 that represents a variation of the
intensity in function of the storm duration in Beirut. The last 5 years recorded will be
considered and assuming a 15 min duration (duration of storm is equal to concentration
time) → i = 0.08m/h
The 15 minutes duration was assumed based on the longest road that should be traveled by
the water to reach the manhole. Assuming an average water speed of 0.5 m/s and having
the longest distance to be 450 m, the time is calculated to be 15 min.
3. The areas are computed and tabulated in table 7
Figure 12. Rainfall intensity vs duration
22
Table 7. Drainage areas and properties
Drainage
Area
Area
(m2)
Cumulative
Area (m2)
C factor
A1
A2
A3
A4
20317
85953
102935
86202
20317
106270
209205
295407
0.5
0.5
0.5
0.5
Table 8. Computation of slopes
Manholes
Elevations
(m)
Difference in
elevations
Distance to
previous
MH (m)
Slope
MH1
MH2
MH3
MH4
310
298
285
262
12
13
23
391
382
380
0.031
0.034
0.061
Calculations to compute the diameter for pipe 1 from MH1 to MH2:
For tc = 15 min, the rainfall intensity i is 0.08 m/hr
C = 0.5 and A = 20317 m2
Qp = kCiA
è Qp= 0.5 x 0.08 x 20317 = 812.68 m3/hr = 0.226 m3/s
Qp =
1.M<&NO.PQ )&R S.T )
G
=
1.M<&NO.PQ)&1.1M<S.T )
1.1<M
è d = 335 mm
Take d = 350 mm
Qfull =
U
VWXYY
1.M<&NO.PQ)&R S.T)
G
=
1.002
1.033
=
= 0.89 è
1.M<&1.M3O.PQ)&1.1M<S.T )
1.1<M
Z
[WXYY
è Qfull = 0.255 mm
= 1.02
VWXYY
1.033
Vfull = \ O = \
= 2.65 m/s è V = 1.02 x 2.65 = 2.70 m/s
B
×1.M3O
]
]
23
Calculations to compute the diameter for pipe 2 from MH2 to MH3:
tc = 15 +
H
[
= 15 +
M^<
0.A(21)
= 17.4 min
For tc = 17.4 min, the rainfall intensity i is 0.078 m/hr
C = 0.5
A = 106270 m2
Qp = kCiA
è Qp =
<120A1×1.1Aa×1.3
M211
= 1.15 m3/s
1.M<&NO.PQ )&R S.T ) 1.M<&NO.PQ)&1.1MKS.T )
Qp =
=
=1.39 è d = 605 mm
G
1.1<M
Take d = 650 mm
U
VWXYY
=
<.<3
<.M^
Z
= 0.83 è
[WXYY
=1
VWXYY
<.M^
Vfull = \ O = \
= 4.188 m/s è V = 1 x 4.188 = 4.188 m/s
B
×1.23O
]
]
Calculations to compute the diameter for pipe 3 from MH3 to MH4:
tc = 17.4 +
H
[
= 10 +
Ma0
K.<^(21)
= 26.44 min
For tc = 26.44 min, the rainfall intensity i is 0.06 m/hr
C = 0.5
A = 209205 m2
Qp = kCiA
è Qp =
Qp =
01^013×1.12×1.3
M211
1.M<&NO.PQ )&R S.T )
G
=
= 1.74 m3/s
1.M<&NO.PQ)&1.12<S.T )
1.1<M
24
è d = 633 mm è Take d = 650mm
11. Waste Water System
In order to design the waste water network, 20 manholes will be placed along the main
road of Beit el Chaar. However, as shown in figure 13, the first 10 manholes will be considered
for the design making sure that the spacing between 2 successive manholes is always less than
120m. The manholes used are drop manholes, because it is considered that the remaining sewer
system is connected to the main pipe that will be designed.
Plus, the pipes will be placed in parallel to the ground surface, with a uniform cover of 1.5
m. Therefore, the slope of the pipes will be the same as the ground slope and it will be used in the
calculations.
Figure 13. Location of manholes throughout the main street
It was previously calculated that the total water demand in Beit el Chaar is 7207500 L/d. It will be
assumed that 70% of this amount is wasted.
7207500 x 0.7 = 5045250 L/d = 0.0584 m3/s
25
Assuming that this amount is uniformly distributed to all 20 manholes, we will have 0.0584 ÷ 20
= 0.00292 m3/s that enters each manhole and will accumulate to yield 0.0584 m3/s at the last
manhole.
However, a maximum and a minimum peak factor will be considered based on the population of
Beit el Chaar. Having a population of 14800 and referring to table 9, the maximum factor is 3.4
and the minimum is 0.33 by interpolation.
Table 9. Maximum and minimum factors for average daily flow
Finally, multiplying the average value of 0.00292 by the peak maximum and minimum, the
following values are obtained:
Qmax = 0.00292 x 3.4 = 0.00993 m3/s
Qmin = 0.00292 x 0.33 = 0.000964 m3/s
The design will be according to Qmax, and at the end a check will be performed on Qmin.
Considering only the first 10 manholes, the obtained results are detailed in tables 11 and 12.
26
Table 10. Distribution of Q to the manholes and calculation of slopes, diameters and velocities
Manholes
MH1
Q
Elevation Δ Z distance
D D used Q full
slope
(m3/s)
(m)
(m)
(mm) (mm) (m3/s)
(m)
0.0099
MH2
309
0.0199
2
70
0.029 105.4
200
0.0548
1.75
0.18
0.64
1.12
2
68
0.029 136.0
200
0.0556
1.77
0.36
0.77
1.36
2
67
0.030 157.8
200
0.0561
1.78
0.53
0.87
1.55
2
77
0.026 180.4
200
0.0523
1.66
0.76
0.96
1.60
2
71
0.028 193.2
200
0.0545
1.73
0.91
1.02
1.77
3
90
0.033 200.4
250
0.1075
2.19
0.55
0.88
1.93
2
62
0.032 213.6
250
0.1057
2.15
0.66
0.93
2.00
2
65
0.031 226.6
250
0.1033
2.10
0.77
0.97
2.04
2
66
0.030 237.5
250
0.1025
2.09
0.87
1
2.09
307
MH3
0.0298
305
MH4
0.0397
303
MH5
0.0496
301
MH6
0.0596
299
MH7
V full
V
Q/Qfull V/Vfull
(m/s)
(m/s)
0.0695
296
MH8
0.0794
294
MH9
0.0893
292
MH10
0.0993
290
A sample calculation of the flow in pipe 1 (between MH1 and MH2) is detailed below:
QMH1 =
1.M<&NO.PQ)&1.10^S.T )
1.1<M
= 0.0099 è d =105 mm
Take d = 200 mm
Qfull =
Vfull =
U
VWXYY
1.M<&NO.PQ)&R S.T)
G
VWXYY
\ O
N
]
=
=
1.M<&1.0O.PQ)&1.10^S.T )
1.1<M
= 0.055 m3/s
1.133
=\
= 1.75 m/s
O
×1.0
]
1.11^^
1.133
= 0.18 è
Z
[WXYY
= 0.64
è
27
V = 1.75 x 0.64 = 1.12 m/s
Table 11. Check for minimum factor for average daily flow
Manholes Q (m3/s)
MH1
0.00096
MH2
0.00193
MH3
0.00289
MH4
0.00385
MH5
0.00482
MH6
0.00578
MH7
0.00674
MH8
0.00771
MH9
0.00867
MH10
slope
D used
(mm)
Q full
(m3/s)
V full
(m/s)
Q/Qfull
0.029
200
0.0548
1.75
0.02
0.35
0.61
0.029
200
0.0556
1.77
0.03
0.37
0.66
0.030
200
0.0561
1.78
0.05
0.43
0.77
0.026
200
0.0523
1.66
0.07
0.49
0.82
0.028
200
0.0545
1.73
0.09
0.52
0.90
0.033
250
0.1075
2.19
0.05
0.43
0.94
0.032
250
0.1057
2.15
0.06
0.45
0.97
0.031
250
0.1033
2.10
0.07
0.49
1.03
0.030
250
0.1025
2.09
0.08
0.98
2.05
V/Vfull V(m/s)
0.00964
All diameters are equal or greater than 200 mm which is the minimum accepted diameter of a
waste network pipe. Plus, the velocity ranged between 0.61 m/s and 2.43 m/s, which is perfect
considering that it should not go below 0.6 m/s or above 3 m/s.
28
12. Cost estimate
In order to estimate the cost of this project, many factors will be considered: the length
(weight) of pipes needed, the pipe material used, the amount of soils and gravels needed, the rent
of equipment and the manpower to perform all activities that should take place like excavation,
backfilling, compaction, traffic control, in addition to safety and insurances.
This estimation is totally based on approximate values since nobody from the team members have
experience in that field. The costs are detailed in table 11 as follow:
Table 12. Cost estimate
Material/Activity including labor
Lump Sum Cost ($)
Pipes (for water distribution,
storm and waste networks)
675,000
Valves, bends, fittings,
anchorages...
70,000
Excavation
210,000
Placing pipes
65,000
Backfilling and compaction
40,000
Recovered damages (asphalt,
pavements, roads…)
175,000
Storage tank
50,000
Safety measures
5,000
Traffic control measures
3,000
Subtotal #1
1,293,000
Insurance (3% of subtotal #1)
39,000
Total cost
1,332,000
29
13. Conclusion
This project was a tough challenge for students, but it was managed to design a water
network system, a storm drainage system and a waste network for a whole city. Some errors might
have stood in the way especially in the EPAnet part where the limited capabilities of the team
members in using the software did not allow to obtain the optimum design (pressure went below
and beyond its limits), however, suggestions were made to solve this issue. Thus, overall, it was a
successful project.
As an outcome, it was understood that infrastructure problems in our country are not due
to lack of knowledge or expertise in this field. Even undergraduate students are able to come up
with a real preliminary design for a whole city. Therefore, it is necessary to raise awareness
regarding this topic, and take actions in order to solve the water crisis that is constantly faced.
30
14. References
Note: All the data related to the city itself was provided by the municipality itself including
maps, roads, weather, area, population…
-
Shammas, N. and Wang, L., 2011, Water Supply and Wastewater Removal, 3rd ed., Wiley
-
City
of
Lebanon
Specifications for
Storm Water Drainage
and
Retention.
https://www.lebanonmissouri.org/DocumentCenter/View/1443/StormWaterDrainageRetention
?bidId=
31