Feasibility Study of Piping Network Installation as a ...

Feasibility Study of Piping Network Installation as a Transition from Scattered Groundwater Extraction to Fully Centralized Water Supply

Distribution System

Agnes Ferinna1*, Herr Soeryantono1, Nyoman Suwartha1

1. Department of Civil Engineering, Faculty of Engineering, Universitas Indonesia, Depok, 16425, Indonesia

*E-mail: [email protected]

Abstract

The objective of this study is to measure the feasibility level of various proposed solutions to the current practice of water distribution system in Depok, West Java. The feasibility study is carried out through financial analysis in terms of benefit over cost ratio (BCR) and incremental rate of return (IRR). All proposed solutions are aimed to eliminate shallow-individual well utilization in Depok which has caused negative impacts regarding the geohydrological, environmental, groundwater sustainability, health and economy aspects. They consist of four options which are; 1) regionally centralized system that relies on deep well, 2) fully centralized system which relies on piping network, 3) staging progress in which deep wells are to be constructed and operated first until payback period has been reached and 4) staging progress in which deep wells are to be constructed and operated first until the accumulated benefit equals to the initial cost of piping network. The result of the financial analysis shows that option-1 is more desirable in term of the benefit over cost ratio with BCR = 1.53 and option-4 is more desirable in term of the incremental rate of return with IRR = 33.42%. The decision, however, cannot be made since it depends on the contract type of the project and should be evaluated further from other point of views. Keywords: B/C ratio, Deep well, Depok, Feasibility study, Fully centralized water distribution system, Incremental rate of return (IRR), Piping network. Studi Kelayakan Instalasi Jaringan Pipa sebagai Transisi Penggunaan Sumur Dalam

Regional Menjadi Sistem Distribusi Air Baku Terpusat

Abstrak

Paper ini membahas tentang kelayakan finansial dengan menggunakan parameter benefit over cost ratio (BCR) dan incremental rate of return (IRR) dari berbagai solusi untuk memperbaharui sistem penyediaan air baku di Depok, Jawa Barat. Solusi yang diajukan dilatarbelakangi oleh banyaknya eksploitasi air tanah berupa pengunaan sumur dangkal dan tidak adanya jaringan perpipaan suplai air baku di Kota Depok. Solusi tersebut terdiri dari dua desain utama, yakni: sistem distribusi terpusat secara regional melalui konstruksi sumur dalam dan sistem distribusi terpusat secara keseluruhan melalui instalasi jaringan perpipaan. Kedua desain tersebut diskenariokan menjadi empat opsi implementasi, yaitu: 1) konstruksi sumur dalam 2) instalasi jaringan pipa 3) proses bertahap dalam bentuk instalasi jaringan pipa setelah operasi sumur dalam mencapai periode pengembalian atau payback period dan 4) proses bertahap dalam bentuk instalasi jaringan pipa setelah operasi sumur dalam mencapai titik impas atau breakeven point. Hasil analisis finansial menunjukkan bahwa opsi-1 lebih menguntungkan dari segi perbandingan keuntungan biaya dengan nilai BCR = 1,53 sedangkan opsi-4 lebih menguntungkan dari segi laju pengembalian investasi dengan nilai IRR = 33,42%. Akan tetapi pengambilan keputusan tidak dapat secara langsung ditentukan karena akan bergantung pada jenis kontrak dan harus dievaluasi dari berbagai aspek lain, seperti: aspek lingkungan, ekonomi dan hukum. Kata kunci: B/C rasio, Depok, Laju pengembalian (IRR), Sistem distribusi terpusat secara keseluruhan, Jaringan pipa, Studi kelayakan, Sumur dalam.

Feasibility Study..., Agnes Ferinna, FT UI, 2013

INTRODUCTION

Domestic water, the term used to refer treated water, has become such a vital social object

that it has economic value now (Direktorat Jenderal SDA Departemen Permukiman dan

Prasarana Wilayah, 2009). High prices that keep climbing up from time to time have to be

paid so that people can gain access to domestic water from Perusahaan Daerah Air

Minum/PDAM. Nevertheless, the inclining trend of water need cannot be prohibited due to

massive development and population in the society. Values ranging from 4 % to 8 % of water

need increase are recorded per year in Indonesia. Rapid growth of water price urges people to

utilize another water source that costs relatively lower than the clean water provided by

PDAM. Groundwater, as a form of sub-surface water, is tend to be utilized as the substitute of

clean water supply more than surface water due to its availability that is not fixed by spatial

dimensions, good quality, also its simplicity and relatively low pricing during exploitation

(Cipta Karya, 2012).

However, growing practice of groundwater utilization can put the public’s health at risks

to exposure of Escherichia coli or commonly referred as E. coli that emerges due to poor well

maintenance and construction (particularly shallow dug wells) combined with the effluent

from septic systems and sewage discharges in the surrounding environment (The British

Columbia Groundwater Association, 2007). The presence of Fecal Coliform bacteria or E.

coli indicates contamination of water with fecal waste that may contain other harmful or

disease causing organisms, including bacteria, viruses, or parasites. Drinking water

contaminated with these organisms can cause stomach and intestinal illness including diarrhea

and nausea, and even lead to death. These effects may be more severe and possibly life

threatening for babies, children, the elderly or people with immune deficiencies or other

illnesses. Therefore, it is necessary to implement an adequate distance between groundwater

well and septic system which is more than 11 meters if the septic tank (or other types of

contamination source) is at the upstream part of the well (SNI 03-2916-1992). Whilst, most

houses at developed cities in Indonesia have limited space with relatively narrow span of their

width and length. Residential developer, for example, construct their houses varying from

type 21 (6 by 3.5 meter), type 36 (6 by 6 meter), type 45 (6 by 7.5 meter), type 54 (6 by 9

meter) and type 60 (6 by 10 meter). From which none of them have both sufficient width and

length of more than 11 meter, therefore the safe distance stipulated by the SNI is impossible to

be implemented.


Depok, one of the developing cities in West Java, can’t seem to detach its dependency on

groundwater. Eighty percent of the built environment at Depok city utilizes groundwater to

fulfill their water need whereas the other twenty percent, which is about 34,617 units, use

clean water that is provided by PDAM (Pemda Depok, 2012). The clean water from PDAM is

distributed indirectly from the treatment plant in Bogor since there aren’t any water intake and

piping network located in Depok at all. This triggers another issue for those people who might

actually want to utilize domestic water from PDAM but having problem since the availability

of piping network is limited for several areas at Depok only.

In this paper, author proposes several solutions to solve the water supply distribution

system issue that arises in Depok which compose of two primary designs, they are; deep well

and piping network. Both designs are then schemed onto four different implementation

scenarios in which will be analyzed and evaluated in term of their feasibility level through

financial analysis tool. The financial parameters that are utilized in this study are incremental

rate of return (IRR) as well as benefit over cost ratio (BCR).

THEORETICAL REVIEW Steady Radial Flow to a Well in an Unconfined Aquifer

When a well is pumped, water is removed from the aquifer surrounding the well, and the

water table or piezometric surface, depending on the type of aquifer, is lowered. The

drawdown at a given point is the distance the water level is lowered. A drawdown curve (or

cone) shows the variation of drawdown with distance from well. The drawdown curve

describes a conic shape known as the cone of depression, whereas the outer limit of the cone

of depression (zero drawdown ) defines the area of influence of the well.

Figure 1. Cone of Depression in Unconfined Aquifer

Source: Buddemeier, 2000


In order to determine the drawdown due to well pumpage, The Theis Solution is

commonly employed for confined aquifer cases. The Theis Solution can also be used for

unconfined aquifer cases but several adjustments in its formula must be done, they are;

substitution of storativity value with specific yield (S = Sy) and transmissivity with the

multiplication of hydraulic conductivity and the aquifer thickness (T = K.b). The adjusted

formulas according to the Thies Solution for uncconfined aquifer are stated below;

! =!!. !!4!. ! …… (1)

ℎ! − ℎ =!4!"! ! …… (2)

Where u is an input value to determine the well function W(u), Sy is the specific yield of

the aquifer, r is the radial distance of observed drawdown, T is the transmissivity of the

aquifer, t is the well pumping duration, ho – h is the drawdown caused by well pumpage and

Q is the pumping rate done of the well.

Various values of specific yield and hydraulic conductivity of the aquifer can be

determined by using their representative values tabulated on Table 1. and Table 2. Whereas

the well function can be determined by analyzing the value of u and matching it to Table 3.

Table 1. Well Function for Thies Solution

Source: Wenzel, 1942

Piping Network’s Design Formula

Single Line Formulation. Energy must be conserved between any two points. Along the

path between nodes A and B that only includes pipes, conservation of energy is written as:

!! − !! = ℎ!,!! ∈ !"#$!

= !! !! !! ∈ !"#$!

…… (3)


Where HA and HB are the total energy at nodes A and B, hLl, Kl, Ql are the head loss, loss

equation coefficient and flow rate in pipe l and n is the exponent from the head loss equation.

The sign for the flow rate is defined using the !! symbol and this symbol does not have

its conventional meaning. This symbol is intended as a short form notation and reminder of

how the signs of this relationship should be interpreted. The absolute value of Q is raised to

the power of n and the sign of the pipe term is based on the flow direction. If flow is moving

from node A toward node B then the sign should be taken positive and a negative sign is used

if flow is away from B toward A. Equation 3 can be written for a closed or pseudo-loop or a

single pipe. lpath defines the set of pipes in the path.

A closed loop is one of that begins and ends at the same node. Since each location in the

network has a unique energy the net energy loss around a closed loop is zero. For a loop

beginning and ending at node A.

!! − !! = 0 = ℎ!,!! ∈ !!""#

= 0…… (4)

Where lloop is the set of pipes in the closed loop.

A pseudo-loop is a path of pipes between two points of known energy such as two tanks or

reservoirs. Equation 3 applies directly to pseudo-loops. Pseudo-loop equations include

additional information regarding the flow distribution and are needed for some solution

methods. Finally, Equation 3 also applies directly for individual pipes with HA and HB being

the total heads at the two ends of the single pipe or:

!! − !! = !! !! ! …… (5)

System of Loop Equations. The smallest set of equations is the loop equations that

include one equation for each closed loop and pseudo-loop for a total of nloop + nploop

equations where nloop and nploop are the number of closed and pseudo-loops, respectively.

In order to determine the totoal number of loop equation on a piping network we can utilize

Equation 6 as follows.

! = ! + ! + ! − 1…… (6)

With:

P : Number of pipe elements in the network

J : Number of interior nodes

L : Number of interior loops

F : Number of pseudoloops


The unknowns in the loop equations are ΔQ’s that are defined as the corrections to

the flow rate around each loop. Beginning with a flow distribution that satisfies conservation

of mass, the corrections maintain those relationships. When zero corrections are needed in all

loops, the flow rates in each loop and each pipe has been found. After the flows have been

determined, Equation 3 is applied beginning at a location of known total energy (e.g.: root) to

determine the nodal heads.

The Hardy Cross method is one approach to solve the loop equations. This method is

first determines corrections for each loop independently then applies the corrections to

compute the new pipe flows. With the new flow distribution, another set of corrections is

computed. Hardy Cross introduced this method in 1936 and, although amendable to hand

calculations, it is not efficient compared to methods that consider the entire system

simultaneously solves for all loop corrections using the Newton-Raphson method with the

corrections as the unknowns.

RESEARCH METHODOLOGY

Region Division. The region division that will be used in the design is in accordance to

the districts located in Depok. There are eleven districts that will represent the region division

in Depok, they are; Sawangan, Bojongsari, Pancoran Mas, Cipayung, Sukmajaya, Cilodong,

Cimanggis, Tapos, Beji, Limo and Cinere.

Distribution Point. Distribution point will be located at a single point for each district in

Depok in which their designation is based on two major considerations, they are; road

network availability and servicability level. Road network availability defines the whole

piping route that will connect the water distribution components. The availability of road

network should be sufficient so that all components (deep wells, water treatment plants,

reservoirs and distribution points) can be connected fully. Servicability level defines the

capability of each point in distributing the water to further service areas in the represented

district. However, due to the limitation of road network, the second consideration might not

be applicable.

Water Demand Projection. The discharge specification for all designs will be based on

the water demand projection. The water demand will consider three primary aspects , they

are; domestic as well as non-domestic water demand and existing water tap. The current

generated water demand is then projected according to the population growth at each district

in Depok onto the end of the design life which is 25 years for both deep well and piping

network.


Table 2. Flow Rate Specification of Deep Well

Source: Author, 2013

Table 3. Flow Rate Specification of Piping Network


Drawdown Estimation. Drawdown is the depth of groundwater level that decreases as

pumping occurs on the surface. The aquifer stratification in Depok is assumed to be phreatic

or unconfined in which to formulate the drawdown, Theis Solution for unsteady condition is

used. The aquifer parameters which consist of hydraulic conductivity/K, transmissivity/T as

well as storativity/S are assumed to be homogeneous and do not vary according to spatial

distribution. They are enlisted on Table 4.

Table 4. Aquifer Parameters in Depok

Source: *Schmidt, 2004; **Herlambang and Indriatmoko, 2005

Water Treatment Plant Location. The water treatment plant will be located at the intake

point, prior entering the distribution system through the piping network. The selection of

intake location will be in accordance with the existing water treatment plant described on the

“Depok Master Plan 2000-2010”. According to the “Depok Master Plan 2000-2010”, the

1 Sawangan 0,930 0,186 0,136 0,8802 Pancoran Mas 1,573 0,291 1,835 3,1173 Sukmajaya 1,558 0 0,153 1,7114 Cimanggis 1,692 0 0,258 1,9505 Beji 1,454 0,261 0,955 2,1486 Limo 0,701 0 0,090 0,7907 Bojongsari 0,710 0 0,012 0,7228 Cipayung 0,960 0,112 0,009 0,8589 Cilodong 1,191 0 0,022 1,213

10 Tapos 1,483 0 0,017 1,49911 Cinere 0,703 0 0,027 0,730

12,955 0,849 3,513 15,618Total

No. DistrictDomestic Non-Domestic TotalExisting Water

Tap

Q2038* (m3/s)

1 Sawangan 0,880 0,176 1,056 0,106 1,161 1,336 0,134 1,4692 Pancoran Mas 3,117 0,623 3,741 0,374 4,115 4,732 0,473 5,2053 Sukmajaya 1,711 0,342 2,053 0,205 2,258 2,597 0,260 2,8564 Cimanggis 1,950 0,390 2,340 0,234 2,574 2,960 0,296 3,2565 Beji 2,148 0,430 2,578 0,258 2,836 3,261 0,326 3,5876 Limo 0,790 0,158 0,948 0,095 1,043 1,199 0,120 1,3197 Bojongsari 0,722 0,144 0,866 0,087 0,953 1,096 0,110 1,2058 Cipayung 0,858 0,172 1,030 0,103 1,133 1,303 0,130 1,4339 Cilodong 1,213 0,243 1,455 0,146 1,601 1,841 0,184 2,02510 Tapos 1,499 0,300 1,799 0,180 1,979 2,276 0,228 2,50411 Cinere 0,730 0,146 0,876 0,088 0,963 1,108 0,111 1,219

15,618 3,124 18,742 1,874 20,616 23,708 2,371 26,079Total

No. DistrictQ2038 (m

3/s)Qmax =

1,15*Total BWater

DemandHydrant (20 %)

Total A Q installation (10 %)

Q designLeakage (10 %)

Total B

Soil Parameter Notation and Unit ValueHydraulic Conductivity* K (m/day) 1,3Storativity** S 0,2Transmissivity** T (m2/day) 250 - 500


water treatment plants in Depok have been adapted to the standard design issued by the SNI

6773-2008.

Reservoir Location. Reservoir/water storage will be located at all distribution points in

deep well design whereas for the piping network, reservoir is located at the upstream part of

the water treatment plant as well as some various points at the pipe branch that will be

installed a pump which has less capacity than the actual flow rate of the pipe line.

Piping Route Designation. There are two types of pipe that will be installed onto the

piping network system, they are; transmission pipe and distribution pipe. All pipe lines will

follow the existing road network in Depok which generally for transmission pipe the route

will follow from lower ground elevation to the higher one, while the distribution pipe will

follow from higher ground elevation to the lower one. This is carried out regarding to the

effort of avoiding pump installation in distribution pipe whereas it is necessary to install a

pump in transmission pipe so that the water generated from the water treatment plant (which

is located at relatively lower area since the intake is river) can be transported to the upstream

reservoir.

Hydraulic Design of Piping Network. The material of pipes that are used is High

Density Poliethylene or more commonly referred as HDPE. HDPE pipes are commonly sold

with a maximum length of six meter in which in this preliminary design, a single pipe line of

both transmission and distribution pipes are in term of 6 meter. The HDPE pipes are

available in various nominal diameter sizes with the smallest diameter of 110 mm and the

largest diameter of 1600 mm. The smaller the pipe’s diameter, the greater the head losses and

consequently, pump is required to be installed onto a pipe line that has great losses so that the

pressure and its serviceability can be maintained throughout the design life. Diameter plays a

great role in determining the results of piping network’s hydraulic quality. Deep

understanding of the network mechanism is required in order to give insight on deciding the

initial guess of the pipe’s diameter so that the convergence during iteration process of the

Hardy Cross Method can be done faster. The following figure illustrates the design

mechanism of piping network as well as the effects of diamater sizing onto the design

formulation.

Figure 2. Effects of Diameter Sizing



Figure 3. Design Mechanism of Piping Network


Control of Velocity and Pressure. The final results of the Hardy-Cross Method are the

flow rate values of each interval including their direction. In order to maintain the safety of

the distribution system as well as to reduce maintenance frequency, a set of control regarding

the maximum and minimum range of pressure and velocity must be fulfilled. These criteria

are based on various factors, such as; minimum flow velocity to avoid sedimentation in a

pipe, maximum velocity to avoid water surge in a pipe and so on. Most criteria values are

obtained from the hydraulic specification of the pipe and its material. Some others are

obtained from design quote of water distribution system in a city scale.

Table 5. Piping Design Properties

Source: various sources, 2013

Cost Estimation. The expected final output of cost estimation is in terms of bill of

quantity, in which relies on unit price of all works and quantity of works. Unit price of works

is related with the current unit price of material, manpower and equipment whereas the

quantity of works is related with the quantification of all activities intended for the

transmission pipe installation as well as the deep well construction, in which all depend on the

preliminary designs. The following figures illustrate the work breakdown structures used in

executing the cost estimation.

Minimum pressure due to fire 140 kPa (Domestic Water Supply System Design Criteria of the County of Sutter) Maximum pressure due to self capacity 630 kPa (HDPE pipe specification) Minimum velocity due to valve 1,159 m/s (Author, 2013) Minimum velocity due to sedimentation 1,000 m/s (Engineering Toolbox, 2013) Maximum velocity due to water hammer 4,572 m/s (Engineering Toolbox, 2003)


Figure 4. Work Breakdown Structure of Deep Well Construction


Figure 5. Work Breakdown Structure of Piping Network Installation


Benefit Estimation. The benefit will be generated in accordance to the total money

produced from selling the water to the consumers. The water pricing rate is adapted from the

water pricing rate stipulated in Jakarta in which it is classified onto four different consument

categories. The pricing rate including the consumer categories description is enlisted on the

following tables.

Table 6. Water Pricing Rate

Source: Peraturan Gubernur Prov. DKI Jakarta Nomor 11 Tahun 2007

0 - 10 m3 11 - 20 m3 > 20 m3

1 Group I Rp. 1.050 Rp. 1.050 Rp. 1.0502 Group II Rp. 1.050 Rp. 1.050 Rp. 1.5753 Group III A Rp. 3.550 Rp. 4.700 Rp. 5.5004 Group III B Rp. 4.900 Rp. 6.000 Rp. 7.4505 Group IV A Rp. 6.825 Rp. 8.150 Rp. 9.8006 Group IV B Rp. 12.550 Rp. 12.551 Rp. 12.5527 Group V Rp. 14.650 Rp. 14.651 Rp. 14.652

No. GroupUnit Price of Water


Table 7. Consumer Categories

Source: Peraturan Gubernur Prov. DKI Jakarta Nomor 11 Tahun 2007

The pricing rate is then multiplied onto the volume of annual water consumption per

facility. Note that there aren’t any benefits generated at the first year of the design life (in the

year of 2014) because the initial year will be designated to the construction period of the

water distribution components (deep wells or piping network). The other important point is

that in this scenario, the consumer’s growth rate is 2.5 % per year with the initial consumer

percentage of 5 % (in the year of 2015).

The annual cost is assumed to be 60 % of the total annual benefit generated from both the

domestic and non-domestic water demand consumption. The annual cost will be designated

for the maintenance, repair and operation cost required in carrying out the water supply

distribution system.

Table 8. Benefit and Cost Projection for 25 Years


Group I Group II Group III AChurch Public hospital Water tank vehicleMosque Very modest residential Modest residentialHydrant etc. Water stationSocial institutions etc.etc.

Group III B Group IV A Group IV BNon-commercial private institution High-end residential High-end hotelKiosk Foreign consulate and institutions Beauty centerMedium residential Government institutions Cafe and night clubSmall commercial places Commercial private institution Banketc. Courses and educational building Service station and gas station

Group V Medium trading places Rumah tokoHigh institutions Barber Apartment and high-rise buildingetc. Taylor Industrial areas

Restaurant etc.Modest hotelClinic/private hospital/laboratoryetc.

0 2013 -Rp -Rp -Rp 1 2014 -Rp -Rp -Rp 2 2015 21.109.632.554Rp 46.135.084.672Rp 55.782.175.233Rp 3 2016 32.995.779.135Rp 72.232.903.153Rp 87.392.392.787Rp 4 2017 45.851.299.580Rp 100.533.380.653Rp 121.704.334.842Rp 5 2018 59.742.297.394Rp 131.183.759.565Rp 158.897.301.882Rp 6 2019 74.738.931.483Rp 164.340.163.650Rp 199.161.341.267Rp 7 2020 90.915.651.274Rp 200.168.105.981Rp 242.697.858.695Rp 8 2021 108.351.445.009Rp 238.843.025.072Rp 289.720.263.444Rp 9 2022 127.130.101.943Rp 280.550.850.711Rp 340.454.649.242Rp 10 2023 147.340.489.191Rp 325.488.601.126Rp 395.140.512.686Rp 11 2024 169.076.844.038Rp 373.865.013.182Rp 454.031.511.266Rp 12 2025 192.439.082.555Rp 425.901.207.406Rp 517.396.263.123Rp 13 2026 217.533.125.409Rp 481.831.389.738Rp 585.519.190.821Rp 14 2027 244.471.241.810Rp 541.903.591.992Rp 658.701.411.510Rp 15 2028 273.372.412.584Rp 606.380.453.145Rp 737.261.675.991Rp 16 2029 304.362.713.408Rp 675.540.043.652Rp 821.537.359.346Rp 17 2030 337.575.719.319Rp 749.676.735.133Rp 911.885.505.903Rp 18 2031 373.152.931.644Rp 829.102.117.885Rp 1.008.683.931.498Rp 19 2032 411.244.228.574Rp 914.145.968.816Rp 1.112.332.386.120Rp 20 2033 452.008.340.677Rp 1.005.157.272.532Rp 1.223.253.780.209Rp 21 2034 495.613.352.687Rp 1.102.505.298.442Rp 1.341.895.478.049Rp 22 2035 542.237.233.015Rp 1.206.580.736.935Rp 1.468.730.661.878Rp 23 2036 592.068.392.477Rp 1.317.796.897.809Rp 1.604.259.770.539Rp 24 2037 645.306.273.827Rp 1.436.590.974.316Rp 1.749.012.016.699Rp 25 2038 702.161.973.765Rp 1.563.425.376.383Rp 1.903.546.986.872Rp

n Year Benefit from Non-Domestic Water Demand

Maintenance, Repair and Operation Cost

Benefit from Domestic Water Demand


Staging Timeline. There will be two staging scenarios that will be implemented, they

are: at a point after the payback period of the deep well construction has been reached and at a

point after the annual benefit generated from the deep well construction has reached the value

of the piping network installation initial cost.

Figure 6. Implementation Diagram of Option-1, Option-2, Option-3 and Option-4* Source: Author, 2013

*top – bottom RESULTS

Table 9. Deep Well Specification


Sawangan 4 1670 459 Rp. 6.205.383.120Pancoran Mas 10 8285 459 Rp. 26.794.354.554Sukmajaya 7 10839 459 Rp. 32.441.825.567Cimanggis 8 6692 459 Rp. 21.609.410.088Beji 8 6257 459 Rp. 20.427.189.675Limo 3 1274 459 Rp. 4.747.556.855Bojongsari 3 1461 459 Rp. 5.255.931.779Cipayung 4 2121 459 Rp. 6.596.060.259Cilodong 5 2394 459 Rp. 7.546.626.898Tapos 6 3848 459 Rp. 11.705.450.414Cinere 3 1296 459 Rp. 4.146.721.784

Total Rp. 151.439.315.484

DistrictQuantity of Deep Well

Length of Transmission Pipe (meter) Diameter (mm) Total Cost

25 20 10 5 15 0

Deep Well

Design Life

25 20 10 5 15 0

Piping Network

Design Life

25 20 10 5 15 0

Deep Well

Design Life

Piping Network

Payback Period of Deep Well

25 20 10 5 15 0

Deep Well

Design Life

Piping Network

Breakeven Period of Deep Well


Figure 7. Piping Network Specification


Table 10. Piping Network Specification


Table 11. Financial Properties of all Design Options


Interval Length (meter) Diameter (mm) CostA 5104 1200 Rp. 56.812.062.598B 3498 710 Rp. 16.771.820.835C 6006 710 Rp. 28.775.096.737D 8492 710 Rp. 41.367.797.055E 6534 459 Rp. 17.959.847.477F 6886 612 Rp. 27.702.567.463G 8096 1000 Rp. 66.090.760.984H 3344 459 Rp. 9.112.157.587I 7062 612 Rp. 28.409.555.041J 3894 710 Rp. 18.902.440.285K 6820 204 Rp. 11.386.503.436L 2794 1200 Rp. 31.156.480.767M 2024 1600 Rp. 38.420.388.894N 5192 1600 Rp. 95.885.168.975O 3938 1600 Rp. 73.250.657.994P 2486 800 Rp. 15.217.161.837Q 4466 204 Rp. 7.472.213.449R 2486 1200 Rp. 27.948.232.626S 9834 1600 Rp. 181.246.596.780T 1100 1400 Rp. 16.600.583.876U 7744 306 Rp. 15.934.455.643V 7062 800 Rp. 40.585.015.811W 9482 1200 Rp. 104.538.993.359

Total Rp. 971.546.559.512

Option-1 Option-2 Option-3 Option-4

Initial Cost* Rp. 151.439,32 Rp. 971.546,56 Rp. 151.439,34 Rp. 151.439,35Annual Benefit* refer to Table 4.52. refer to Table 4.52. refer to Table 4.52. refer to Table 4.52.Annual Cost** refer to Table 4.52. refer to Table 4.52. refer to Table 4.52. refer to Table 4.52.i (%)*** 6 6 6 6NPV Benefit Rp. 8.375.452,50 Rp. 8.375.452,50 Rp. 8.375.452,51 Rp. 8.375.452,52NPV Cost Rp. 5.478.227,11 Rp. 6.298.334,35 Rp. 5.842.837.08 Rp. 5.714.034,59B/C Ratio 1,53 1,33 1,40 1,43IRR (%) 27,62 12,79 20,84 33,42

* in Million Rp.** 60% Annual Benefit*** Adapted from Current BI Rate

between year 4 and year 5 between year 12 and year 13

between year 4 and year 5 as well as between year 12 and year 13

between year 4 and year 5 as well as between year 18 and year 19

Payback Period

Regionally Centralized System

Fully Centralized System

Staging Progress after Payback Period

Staging Progress after Breakeven


DISCUSSION

Implication of Aquifer Properties. The estimation of drawdown that is carried out is

under the assumption of homogeneous value of various aquifer parameter (storativity and

transmissivity) at all districts in Depok. Practically, this is not applicable in reality due to the

fact that aquifer parmeter vary rapidly according to spatial distribution. However, since direct

field observation is necessary in determining the value of storativity ad transmissivity and it is

not the main scope of this study therefore it is acceptable to use values of aquifer parameter

that are taken from previous researches. Transmissivity and storativity itself directly affects

the morphology of depression cone in terms of the drawdown value and radial distance that

occurs when pumping is applied onto the aquifer. Higher value of storativty is desirable since

it will create narrower drawdown effect and shallower groundwater depletion (radial distance

as well as drawdown decreases). Concern rises when the actual storativity value in Depok is

much lower than the used one. It will then create much wider drawdown effect and greater

groundwater depletion. If this occurs then the design of the deep well should be reevaluated in

term of its location, depth and pump specification. Transmissivity affects moderately in term

of groundwater depletion and drawdown effect. When the transmissivity is high, the radial

distance will increase and the drawdown will oppositely decrease. Lower transmissivity will

then eventually increase the drawdown and decrease the radial distance. Another concern

regarding the value of storativity and transmissivity is when wider drawdown effect occurs

(when storativity is higher and/or transmissivity lower) which will consequently cause to

redefine the depression cone that occurs on each well. Larger maximum radial distance will

require the evaluation of depression cone superposition among the wells. When superposition

occurrs, it is possible that the water yield at each well will be affected which is associated

with more rapid groundwater depletion.

The other parameter that must be concerned is regarding the uncontrolled growth of water

demand and when longer pumping period is applied onto the well. Larger water demand will

cause the well to apply longer and/or larger pumping rate. When the variables of pumping

period (t) and pumping rate (Q) are much higher than the designated one, it will create greater

drawdown and wider maximum radial distance. This will also have to be carefully monitored

since it will directly cause impacts in the design of the deep well.

Maintenance. The management of the water supply distribution system has been

considered from the preliminary design in which to decrease and reduce the complexity of the

system maintenance. The various design consideration consist of the following elements;


1. Piping route designation in which each distribution point will be connected with at

least two pipe branches. This is done so that the piping network can still provide

water demand fulfillment on that distribution point even when one of the pipe

branches is under repairment.

2. Installation of a single gate valve as well as a single check valve at each pipe line

(per 6 meter of the whole pipe branch). This is implemented in order to ease up the

complexity of piping network maintenance. It is beneficial when the pipe line is

damaged at some points and needs repairment. It is not necessary to fully shut down

the whole water distribution since every pipe line has a gate valve so that the water

flow can be shut down for most of the pipe segments.

3. The sedimentation control has been implemented along the whole piping system in

which it is beneficial to avoid the decrease of pipe’s diameter so that the flow

velocity does not increase. When sedimentation occurrs, the settled particles will

accumulate along the wall of the pipe. As more settled particles reside on the pipe’s

wall, the diameter of the pipe will be reduced and consequently the flow velocity

increase making the head losses become larger. As head losses value develop

greater, more additional lifting head is required and mostly it will affect the cost of

pump installation and operation. Other direct impact is the unfulfillment of the

pressure and velocity control in which the other safety aspects regarding the other

hydraulic properties are not met onto the necessary limit.

4. The minimum velocity to fully lift the disc of the check valve has also been checked

at the preliminary design of the whole piping network. The check valve’s disc must

be fully lifted when water flow passes it so that the check valve internal will not

rapidly wear and suddenly fail (Rahmeyer, 1993).

5. Maximum velocity to avoid water surge along the pipe has also been checked at the

preliminary design of the piping network. Water surge or water hammer is a

pressure surge caused when water in motion is forced to stop or change direction

suddenly. When a surge occurs, water travels down the pipe at the speed of sound. It

then travels back when it hits an obstruction. The wave continues to travel back and

forth, creating tremendous water pressure, until it tapers out. The direct impacts

caused by water surge in pipe are the weakening of pipes and joints in which at

some pooint they will begin leaking. The most common causes of water surge are a

valve somewhere in a pressurized water system being opened or closed too quickly

or a pump suddnly turned on or off (e.g.: due to power failure). Limiting the


maximum flow velocity that occurrs along the pipe is one of so many methods to

reduce the occurrence of water surge. Another efficient method is to install air

valves and air chamber onto the whole piping system so that the water pressure

inside the pipes can be relieved.

6. Minimum pressure during fire and peak demand has also been controlled in the

preliminary design of the piping network. The pressure on all points in the piping

network must be at least 140 kPa so that the water fulfillment can always be

maintained under various conditions.

7. The last parameter that has been controlled in the preliminary design of the piping

network is the maximum allowable pressure that can be supported by the HDPE

pipe. HDPE with the code of PN-6,3 is selected as the pipe that is used for the

piping network design in which has the maximum allowable pressure of 630 kPa.

However, there are actually other aspects that must be considered such as the monitoring

of flow rate along the pipe. Since the flow rate may fluctuate according to time, it is necessary

to install devices that can monitor flow rate along the whole piping system (e.g.: orifice plate,

venturimeter and pitot pipe). Another aspect that needs to be considered is the installation of

sediment flushing devices that can remove smooth particle of impurities from the piping

system which is not good for the hydraulic condition of the pipes, the operation of pump and

the physical parameter of the generated water (in term of water’s color).

Feasibility Study. Decision upon the implementation of water supply distribution

network in Depok should not be based on those financial parameters only since this project is

classified as public sector project that is theoretically more suitable if reviewed from

economic point of view (Blank and Tarquin, 1976). Another argumentation comes from the

environment and groundwater sustainability aspects due to the long period of groundwater

utilization when deep wells are to be constructed (which both advantageous options have deep

well construction stage). At some time, the utilization of groundwater for long period of time

(even pumped from relatively deeper aquifer) will affect the public health in Depok since

groundwater contamination also grows according to temporal and spatial dimension in which

it can possibly develop onto deeper and wider aquifer (Peterson, 2000). It also has to be noted

that it is essential that water demand shall be fulfilled not from sub-surface water but instead

from treated surface water and if at any points groundwater are to be utilized, it is then their

obligation to deliver back the groundwater storage through any forms of groundwater

rehabilitation methods (Peraturan Menteri Energi dan Sumber Daya Mineral Republik

Indonesia No. 15 Tahun 2012).


Legal Constraints of Staging Progress. Another concern arises from the law and

implementation of the staging progress in which is impossible to be implemented here in

Indonesia. The direct impacts of all design options that involve the staging progress between

deep well construction as well as piping network installation are that there will be negative

salvage value (considered as additional cost) in the future in order to demolish the deep wells.

This is not easily applicable since the construction law in Indonesia is not suitable for the case

of negative salvage value in term of demolition fee of infrastructure just for the consideration

of proceeding onto the staging progress. Therefore, option-3 and option-4 which all include

staging progress from deep well to piping network are not feasible to be implemented

regardless of how beneficial their BCR and IRR are.

Table 12. Feasibility Study Results


CONCLUSION

1. The depth of the typical deep well is 100 meter equipped with submersible pump at

minimum suction head capacity of 100 meter and each will be connected with a single

transmission pipe line made of HDPE which is also equipped with a pump with varying

minimum lifting capacity.

2. The piping network design consists of 23 pipe elements, 17 nodes and 4 closed-loops in

which utilize pipe diameter ranging from 200 mm–1600 mm spanning in total length of

124,3 km, while the water storage utilizes fabricated water tank with the volume

System Feasibility Study

With:Option-1: Regionally Centralized System (deep well construction)

Payback Period between year 4 and year 5Option-2: Fully Centralized System (piping network installation)

Payback Period between year 12 and year 13Option-3: Staging progress after payback period of option-1

Payback Period between year 4 and year 5 as well as between year 12 and year 13Option-4: Staging progress after breakeven of option-1

Payback Period between year 4 and year 5 as well as between year 18 and year 19

ImpactFactAspect

BCR ≥ 1 is economically acceptable and the greatest BCR among all alternatives is selected (Blank and Tarquin, 1976).IRR ≥ Minimum Attractive Rate of Return is desirable and the greatest IRR among all alternatives is selected (Blank and Tarquin, 1976).

Option-1 is selected.

Option-4 is selected.

BCR for option-1 , option-3 and option-4 may decrease (if reviewed from economic analysis).BCR for option-1 , option-3 and option-4 may decrease since additional cost to rehabilitate groundwater is necessary.

Groundwater efficieny is essential through reducing, reusing, recycling, rehabilitating, and making it as the last resource option of water fulfillment (Peraturan Menteri Energi dan Sumber Daya Mineral Republik Indonesia No. 15 Tahun 2012).

Groundwater sustainability

Option-1 : 1,53; Option-2 : 1,33; Option-3 : 1,40 and Option-4 : 1,43 with interest rate of 6 % (Bank Indonesia, Juni 2013)Option-1 : 27,62%; Option-2 : 12,79%; Option-3 : 20,84%; Option-4 : 33,42% with interest rate of 6 % (Bank Indonesia, Juni 2013)

Additional cost in health care system and health insurances.

Long time deep well utilization may be prohibited, additional cost to rehabilitate groundwater in the form of injection or recharge well.

Benefit over cost ratio (BCR)

Incremental Rate of return (IRR)

Aquifer continues to accumulate pollutants for decades, thus steadily diminishing the amount of clean water they can yield for human use (Sampat and Peterson, 2000).

Health


capacity of 1000 m3 and is located at the upstream area of Depok prior entering the

distribution system.

3. The total cost generated from the regionally centralized water supply distribution

system is Rp. 151,439,315,484.00 while the total cost generated from the fully

centralized water supply distribution system is Rp. 971,546,559,512.00. With the cost of

piping network installation nearly reaches 6.5 times of the deep well construction cost.

4. The results of the financial analysis show that there are two most advantageous options

for investors among all, they are; option-1 which is the regionally centralized water

supply distribution system with the BCR value of 1.53 and IRR value of 27.62% and

option-4 which is the staging progress which the scheme of piping network installation

after break even point has reached with the BCR value of 1.43 and IRR value of 33.42

%, decision can be made upon these two options in accordance to the contract type of

the project. In addition, the decision should also be evaluated further in terms of

environmental and groundwater sustainability aspects as well as economy and legal

procurement (construction law) analysis in which can directly affect the feasibility of

the whole design options.

RECOMMENDATION

There are various recommendations that can be consulted in order to improve the design

of the regionally as well as the centralized water supply distribution system that are executed

in the study. Most of them are to use better formulations at every stage of calculation

processes and to utilize more accurate and reliable secondary data so that the result’s

precision and accuracy can be assured. The other is to carry out further feasibility study in

term of economic analysis as well as groundwater and environmental sustainability aspects in

order to have further insights in evaluating the procurement project of water supply

distribution system in Depok.

Whereas, the recommendations to improve the existing water supply distribution system

in Depok are as follows:

1. Monitor and analyze the water quality of groundwater and surface water that will

utilized for the distribution system. If the water quality of groundwater and surface

water does not fulfill the standard for drinking water supplies, then advanced water

treatment processes are necessary to be implemented. However, if the quality is

significantly higher than the standard and even advanced water treatment processes


cannot improve the water quality then relocation of both the deep well and river intake

has to be considered.

2. Improve the capacity of water intake in the existing water treatment plant in Depok

since the existing capacity is less than the designated capacity in this study.

3. Reduce the construction and use of shallow groundwater well in Depok to avoid

health aspect degradation due to poor groundwater quality.

4. Arrange a local institution in which its duty is to monitor and evaluate the

groundwater quality in the residential level so that the utilization of well in Depok can

be controlled thouroughly.

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