ALTERNATIVE STUDY REPORTenvironmentclearance.nic.in/writereaddata/Online/TOR/0_0... · 2014-11-11 · Dugar HEP is in hilly terrains of the Higher Himalayas situated in the State

Dugar Hydro Power Limited

Dugar Hydropower Project

ALTERNATIVE STUDY REPORT

Report No. R-71.2471.00.003_R0

May 2013

smrTypewritten textANNEXURE-V A


Dugar Hydro Electric Project

Alternative Study Report i/77

AF-Consult Switzerland Ltd Täfernstrasse 26, CH-5405 Baden, Schweiz Phone +41 (0)56 483 12 12. Fax +41 (0)56 483 12 55. www.afconsult.com

Date Name Signature

Created 01.05.2013 Martina

Checked 07.05.2013 Markus

Approved 14.05.2013 Sai

Index of versions

No. Page(s) Date Remark Created

(Initial/Signature)

Approved

(Initial/Signature)

1 All 14.05.2013 First release FRM SSE

Project name Dugar HEP

Document title Alternative Study Report

Project number 2471

Name of department Hydropower

Document path N:\Working Designs\2471_Dugar\Engineering\Reports\Reports-Final\00

General\R_71_2471_00_003_Alternative Study Report R0.docx



Alternative Study Report 3/77

R-71.2471.00.003_R0 May 2013

TABLE OF CONTENTS

1 INTRODUCTION ............................................................................ 9

2 PROJECT LOCATION ................................................................... 10

3 AVAILABLE DOCUMENTS/DATA ............................................... 11

4 BASIC PROJECT PARAMETER FOR ALTERNATIVES .................. 11

5 CONSIDERED ALTERNATIVES .................................................... 12

5.1 Dam axes considered in the Inception Report ...................................................................... 12

5.2 Alternative I-A.................................................................................................................................. 13

5.3 Alternative II-A ................................................................................................................................ 13

5.4 Alternative III-A ............................................................................................................................... 16

5.5 Alternative IV-A ............................................................................................................................... 19

5.6 Layout of surge shaft, pressure shaft and tunnels, powerhouse complex and

tailrace tunnels ............................................................................................................................... 21

6 EXPECTED ENERGY GENERATION ............................................. 26

6.1 Basic Considerations ...................................................................................................................... 26

6.2 Expected Energy Production for the 50% Dependable Year ............................................. 32

7 COST ESTIMATE OF THE DIFFERENT ALTERNATIVES .............. 34

7.1 General considerations ................................................................................................................. 34

7.2 Civil works (C) .................................................................................................................................. 35

7.3 Hydromechanical steel structures (HSS) ................................................................................. 37

7.4 Electromechanical equipment (EM) ......................................................................................... 37

7.5 Other cost ......................................................................................................................................... 37

7.6 Cost summary of basic alternatives .......................................................................................... 38

8 OPTIMIZATION OF BASIC ALTERNATIVES ............................... 41

8.1 Cost Saving Potential of the Basic Alternatives ..................................................................... 41




R-71.2471.00.003_R0 May 2013

8.2 Results of optimized alternatives .............................................................................................. 46

9 ECONOMIC EXAMINATION WITH OPTIMIZED LAYOUTS ....... 50

9.1 Developers Equity in the Project ............................................................................................... 50

9.2 Loan Component ............................................................................................................................ 51

9.3 Interest Rate on Loan Capital ..................................................................................................... 51

9.4 Repayment Period .......................................................................................................................... 51

9.5 Fixation of Tariff .............................................................................................................................. 51

10 CONCLUSION AND NEXT STEPS ................................................ 57

APPENDIX

1 DRAWINGS – BASIC LAYOUTS

2 UNIT RATES FOR CIVIL WORKS




R-71.2471.00.003_R0 May 2013

LIST OF FIGURES

Figure 1: Location Map of Dugar HEP ........................................................................................................ 10

Figure 2: Alternatives studied in the Inception Report .............................................................................. 13

Figure 3: Layout presenting main dam, cofferdams, diversion tunnels and power intakes of Alternative II-

A ................................................................................................................................................................. 14

Figure 4: Cross section through main dam of Alternative II-A ................................................................... 15

Figure 5: Layout presenting main dam, cofferdams, diversion tunnels and power intakes of Alternative

III-A ............................................................................................................................................................. 17

Figure 6: Cross section through main dam including auxiliary powerhouse (Alternative III-A) ................. 18

Figure 7: General layout of Alternative IV-A .............................................................................................. 20

Figure 8: General layout of powerhouse complex ..................................................................................... 22

Figure 9: Longitudinal section of powerhouse complex ............................................................................ 22

Figure 10: Layout of access for Alternative II-A ......................................................................................... 24

Figure 11: Layout of access for Alternative III-A ........................................................................................ 25

Figure 12: Layout of access for Alternative IV-A ........................................................................................ 26

Figure 13: Duration curve for all alternatives for 50% and 90% dependable year .................................... 28

Figure 14: Efficiency for different turbine types ........................................................................................ 30

Figure 15: Efficiency for Francis adopted for energy calculation ............................................................... 31

Figure 16: Definition of gate block............................................................................................................. 43

Figure 17: Construction cost for gate blocks ............................................................................................. 44

Figure 18: Capacity of spillway tunnel vs. internal tunnel diameter (length of tunnel 250 m) ................. 45

Figure 19: Capacity of spillway tunnels vs. internal tunnel diameter (length of tunnel 350 m) ................ 45

Figure 20: Levelised Tariff for all Alternatives ........................................................................................... 55




R-71.2471.00.003_R0 May 2013

LIST OF TABLES

Table 1: Duration curve for all alternatives for 50% and 90% dependable year ....................................... 27

Table 2: Environmental flow for Alternative II-A ....................................................................................... 29

Table 3: Environmental flow for Alternative III-A ...................................................................................... 29

Table 4: Environmental flow for Alternative VI-A ...................................................................................... 29

Table 5: Basic parameters for main plant .................................................................................................. 31

Table 6: Basic parameters for auxiliary plant ............................................................................................ 32

Table 7: Expected energy production for main and auxiliary plant .......................................................... 33

Table 8: Expected energy production for main and auxiliary plant .......................................................... 34

Table 9: Total investment costs for Alternative II-A (basic alternative) .................................................... 39

Table 10: Total investment costs for Alternative III-A (basic alternative) ................................................. 39

Table 11: Total investment costs for Alternative IV-A (basic alternative) ................................................. 40

Table 12: Summary of total investment costs for all basic alternatives .................................................... 40

Table 13: Cost comparison for different components for all alternatives ................................................ 41

Table 14: Feasibility for different concrete dam type based on findings of Inception Report ................. 42

Table 15: Update of suitability of different concrete dam types based on findings of cost comparison .. 46

Table 16: Total investment costs for Alternative II-A (optimized layout) .................................................. 47

Table 17: Total investment costs for Alternative III-A (optimized layout) ................................................. 47

Table 18: Total investment costs for Alternative IV-A (optimized layout) ................................................. 48

Table 19: Comparison of investment costs for all alternatives (optimized layout) ................................... 48

Table 20: Expected energy production for main and auxiliary plant (optimized layouts) ........................ 49

Table 21: Total investment cost for Alternative II-A (optimized layout with one HRT) ............................ 49

Table 22: Expected total investment cost for main and auxiliary plant (optimized layouts and alternative

II-A with one HRT) ...................................................................................................................................... 50

Table 23: Free Power to State Government .............................................................................................. 52

Table 24: Basic Parameters for Economic Evaluation ............................................................................... 54

Table 25: Summary of Economic Evaluation ............................................................................................. 56

© The Copyright remains with AF-Consult Switzerland Ltd.




R-71.2471.00.003_R0 May 2013

Abbreviations

masl Meter above sea level

AFC AF Consult Pvt. Ltd.

CEA Central Electricity Authority

COD Date of Commercial Operation

CVC Conventional Concrete

CWC Center Water Commission

DHPL Dugar Hydro Power Limited

DPR Detailed Project Report

FRL Full Reservoir Level

G&D Gauge and Discharge

GSI Geological Survey of India

HEP Hydro Electric Project

HRT Head Race tunnel

HSE Health Safety & Environment

IMD Indian Meteorological Department

IWT Indus water treaty

MAF Million Acre Feet

MDDL Minimum Draw-Down Level

PFR Pre-Feasibility Report

PMF Probable Maximum flood

PPE Personal Protective Equipments

RCC Roller Compacted Concrete

SPF Standard Project Flood

SRTM Shuttle Radar Topography Mission

TWL Tail Water Level

USGS United States Geological Survey

WBS Work Breakdown Structure

SI Units and Prefixes

- Units

Base quantity Name Symbol

Length meter m

Mass kilogram kg

Time second s

Hour h

Power watt W




R-71.2471.00.003_R0 May 2013

- Prefixes

Factor Name Symbol

109 Giga G

106 Mega M

103 kilo k

10-3

milli m

- Units used in the Report

Installed Capacity MW

Energy kWh / GWh

Storage 106 m

3/hm

3

Sediment volume Ham / 104 m

3

Storage Volume (Million acre feet – MAF) MAF / 1233.4818 hm3




R-71.2471.00.003_R0 May 2013

1 INTRODUCTION

AF Consult Switzerland Ltd. (AFC) has been contracted by Dugar Hydro Power Ltd. (DHPL)

to provide consultancy services for the preparation of Detailed Project Report (DPR) and

assistance to DHPL in obtaining concurrence of Central Electricity Authority and other

Governmental authorities as required, for Dugar Hydroelectric Project (HEP) on the Chenab

River in Chamba District of Himachal Pradesh by Consultancy Service Agreement dated 5th

November, 2012. The contract is scheduled to take 18 months and to be completed on 5th

May, 2014.

This green-field project has been awarded to the consortium “Tata Power Company Ltd.

and SN Power Holding Singapore Pte. Ltd.” (Owner) in May 2011, by Directorate of Energy -

Government of Himachal Pradesh on Build-Own-Operate-Transfer (BOOT) basis for a

period of 40 Years from Commercial Operation Date. To implement the project, the Owner

has constituted a Special Purpose Vehicle (SPV) by the name of M/s Dugar Hydro Power

Ltd. (DHPL).

The scope of works under this Consultancy Service Agreement broadly categorized in two

parts - Site Investigation Works and Engineering Desktop Studies, required for preparation

of DPR of Dugar HEP. Site Investigation Works mainly includes topographic survey,

geological and geotechnical investigations, geophysical survey, geological mapping,

seismo-tectonic evaluation, construction material survey, route survey and hydro-

meteorological investigations. The initial task of the consultant was to prepare an

Inception Report with the aim of review of available data, to describe the findings gained

during the site visits, and to highlight the required main data and elements to develop an

alternative study.

The main objective of the present report is the performance of a comprehensive

alternative study to determine the most attractive solution in a technical and particularly in

an economic sense. The study is divided into various working steps. In a first step the so-

called basic alternatives are prepared. Description of the layouts for each alternative are

presented in chapter 5, followed by the calculation of the expected energy generation

(chapter 6) and the cost estimates summarising the investment costs for each basic

alternative (chapter 7). In a second step the cost saving potential is determined for each

basic alternative, again followed by the recalculation of the expected energy generation

and an update of the cost estimates (chapter 8) for the optimized alternatives. Chapter 9

presents an economic examination of all alternatives (basic and optimized) followed by the

conclusion which summarizes the results and findings of the Alternative Study. In common

accordance with the client the final alternative for the further preparation of the power

potential study and the DPR will be selected.




R-71.2471.00.003_R0 May 2013

2 PROJECT LOCATION

Dugar HEP is in hilly terrains of the Higher Himalayas situated in the State of Himachal

Pradesh, India. The project is located on the Chenab River in district Chamba of Himachal

Pradesh. Presently there are 12 districts in Himachal Pradesh including that one of

Chamba, which has an estimated geographic area of 6528 km2 and is surrounded on all

sides by lofty hill ranges. The territory is wholly mountainous with altitude ranging from

600 to 6500 masl. The district has 6 Sub-Divisions which comprises 7 tehsils and 3 sub-

tehsils. Dugar HEP is located near Killar village which is under Pangi Tehsil, and is about 16

km from Pangi and about 63 km from district headquarter Chamba. The location map of

the project area is shown in Figure 1.

Figure 1: Location Map of Dugar HEP




R-71.2471.00.003_R0 May 2013

The “Access Availability” to the project site, as well as a description about the “Chenab

Basin” are given in the Inception Report (Nr. R-71.2471.00.001). It has to be noted that the

Dugar HEP lying on the Chenab River is governed by the “Indus Water Treaty”.

3 AVAILABLE DOCUMENTS/DATA

[1]. Pre-Feasibility Report of Dugar HEP, prepared by DHPL

[2]. Survey of India (SOI) Toposheet No. 52 C/8; Scale 1:50000

[3]. Survey of India (SOI) Toposheet No. 52H; Scale 1:250000

[4]. Topographical Survey provided by DHPL.

[5]. Hydrological data provided by DHPL.

[6]. Report on Design Storm Study for Dugar HEP by IMD Delhi

[7]. Inception Report (January 2013) by AFC

[8]. Hydrology & Sedimentation Study Report (March 2013) by AFC

4 BASIC PROJECT PARAMETER FOR ALTERNATIVES

The newly derived project parameters which are used throughout the Alternative Study are

described in the following. Additional parameters were defined within the Inception Report

and are not repeated. For further details it is referred to the Inception Report (No. R-

71.2471.00.001 R2, January 2013).

Required live storage: The minimum required live storage has been discussed during the

meeting in November 2012. A value of 15 hm3 has been determined to be considered as

necessary minimum live storage. This value enables the operation of the scheme on daily

mode as well as on partial (i.e. reduced) weekly mode.

Design floods: The design floods at Dugar site have been estimated by a flood frequency

analysis utilizing the maximum observed flood peaks at Udaipur G&D site during the period

1974 to 2008 as well as a hydro-meteorological approach. Details regarding the applied

methods as well as all calculated design floods are described in the Hydrology and

Sedimentation Study Report (No. R-71.2471.00.002 R1, March 2013). For the Alternative

Study two flood values are decisive for the determination of the general layout of the

diversion scheme, as well as of the permanent structures such as spillway and bottom

outlets. These floods are the Q25 for the river diversion works and the probable maximum

flood (PMF) for the main diversion structures. The flood value for a return period of 25




R-71.2471.00.003_R0 May 2013

years has been determined to be 2,517 m3/s whereas the PMF has been calculated to be

8,762 m3/s.

Environmental flows: A minimum discharge has to be released due to environmental

considerations. With the clearance of the 1st

stage of the TOR given by the Ministry of

Environment & Forest (MoEF) in December 2012 a new standard concerning the

environmental flow (ecological water release) has to be considered for the further design

works of Dugar HEP. The released discharges are based on the seasonal average flows for

the 90% dependable year. The different seasons are defined as “lean season” (months of

December to March), a “transition season” (months of April to May and October to

November) and a “monsoon season” (months of June to September).

Season Average flow of 90%

dependable year (m

3/s)

Environmental release

due to new guidelines (m

3/s)

Lean

to be calculated for

each alternative

20%

Transition 20%

Monsoon 30%

Design discharge of main plant: The design discharge has not been optimized. The applied

value remains 452 m3/s for the Alternative Study. After the final decision of the most

attractive alternative a power potential study will be carried out to start with the

optimization process of the design discharge of the main plant.

5 CONSIDERED ALTERNATIVES

5.1 Dam axes considered in the Inception Report

Four different dam sites have been taken into consideration in the Inception Report and

visited in the course of the site visit in November 2012. The site of Alternative I-A is located

at km 5+510 (starting from the upstream concession limit). Alternative II-A is situated

approximately 1.06 km downstream of the bridge of the Sach-Pass road at km 8+240 while

Alternative III-A is positioned at km 10+309. Alternative IV-A is located after the 90° bend

of the river at km 11+010.




R-71.2471.00.003_R0 May 2013

Figure 2: Alternatives studied in the Inception Report

In the following subchapters the alternatives of the Inception Report will be described in

more detail. The herein proposed “basic” layouts will be the basis for the first cost

estimations. However, it should be noted that all components will be reviewed within

chapter 8 for their cost saving potential.

5.2 Alternative I-A

The total storage capacity of Alternative I-A is only 5.884 hm3. Considering that a minimum

required live storage of 15 hm3 is asked for by SN Power for the operation of the plant, this

alternative has not been considered further in the Alternative Report.

5.3 Alternative II-A

The two power intakes are situated in the reservoir just upstream of the dam structure at

elevation 2,077.35 masl. (invert level). The invert level of the power intakes is defined by

the minimum draw down level, which is at elevation 2,094.35 masl., providing a minimum

cover above the intake in order to avoid air entraining.




R-71.2471.00.003_R0 May 2013

Figure 3: Layout presenting main dam, cofferdams, diversion tunnels and power intakes of

Alternative II-A

The reservoir is created by an approximately 102 m high dam which will be able to store a

water volume of 28.660 hm3. As a first draft the dam is designed as a concrete gravity dam.

The concrete dam section is founded on solid rock on the excavated river bed at

approximately 2,005 masl. (Assuming a depth of the alluvial deposits of 22 m). The dam

section has a vertical front while the downstream face is sloping with an inclination of

1(V):0.8(H). The crest is 8 m wide and approximately 159 m long. The dam crest is set at

elevation 2,107 masl.

To minimise leakage past the dam and uplift from the foundation, a grout curtain shall be

established close to the upstream face of the dam in combination with the provision of

drain holes at the downstream side of the curtain. The depth of the grout curtain is

assumed to be equal to 2/3 of the water head (difference between upstream and

downstream water level), while the depth of the drainage holes is assumed to be equal to

2/3 of the depth of the grout curtain length.

For concrete gravity dams an overflow spillway on the dam crest followed by a chute on

the downstream dam face, including flip bucket, and a plunge pool acting as energy

dissipater. This is a common economical solution. For Dugar HEP a gated spillway has to be




R-71.2471.00.003_R0 May 2013

selected due to the maximum allowable water level of 2,105 masl. which equals the Full

Reservoir Level (FRL). This consideration asks for a gated spillway arrangement. Therefore,

the present concrete gravity dam structure comprises six gated ogee crest spillway

openings with a width of 12 m. The sill elevation is set to 2,092.5 masl. With this gate

arrangement of the spillway a discharge of 6’250 m3/s during PMF can be expected. The

maximum water level rises up to 2,105 masl at the dam location. A bridge over the spillway

openings is foreseen to allow access from one bank to the other.

Figure 4: Cross section through main dam of Alternative II-A

The dam includes four bottom outlets. Two sliding gates per outlet are foreseen. The more

downstream one is the operation gate, which normally is closed, while the more upstream

one is a maintenance gate, which is used as stoplog and normally always open. The

selected opening size of the gates is 6 m by 5 m (height by width). The inlet elevation is set

to 2,036 masl. This level has been chosen to ensure the discharge of a sufficient water

volume in combination with a sufficiently low tailwater level particularly during flushing

operations, i.e. accumulations in the inlet area may require to be flushed/scoured by

periodic opening of the bottom outlet gates. The bottom outlets shall be used to discharge

approximately one third of the water in the case of a PMF. With a normal storage level at

2,105 masl., the bottom outlets have an approximate total discharge capacity of

2,840 m3/s. In addition, they shall be used to lower the reservoir level in a case of

emergency.

Two diversion tunnels of 346 m and 473 m respectively length with an inner diameter of

10.5 m are provided at the right bank. The tunnels are designed in a way that during wet

seasonal flows (Q25,monsoon) the water can be diverted through the tunnels without

overtopping of the embankment cofferdams. The resulting crest elevation of the

cofferdams are 2,059.8 masl (upstream) and 2,043.0 masl (downstream).




R-71.2471.00.003_R0 May 2013

An auxiliary hydropower plant is to be installed into the dam harnessing the required

environmental flow release during the lean and the transition season and partially during

the monsoon season (the rest will be flow over the overflow spillways or through the

bottom outlets). Two Francis turbines with a total design discharge of 28.0 m3/s (Pinstalled =

16.7 MW) are foreseen. The auxiliary powerhouse is located in the left side of the dam

structure next to the bottom outlets. The inlets are foreseen at elevation 2,082 masl. The

turbine setting level is set to 2,082.2 masl. Access to the auxiliary powerhouse is granted

by a vertical shaft (5 m by 4 m) connected with the erection bay by a horizontal adit,. The

shaft, which will be used for the transportation of equipment, is located downstream of

the dam crest. Access for the personnel will be foreseen by means of a stairway from the

dam crest to the erection bay of the auxiliary powerhouse.

The two headrace tunnels with a length of 2,230 m and 2,265 m to convey the water to the

surge shaft and the powerhouse both located underground on the south bank of the

Chenab River. For all alternatives the same layout is foreseen starting from the upstream

surge shaft. Details are presented in subchapter 5.6 herein.

Access to the dam and the power intakes is granted by a permanent road on the left

abutment which starts at Shukhrali bridge. The length of this road is approximately 1.7 km.

During construction a temporary road, also starting from the Shikhrali bridge enables

access to the diversion tunnels and to the dam construction site. The length of this road is

approximately 1 km.

The layout of the scheme of Alternative II-A is presented in five drawings:

SK-71.2471.2A.001 General layout (Layout Plan)

SK-71.2471.2A.002 General layout (L-section through HRT-2)

SK-71.2471.2A.003 Concrete gravity dam – Upstream View

SK-71.2471.2A.004 Concrete gravity dam - Plan

SK-71.2471.2A.005 Concrete gravity dam - Sections

5.4 Alternative III-A

The two power intakes are situated in the reservoir just upstream of the dam structure at

elevation 2,081.0 masl. The invert level of the power intakes is defined by the minimum

draw down level, which is at elevation 2,098.5 masl., providing a minimum cover above the

intake in order to avoid air entraining.




R-71.2471.00.003_R0 May 2013

Figure 5: Layout presenting main dam, cofferdams, diversion tunnels and power intakes of

Alternative III-A

The reservoir of Alternative III-A is created by a 114 m high dam which will be able to store

a water volume of 54.217 hm3. As for Alternative II-A, a concrete gravity dam is foreseen to

function as base solution. Any changes to the dam type in respect to possible cost savings

will be discussed within chapter 8. The concrete dam section is founded on solid rock on

the excavated river bed at approximately 1,993 masl. (assuming a maximum depth of the

alluvial deposits of 20 m). The cross section of the dam has been kept similar to the one of

Alternative II-A, i.e. vertical front of the upstream face and an inclined downstream face

(inclination 1(V):0.8(H)). The crest is 8 m wide and approximately 178 m long. The dam

crest is set at elevation 2,107 masl.

The grout curtain arrangement as well as the provision of drainage holes is analogue to

Alternative II-A, i.e. a grout curtain shall be established close to the upstream face of the

dam and drain holes at the downstream side of the curtain to control leakage past the dam

and reduce the uplift acting on the foundation. The depth of the grout curtain and

drainage holes are assumed analogue to Alternative II-A.

For Alternative III-A the same spillway layout as for Alternative II-A has been foreseen. This

implies that the gate arrangement also remains the same as presented for Alternative II-A.

Again, a bridge over the spillway openings is foreseen to allow access from one bank to the

other.

The dam also includes four bottom outlets with the same dimensions and gate

arrangement as for Alternative II-A. The inlet elevation is set based on the same

consideration as carried out and described for Alternative II-A to 2’020.5 masl. At a normal




R-71.2471.00.003_R0 May 2013

storage level at 2,105 masl., the bottom outlets have an approximate total discharge

capacity of 3,140 m3/s.

Two diversion tunnels of length 358m and 489 m respectively with an inner diameter of

10.5 m are provided at the right bank. The tunnels are designed in a way that during wet

seasonal flows (Q25, monsoon) the water can be diverted through the tunnels without

overtopping of the embankment cofferdams. The resulting crest elevations of the

cofferdams are 2,047.9 masl (upstream) and 2,028.5 masl (downstream).

The same arrangement for an auxiliary hydropower plant, as for alternative II-A is also to

be installed into the dam for harnessing the environmental flow release. The auxiliary

powerhouse is located on the right side next to the bottom outlets. The inlets are foreseen

at elevation 2,082 masl. Two Francis turbines with a total design discharge of 29.0 m3/s

(Pinstalled = 22.1 MW) are foreseen. The turbine setting level is set to 2,011.3 masl. The

access arrangement to the auxiliary powerhouse from the dam crest for equipment and

personal is the same as for alternative II-A.

Figure 6: Cross section through main dam including auxiliary powerhouse (Alternative III-A)

In contrast to Alternative II-A and of course due to the close-by location of the dam axis to

the powerhouse, the length of the headrace tunnel is decreased tremendously. The length

of the two headrace tunnel is 410 m and 368 m respectively.




R-71.2471.00.003_R0 May 2013

During the construction access to the dam construction side and the diversion tunnels will

be given by a road which takes off from the main road (Killar-Kishtwar Road) and continues

to the powerhouse construction site. From an intermediate turn around elevation 2,150

masl. The road will continue along the river in upstream direction towards the dam crest.

This part will function during the operation of the scheme as permanent access to the dam

crest. During construction this road will continue to the diversion tunnels and the dam

construction area. Additionally, the road will be developed to a temporary bridge spanning

over the Chenab River from where it will give access to the power intakes.

The layout of the scheme of Alternative III-A is presented in five drawings:

SK-71.2471.3A.001 General arrangement – Layout plan

SK-71.2471.3A.002 General arrangement – L-section

SK-71.2471.3A.003 Concrete gravity dam - Upstream view


SK-71.2471.3A.005 Concrete gravity dam - Sections

5.5 Alternative IV-A

Alternative IV-A has been included in the Inception Report due to the consideration that

the units installed in the main powerhouse could be utilised for harnessing the discharge of

the environmental flow. Due to the close location of this alternative to the outlets of the

main powerhouse it is not necessary to install an auxiliary powerhouse at the dam toe.

Alternative IV-A utilizes a gross head of 96 m. Due to the general arrangement of the

scheme (i.e. intakes, dam and powerhouse within one area) the two power intakes have to

be located further away from the dam structure. The general arrangement of the scheme

is shown in Figure 7 below. The inverts level of Intake structure is at elevation 2’083.6

masl. The invert level of the power intakes is defined by the minimum draw down level,

which is at elevation 2’100.6 masl., providing a minimum cover above the intake in order

to avoid air entraining.




R-71.2471.00.003_R0 May 2013

Figure 7: General layout of Alternative IV-A

The reservoir is created by a 125 m high dam which will be able to store a total water

volume of 63.070 hm3. As discussed in the Inception Report the site of Alternative IV-A

does not allow the construction of a concrete arch gravity or a double curved arch dam.

Therefore the proposed concrete gravity dam has to be considered as only sole solution –

in contrast to Alternative II-A and III-A where more advanced dam types are in general

feasible.

The proposed concrete gravity dam is founded on solid rock on the excavated river bed at

approximately 1,982 masl. (assuming a depth of the alluvial deposits of 20 m). The dam

section has a vertical front while the downstream face is sloping with an inclination of

1(V):0.8(H). The crest is 8 m wide and approximately 181 m long. The dam crest is set at

elevation 2,107 masl.

The grout curtain arrangement as well as the provision of drainage holes are analogue to

Alternative II-A and III-A, i.e. a grout curtain shall be established close to the upstream face

of the dam and drain holes at the downstream side of the curtain to control leakage past

the dam and reduce the uplift acting on the foundation. . The depth of the grout curtain

and drainage holes shall be assumed analogue to the other alternatives..

For Alternative IV-A the same general gate arrangement for the spillway as foreseen for

Alternatives II-A and III-A has been anticipated. This implies that the gate dimensions as

well as the sill elevation remain the same. Again, a bridge over the spillway openings is

foreseen to allow access from one bank to the other.




R-71.2471.00.003_R0 May 2013

As for Alternative II-A and III-A four bottom outlets with the dimension of 6 m by 5 m

(height by width) are proposed. The inlet elevation is set based on the same consideration

as carried out and described above to 2,016 masl. The foreseen gate arrangement is the

same as for alternatives II-A and III-A. At a normal storage level at 2,105 masl., the bottom

outlets have an approximate total discharge capacity of 3,320 m3/s.

Due to the location of Alternative IV-A in the immediate vicinity of the main powerhouse

complex the required length of the diversion tunnels becomes longer than those necessary

for Alternative II-A and III-A since they are also utilised for the construction of the tailrace

channel outlets. Hence, two diversion tunnels of 510 m respectively 625 m length with an

inner diameter of 10.5 m are provided at the right bank. The tunnels are designed in a way

that during wet seasonal flows (Q25,monsoon) the water can be diverted through the tunnels

without overtopping of the cofferdams. The resulting crest elevation of the cofferdams are

2,027.6 masl. (upstream) and 2,007 masl. (downstream).

As for Alternative III-A and of course due to the close-by location of the dam axis to the

powerhouse, the length of the headrace tunnel is similar to those foreseen for Alternative

III-A. The resulting length of the two headrace tunnels is 330 m respectively 370 m. The

foreseen inner diameter of the tunnels is set to 10 m.

For this alternative most of the construction activities will be close to the dam site and the

powerhouse complex. Therefore all necessary construction sites (with one exception) can

be reached by means of access roads diverting from the main state road to Killar. The only

exception is the access to the power inlet which are located further upstream. Long and

steep roads plus an additional bridge would be necessary to reach this location. To easen

the access two ropeways have been foreseen one for the transportation of material and

equipment and one for personnel.

The layout of the scheme of Alternative IV-A is presented in five drawings:

SK-71.2471.4A.001 General arrangement – Layout plan

SK-71.2471.4A.002 General arrangement – L-section

SK-71.2471.4A.003 Concrete gravity dam - Upstream view


SK-71.2471.4A.005 Concrete gravity dam – Sections

5.6 Layout of surge shaft, pressure shaft and tunnels, powerhouse complex and tailrace tunnels

The layout of the surge shaft, pressure shaft and pressure tunnel, the powerhouse

including transformer cavern and tailrace tunnels has been kept the same for all three

alternatives. The general layout is shown below.




R-71.2471.00.003_R0 May 2013

Figure 8: General layout of powerhouse complex

Two surge shafts are foreseen approximately 75 m upstream of the powerhouse complex.

The diameter of the shafts is presently set to 32 m for Alternative II-A and 18 m for

Alternative III-A & IV-A. However, further details of the final layout of the surge shaft will

be elaborated during the next phase after the determination of the final axis. The height of

the shaft varies for each alternative and is therefore approximately 60 to 70 m.

A pressure shaft with a depth of approximately 60 and an inner diameter of about 7.5 m

conveys the water through the horizontal pressure tunnel (length approximately 100 m,

inner diameter 7.5 m) to the turbines in the main powerhouse cavern.

Figure 9: Longitudinal section of powerhouse complex




R-71.2471.00.003_R0 May 2013

The dimensions of the powerhouse are set to a length of 110 m, a width of 20 and a height

of about 42 m. The main powerhouse is equipped with four Francis units with an installed

capacity of 91.3 MW (for Alternative II-A) and 92 MW (for Alternative III-A and IV-A). The

transformer cavern is located 40 m downstream of the main powerhouse cavern. The

dimensions are set to a length of 110 m, a width of 14 m and a height of 22 m.

The tailrace tunnel is about 410 m long. The inner diameter is presently set to 10 m.

A pothead yard is foreseen on the right river bank.

Temporary and permanent access to the surge shaft, pressure tunnel and shaft, and the

powerhouse complex is slightly different for all alternatives and will be described in the

following:

Alternative II-A: During construction access to the powerhouse complex is granted by

construction adit (width 4.5 m) which connects the right river abutment by means of a

bridge with the left abutment and in that respect with the portal of the adit. This

construction access has been extended to provide access to the downstream end of the

headrace tunnel. Access to the pressure tunnel is provided by an additional construction

tunnel at lower level which connects the tailrace tunnel with the pressure tunnel. Access to

the top of the surge shaft is given by means of an additional tunnel starting from the left

abutment to the middle of both surge shafts. Access from the river to this tunnel is

provided by means of vertical steel construction which includes a lift. Smaller equipment

and personnel can be moved by means of this device. This access tunnel should be used

later on for permanent use. Permanent access to the powerhouse and transformer cavern

are granted by means of another tunnel which is located further downstream. A bridge

connecting the right and left abutment will guide to the portal of this permanent access.




R-71.2471.00.003_R0 May 2013

Figure 10: Layout of access for Alternative II-A

Alternative III-A: The temporary and permanent access to the powerhouse and

transformer cavern as well as the connection between pressure tunnel and tailrace tunnel

is analogue to Alternative II-A. Access to the surge shaft is given by an additional tunnel

which starts in the vicinity of the power intakes. During construction this place is reached

by means of an access which has been described above. The same tunnel will used later on

for permanent access from the dam crest.




R-71.2471.00.003_R0 May 2013

Figure 11: Layout of access for Alternative III-A

Alternative IV-A: The temporary and permanent access to the powerhouse and

transformer cavern is analogue to Alternative II-A. The connection between the pressure

tunnel and the tailrace tunnel as provided for Alternative II-A is also given for Alternative

III-A. The main difference in respect to access between Alternative II-A and III-A is the

access to the surge shaft. During construction access to the upper part of the surge shaft is

provided by a tunnel which starts close to the power intakes at the left river bank. Access

to this place is given by means of ropeways which connect the right and left abutment. The

ropeway, one for material and equipment and one for personnel, is also used for the

access to the power intakes. The tunnel from the surge shaft to the intake will be used for

permanent access to the intake structure later on. Additionally it is foreseen to extend this

access tunnel to the dam crest, again for permanent access. Additional access roads to the

construction site are to be foreseen from the main state road to Killar. The necessary

layout of tunnels and roads is shown below.




R-71.2471.00.003_R0 May 2013

Figure 12: Layout of access for Alternative IV-A

6 EXPECTED ENERGY GENERATION

6.1 Basic Considerations

The following basic considerations have been taken into account for the determination of

the total energy production of the different alternatives (divided into production in the

main plant and auxiliary plant),:

i) The duration curve, as presented in the table below, for the different alternatives of 50% dependable year (1980-81) and 90% dependable year

(1993-94):




R-71.2471.00.003_R0 May 2013

Table 1: Duration curve for all alternatives for 50% and 90% dependable year

The duration curves of the 50% and 90% dependable years for the different

alternatives are also presented graphically in the following three figures:

Catchment Area 7667 km2 7823 km2 7840 km2

50% 90% 50% 90% 50% 90%

1980-81 1993-94 1980-81 1993-94 1980-81 1993-94

Inflow Discharges

Month Decade m3/s m3/s m3/s m3/s m3/s m3/s

June I 512.82 395.41 523.25 403.46 524.39 404.34

II 624.00 611.28 636.69 623.72 638.08 625.08

III 902.40 594.29 920.76 606.38 922.76 607.70

July I 947.93 840.39 967.22 857.49 969.32 859.35

II 988.67 843.11 1008.78 860.27 1010.98 862.13

III 823.66 585.31 840.42 597.22 842.25 598.52

Aug I 972.45 643.20 992.24 656.28 994.39 657.71

II 549.27 516.45 560.45 526.96 561.67 528.11

III 613.86 608.08 626.35 620.45 627.71 621.80

Sep I 389.97 461.97 397.90 471.37 398.77 472.39

II 275.93 319.39 281.55 325.89 282.16 326.60

III 214.31 259.59 218.67 264.87 219.15 265.45

Oct I 194.46 169.04 198.42 172.48 198.85 172.85

II 150.75 139.85 153.81 142.69 154.15 143.00

III 123.60 103.78 126.11 105.90 126.39 106.13

Nov I 108.71 99.76 110.93 101.79 111.17 102.01

II 100.15 103.39 102.19 105.50 102.41 105.73

III 93.92 96.00 95.84 97.95 96.04 98.17

Dec I 87.83 88.09 89.61 89.88 89.81 90.07

II 87.05 87.05 88.82 88.82 89.01 89.01

III 83.73 72.29 85.44 73.77 85.62 73.93

Jan I 83.93 64.73 85.64 66.05 85.83 66.20

II 80.69 62.53 82.33 63.80 82.51 63.94

III 84.44 58.52 86.16 59.71 86.35 59.84

Feb I 76.41 59.16 77.97 60.36 78.13 60.49

II 82.64 58.77 84.32 59.96 84.50 60.09

III 83.51 78.49 85.21 80.08 85.40 80.26

Mar I 78.75 57.60 80.35 58.77 80.52 58.90

II 77.97 68.37 79.55 69.76 79.73 69.91

III 84.68 82.91 86.40 84.60 86.59 84.78

Apr I 91.33 88.48 93.19 90.28 93.39 90.47

II 130.25 89.77 132.90 91.60 133.19 91.80

III 193.82 113.77 197.76 116.09 198.19 116.34

May I 394.25 149.58 402.27 152.62 403.14 152.95

II 415.78 174.10 424.24 177.64 425.16 178.03

III 525.29 251.79 535.97 256.92 537.14 257.47

Lean

Seaso

nTra

nsi

tio

n s

easo

nTra

nsi

tio

n s

easo

n

Alternative II-A Alternative III-A Alternative IV-A

Mo

nso

on

Seaso

n




R-71.2471.00.003_R0 May 2013

Figure 13: Duration curve for all alternatives for 50% and 90% dependable year

ii) The new guidelines concerning the environmental flow (ecological water release) as stated in the inception report. The released discharges are based on

0

200

400

600

800

1000

1200

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Dis

cha

rge

[m

3/s

]

Exceedance

DUGAR HEP

Duration Curves - Alternative II-A

50% dependable year (1980-81) 90% dependable year (1993-94)

0

200

400

600

800

1000

1200

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Dis

cha

rge

[m

3/s

]

Exceedance

DUGAR HEP

Duration Curves - Alternative III-A


0

200

400

600

800

1000

1200

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Dis

cha

rge

[m

3/s

]

Exceedance

DUGAR HEP

Duration Curves - Alternative IV-A





R-71.2471.00.003_R0 May 2013

the seasonal average flows of the 90% dependable year. Definition of seasons

can be found in chapter 4.

Table 2: Environmental flow for Alternative II-A

Season Average

discharge (m

3/s)

Relation of

release (m

3/s)

Environmental

flow (QEF) (m

3/s)

Lean 69.88 20% 14.0

Transition 131.61 20% 26.3

Monsoon 556.54 30% 167.0

Table 3: Environmental flow for Alternative III-A

Season Average

discharge (m

3/s)

Relation of

release (m

3/s)

Environmental

flow (QEF) (m

3/s)

Lean 71.30 20% 14.3

Transition 134.29 20% 26.9

Monsoon 567.86 30% 170.0

Table 4: Environmental flow for Alternative VI-A

Season Average

discharge (m

3/s)

Relation of

release (m

3/s)

Environmental

flow (QEF) (m

3/s)

Lean 71.45 20% 14.3

Transition 134.58 20% 26.9

Monsoon 569.1 30% 171.0

iii) To harness the environmental flow with additional turbines (auxiliary plant) will be adapted to the alternatives where the tail water level does not reach the

dam toe during normal inflow conditions. This means alternatives II-A and III-A

release the ecological water at the dam toe, while for alternative IV-A no

release at the dam toe is foreseen.

iv) The auxiliary plant is equipped with two Francis turbines with a design discharge of 14.0 m

3/s each for alternative II-A and 14.3 m

3/s each for alternative III-A.

These means that at the beginning and the end of the monsoon season when




R-71.2471.00.003_R0 May 2013

QIN > QEF >QD certain energy losses due to water spill at the dam will occur for

alternatives II-A and III-A.

v) No optimization of the installed capacity of the main plant has been carried out. The chosen installed capacity for the comparison of all alternatives is the one

which harnesses the same inflow water volume for the 50% dependable year.

This means the design discharge for the main plant for alternatives II-A and III-A

is fixed at 452 m3/s, while the one for alternative IV-A results 481 m

3/s

(452 m3/s + 29 m

3/s).

vi) Due to the higher discharge for ecological water release the main plant for alternatives II-A and III-A will be operated fewer days at full capacity than

foreseen in the feasibility study, i.e. the overall plant load factor for alternatives

II-A and III-A is somewhat smaller than that one for alternative IV-A.

vii) The efficiency for Francis turbines varies to a certain extent for flows differing from the design discharge. Indications for the variation in efficiency can be

found in the technical literature. For details see the following charts below.

Values according to technical literature

Figure 14: Efficiency for different turbine types




R-71.2471.00.003_R0 May 2013

Figure 15: Efficiency for Francis adopted for energy calculation

The basic parameters for the main plant of the different alternatives are as follows:

Table 5: Basic parameters for main plant

Alternatives

Parameter II-A III-A IV-A-1

Nominal discharge (QN) m3/s 452.0 452.0 481.0

Gross head for QN m 94.1 94.1 94.1

Head losses water

conveyance system

m 2.6 1.9 1.9

Nominal head for QN m 91.5 92.2 92.2

Machine efficiency (full

capacity)

- 0.90 0.90 0.90

Total installed capacity MW 365.2 368.0 392.0

Number of units - 4 4 4

Installed capacity per

unit

MW 91.3 92.0 98.0

The basic parameters for the auxiliary plant of the different alternatives are as follows.

Note that for alternative IV-A no auxiliary plant has been foreseen. The main turbines will

be used to release the ecological water:




R-71.2471.00.003_R0 May 2013

Table 6: Basic parameters for auxiliary plant

Alternatives

Parameter II-A III-A IV-A-1

Nominal discharge m3/s 14.0 14.5 ---

Average gross head m 69.43 88.21 ---

Head losses water

conveyance system

m 2.00 2.00 ---

Nominal head m 67.43 86.21 ---

Machine efficiency (full

capacity)

- 0.90 0.90 ---

Total installed capacity MW 16.7 22.1 ---

Number of units - 2 2 ---

Installed capacity per

unit

MW 8.35 11.05 ---

6.2 Expected Energy Production for the 50% Dependable Year

For comparison of the three alternatives the energy production has been determined using

the available water volumes corresponding to the 50% dependable year and the basic

parameters for main and auxiliary plants as given in the subchapter above. As already

mentioned before, alternative IV-A is without extra installation of an auxiliary plant at the

dam toe, because the environmental flow will be assured using the units housed in the

main powerhouse.

The resulting energy production with the main and the auxiliary plant for the different

alternatives are as presented in the table below:



Alternative Study Report

R-71.2471.00.003_R0

Table

The operating hours consider:

- The units housed in the main powerhouse are operating always at full capacity.

- In the case of Alternative IVsatisfy the requirements of the environmental water release operates always 24 hours

a day but not always at full capacity. However, the operating hours given in the table

above correspond to the equivalent hours of this unit with full capacity. A tentative

operation mode during a hydrological mean (50% dependable year) year, as used for

the determination of the energy production, is presented in the table below:

Table 7: Expected energy production for main and auxiliary plant

The operating hours consider:

The units housed in the main powerhouse are operating always at full capacity.

In the case of Alternative IV-A: The unit housed in the main powerhouse used to

satisfy the requirements of the environmental water release operates always 24 hours


e correspond to the equivalent hours of this unit with full capacity. A tentative



33/77

May 2013

Expected energy production for main and auxiliary plant

The units housed in the main powerhouse are operating always at full capacity.

A: The unit housed in the main powerhouse used to

satisfy the requirements of the environmental water release operates always 24 hours


e correspond to the equivalent hours of this unit with full capacity. A tentative






R-71.2471.00.003_R0 May 2013

Table 8: Expected energy production for main and auxiliary plant

- In the auxiliary plant the two units operates during monsoon and transition season 24 hours a day and during the lean season only one turbine is operating 24 hours a day,

i.e. the days of the lean season are considered with 12 hours at full capacity.

The overall plant load factor is determined using both plants, the main and the auxiliary

ones, operating all available turbines (4 units in the main plant and two in the auxiliary

plant) always at full capacity, i.e. it represents an equivalent and not a real plant load

factor.

7 COST ESTIMATE OF THE DIFFERENT ALTERNATIVES

7.1 General considerations

For each alternative the expected project costs for design and construction of civil “C”,

hydromechanical steel structures “HSS” and electromechanical equipment “EM” have been

determined. To calculate the total investment cost, other costs such as for, Establishment

and Tools & Plants (II), Buildings (III), Land acquisition (IV), Roads & Bridges (V) and Other

direct & indirect charges as per CEA (VI) have been added.

Cost has been worked out as per the “CEA Guidelines for Formulation of Detailed Project

Reports for Hydro Electric Schemes, Their Acceptance and Examination for Concurrence”,

April 2012 (Revision 3.0).

QIN Q24h Required Q24h > Qrelease

QD Time QD Time QD Time QD Time Qreleasem3/s m3/s h/day m3/s h/day m3/s h/day m3/s h/day m3/s m3/s

1'074.0 0.00%1'007.2 2.00% 120.75 24.0 120.25 24.0 120.25 24.0 120.25 24.0 481.50 170.7 yes

986.2 5.00% 120.75 24.0 120.25 24.0 120.25 24.0 120.25 24.0 481.50 170.7 yes911.3 10.00% 120.75 24.0 120.25 24.0 120.25 24.0 120.25 24.0 481.50 170.7 yes662.4 15.00% 120.75 24.0 120.25 24.0 120.25 24.0 120.25 24.0 481.50 170.7 yes639.6 16.51% 120.75 24.0 120.25 24.0 120.25 24.0 120.25 24.0 481.50 170.7 yes586.8 20.00% 120.75 24.0 120.25 24.0 120.25 24.0 120.25 24.0 481.50 170.7 yes556.2 22.82% 120.75 24.0 120.25 24.0 120.25 24.0 120.25 24.0 481.50 170.7 yes532.6 25.00% 120.75 24.0 120.25 24.0 120.25 24.0 120.25 24.0 481.50 170.7 yes421.9 30.00% 96.08 24.0 96.08 24.0 113.00 20.2 113.00 20.2 192.16 170.7 yes406.1 33.42% 96.60 24.0 96.60 23.4 113.00 15.6 113.00 15.6 193.20 170.7 yes398.9 35.00% 84.53 24.0 120.25 21.2 120.25 21.2 120.25 21.2 84.53 26.9 yes231.8 40.00% 84.53 24.0 120.25 15.4 120.25 15.4 120.25 15.4 84.53 26.9 yes198.4 45.00% 84.53 24.0 120.25 11.3 120.25 11.3 120.25 11.3 84.53 26.9 yes144.7 50.00% 48.30 24.0 120.25 8.7 120.25 8.7 120.25 8.7 48.30 26.9 yes123.1 55.00% 102.64 24.0 120.25 8.2 120.25 8.2 120.25 8.2 102.64 26.9 yes102.4 60.00% 101.69 24.0 120.25 2.1 120.25 2.1 120.25 2.1 101.69 26.9 yes93.9 65.00% 89.76 24.0 120.25 0.7 120.25 0.7 120.25 0.7 89.76 26.9 yes90.3 68.85% 84.50 24.0 120.25 0.6 120.25 0.6 120.25 0.6 84.50 26.9 yes89.3 70.00% 81.83 24.0 96.08 0.5 120.25 0.5 120.25 0.5 81.83 14.3 yes86.5 75.00% 77.47 24.0 96.60 0.5 120.25 0.5 120.25 0.5 77.47 14.3 yes85.8 80.00% 72.13 24.0 120.25 0.7 120.25 0.7 120.25 0.7 72.13 14.3 yes85.4 85.00% 66.79 24.0 120.25 0.9 120.25 0.9 120.25 0.9 66.79 14.3 yes82.8 90.00% 61.44 24.0 120.25 1.3 120.25 1.3 120.25 1.3 61.44 14.3 yes80.0 95.00% 56.10 24.0 120.25 1.5 120.25 1.5 120.25 1.5 56.10 14.3 yes77.7 100.00% 50.76 24.0 120.25 1.7 120.25 1.7 120.25 1.7 50.76 14.3 yes

U1 U2 U3 U4




R-71.2471.00.003_R0 May 2013

7.2 Civil works (C)

The estimate of cost for civil works is based on the planning and preliminary design of

different components of works for each alternative.

A provision of 3% of the cost has been made to cover contingencies and work charged staff

in the estimates of different components of civil works. The contingencies have not been

taken on items for which a lump sum amount has been provided.

The estimates are based on the prices prevailing in April 2013, for materials, equipment,

labour etc. The considered unit prices are given in Appendix 1 and the cost for all civil items

are summarized in chapter 7.6 of this report.

7.2.1 River Diversion works

The river diversion works for the concrete gravity dam layout consist mainly of upstream

and downstream cofferdams and diversion tunnels. Hence, the civil work cost consists of

the cost for the diversion tunnels and the cofferdams.

The quantity of concrete (surface, backfill and lining), reinforcement, excavation

(underground and surface) and support works (shotcrete with wire mesh, rockbolts,

drainage holes, ribs etc.) have been estimated to calculate the cost of diversion tunnels for

each alternative. For the determination of the tunnel cost, 5 rock classes are considered

with the following distribution:

Rock class I Good rock 20%

Rock class II Fair rock 35%

Rock class III Poor rock 30%

Rock class IV Very poor rock 10%

Rock class V Extremely poor rock 5%

Quantities of cofferdam material for compacted random fill, jet grouting, filter material,

riprap etc. are considered for the cost of cofferdam for each alternative.

7.2.2 Dam

The cost of the concrete gravity dam consists of cost for surface excavation (soil and rock

excavation), different grades of concrete, reinforcement steel, support works (shotcrete,

rockbolts, drainage holes etc.) and the grout curtain (drilling and grout material).

The required quantities of excavation, concrete, reinforcement, support works, grout

curtain etc. have been computed for each alternative.




R-71.2471.00.003_R0 May 2013

7.2.3 Intake

The cost of the Power Intake consists of cost for surface excavation, concrete,

reinforcement steel, support works (shotcrete, rockbolt, drainage holes etc).

The quantities of excavation, concrete, reinforcement, support works have been computed

for each alternative.

7.2.4 Head Race Tunnel Quantity of concrete (surface for portal, backfill and lining), reinforcement, excavation

(underground and surface) and support works (shotcrete with wire mesh, rockbolts,

drainage holes, ribs etc.) have been estimated to calculate the cost for the Head Race

Tunnels for each alternative. For determination of the tunnel cost, 5 rock classes are

considered with the following distribution:

Rock class I Good rock 20%

Rock class II Fair rock 35%

Rock class III Poor rock 30%

Rock class IV Very poor rock 10%

Rock class V Extremely poor rock 5%

7.2.5 Surge Shaft

Cost for surge shaft is basically composed of the cost for underground rock excavation,

support works such as shotcrete with wire mesh, rockbolts, drainage holes, ribs as well as

permanent concrete lining with reinforcement.

7.2.6 Pressure Shaft/ Tunnel

The cost for the pressure shafts are determined in the same way as for the HRTs with the

only difference that in addition a steel liner is considered. A higher unit price has been

considered for the excavation of the vertical shafts than of the horizontal tunnels.

7.2.7 Adits and Access Tunnel in Powerhouse Area

The cost for Adits and Access tunnels in Powerhouse Area are determined in the same way

as done for the Headrace Tunnels.

7.2.8 Powerhouse complex

Cost for civil works for the powerhouse are determined based on the underground rock

excavation, concrete (substructure and superstructure), support works such as shotcrete

with wire mesh, rock bolts, drainage holes, ribs and reinforcement.




R-71.2471.00.003_R0 May 2013

The civil cost of transformer cavern is also included in the cost of Powerhouse complex.

7.2.9 Tailrace Tunnel

The cost for the tailrace tunnels is determined in the same way as the costs for the

Headrace Tunnels.

7.2.10 Switchyard

The cost of switchyard consists of cost of surface excavation (soil and rock excavation),

concrete, reinforcement steel, support works (shotcrete, rockbolt, drainage holes etc) etc.

7.3 Hydromechanical steel structures (HSS)

This head includes the cost of hydromechanical equipment comprising of gates, stoplogs,

hoists, its supporting structures and trash racks etc. The cost for these items are provided

on the dam, intake, diversion tunnel, power house, draft tube and tailrace for storage of

water, controlling discharge, generation of power and for maintenance purposes.

7.4 Electromechanical equipment (EM)

The estimated cost of Electro – mechanical equipments with 10% over load including unit &

station auxiliary systems, Electrical & Mechanical BOP equipments, Generators

transformers, GIS equipment & Pothead yard equipments is based on current price level

for similar machines.

The cost includes all taxes & duties, service taxes, insurance & transportation, erection &

commissioning of the equipment on turnkey basis.

The taxes & duties, insurance & transportation are based on prevailing rates. The erection

& commissioning charges has been considered as 8% of equipment cost.

7.5 Other cost

7.5.1 Establishment, Tools and Plants

This provision includes establishment cost during construction and cost of survey

instruments, camp equipment, office equipment and other small tools. This provision also

includes establishment for carrying out site supervision, quality control and cost control

cell. The establishment cost is evaluated as per section 16.5 of the CEA Guidelines, April

2012. Establishment cost is evaluated as percentage of the cost of the civil works. In the

present case cost of civil works (I works as per CEA format) is more than 750 Crores for all

alternatives, therefore, establishment cost is considered as 60 Crores plus 4% of the civil




R-71.2471.00.003_R0 May 2013

works cost exceeding 750 Crores. For tools & plants a provision of 2 Crores has been kept

as per section 16.6 of CEA guidelines. The costs of this provision for each alternative have

been given in Section 7.6 of this report.

7.5.2 Buildings

Provision has been made under this sub-head for permanent and temporary residential

buildings for various categories of staff, non-residential buildings for offices, workshops,

stores, rest houses and field hostels and other service buildings such as hospital, school

and utility services etc. The cost for buildings has been considered the same for all

alternatives.

7.5.3 Land

This covers the provision for acquisition/purchase of land for permanent works, approach

roads, camp sites, workshops, stores, offices and permanent colony for the maintenance

staff etc. The costs of land for each alternative have been given in Section 7.6 of this

report.

7.5.4 Roads and bridges

Provision has been made under this sub-head for construction of roads and bridges.

Provision has also been made for remodelling and strengthening of main highway and

bridges, including winter road treatment and snow removal to make them suitable for

transport of heavy equipment.

7.5.5 Other direct and indirect charges

This head includes expenses during pre-construction, capital cost and maintenance of

electrification, water supply, sewage disposal and drainage works, recreation, medical, fire

fighting equipment, inspection vehicles etc., cost of plantation, maintenance cost during

construction, compensatory afforestation, measures for maintaining environment and

ecological balance of the area, public health measures, treatment of catchment area etc.

7.6 Cost summary of basic alternatives

The resulting costs for each basic alternative are as presented in the following three tables

all alternatives with the same dam type – gravity dam - and the same powerhouse

complex):




R-71.2471.00.003_R0 May 2013

Table 9: Total investment costs for Alternative II-A (basic alternative)

Table 10: Total investment costs for Alternative III-A (basic alternative)

1 River diversion works 10'440 449 10'889 5.6%

2 Dam 39'810 4'413 106 44'329 22.8%

3 Intake 3'750 1'687 5'437 2.8%

4 Head race tunnel 35'380 35'380 18.2%

5 Surge shaft 8'280 8'280 4.3%

6 Adits to surge shaft 900 900 0.5%

7 Pressure tunnel and pressure shaft 1'190 3'431 4'621 2.4%

8 Adits and access tunnels in PH area 3'450 25 3'475 1.8%

9 Powerhouse cavern for main units 8'190 739 49'451 58'381 30.0%

10 Transformer cavern & GIS 7'358 7'358 3.8%

11 Tail race tunnel 10'240 541 10'781 5.5%

12 Pothead yard i/c connection to National Grid 700 412 1'112 0.6%

13 Auxiliary plant incorporated in the dam 220 3'555 3'776 1.9%

I Total Construction Cos: 122'330 11'506 60'883 194'719 100.0%

Rate in respect to total construction cost A [%] 62.8% 5.9% 31.3% 100.0%

II Establishment and Tools & Plants 8'830 4.5%

III Buildings 2'472 1.3%

IV Land Acquisition 3'221 1.7%

V Roads & Bridges 2'378 1.2%

VI Other direct & indirect charges as per CEA 11'073 5.7%

222'693 114.4%

S.NO. COMPONENTAlternative II-A - basic

Amount (INR in Lacs)

TOTAL INVESTMENT COSTS

C HSS RATE [%]TOTALEM


2 Dam 49'130 4'528 106 53'764 31.6%

3 Intake 2'990 1'646 4'636 2.7%

4 Head race tunnel 6'410 6'410 3.8%

5 Surge shaft 3'540 3'540 2.1%

6 Adits to surge shaft 810 810 0.5%





11 Tail race tunnel 10'240 541 10'781 6.3%


13 Auxiliary plant incorporated in the dam 220 4'191 4'412 2.6%








198'566 116.5%

S.NO. COMPONENTAlternative III-A - basic



C TOTAL RATE [%]HSS EM




R-71.2471.00.003_R0 May 2013

Table 11: Total investment costs for Alternative IV-A (basic alternative)

The comparison of the total investment costs of the different basic alternatives are as

illustrated in the table below:

Table 12: Summary of total investment costs for all basic alternatives

Alternative III-A leads to the lowest investment cost for the basic solution.

The following table shows the cost comparison of the different components, as river

diversion works, dams, headrace tunnels, auxiliary plant and land acquisition, which

interferes mainly on the variable cost. This is overall due to the entire arrangement of the

water conveyor system from the upstream surge shaft on, as well as the whole

underground powerhouse complex (including electromechanical equipment) are the same

for alternatives II-A and III-A, while for Alternative IV-A the installed capacity is somewhat

higher and consequently also the costs. Furthermore as already mentioned in Chapter 6.1

the environmental water release for alternative IV-A will be harnessed with the units

installed in the main plant. Therefore no auxiliary plant for this alternative is required.


2 Dam 52'160 4'528 106 56'794 32.9%

3 Intake 2'890 1'605 4'495 2.6%

4 Head race tunnel 5'650 5'650 3.3%

5 Surge shaft 3'480 3'480 2.0%

6 Adits to surge shaft 1'460 1'460 0.8%





11 Tail race tunnel 10'240 541 10'781 6.2%


13 Auxiliary plant incorporated in the dam 0 0.0%








200'099 115.9%

S.NO. COMPONENTAlternative IV-A - basic


TOTAL RATE [%]


C HSS EM


base base baseI Total Construction Cost: 194'719 170'371 172'600

II - VI Total other costs 27'974 28'194 27'499

Total Investment Cost: 222'693 198'566 200'099112.2% 100.0% 100.8%




R-71.2471.00.003_R0 May 2013

Table 13: Cost comparison for different components for all alternatives

The above figures show that:

- The cost saving for the smaller dam in alternative II-A with respect to the more downstream alternatives and smaller cost for land acquisition do not compensate the

higher cost of the long required headrace tunnel (internal diameter of 10.0 m for basic

solutions).

- The cost saving in alternative IV-A for the not required additional auxiliary plant does not compensate the higher cost for the higher dam and the longer diversion tunnel, as

well as the higher cost due to increased capacity in the main powerhouse

Due to the above described facts the alternative III-A leads to the lowest investment cost.

8 OPTIMIZATION OF BASIC ALTERNATIVES

8.1 Cost Saving Potential of the Basic Alternatives

For the sake of comparison of the selected alternatives in a first step the same dam type

(concrete gravity dam) and the same gate arrangement (4 gated spillway openings at the

top of the dam and two bottom outlet openings), as well as an arbitrary chosen internal

diameter of the headrace tunnels with 10.0 m, have been considered for all three

alternatives. The corresponding results of the first step are presented in chapter 6 “Energy

production” and chapter 7 “Cost estimate”. The second step consists in identifying the

potential of cost saving to obtain the most optimized layout for each alternative. The

possibilities to lower the construction cost are in general:

- Changing the dam type from a gravity dam into an arch-gravity or double curved arch dam.

- Taken into account an optimized internal diameter for the headrace tunnel.


base base base

1 C River diversion works 10'440 10'680 13'1802 C Dam 39'810 49'130 52'1604 C Head race tunnel 35'380 6'410 5'650

9 EM Powerhouse 49'451 49'765 51'10510 EM Transformer & GIS 7'358 7'358 7'44012 HSS Auxiliary Plant 220 220 012 EM Auxiliary Plant 3'555 4'191 0

IV Land Acquisition 3'221 4'751 4'836

TOTAL 149'437 132'505 134'370112.8% 100.0% 101.4%




R-71.2471.00.003_R0 May 2013

The following comment has been given in the Inception Report (No. 71.2471.00.001) about

the feasibility/suitability of different concrete dam types in respect to morphology and

geology matters:

Table 14: Feasibility for different concrete dam type based on findings of Inception Report

Alternative Gravity Arch-Gravity Double Curved Arch

II-A feasible feasible feasible

III-A feasible feasible feasible

IV-A feasible not suitable not suitable

As described in the Inception Report the non-suitability of the arch-gravity and double

curved arch dam type for alternative IV-A is due to:

- Extremely asymmetrical cross section

- Unfavourable discontinuity planes in the right abutment

Concerning the possibility for the construction of a double curved arch dam at the dam

sites of alternatives II-A and III-A the evacuation of the PMF (Probably Maximum Flood –

8’700 m3/s) has to be guaranteed and therefore the required evacuation system, as

spillway and bottom outlets have to be able to discharge the arriving flood to the

downstream side of the dam. In the case of Dugar HEP an important rule plays the fact that

the reservoir level immediately upstream of the dam cannot be raised above the maximum

normal reservoir level (FRL). The consequence of this requirement is that an ungated

evacuation systems cannot be foreseen. This implies that only gated evacuation systems

are to be installed either in the dam body or in other adjacent structures, as surface

spillways or spillways with underground evacuation tunnels.

In the following it will be highlighted if an evacuation system with less construction cost

than the possible available cost saving due to the change of the dam type from an arch-

gravity dam into a double curved arch dam can be found. Considering that the already 4

bottom outlets foreseen in the arch-gravity dam would be placed in the lower part of the

double curved arch dam, the capacity of the additional spillway system has to be the same

as for the surface spillways considered for the arch-gravity dam. The capacity has to be

equal to 6’250 m3/s.

The cost saving for a double curved arch dam with respect to the gravity dam is estimated

in the order of 55%, which leads to a cost reduction of:

- 12’000 INR Lacs for alternative II-A; and

- 14’500 INR Lacs for alternative III-A.




R-71.2471.00.003_R0 May 2013

In the case a surface spillway located at the projection of the dam crest, equipped with the

same 6 gates (opening width 12 m and gate height 12.5 m) as for the gravity dam solution,

would be foreseen in one or both abutments. The construction cost of the whole spillway,

including forebay, gate block and chute with flip bucket can be estimated. For definition of

gate block see the sketch below. In a first step only the cost for excavation, including

support measures plus the construction cost for the structure of the gate block are

considered.

Figure 16: Definition of gate block

Considering a pier thicknesses of 3.5 m, the total width of the gate blocks results in a

length of 118.0 m for all openings on the same abutment and 57.0 m for three openings on

each abutment. With an excavation slope of 1 horizontal to 4 vertical and considering a

berm with a width of 4 m every 12 m in height an overall excavation slope of 1 : 1.71 (H :

V) is resulting. This slope corresponds to an inclination of around 60° in respect to the

horizontal. If the natural terrain slope is also 60° or more, no intersection between

excavation slope and the natural terrain is possible. For flatter slopes the cost is a function

of the terrain slope of the abutments at the dam site. The total construction cost

(excavation, support measures and construction of gate structure) for the 38 long gate

block versus slope inclination of the abutment terrain is shown in the Figure 17 below. For

the cost calculation the following prices have been considered:

- 525 INR per m3 of surface rock excavation;

- 30% of the excavation cost for support measures;

- 1’500 INR Lacs for one spillway opening.



Alternative Study Report

R-71.2471.00.003_R0

As depicted in this chart the total construction cost of the whole surface spillway placed in

the abutments of the dam will never be lower than the cost saving due to dam type

changing, because to the indicated cost in the picture additional costs for the

chute, including flip bucket (excavation plus reinforced concrete structure) and the

excavation of the forebay has to be added. The excavation height is around 170 and 300 m

for alternative III-A and alternative II

started at elevation 2’260 and 2’390 masl for alternative III

respectively.

Due to the mentioned arguments before the solution with surface spillway openings in the

abutments is technically and economically not fe

as a possible evacuation system for a dam layout with a double curved arch dam.

This implies that only the solution with

invert of such tunnels could be placed more or less

structures. In the following charts the required internal diameter of the concrete lined

evacuation tunnels for different tunnel lengths (250 m and 350 m) are presented.

Figure 17: Construction cost for gate blocks



changing, because to the indicated cost in the picture additional costs for the



A and alternative II-A respectively. This means the excavation has to be

started at elevation 2’260 and 2’390 masl for alternative III-A and alternative II

Due to the mentioned arguments before the solution with surface spillway openings in the

abutments is technically and economically not feasible and can therefore be dropped out

as a possible evacuation system for a dam layout with a double curved arch dam.

This implies that only the solution with underground evacuation tunnels

invert of such tunnels could be placed more or less at the same elevation as the intake

structures. In the following charts the required internal diameter of the concrete lined

evacuation tunnels for different tunnel lengths (250 m and 350 m) are presented.

44/77

May 2013



changing, because to the indicated cost in the picture additional costs for the spillway



xcavation has to be

A and alternative II-A

Due to the mentioned arguments before the solution with

Documents

ALTERNATIVE STUDY REPORTenvironmentclearance.nic.in/writereaddata/Online/TOR/0_0... · 2014-11-11 · Dugar HEP is in hilly terrains of the Higher Himalayas situated in the State