4.6 Facility Design 4.6.1 Design Criteria

The Study on Water Supply Systems in Mandalay City and in the Central Dry Zone Part II Study for Mandalay City

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4.6 Facility Design

4.6.1 Design Criteria

(1) Intake Facility

(a) Water Level at Intake Site

High Water Level: +70.0 m

Low Water Level: +61.0 m

(b) Design flow (Qi): Qi=1.1 x (daily maximum demand)

(2) Water Treatment Plant

(a) Detention time of receiving well: 1.5 min of daily maximum flow

(b) Overflow rate of sedimentation basin: 30 mm/min

(c) Filtration rate of rapid sand filter: 120 m/d

(d) Treated Water Reservoir

Detention time: 2hours of daily maximum demand

(3) Distribution Pipeline

All distribution pipelines shall be designed to satisfy peak hourly flow and required

residual head.

(a) Peak hourly flow

Peak hourly flow =1.5 x (daily maximum demand)

(b) Velocity Calculation: Hazen-Williams, C=110

(c) Residual Head (Hr) in distribution pipeline

Peak hourly flow of daily average: Hr>13 m

Peak hourly flow of daily maximum: Hr>5 m

In case of firefighting during peak hourly flow of daily maximum:

Hr>0 m in a fire hydrant

(d) Pipe material

100 to 1350 mm in diameter: Ductile Iron Pipe

Less than 100 mm in diameter: High Density Polyethylene Pipe

4.6.2. Expansion of the Existing Water Supply System

(1) Concept

1) The faults of existing facilities would be repaired to make use of the potential

capacity.


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2) Construction for the expansion would be done for increasing the water supply volume

to reduce the present gap between demand and supply of water.

3) The consistency between the existing facilities and the facilities to be expanded

would be ensured for their effective operation to operate effectively.

(2) Installation of new pumps at BPS1

1) There is adequate space and concrete foundation for future installation of three pumps.

The proposed pumps will be installed making good use of them.

2) The capacity of proposed pumps is decided through the analysis of distribution

pipeline network to provide minimum pressure head of 10m at every supply point.

3) Specification

F400mm x 30 m3/min x 45m x 400kw -2sets

(3) Construction of BPS1 reservoir

1) A new reservoir will be constructed next to the existing BPS1 reservoir.

2) There is one tube well (No.26) with a discharging capacity of 5,000 m3/day in the

same compound for the construction of the proposed reservoir. Therefore a new tube

well will be drilled in a area, where is not affected by construction of the reservoir, as

the alternative to this tube well.

3) The Water volume of 15,900 m3/day would be newly conveyed to the BPS1 reservoir

from the three proposed production wells.

4) Structure

• Reinforced concrete structure

• Required Volume : 12,500 m3.

• Shape : Effective Depth 6 m x Length 94m x Width 22.5 m = 12,500 m3

(4) Installation of pumps at BPS2

1) Since an existing pump is deteriorated, and a lot of water leaks from the pump, it

would be replaced with a new one of the same specification.

2) Specification : φ200 mm x 7.5 m3/min x 50 m x 110kW -1set


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(5) Installation of disinfection equipment at BPS1

• Chemical : Calcium hypochlorite, Ca(ClO)2･2Ca(OH)2

• Specific Gravity in Solid : 0.84

• Effective Density : More than 70%

• Design Concentration : 0.5~2.0 mg/l, 1.0 mg/l (Average)

• Facilities :

Solution tank with a mixer, 4 m3 -2 sets

Apparatus for Distribution and Dosing -1 set

(6) Installation of distribution pipeline and flow meter at BPS1

1) There is no flow meter in the existing distribution main. Two flow meters will be

installed in the distribution main near the BPS1 to measure the amount of supplied

water for effective management of the distribution system. The total amount of water

supply would be 134,900 m3 /day in daily maximum (119,000 m3 /day from the

existing 26 tube wells and 15,900 m3/day from the three proposed tube wells).

2) Specification :

Electromagnetic flow meters for 900mm diameter pipes –2sets

(7) Groundwater development plan

1) 5 wells (2 in the north and 3 in the south) will be newly constructed. They would be

located in the expanded area of the existing well field. The water from northern 2

wells will be conveyed to the existing ground reservoir at Mandalay Hill, and the

water from the southern three wells will be conveyed to BPS1.

2) Well Structure : Considering the results of the hydro-geological studies and the actual

depth of existing 28 wells, depth and daily maximum pumpage rate of the proposed

wells are decided at 150 m and 5,300 m3 /day respectively.

3) Specification of Production Well

• Well Casing diameter : φ300mm

• Well depth : 150m

• Specification

Pump Type : Submersible motor pump

North wells 200 mm x 110kW x 4.5 m3/min x 2sets


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South wells 200 mm x 90kW x 4.5 m3/min x 3sets

4) Water Conveyance: Two pipelines will be laid for conveyance of water from the

proposed production wells.

Lengths of the lines are shown below. See Fig. 4.6.2.2 and Fig. 4.6.2.3.

North line : φ300 mm - L=300 m, φ500 mm - L=2,570 m

South line : φ300 mm - L=300 m, φ400 mm - L=300 m, φ500 mm - L=2,670 m

• The facility drawings are shown in Fig.4.6.2.1 and Fig. 4.6.2.3.

4.6.3. Proposed Intake & Water Treatment Plant

(1) Basic Conditions

a) Water Quantity

In the Year 2010 m3/day m3/hr m3/min m3/sec

Intake 110,000 4,583 76.39 1.273

Transmission 100,000 4,167 69.44 1.157

In the Year 2020 m3/day m3/hr m3/min m3/sec

Intake 220,000 9,167 152.8 2.546

Transmission 200,000 8,333 138.9 2.315

b) Water Quality Raw Water Treated Water

PH 7.3 6.5-8.5

Turbidity (NTU) 100 1.5-2.0

(2) Intake Facilities

1) Facility Plan : Entering Basin, Screens, Pump pit, Pump room, Emergency generator,

Buildings, and River bed protection.

2) Structure type : Reinforced concrete

3) Entering Basin


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The designed water speed is 0.5 m/sec to prevent entry of big sand particles into the

pump pit. The effective water depth at the entering basin is designed to be 1.0m,

against the designed LWL, so as to reduce the construction cost.

• Designed water level : LWL = 61.0m, HWL = 70.0m

• Channel : Effective depth 1.0m x Width 3.0m / line –2lines

4) Screens

Both coarse screen and fine screen will be installed. The course screen would

remove large matter, like a floating wood or stones from raw water. The fine screen

would remove smaller particles. A Jib crane for lifting big obstacles and a lifting

device for removing accumulated mud or sand from the basin will be installed.

Footsteps will be furnished for descending into the basin.

5) Pump Pit

The pump pit is designed with its bottom lowered enough to retain sufficient water

depth for pump suction. The pit is also designed to be in two lines so that one line is

open when the other is being cleaned. The pit will be partitioned from the screening

canal by a wall with three holes at different levels for entry of water. A gate will be

installed at the lowest one. In the rainy season, the gate would be closed so that water

enters through the upper two holes. Sand sediments would not enter the pump pit by

this operation. When river water level lowers below the middle hole in the dry season,

the gate should be opened after removing the sediments in front of the gate.

6) Pump Room

As the placing level of pumps is 12m below the ground level, the scale of structure

required has much influence on the construction cost. Therefore, dry installed

submersible pump is recommendable to be installed, because it needs the smallest

area among the different types.

Besides the small installation space required, the dry installed submersible pump has

various advantages as follows.

a) High passage ability of solid particles, like sand, gravels or floating matter/stuff

b) High water proof performance accepts occasional flood.

c) High efficiency of energy consumption by motor unified with pump body.

d) Easy maintenance of pump.


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The cost of this type of pump does not differ so much from other types.?

• Number of pumps:

2 units + 1 spare unit; in 2010, Total pumpage rate is 110,000 m3/day

4 units + 1 spare unit; in 2020, Total pumpage rate is 220,000 m3/day

A fan for ventilation will be installed to avoid any oxygen shortage.

The Operation and Control House will be constructed over the pump room. A

traveling crane will be installed for maintenance and repairing of equipment of

pumping system. Control panels of pumps, fans and cranes and so on, will be placed

in the house.

7) Generator for Emergency Purpose

Electricity power failures often occur in Mandalay City. One generator and oil tank,

which have a capacity to operate one pump, should be installed for using during

emergency of electricity failure.

8) Buildings and Landscaping Operation and Control House Reinforced concrete, One story, 180m2

Electric Room Reinforced concrete, One story, 200m2

Workshop Reinforced concrete, One story, 65m2

Landscaping Roads, Fences

9) River Bed Protection

A structure will be constructed in order to protect riverbed surrounding the entrance

canal from scouring by the river flow.

• Structure : Masonry and concrete block (0.5m x 0.5m x 0.3m)

• Area to be covered : Surrounding 10m width

(3) Water Treatment Plant

1) System

Considering the following conditions in Mandalay City, a system of sedimentation

with coagulant and rapid sand filter is proposed.

a) The fluctuation of water quality is big, especially with turbidity level varying from

some tens to a few hundreds NTU, through the year (see Chapter 4.5.4).

b) Since there is no better location, the site of proposed WTP had to be selected in an


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area that gets inundated by back water of the Ayayarwaddy River. Therefore, land

reclamation for the plant is required to raise the ground elevation up to 73.0 m.

2) Treatment System

a) Water ① Grit Chamber ② Raw Water Intake ③Conveyance Pipe ④Receiving

Well ⑤ Distribution Chamber ⑥ Chemical Mixing Chamber ⑦ Flocculation

Basin ⑧ Sedimentation Basin ⑨Rapid Sand Filter ⑩ Clear Water Reservo ir

b) Sludge ① Sludge Drying Bed ② Drainage

c) Chemical for Treatment

Flocculant; Aluminum Sulfate

Disinfection; Chlorine Gas

(4) Capacity of Facilities

The capacity of facilities is summarized as shown in Table 4.6.1 below. Drawings of

facilities are shown in Fig. 4.6.3.1 to Fig. 4.6.3.7.

Table 4.6.1Capacities of Treatment Facilities Facility Item Unit Capacity Remark

Grit Chamber Overflow Rate mm/min 350

Mean Flow Velocity cm/sec 4

Rate of Length / Width 4.0 (20 / 5)

Basin pcs 4

Mean Diameter of sand to be removed mm 0.1

Receiving Well Shape Rectangular

Distribution Chamber Detention Period min 1.5

Effective Depth m 4.5

Basin pc 1

Free Board cm 60

Mixing Chamber System Mechanical Agitation

Basin pcs 8

Detention Period min 1.5


Circumference Speed m/sec 1.5

Flocculation Basin System Horizontal Flow

Basin pcs 8


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Detention Period min 30.0

Sedimentation Basin Shape Rectangular

Basin pcs 8

Overflow Rate mm/min 30.0

Rate of Length / Width 4.5 (54/12)


Mean Flow Velocity m/min 0.4

Water Collecting Rate at Trough m3/m/day 500

Rapid Sand Filter System Self Back Washing Gravity

Basin pcs 32

Shape Rectangular

Area/ 1Basin m2 57.42 6.6x8.7

Rate of Filtration m/day 120.0

Thickness of Sand cm 60.0

Diameter of Sand mm 0.6

Back Washing Type Surface & Back washing

Back Washing Self Back Washing

Back Washing Speed m3/m2/min 0.6

Back Washing Period min 6.0

Back Washing Pressure m 3.0

Surface Washing Pressure Water

Surface Washing Speed m3/m2/min 0.2

Surface Washing Period min 6

Surface Washing Pressure m 15

Chlorination Chamber System Horizontal Flow

Basin pcs 8

Clear Water Reservoir Detention Period hr 2.0

Basin Nos 4


Chemicals Alum Density % 10.0

Infusion volume mg/l 30.0

Intermediate Chlorination Infusion volume mg/l 2.5

Post Chlorination Infusion volume mg/l 2.5

Sludge Drying Bed Sludge amount Disposed m3/day/basin 590.0

Sludge Load Rate kg/ m3/year 500.0


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Basin pcs 4


Area m2/unit 2,320

Length m 34.0~38.0

Width m 64.0

Structure Declining Wall Rock Masonry

Bottom Gravel Pavement

Drainage Overflow & Under Drain

4.6.4 Proposed Distribution Reservoirs

Two ground reservoirs will be constructed around Mandalay Hill.

(1) The places of newly constructed reservoir are decided as considering the following

conditions.

• The place should be located in the altitude enable to do the gravity distribution.

(Designed water level: HWL= 106 m, LWL= 100 m)

• The location should be public space and not to harm the natural and social conditions

by the construction.

• The ground is recommended to be as flat and in good geological character as possible

to reduce the construction cost.

(2) Structure

l Reinforced concrete

l Required Volume :

West side, 17,000 m3 (near the existing ground reservoir)

East side, 25,000 m3

l Shape :

Effective Depth 6m x Length 70m x Width 41m = 17,200 m3 (West)

Effective Depth 6m x Length 100m x Width 42m = 25,200 m3 (East)

N

L=300m L=2570m

φ300 φ500

Proposed Tube Well

Transmission Pipe

Mandalay HillReservoir

Fig.4.6.2.2 Proposed Groundwater Development Plan (North)2-190

Proposed Tube Well

L=30

0mL=

300m

φ40

0φ

300

Transmission Pipe

BPS1 Reservoir

L=2670m

φ500

Fig.4.6.2.3 Proposed Groundwater Development Plan (South)

N

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Fig. 4.6.3.1 Proposed Raw Water Conveyance Plan

Proposed Water Treatment Plant

Proposed

Proposed

4.6 Facility Design 4.6.1 Design Criteria

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