Case Study on the Reservoir Seepage at Concentrated Solar Thermal Power Plant, Rajasthan, India

Abstract

Rajasthan Sun Technique Energy Pvt. Ltd. has implemented a 125 MW large-scale grid
connected concentrated solar thermal power project in Jaisalmer district, Rajasthan, India.
This manuscript is a critical evaluation of the design and construction of raw water reservoir
liner system at the concentrated solar thermal power plant. The initial liner consisted (from
bottom to top) of compacted earth, sand layer, HDPE liner, cement plaster and a PCC layer.
The initial liner failed and caused the intrusion of saline ground water into the raw water
reservoir and seepage loss of fresh water into the surroundings, prior to the commencement of its
intended function. To mitigate the above problems, the designer proposed a rectification scheme,
which was also found to be ineffective. The present study elaborates on reasons that caused the
malfunctioning of the above liner system. Finally, remedial measures that were proposed to
rectify the problems have been discussed, in detail.

Full text

CASE STUDY ON THE RESERVOIR
SEEPAGE AT CONCENTRATED SOLAR
THERMAL POWER PLANT, RAJASTHAN,
INDIA
R.K. ANJANA, D.N. ARNEPALLI, S. JAIN, P. CHERISHMA AND
S.R. GANDHI
Department of Civil Engineering, Indian Institute of Technology Madras
K. DIVAKARA RAO
Areva Renewable Energies India Pvt. Ltd.
ABSTRACT
Rajasthan Sun Technique Energy Pvt. Ltd. has implemented a 125 MW large-scale grid
connected concentrated solar thermal power project in Jaisalmer district, Rajasthan, India.
This manuscript is a critical evaluation of the design and construction of raw water reservoir
liner system at the concentrated solar thermal power plant. The initial liner consisted (from
bottom to top) of compacted earth, sand layer, HDPE liner, cement plaster and a PCC layer.
The initial liner failed and caused the intrusion of saline ground water into the raw water
reservoir and seepage loss of fresh water into the surroundings, prior to commencement of its
intended function. To mitigate the above problems, the designer proposed a rectifi cation scheme,
which was also found to be ineffective. The present study elaborates on reasons that caused the
malfunctioning of the above liner system. Finally, remedial measures that were proposed to
rectify the problems have been discussed, in detail.
1. INTRODUCTION
Many power plants today use fossil fuels as a heat source to boil water for generating steam. The steam
from the boiling water spins a large turbine, which drives a generator to produce electricity. However,
a new generation of power plants with concentrating solar power systems uses the sun as a source of
heat. Concentrated solar power (CSP) systems concentrate a huge amount of solar thermal energy onto
a small area with lenses or mirrors to generate solar power. This solar power is converted into thermal
energy, which in turn is used to drive a heat engine (usually a steam turbine). This turbine is connected
to an electrical power generator (Boerema et al. 2013). Concentrating technologies exist in fi ve common
forms, namely parabolic trough, enclosed trough, dish stirlings, concentrating linear Fresnel refl ector, and
solar power tower (Letcher 2008). Due to the differences in the way that the solar concentrators track the
sun’s irradiance and focus light, different types of concentrators produce different peak temperatures and
correspondingly varying thermodynamic effi ciencies. New innovations in CSP technology are leading
systems to become more energy-effi cient and cost-effective. Giovanni Francia (1911–1980) designed
and built the fi rst concentrated-solar plant in Sant’Ilario, Italy in 1968. This plant served as the basis of
architecture for today’s concentrated-solar plants in the world. The plant was built with a solar receiver
6th Asian Regional Conference on Geosynthetics - Geosynthetics for
Infrastructure Development, 8-11 November 2016, New Delhi, India
579
Invited Lecture

580 R.K. Anjana, et al.
in the centre of a fi eld of solar collectors. The plant was able to produce 1 MW with superheated steam
at 100 bar and 500 °C.
Rajasthan Sun Technique Energy Private Limited, a wholly owned subsidiary of Reliance Power, India,
was awarded the CSP project in December 2010, based on international competitive bidding conducted
by NTPC Vidyut Vyapar Nigam Limited, which is a subsidiary of NTPC Ltd., India. The project is
located at Dhirubhai Ambani solar park at Pokaran in Jaisalmer district of Rajasthan, India. This is also
the largest plant in the world in terms of compact linear Fresnel refl ective (CLFR) technology usage. The
CSP plant is expected to generate about 250 million kilowatt hours of clean and green energy annually,
equivalent to consumption of a quarter million households, contributing to India’s energy security goal.
The project will reduce CO2 emissions by about 2,40,000 tonnes per year which is equivalent to CO2
sequestered by 6 million tree seedlings grown for 10 years or taking 80,000 cars off the road. The CFLR
technology for the project is provided by AREVA Solar (the US subsidiary of the AREVA SA of France),
which is proved to have minimal environmental spill, lesser land requirement and is more effi cient than
other solar thermal technologies available. The refl ectors focus the solar radiation to an overhead pipe
that contains an effi cient heat-absorbing fl uid. This fl uid transfers heat to water, producing steam to drive
a steam turbine which in turn is connected to a generator.
Water is a crucial resource required for the successful operation of solar thermal plants. It is required
mainly for the regular cleaning of solar receptors and production of steam to run the turbine. Raw
water is stored in huge reservoirs at the CSP plant. In order to minimise seepage losses, a liner system
(consisting of compacted earth, sand layer, HDPE liner, cement plaster and a PCC layer) was initially
designed. However, this liner system was faulty and it failed to serve its purpose. Rectifi cation schemes
were proposed further, which also proved to be ineffective to perform the intended function. The paper
discusses the possible fl aws in the previous designs, proposes new measures to mitigate losses as well as
contamination of reservoir water and elaborates on the importance of proper usage of geosynthetics in
liner applications.
2. STATE OF CSP IN INDIA
CSP technology concentrates solar radiation to produce heat and convert water into steam. Therefore, the
technology requires direct solar radiation to fall on refl ective mirrors to concentrate at a particular point.
The direct normal irradiance (DNI) map of India depicts that several states in India are suitable for solar
thermal projects, namely Gujarat, Rajasthan and Maharashtra in the west, Jammu and Kashmir, Himachal
Pradesh and Uttarakhand in the north, and Karnataka, Andhra Pradesh and Tamil Nadu in the south of
India (Indian Solar Resource Maps 2010). Of these nine states, the entire land masses of Gujarat and
Rajasthan receive good DNI on yearly average. According to the trans-mediterranean renewable energy
cooperation (TREC), each square kilometre of hot desert receives solar energy equivalent to energy
produced from 1.5 million barrels of oil (Wolff et al. 2008). The Thar desert, in Rajasthan, receives
more than 2,000 kWh of DNI per square metre per annum, estimated to be suffi cient to generate 700-
2100 GW of energy (Bhushan et al. 2015). Therefore, theoretically, India has a good potential for CSP
technology. From an environmental impact perspective, it was found that a typical CSP plant produced
7 MWh by utilising 20,000 litres of water per day, which means 2.85 cubic metres of water per MWh.
According to the central electricity authority (CEA), a typical 2 x 500 MW coal-based power plant uses
4,000 cubic metres of water per hour, mainly for fl y ash disposal and cooling, which translates into 3.5-
4.0 cubic metres of water per MWh (International Energy Agency Report 2010). This means that water
consumption of a CSP plant is 20 to 40 % less than that of coal-based thermal power plants. Hence, the
energy industry can be immensely benefi tted by adopting newer technology of CSP over conventional
methods.

581
Case Study on the Reservoir Seepage at Concentrated Solar Thermal Power Plant, Rajasthan, India
In India, capital cost for thermal power is INR 50 million/MW against INR 150 million/MW for solar
thermal power. In terms of cost of generation, thermal power stands at INR 3/kWh whereas solar thermal
power is at INR 15/kWh (Central Planning Authority 2004). A comparison of thermal power generation
with CSP generation options for India shows that thermal power is the cost-effective option—both in
terms of the capital cost and the fi nal cost of generation. The prices may come down on account of an
indigenous manufacturing base and cheaper fi nances made available to developers. CSP is still in the
initial stage of the technology maturity curve. Though there have been signifi cant R&D activities on
CSP for several decades now, the technology needs governmental support through subsidies to develop
demonstration projects and build an environment that promotes investment. On the other hand, thermal
power plants have the highest CO2 emission factors and are also responsible for local air pollution
(SOx, NOx, particulates). Thermal power plants emits nearly 1000 tonnes of green house gases into the
atmosphere for every one GWh of power generated, where as the emissions from CSP are considered
to be insignifi cant. In view of natural resource requirement and green house gas emissions, solar power
plants are considered to be favourable as compared to their counter parts. Further, solar power plants
depend on reliable environmental friendly energy sources.
3. ROLE OF LINER SYSTEMS IN WATER RESERVOIRS
The fi eld of barrier systems was restricted to canal linings initially. In later stages, it expanded to
landfi ll linings. A detailed account of the chronological developments in the area of landfi ll engineering;
limitations with conventional liners, invention of the modern geosynthetic materials and their application
in landfi ll engineering and their long term performance has been presented by the authors in a companion
study (Anjana and Arnepalli 2015). While thermoset liners may have been used prior to the 1930s, the
use of polyvinyl chloride sheeting for liners began in the 1940s. Uncovered PVC geomembranes had
a tendency to undergo progressive brittleness and cracking. Other thermoplastic liner materials, less
susceptible to this problem, followed in rapid succession. Giroud was instrumental in the development of
the double liner concept, which he presented in a paper in 1973 (Giroud 1986). Giroud employed a double
liner system in a liquid impoundment in 1972 and a second time in 1974. This author is also credited for
the fi rst use of a geonet associated with two geomembranes to form an entirely geosynthetic double liner
system in 1980.
Atmospheric exposure and possible degradation of polymeric geomembrane is a complex subject
(Arnepalli and Rejoice 2013a; 2013b). To shield the liner from UV radiation, temperature extremes,
ice damage, wind stresses, accidental damage, and vandalism, a cover is usually required. For potable
water storage, service lifetimes of approximately 20 years must be considered (Koerner 2005). This is
similar to general water storage for agricultural use. PVC has been widely used, due in large part to its
ease of installation compared with that of other materials. As noted earlier, it must be covered to prevent
excessive degradation, and this tends to offset its lower installation cost when compared with other liner
materials that are not soil covered. Indeed, there are other types of geomembranes that can be used for
potable or storage water containment, due to the relative inertness of water. Also, geomembranes are used
as covers above the surface of storage reservoirs for liquids, to minimise evaporation losses.
Raw water, which is used to produce steam in the solar thermal power plants, is stored in huge reservoirs
at the CSP plants. These reservoirs need to have effi cient lining systems in place for the purpose of
minimizing seepage losses as well as restricting the contamination from the surroundings. High density
polyethylene (HDPE), linear low density polyethylene (LLDPE) and poly vinyl chloride (PVC) are the
most widely used polymers for manufacturing geomembranes. In the early 1980s, HDPE essentially
replaced PVC as the geomembrane of choice because of its broad chemical resistance, its high strength,
its relative inherent fl exibility achieved without addition of plasticizers and additives, its weathering
resistance that allows it to be left uncovered, and its ability to be integrally fusion-welded by thermal

582 R.K. Anjana, et al.
methods rather than by using solvents and adhesives. Today, various types of polyethylene are being
commonly used for the containment of liquids.
4. INITIAL LINER SYSTEM AT CSP PLANT
The designer had proposed a initial liner consists (from bottom to top) of compacted earth, 50 mm thick
sand, 250 μm HDPE sheet, 10 mm cement plaster and 75 mm thick PCC layer, as depicted in Fig. 1.
Fig. 1: Schematic view of initial liner with 250 μm HDPE sheet
(Drawing supplied by Areva Renewable Energies India Pvt. Ltd.)
It has been reported that, the above liner was ineffective and caused the intrusion of ground water into
the raw water reservoir as well as loss of fresh water into the surrounding via seepage, prior to the
commencement of its intended function. The possible reasons behind the malfunction of the above liner
system are discussed in detail in the following sections.
4.1 Role of Perched Ground Water and its Impact on the Performance of the Liner
During the initial design of the liner, the designer
underestimated the existence of perched (or
local) aquifer below the footprint of the raw water
reservoir(s) and its impact on overall performance
of the initial liner system with 250 μm HDPE
sheet. In addition to this, the recharge capacity of
this perched aquifer was proved to be signifi cant.
Investigations showed that the pumping of water
from tube wells that were installed in the near
vicinity of raw water reservoir at a rate of 9900
liters/hr resulted in decrease of water level in the
tube wells to 8.4 m below the ground level from
its original level in a short period of time (about
three minutes). This indicates the storativity
(storage capacity) of the perched aquifer is quite
low. To demonstrate the rate of ground water
recharge in this perched aquifer, the observed
recuperation rates in the tube wells 1 and 2 are
plotted in the form of Fig. 2.
0 200 400 600 800 10
0
10
9
8
7
6
5
4
3
2
1
0
-1
Tube well 1 (5 m from boundary of the reservoir)
Tube well 2 (7 m from boundary of the reservoir)
Bed level of rain water harvesting pond (RL of 222 m)
Water level in bore hole (m)
Time (min)
Natural ground level (RL of 224 m)
Bed level of water reservoir (RL of 220 m)
Fig. 2: The observed recuperation rates in tube wells
(Data adapted from report submitted by Geo-Appraisal
Pvt. Ltd.)

583
Case Study on the Reservoir Seepage at Concentrated Solar Thermal Power Plant, Rajasthan, India
It can be observed from the Fig. 2 that, the recuperation rates are very dramatic and water level in these
tube wells have reached their levels prior to the pumping (i.e., 1.5 m to 2 m below the ground level)
within a period of 12 hours. This indicates that the recharge capacity of this perched aquifer is quite high.
This may be due to its near vicinity to the rain water harvesting pond, whose average bed level is at RL
222 m (2 m below the ground level and 2 m above the bed level of the raw water reservoir). Further it can
be noted from the Fig. 2, that, the higher recuperation rates caused the rise of water level in these tube
wells to bed level of the raw water reservoir (i.e., RL 220 m) within fi rst 10 minutes of recuperation. This
indicates the existence of persistent local ground water above the bed level of the raw water reservoir (to
the maximum extent of 2.5 m above the bed level). Though the unanticipated high ground water level
below the raw water reservoir may be due to existence of perched aquifer, however its impact in terms
of upward hydraulic gradient that may exert at bed level of reservoir has been conveniently ignored by
the designer.
The elevation of ground water in the perched aquifer is highly dependent on climatic conditions of the site
and water level in the rain water harvesting pond, which in turn alters the magnitude of upward hydraulic
gradient (i.e., 2.5 m to 0.4 m) exerting at the base of the raw water reservoir. This upward hydraulic
gradient at the base of raw water reservoir might have caused uplift of the entire liner including the 75
mm thick PCC layer and might have led to cracking of the concrete layer, in addition to the opening
of construction and expansion joints in it. It can also be noted from investigations that, majority of
chemical constituents in ground water are substantially higher than the prescribed values for construction
and potable purposes. As a result the salty ground water is unsuitable for drinking and construction
purposes.
4.2 Failure of HDPE Geomembrane
Observations showed that the 250 μm thick HDPE sheet has been punctured invariably during the
installation, as depicted in Fig. 3. It can also be observed from the fi eld notes that, at least one row of 75
mm thick PCC panels has been constructed without cement mortar between the HDPE sheet and concrete
panels. This might have caused further puncturing of 250 μm HDPE sheet due to gravel particles present in
the concrete. As reported in the fi eld note, the HDPE liner is found to be damaged in many locations, prior
to its installation. Further it is reported that, the seaming of joints between the adjacent sheets of HDPE liner
is not executed as per the design drawing, particularly in terms of maintaining required overlap width.
Fig. 3: Photographic view of punctured 250 micron HDPE Liner
(Photograph supplied by Areva Renewable Energies India Pvt. Ltd.)
As a result, the initial liner system was ineffective in terms of its performance as an advective and
diffusive barrier. Further, the above scenarios might have transformed the entire raw water reservoir with
its initial liner system as a hydraulic trap or hydraulic containment, as depicted in Fig. 4.

584 R.K. Anjana, et al.
Fig. 4: Schematic representation of hydraulic trap concept
(Adapted from Rowe et al., 2004)
To understand the synergetic effect of existence of upward hydraulic gradient at the base of the reservoir
due to the perched aquifer, adverse chemical composition of ground water and ineffective initial liner
system on the quality of water to be stored in raw water reservoir, the variation of observed chemical
properties such as pH, EC and chloride contents of water during initial leak testing of reservoir-1 is
presented in the form of Figs. 5 and 6. It can be observed from the above Fig. 6 that, both concentration
of chloride and electrical conductivity value of the water in the reservoir increases gradually over a period
of 140 days. This is mainly due to ingress of contaminants by advection phenomena owing to upward
hydraulic gradient and by diffusion mechanism because of upward concentration gradient at the base
of the reservoir. The relative contribution of these mechanisms (i.e., advection and diffusion) towards
contamination of water in the raw water by the salty ground water primarily depends on net magnitude &
direction of hydraulic gradient acting on the liner system.
-20 0 20 40 60 80 100 120 140 160
8.8
9.0
9.2
9.4
9.6
9.8
10.0
10.2
Water level increase from 80 to 95 %
pH
EC
Duration (days)
pH
Water level increase from 40 to 80 %
0
500
1000
1500
2000
2500
3000
EC (PS/cm)
Fig. 5: Variation of pH and electrical conductivity of water in reservoir-1 during initial leak testing
(Data supplied by Areva Renewable Energies India Pvt. Ltd.)

585
Case Study on the Reservoir Seepage at Concentrated Solar Thermal Power Plant, Rajasthan, India
-20 0 20 40 60 80 100 120 140 160
8.8
9.0
9.2
9.4
9.6
9.8
10.0
10.2
Water level increase from 80 to 95 %
pH
EC
Duration (days)
pH
Water level increase from 40 to 80 %
0
500
1000
1500
2000
2500
3000
EC (PS/cm)
Fig. 6: Variation of chloride and electrical conductivity (EC) of water in reservoir-1 during initial leak testing
(Data supplied by Areva Renewable Energies India Pvt. Ltd.)
If the water level in the raw reservoir is lower than the water level in perched ground water (as depicted
in Fig. 4); this will induce advective fl ow of salty ground water into the raw water reservoir. The severity
of contamination of reservoir water depends on the magnitude of the damage that occurred to the liner
system during construction, which in turn decides the impervious nature of the liner in terms of its
permeability and the net upward gradient acting at the base of the raw water reservoir. If the water level
in the reservoir is higher than the water level in perched ground water, as illustrated in Fig.7; this will
induce diffusive transport of contaminants from salty ground water into the raw water reservoir, even
though the net hydraulic gradient is downward. In this scenario the fresh water from raw water reservoir
will also leaks into the ground water. As a result loss and contamination of fresh water will takes place,
simultaneously.
Fig. 7: Schematic representation of hydraulic trap concept
(Adapted from Rowe et al., 2004)

586 R.K. Anjana, et al.
It is worth mentioning here that, intact HDPE liners have demonstrated their ability as an effective
advective and diffusive barrier towards many ionic inorganic contaminants. For all practical purposes
these liners can be treated impervious, if they are constructed properly. This indicates that, the initial
liner system failed to perform its intended function due to the above mentioned technical reasons. It
was observed that the peak chloride concentrations in raw water reservoir-2 is substantially higher than
that of reservoir-1, however their residual concentrations are comparable. This indicates that advection
is predominant contaminant migration mechanism in case of reservoir-2, whereas diffusion controls the
level of contamination of water in reservoir-1. Further, it was noted that the concentration of chloride,
electrical conductivity and other ions (salts) in both the reservoirs are higher than the prescribed values
for its use in plant. This demonstrates the unsatisfactory performance of initial liners with 250 μm HDPE
sheets of reservoirs 1 and 2, as an advective and diffusive barrier.
5. INITIAL RECTIFICATION SCHEME
In order to minimize the seepage losses, to mitigate the contamination of fresh water by the salty ground
water and to enhance the performance of the liner, the designer proposed the rectifi cation scheme as
shown in Fig. 8.
Fig. 8: Schematic view of proposed rectifi cation scheme
(Drawing supplied by Areva Renewable Energies India Pvt. Ltd.)
It can be noted from Fig. 8 that, the proposed rectifi cation scheme consists of infi ltration gallery along
the periphery of reservoir bottom to control the head in perched aquifer, so that the upward gradient
exerted at the base of the reservoir can be minimized. In addition, the proposed scheme envisaged the
construction of new reservoir lining with 1 mm thick HDPE geomembrane, to minimize the seepage loss
from the reservoir.
5.1 Failure of the Rectifi cation Scheme
It can be noted from the Fig. 8 that the longitudinal and transverse infi ltration trench consists of 250 mm
diameter HDPE perforated pipe wrapped with non-woven geotextile, encapsulated in well graded gravel.
This arrangement may be ineffective in controlling the ground water level, as the infl uence zone of the
infi ltration trench is limited to few meters away from its boundary. As a result mound of water table may
form between the adjacent infi ltration trenches, as shown in Fig. 9.

587
Case Study on the Reservoir Seepage at Concentrated Solar Thermal Power Plant, Rajasthan, India
Fig. 9: Schematic representation of anticipated ground water mound between infi ltration trenches
(Adapted from Rowe et al, 2004)
It can be observed from the Fig.9 that, the water head at the center distance between infi ltration trenches
is maximum and is low at the edge of the infi ltration trench. This scenario may reduce the head that
caused the upward gradient at the edge of the trench, however it will have insignifi cant role in reducing
the head at the center distance between the trenches. As a result the upward gradient exerted on the
liner, particularly at the middle of the reservoir base, is more or less same as earlier. This will cause
of uplift and cracking of the concrete panels and liner almost at the middle of the reservoir base, as
depicted in Fig. 10.
Fig. 10: Photographic view longitudinal crack at middle of reservoir base
(Photograph supplied by Areva Renewable Energies India Pvt. Ltd.)
Further the above scenario is responsible for formation of random crack pattern throughout the reservoir
base, as shown in Fig. 11.
Fig. 11: Photographic view random alligator cracks at reservoir base
(Photograph supplied by Areva Renewable Energies India Pvt. Ltd.)

588 R.K. Anjana, et al.
As shown in Fig. 8, the 250 mm diameter HDPE pipe perforated with 8 mm diameter hole is wrapped
with non-woven geotextile in view of protecting the pipe (particularly perforated holes) from physical
clogging owing to the presence of grit or fi nes in the ground water. This arrangement may be effective in
protecting the pipe from the physical clogging during its early service life. However, this may enhance
the chemical clogging of the geotextile wrapped around the pipe, as confl uence of fl ow of salt water
near the pipe gives rise to high mass loading per unit time, and hence, increases the rate of clogging of
geotextile and possibly drainage gravel. As a result, the long term performance of infi ltration trench may
not be assured.
As shown in Fig. 8, the 1 mm thick HDPE geomembrane is fi rmly sandwiched between 20 mm thick
cement paste. This might have caused shearing of intact geomembrane as well as welded seams due to the
uplift of entire liner system, as illustrated in Fig. 11, even though the break strain of HDPE geomembrane
is 800 percent. The geomembrane only need maximum of 8 mm uplift perpendicular to its plane to reach
its break strain. This is mainly due to the fact that, the movement of geomembrane in lateral direction is
completely restricted in planar direction. The uplift of the entire liner by 8 mm is very much possible, as
the width of the surface crack on concrete panel is almost 30 mm (refer Fig. 12).
Fig. 12: Photographic view random alligator cracks at reservoir base
(Photograph supplied by Areva Renewable Energies India Pvt. Ltd.)
6. PROPOSED FINAL REMEDIAL MEASURES
In view of the entire history of the project, the following remedial measures can be adapted to mitigate
the seepage loss as well as contamination of ground water.
As depicted in Fig. 13, the remedial measure-1 involves (from bottom to top) placement of approximately
150 to 250 mm thick drainage layer using 50 mm size uniform gravel on top of the existing reservoir base
and a suitable geonet on slopes, followed by laying of 250 gsm non-woven geotextile with prescribed
percent open area and pore size distribution, as separator layer. On top of this geotextile, a 50 mm thick
protection layer using fi ne sand is envisaged to safeguard the liner from indentation due to the gravel in
drainage layer. A 1.5 mm thick high quality HDPE geomembrane is placed on top of the protection layer,
which is expected to perform as an effi cient advective-diffusive barrier. The HDPE geomembrane is
covered with a suitable concrete panel or fl y ash bricks without pointing their joints with cement mortar.
Further a 250 gsm nonwoven geotextile is essential in between HDPE geomembrane and concrete panel
or fl y ash bricks to protect the geomembrane from puncturing.

589
Case Study on the Reservoir Seepage at Concentrated Solar Thermal Power Plant, Rajasthan, India
Fig. 13: Schematic view of Remedial Measure-1 (Figure not to scale)
The remedial measure-2 involves fi lling of the entire reservoir with sand up to RL of 224 m and
construction of new liner system above the ground level, as shown in Fig. 14.
Fig. 14: Schematic view of remedial measure-2 (Figure not to scale)
7. CONCLUDING REMARKS
The attributes and challenges of CSP have set the ground for a possible way forward. Globally, CSP has
a bright future. Countries such as USA, Spain and Israel are shaping the future. India too is optimistic
about CSP and has set very aggressive targets in the near future. However, to set the ground right in the
fi rst place, every stage of the plant should be designed with extreme care and caution by considering
all possible critical scenarios. Since, CSP is water-intensive, suitable design of the liner systems for
the raw water reservoir is highly essential. This study is the best example to show how inconsideration
of critical design parameters leads to the failure of the system. All the subsurface features need to be
carefully considered before designing the liner system, as demonstrated by the study. Also, proper usage
of geosynthetics should be carried out, having the material properties and geometrical considerations of
the material in mind.

590 R.K. Anjana, et al.
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