Kaigah HPP -Executive Summary

8/12/2019 Kaigah HPP -Executive Summary

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ASSOCIATEDTECHNOLOGIES(PVT)LIMITED

FEASIBILITYSTUDYREPORT

Executive

Summary

FEBRUARY 2014

545 MW KAIGAH

HYDROPOWER PROJECT


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Feasibility Study of 545 MWKaigah Hydropower Project Executive Summary

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Table of Contents

1. PROJECT HISTORY ................................................................................................... 4

2. PRESENT STUDY ....................................................................................................... 4

3. CONFIGURATION OF FEASIBILITY STUDY REPORT ............................................. 6

4. SALIENT FEATURES ................................................................................................. 6

5. PROJECT LOCATION ................................................................................................ 7

6. ACCESSIBILITY .......................................................................................................... 8

7. TOPOGRAPHIC AND HYDROGRAPHIC SURVEYS ................................................. 9

8. HYDROLOGY & SEDIMENTATION .......................................................................... 10

9. GEOLOGICAL AND GEOTECHNICAL STUDIES .................................................... 10

10. NEOTECTONICS AND SEISMIC HAZARD ANALYSIS ....................................... 12

11. PROJECT LAYOUT STUDIES .............................................................................. 12

11.1. Stream Flow Records ....................................................................................... 13

11.2. Hydraulic Scheme ............................................................................................. 13

11.3. Geological and Geotechnical Restr ictions ..................................................... 14

12. CAPACITY OPTIMIZATION AND POWER POTENTIAL ...................................... 15

13. DESIGN OF PROJECT STRUCTURES ................................................................ 15

13.1. Diversion Tunnel ............................................................................................... 15

13.2. Pre-Cofferdam ................................................................................................... 16

13.3. Upstream Cofferdam ........................................................................................ 16

13.4. Downstream Cofferdam ................................................................................... 16

13.5. Dam .................................................................................................................... 16

13.6. Spi llway .............................................................................................................. 17

13.7. Bottom Outlet .................................................................................................... 17

13.8. Intake Structure ................................................................................................. 18

13.9. Headrace Tunnel ............................................................................................... 19

13.10. Surge Tank ........................................................................................................ 20

13.11. Powerhouse, Cavern of Transformers and Appurtenant Works .................. 20


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13.12. Discharge Works ............................................................................................... 21

13.13. Thauti Nullah Derivation and Headrace .......................................................... 22

14. MECHANICAL EQUIPMENT ................................................................................. 22

15. ELECTRICAL EQUIPMENT STUDIES .................................................................. 24

16. POWER TRANSMISSION LINE STUDIES ............................................................ 24

17. TRANSPORTATION STUDY ................................................................................. 24

18. ENVIRONMENTAL STUDIES ................................................................................ 26

19. COST ESTIMATES & FINANCIAL ANALYSIS ..................................................... 26


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EXECUTIVE SUMMARY

Kaigah Hydropower Project has been proposed on the River Kandiah, a tributary of River

Indus upstream of proposed Dasu Hydropower Project. The Project area is spread fromupstream of Karrang village to a few kilometers downstream of Thuati Bridge in Kandiah Valley

with profile length of approximately 23 km. The site is accessible from Islamabad via

Mansehra-to Thakot and via Karakorum Highway to Dasu town at 340 km from Islamabad.

The Project site is about 55 Km from Dasu town.


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1. PROJECT HISTORY

With the financial assistance of Canadian International Development Agency (CIDA) to

Pakistan, identification of Hydropower Potential on Rivers Indus, Jhelum and Swat started

during 1980s, and Montreal Engineering Company Limited (MONENCO) was engaged toundertake the preparation of an inventory of potential hydropower generation sites, alongwith

their ranking.

Later, during the eighties and nineties, identification and ranking studies for hydropower

schemes on the Rivers and tributaries of Azad Jammu and Kashmir (AJK) and Khyber

Pakhtunkhwa (KPK) including Northern Areas of Pakistan were also carried out by WAPDA

and Pakhtunkhwa Hydel Development Organization (PHYDO) in collaboration with the

German Agency for Technical Co-Operation (GTZ). A number of sites for development of

small and medium size hydropower projects, including Kaigah Hydropower Project in the

Kohistan Valley, with power potential of 548 MW, were identified.

PPIB issued LOI to the sponsors in 2008. Associated Technologies (Pvt) Limited (ATL) is the

Main Sponsor and Consultants of Colombian origin M/s. Integral S.A. were taken on board to

carry out the Feasibility study and prepare a bankable Feasibility Study Report (FSR).

2. PRESENT STUDY

A number of site studies and analyses have been made for all Project components, including

the location of dam, spillway, diversion and power / headrace tunnels and the powerhouse.

Reservoir level is fixed at 1500 m.a.s.l taking into account the proposed upstream Karrang

Hydropower Project.

The Consultants studied four layout options with the project components on the right and left

bank side. Drill & Blast alongwith TBM underground construction methods were analysed.

Detailed studies have been carried out for alternative under consideration. As a result of these

studies left bank alternative has been selected for its technical and economic viability.

The left bank layout proposal has a headrace system composed of the main headrace tunnel,

pressure shaft and three penstock tunnels that will deliver the water to the three turbines ofthe project. The headrace tunnel is of approximately 17 km of length with five horizontal curves

with the radius 3 times the diameter of tunnel and a constant slope of 1%. At the end of the

headrace the pressure shaft begins and connects with the powerhouse.

Drill and blast construction method is being considered for the excavation of headrace tunnel

and pressure shaft.

The underground powerhouse is located on Thauti Nullah right bank, followed by tailrace

tunnel of 3.3 km in length until it discharges in the Kandiah River.

The powerhouse is of cavern type where the turbine-generator sets for the three generator

units and the other auxiliary equipment are located. In a parallel cavern the power


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transformers and the corresponding auxiliary equipment are to be installed. The two caverns

are interconnected by an access gallery between the main floors, and by three bar output

galleries.

The scheme has the possibility to include two additional intakes at Thauti Nullah, with a total

additional discharge of 11 m3/s, which will increase the annual energy production, and have a

positive impact on the economic viability. At the chainage 13360 m, the Thauti Nullah

headrace tunnel will deliver the water from the Thauti Nullah river to the main headrace tunnel.

To firm up the location of the project components detailed surface and sub-surface geologicaland geotechnical investigations have been carried out. More than 1100 m of drilling was done

along with test pits and geological mapping.

These investigations have shown a thick alluvial layer on the dam site, which played an

important role to decide the configuration of the dam as Asphalt Faced Rockfill Dam (AFRD).

Detailed neo-tectonic and seismic hazard and risks studies were also carried out, keeping in

view high seismic activity of the area.

The overall findings of the EIA studies show that the Kaigah Hydropower Project is

environmentally and socially viable subject to the development and implementation of a full

Environmental Management Plan brought out in the study.

Detailed construction schedule of Kaigah Hydropower Project has been estimated to be

completed during a period of 55 months.

The EPC cost estimate for Civil and E&M Works along with detailed BoQs is provided in

chapter for costs while the Non-EPC Costs are estimated based on best international practices

and in line with the costs finalized for all other similar projects in Pakistan. The Total Estimated

Project Cost is 1,564.761 million USD.


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Cash flows of Project are discounted at the cost of capital (6.79%) and the NPV of the Project

resulted into USD 464.07 million, which passes the NPV test for the acceptance of Project as

a profitable investment.

3. CONFIGURATION OF FEASIBILITY STUDY REPORT

The Feasibility Report has been prepared in fourteen (14) volumes, which are:

a) Volume 1 Main Report

b) Volume 2 Topographic Survey Study Report

c) Volume 3 Hydrology and Sedimentation Study Report

d) Volume 4 Geological and Geotechnical Study Report

e) Volume 5 Neo-tectonic and Seismic Hazard Analysis

f) Volume 6 Hydropower Planning Study Report

g) Volume 7 Dam & Generation Works Study Report

h) Volume 8 Mechanical Equipment & Hydraulic Steel Structures

i) Volume 9 Electrical Equipment Study Report

j) Volume 10 Transportation Study Report

k) Volume 11 Transmission Line Study Report

l) Volume 12 Environmental & Social Impacts Assessment Study Report

m) Volume 13 Cost Estimates & Financial Analysis

n) Volume 14 Project Drawings

4. SALIENT FEATURES

This report has been finalized with the salient features described as under.

Hydrology (Design f lows)

Design discharge 125 m3/s

Mean Annual Flow 68.3 m3/s

Design flood (PMF) 2113 m3/s

Reservoir

Reservoir length 3500 m

Reservoir area 74300 m2

Max. reservoir operating level 1500 m.a.s.l

Min. reservoir operating level 1480 m.a.s.l

Reservoir capacity at 1500 m.a.s.l 40.39 MCM

Reservoir capacity at 1480 m.a.s.l 19.65 MCM

Dam Structure

Dam height 100 m

Dam crest level 1510 m.a.s.l

Dam crest length 400 m

Spillways

No. of Bays 1

Number of gates Ungated

Discharge capacity 2150 m3/s


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Bottom Outlet

No. of bays 3

Guard gate type sliding gate

Guard gate size (WxH) 3.0 x 6.0 m

Gate type Radial gate

Gate size (WxH) 3.0 x 6.0 mDischarge capacity 407.5 m3/s

Power Waterways

Power Intake

Type Deep Frontal

No. of gates 2

Gate size (WxH) 5.3 x 6.7 m

Deck elevation 1511.0 m.a.s.l

Intake sill level 1464.0 m.a.s.l

Headrace Tunnel

Diameter 7.7 mLength 17058 m

Surge Shaft

Diameter 5.30 m

Height 38.67 m

Surge Tank

Diameter 10.5 m

Height 260 m

Power Generation

Gross head (HWL-Turbine centre line) 527.35 m

Max. Net head 523.9 m

Min. Net head 480.0 mPlant Design discharge 125 m3/s

Installed plant capacity 545 MW

Plant Factor 44.24 %

Turbine Type Pelton vertical

No. of units 3

Turbine centerline level 972.65 m.a.s.l

Generator 3

Design Annual mean energy 2112 GWh

Power house type Cavern .

Size of powerhouse (LxWxH) 105.5x27.1x47.9 m.Transmission line 500 KV

Tailrace Tunnel

Size of tunnel 8 m

Length of tailrace tunnel 3,383.4 m

Project Cost 1564.8 MUSD

Levelized Tariff 9.5 Cents/KWh

5. PROJECT LOCATION

The proposed Kaigah Hydropower Project is identified along Kandiah River with dam nearKarrang village and powerhouse site is on left bank of Kandiah River.


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Kandiah River has its confluence with the Indus River near Kandiah Bridge, about 20

kilometers upstream of Dasu town.

Table 5-1: Coordinates of Dam and Powerhouse SiteSite Latitude Longitude

Dam site 35-28-26.9 72-58-16.9Powerhouse site 35-28-49 73-08-34

The dam site identified near Karrang village is about 28 km in the Kandiah valley from the

confluence of Indus and Kandiah Rivers. It has a reservoir spread over 4 km in the

upstream valley. The dam axis is proposed downstream of confluence of Bangroan Khwar

on the right bank and of Dadli Khwar on the left bank where the Kandiah valley becomes

narrow and the valley slopes become steep and form the entrance of a ravine.

The River bed elevation at dam site has been observed as 1420 m a.s.l and reservoir

level is proposed as 1500 m.a.s.l. The headrace tunnel crosses the mountains on the left

River bank to the powerhouse cavern, which is situated on the left Kandiah bank near

Thauti village. Previously, the headrace tunnel was proposed on the right bank of Kandiah

River which followed a nearly straight line upto then proposed powerhouse location just

opposite to the village Kaigah, on the right bank of River Indus.

The powerhouse cavern was proposed at an elevation approximately 800 m a.s.l but to

cater for the proposed Dasu Hydropower Project, cavern had to be shifted ahead of the

maximum reservoir level of approximately 950 m.a.s.l.

6. ACCESSIBILITY

Dasu town is located about 340 kilometers from Islamabad. The main accessibility to

Dasu town from down country is through the Karakoram Highway. Dam site is accessible

from Dasu town by a jeepable road. Karrang village is located on Kandiah Kalam Road

about 30 kilometers from Kandiah Bridge and connected to the latter through a jeepable

road which has been badly damaged by flashy floods of 2010.

A jeepable road exists in Kandiah valley on its right bank between KKH upto a few

kilometers upstream of Karrang village. The scheme is recommended to be constructed

before upstream identified project Karrang is developed, therefore the improvement ofexisting roads and construction of new access roads between KKH and Karrang are

necessary. The access road must be designed for heavy loads.

The construction of an Indus bridge is necessary to connect the next access road system

in Kandiah valley with the KKH on the left Indus bank. It is estimated that about 28 km

long length of the truckable roads is necessary to be upgraded, including some bridges

to make the various construction sites accessible.

Post flood 2010 conditions necessitate to rebuild the damaged portion of road within

Kandiah valley.


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Adit roads of good quality are of huge importance for the construction and maintenance

of the plant. Additionally the roads shall serve as an improvement in living standards of

the local people by providing them better accessibility, improved medical care and better

education facilities. The present condition of the few roads and the mule paths is poor.

The terrain is characterized by steep embankments in narrow valleys. The roads and mule

paths are subject to landslides, rockfall and avalanches. Therefore, a good quality of

design and construction of the roads is essential.

It has to be mentioned, that the design of the roads has been carried out to prevent

blockage of the road by rockfall, landslides or avalanches as far as possible considering

a justifiable expenditure, but it can not be excluded totally.

Therefore, it will be necessary to provide appropriate equipment (e.g. bulldozer) for

cleaning of the roads or perhaps to close the road for few days due to the danger of

avalanches. For the purpose of road maintenance, local people could be employed.

7. TOPOGRAPHIC AND HYDROGRAPHIC SURVEYS

The topographical survey and mapping comprised of the following elements:

Initial reconnaissance and collection of available data.

Establishment datum and detailed location of ground control points (GCP) for Kaigah

Hydropower Project.

Acquisition of SPOT-5 Digital Elevation Model (DEM) data for the whole project area

(30 m raster data).

Derivation of Digital Elevation Models for the reservoir area from SPOT-5 data and

GCPs.

Topographical mapping of the whole project area using DEM data.

Detailed topographical ground survey and cross sections in the areas of the main

structures of the project and the reservoir:

Dam site and reservoir area 1:1,000

Powerhouse site 1:1,000

Project Layout 1:5,000

The survey has been carried-out for four alternative project layouts, which have been

conceived and selected for field work. The survey locations have covered the weir,

reservoir, power intake, surge shaft, pressure shaft, powerhouse and tailrace areas.

Topographic survey work has been conducted for accessible areas and longitudinal profile

of potential stretch of the Kandiah River. The survey maps, profiles and cross sections of

the river are presented in Volume 2 (Topography and Surveying)


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8. HYDROLOGY & SEDIMENTATION

The hydrological studies have been carried out to establish the proposed project for an

optimal development of hydropower scheme on Kandiah River. The following main

aspects of hydrology and sedimentation were studied in the present work and have been

described in subsequent sections:

Climate

Estimation of flows

Estimation of Flood

Sedimentation

Moreover, a stage-discharge measuring gauging station has been installed on Kandiah

River near Thauti village which is in operation since April 2012.

Probable Maximum Flood (PMF) has been worked out as 2113.7 m3/s whereas estimated

sediment transport for Kandiah River catchment is 1.66 - 2.88 Mt/yr.

The floods at proposed dam and powerhouse sites are obtained by the regional flood

analysis are given in Table 8-2.

Table 8-2: Floods at Proposed Dam and Powerhouse Sites

Return Period

(years)

Flood (m3/sec)

Dam Site Powerhouse site

1800 (km2) 2374 (km2)

5 997.0 1173.9

10 1118.5 1309.6

100 1716.1 1970.9

1000 2170.2 2471.7

10,000 2667.3 3029.5

Dam Break Modelling has also been performed and is included in Volume 3 of the

Feasibility Study Report.

9. GEOLOGICAL AND GEOTECHNICAL STUDIES

Based on the geological mapping, drilling boreholes, seismic refraction survey and test

pits performed and the field observation undertaken in the dam area; it was detected

unconsolidated material including fans, terraces, talus and scree on slope faces. On other

hand, the depth of the alluvium deposit was found to be at less 100 m under the river bed

and the width varies between 150 m to about 350 m at the widest point according to the

geotechnical investigation performed in the dam zone; these factors are duly considered

in the Dam & appertenunt structures design.


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The geomechanics and geology characterization were conducted according to the results

of the field investigation and the laboratory test and constitute Volume-4 of the Feasibility

Study Report.

The field investigations have been carried out to explore its influence in the area of works.

Eleven boreholes were drill at the Dam site and three at the powerhouse.

Table 9-1: Boreholes at Dam and Powerhouse Site Area

Borehole

numberDepth (m) Location

1 90 Right abutment and spillway

2 100 River bed, right abutment

3 100 River bed, right abutment4 90 Left abutment

5 50 Left abutment

6 30 Left abutment near SL-1

7 50 Left abutment near SL-5

8 30 Left abutment

9 30River bed, right u/s of Dam axis near under

sluice-1

10 90 Right bank

11 50 Right bank near spillway-1

14 200 Surge Tank and power house15 30 Intake 2

16 100 Low zone Thauti Nullah

The permeability of the rock was obtained from the Lugeon test performed in the drilled

boreholes. The results data was assuming to be a representative data for the rock mass

even if no representative data were obtained in other areas of the project.


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10. NEOTECTONICS AND SEISMIC HAZARD ANALYSIS

For the neotectonic studies of Kaigah Hydropower Project, a good basis is provided by the

Geological Map produced by Searle and Asif (1995) and Geological Map of the Jijal- Dasu

Region, Indus Kohistan, NW Pakistan produced by Gerold Zeilinger (2001) which indicate

the various lithological units and faults of the area identified on the basis of geologicalmapping conducted along the Karakoram Highway (KKH) and up several tributary valleys,

further supported by satellite image interpretation.

Based on the desk study and field observations following conclusion are made;

Kandiah valley lies in the Khostan Isand Arc, which is sandwitched by the MKT (Mian

Karakorum Thrust) in the north and MMT (Main Mantle Thrust) in the south. The

geology is dominantly comprise Chilas Complex (CC) rocks with subordinate pendants

of Gilgit Complex meta-sedimentary rocks (Gm).

In the valley, terraces are present both in uniformly layered and disturbed forms, Since

the region is characterized by steep slopes where erosion is predominant over

deposition, interaction between faults and younger sedimentation is not likely to be

determined in this region.

Small scale faults and shearing besides the major lineaments have been observed in

rock units during field observation which appear to be the result of localized

adjustments to release the accumulated stress induced by the regional stress regime.

The overall study lead to suggest that the movement has occurred before the recent

period of deposition as no evidences have been observed to support the recent activity.

However, these findings are not intended to be considered as the guideline for the

design of structures due to the reason that both MKT and MMT are active faults

surrounding the project area.

Also, Seismic Risk Analysis is performed in Volume-5 of the Feasibility Study Report.

11. PROJECT LAYOUT STUDIES

Four different layout options have been considered for the Project. A detailed comparative

analysis is performed in the Volume-6 of the Feasibility Study Report. The results clearly

show the economic benefits of the alternative by the left bank over right bank layout. Gross

revenues of the project would increase about 23 MUSD / year, which are equivalent to189 MUSD, considering a useful life of 50 years and a discount rate of 12%.

On the other hand, the incremental costs of project at left bank increases to 47 MUSD, if

we compare this value with the NPV of revenues, it is found that the latter are far superior,

so that the Benefit / Cost represents an attractive indicator and, therefore, recommends

the development of left bank scheme.

The study of alternate layouts for the scheme is based on the following assumptions.


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11.1. Stream Flow Records

A design discharge of 125.0 m3/s on site project was defined at the early stage for the

feasibility study, which is available for about 22.0% of the time (on year to year bases)

based on the Flow Duration Curve for Kandiah River.

In case, the construction of two intakes on Thauti Nullah are also considered. A design

discharge corresponding to the mean annual flow was assumed for the study (11.0 m3/s).

11.2. Hydraulic Scheme

The layouts being considered for the proposed project are both on the left bank and right

bank of river Kandiah. The design criteria being fixed for different components of the

project such as headrace tunnel, tailrace tunnel, pressure shaft, adits and powerhouse are

as following:

The dam and discharge site were fixed during office studies using all the investigationdata and reports and were confirmed during the site visit for any alternative scheme.

There is not other possible site to pleace the dam.

The gross head initially proposed has been taken as such for this study along with the

reservoir operating level, turbine centreline level and discharge level.

Based on the various field studies, the installed capacity of the plant and design

discharge have been fixed.

It is also considered that the headrace tunnel and pressure shaft will have a flow speed

of 3.00 m/s in the concrete lining and 5.00 m/s in the penstock tunnel for pressurized

operation conditions.

The headrace tunnel will fall under rock cover criteria, where the weight of the rock,

vertically above the tunnel will be at least equal to the static water head and horizontally

at least twice the head. This criterion will apply to the powerhouse location as well.

The penstock length will be defined by a gradient of 3 to 1.

The slopes considered in the design will be such that the headrace tunnel will have a

slope less than 3% over its length due the construction method using railroad. In the

other hand the adits can have 12% of maximum slope and they are excavated to allow

gravity drainage.

The tailrace tunnel is proposed to operate at free flow with a flow height equal to 70%

of cross section height with 1,0 m/s design velocity for a design discharge of 125 m3/s,

and has 0.2% constant slope.

For the location of adits portals the important criteria is to consider the geological maps

and to stay away from fan deposits and talus presented in some sections of the river

bank.

In left bank layout presented is important the headrace tunnel crosses perpendicularly

the Kandiah valley fault and shorten the effective tunnel distance affected by it.


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11.3. Geological and Geotechnical Restr ict ions

Along the Kandiah River valley one can see a narrow and deep canyon of steep slopes,

locally smoothed at the bottom by Quaternary accumulations such as alluvial fans, colluvial

and fluvioglacial deposits. The rock on the slopes is covered by a very thin layer of

granular soils mainly due to physical weathering and abundant deposits of talus typeproduced by the constant falling of rock fragments. For more detailed geological

information see the Geology Report (Vol-4). Main rock is the gabbronorite of Chilas

complex, very hard but highly fractured at surface, which outcrops along about 70% of the

headrace tunnel. Also appearing in the middle of the tunnel, as an isolated lithological body

covering about 30% of the tunnel, are psammites and green schist from Gilgit Complex,

these are weaker than the gabbronorite. Most of the bottom and base of the canyon slopes

are covered by talus, fan, moraines and alluvial deposits. Its potential instability could

produce slides because of which its geological and geotechnical condition have been

evaluated in the study.

Figure 11-1: Kandiah River Valley in the Dam Site

At the axis of the proposed dam there is rock of good quality at both abutments, with a

possible talus-colluvial deposit in the spillway zone. On the bottom, there is a wide

alluvium bed, probably of more than 50 m depth. Its characteristics are duly explored to

define the dam type.

In terms of geology and geotechnics there are no restrictions that do not allow the

construction of any of the project alternatives; however, the investigations and their results

have been employed to a logically correct conclusion.

The rock mass classification, in order to estimate the tunnel support, is based on GSI

parameter, which defines five rock types from R1 for the best to R5 for the poorest quality.

Table 11- based on Geology Report which gives rock type along with the percentage as

shown below;


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Table 11-1: Type of Zones Expected in Tunnels

Rock Type Percentage in the excavation

R1 47%

R2 14%

R3 4%

R4 31%

R5 4%

According to GSI classification, the tunnel is divided in different homogenous zones.

12. CAPACITY OPTIMIZATION AND POWER POTENTIAL

Based on the selected project layout (left bank) and the prefixed dam height, study was

carried out to find the optimal installed capacity.

Design discharge of 125 m3

/s has been selected after deliberations. The Project isdesigned for the power potential of 545 MW which yields 2112 GWh of annul energy. The

details are incorporated in Volume-6 of Feasibility Study Report.

13. DESIGN OF PROJECT STRUCTURES

The main features of the Project are summarized below and are discussed in Volume-7 of

the Feasibility Study Report:

Dam: will be an asphalt faced rock fill dam across the Kandiah River, 100 m height

and will develop a superficial reservoir area of approximately 1.500.000 m2.

Diversion tunnel: is located in the right bank of the river, 730 m length, is developedin a D-section and is complemented by a pre-cofferdam, an upstream cofferdam and

a downstream cofferdam.

Spillway: has been designed to evacuate the probable maximum flood (PMF), is in

the left bank of the river and is set by three channel sections.

Bottom outlet: its purpose is to keep a useful volume of the reservoir of 20 million of

cubic meters, evacuating the sediments that can be deposit on it; is a structure

under the spillway structure which is a tunnel that will have a horseshoe section and

440 m length.

13.1. Diversion TunnelThe diversion tunnel is located on the right bank of the River Kandiah, has a length of

730.00 m and has basically an intake structure where the closure gates are located, an

outlet structure, and a concrete plug for the final closure.

During the design flood of 879.20 m3/s, corresponding to 50 years return period the

maximum flow velocity in the tunnel will be of 15.70 m/s and the reservoir level will be of

1453.00 m.a.s.l. Based on that, the level of the upstream cofferdam has been set at

elevation 1455.00 m.a.s.l with a free board of 2.00 m.


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13.2. Pre-Cofferdam

The pre-cofferdam is formed of a rock-fill structure with upstream slopes of 2H:1V and

downstream slopes of 1.5H: 1.0V to retain the design flood of 407.50 m 3/s (2.33 years

return period). The pre-cofferdam will have a crest elevation of 1445.00 m.a.s.l and 210

m width approximately without free board.

13.3. Upstream Cofferdam

It will be a rock-fill structure with upstream slopes of 1.8H: 1.0V and downstream slopes

of 1.5H: 1.0V to retain the design flood of 879.20 m3/s (50 years return period). The

upstream cofferdam will have a crest elevation of 1455.00 m.a.s.l, 220 m width

approximately and 2.00 m free board.

13.4. Downstream Cofferdam

It is a rock-fill structure with upstream slopes of 1.5H: 1.0V and downstream slopes of1.5H: 1.0V to prevent the evacuated backwater flows by diversion tunnel interference with

the construction of the dam. The downstream cofferdam will have a crest elevation of

1425.00 m.a.s.l, 265.00 m width approximately and 2.00 m free board.

13.5. Dam

Two dam sites were considered. The dam location was defined by taking into account

several reasons, most of them regarding to geological and geotechnical aspects such as:

downstream of the dam area a narrower valley zone was detected; however, according to

the. The comparison shows that the geological conditions for dam axis -02 is poor on the

right abutment (heterogeneous properties of the deposit material (scree/talus material))and flushing outlets with spillways has to be placed on the left bank. The right bank has to

be rock fill. Dam axis 01 provide additional 70 m gross head or 13% more power and

energy as compared with alternative dam axis. Considering these factors, dam axis -01

has been found techincally feasible and economically attractive.

The selection of the dam height of Kaigah project has two main constrains that practically

set it, without possibility to perform an optimization study.

The maximum high of the dam is given by the Tailrace Water Level (TWL) of 458 MW

Karrang HPP at level 1510 masl, according with GTZ report On the other hand theminimum level of the crown of the dam is given by the necessary dead volume of the

reservoir to ensure its life without sediment flushing. According with calculations, the

useful capacity of the reservoir will be affected by the sediments, so a higher dam is

desirable but this is not possible for the reason given before. Finally, the height of the dam

is set as the maximum possible with out affect the tailrace level of Karrange project.

Given the particular characteristics of the project, this report discusses the possible dam

types considering: Earth-core rockfill dam (ECRD); Concrete face rockfill dam (CFRD) and

Asphalt face rockfill dam (AFRD), based on the compatibility deformational behavior of the

foundation and the availability of materials in the area. Others types of dams (Concretedams) were dismissed due to the depth required for the dam foundation (see Volume 7):


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The length of the structure will be approximately 440 m and will have a constant slope of

4.60%. Its horseshoe section is a semicircular vault with a diameter of 13.00 m and 6.50

m in gables length, except in the section that corresponds to the sluice chamber in which

a larger space is available for the handling of three radial gates and their respective

auxiliary sliding gates.

The bottom outlet dimensions were defined to evacuate, by open flow, a flood of 407.50

m3/s, which corresponds to a 2.33 years return period. When the reservoir is at maximum

operation level and the three gates are totally opened, this structure will be able to

evacuate a flood of about 1150 m3/s.

13.8. Intake Structure

The following table summarizes the main features of the intake structure:

Table 13-1: Intake Structure Features

Hydraulic capacity - Design flow: 125.00 m3/s

Reservoir levels and crown damlevel

- Minimum operating level: 1480.00 m.a.s.l.- Maximum operating level: 1500.00 m.a.s.l.- Maximum water level in 100 years of return period:

1501.30 m.a.s.l.- Maximum water in 1000 years of return period:

1501.50 m.a.s.l.- Maximum probable water level: 1508.00 m.a.s.l.- Crown dam level: 1510.00 m.a.s.l.

General layout

- Intake structure located on the left abutment of the

reservoir, near the dam and immediately upstreamof the bottom outlet.

- Deep Frontal adduction, consisting on a reductionrectangular section. It is equipped with a trash rack,a trash cleaning equipment and two gates as it isdetailed below.

- Vertical tower divided into three pits: a) auxiliarygate b) service gate: c) aeration pit.

- Lower floor of the intake: 1464.00 m.a.s.l.- Operation floor: 1511.00 m.a.s.l.- Maintenance floor 1502.00 m.a.s.l.- Floor Foundation of the Structure and approaching

channel: 1460.00 m.a.s.l.- Total height of the structure: 51.00 m- Height of the bridge crane: 10.00 m

Intake submergence - Measured between the minimum reservoirelevation and level of the top intake gate: 9.30 m

Trash rack

Inclination

- 80 respect to horizontal axisTrash rack type- Fixed rack divided into six modules, each one with

net area of 23.65 m2, 4.30 m wide and of 5.50 m

high


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- Minimum size retained by the rack: 40 mm,corresponding to the spacing between bars,defined by the type of Pelton turbine.

Gross design speed- Maximum gross speed: 0.88 m/s

Net speed without obstruction rack- Net speed water between bars with the plant at fullcapacity: 1.25 m/s

Net speed with 25% obstructed rack

- Net speed water between bars with the plant at fullcapacity: 1.70 m/s

- The retained waste by the trash rack will beremoved through a trash cleaning equipment.

Auxiliary and main gates

Features

- Vertical gates.- Threshold elevation: 1464.00 m.a.s.l.- Elevation lintel: 1470.70 m.a.s.l.

Dimensions- Width: 5.30 m- Height: 6.70 m- Width / Height: 0.79- Speed: 3.52 m/s- Pressure: H=36.00 mClose type- Main gate: it closes against flow; It works with

hydraulic hoist.- Auxiliary gate: it closes with balanced pressures;

operated by the bridge crane.Crane- Operative Distance: 8.40 m- Capacity: 40.00 ton

13.9. Headrace Tunnel

The headrace system of the Kaigah Hydropower Project is composed of the main

headrace tunnel, pressure shaft and three penstock tunnels that will deliver the water to

the three turbines of the project.

The headrace tunnel begins from the intake structure near the Karrang village and ends

at 17 km downstream of the dam site with the connection with the pressure shaft; three

adit tunnels are proposed to construction and equipment access to the tunnel during the

construction stage and future inspection. The adit tunnel 1 and adit tunnel 2 are located at

5.1 km and 10.5 km respectively and will allow the access in the intermediate part of the

tunnel; and the adit tunnel 3 located at 17.02 km will allow the access to the connection

of the headrace and the pressure shaft. At the chainage 13360 m the Thauti Nullah

headrace tunnel will deliver the water from the Thauti Nullah to the main headrace tunnel.

In addition the pressure system will be protected by a surge system composed by an

elevator shaft of 1.5 m radius of 67 m length and surge tank of 6 m radius of 265 m length.

This system will control the hydraulic oscillation protecting the system against water

hammer.


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The pressure shaft begins at chainage 17.06 km. This branch is inclined and divided in the

last part into three horizontal independent penstock tunnels that will deliver the water to

the three turbines located in the powerhouse.

The characteristic and assumed criterion are described in the following part and detailed

in the drawings (see Volume 14).

13.10. Surge Tank

The surge system is located immediately upstream at the beginning of pressure shaft. Its

geometry is on a vertical axis and consists of an elevator shaft followed by an restricted

orifice and an surge tank which goes out to a yard at elevation 1600 m.a.s.l., and an

exterior protection structure of 4.00 m high.

The surge tank has concrete lining with circular cross section with diameter and heights

as follows:

Elevator shaft: D=5.30 m; and H=38.67 m, between elevations 1299.48 m.a.s.l. and

1338.15 m.a.s.l.

Restricted orifice: D=3.00 m at elevation 1340.00 m.a.s.l.

Surge tank: D=10.50 m; and H=260.00 m, between elevations 1340.00 m.a.s.l. and

1600.00 m.a.s.l.

Exterior protection structure: D=10.50 m; and H=4.00 m on a yard.

The surge tank has the following levels:

Static level: 1500.00 m.a.s.l.

Normal operation level: 1476.00 m.a.s.l.

Maximum oscillation level: 1580.00 m.a.s.l.

Minimum oscillation level: 1361.00 m.a.s.l.

13.11. Powerhouse, Cavern of Transformers and Appurtenant Works

The powerhouse consists of a cavern where the turbine-generator set for the three units

and the other auxiliary equipment are located. In a parallel cavern the power transformers

and the corresponding auxiliary equipment are localized. The two caverns are

interconnected by an access gallery between the main floors, and by three bar output

galleries.

The access to the powerhouse is through a two-way vehicular tunnel that starts from a

yard. The tunnel reaches the right sidewall of the cavern, directly to the assembly room.

A lower auxiliary tunnel, leading down to the floor of the excavation of the powerhouse

cavern at the right sidewall, is connected to the access tunnel of the power house. In

addition, an extension of this auxiliary tunnel is linked to the outflow tunnel. This auxiliary


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tunnel is employed as permanent access to the turbine area and as an emergency exit

way from the powerhouse cavern during the operation stage.

The left sidewall of each of the two caverns is joined to a tunnel that starts at each cavern

vault. Those two tunnels are connected to an upper auxiliary tunnel that emerges to an

independent plaza. Initially during construction, this tunnel is used for the construction of

the vaults of the caves, and finally during operation it will used as an out way for the power

cables to a porch which is located in that plaza, where the transmission line is started. Also

goes through this tunnel, hanging on the vault, the fume pipe.

All previous tunnels are used as part of the ventilation system of the powerhouse and, of

course, as escape ways from the caverns.

The location of the caverns for the powerhouse and the transformers has been selected

on the left bank of the River Kandiah considering the topographical, geological and

geotechnical characteristics of the rock mass, which is formed by diorite. In addition thefollowing requirements were taken into account:

The layout of the final section of the conduction tunnel and the pressure well

The layout of the access tunnel to the powerhouse and the output tunnel for the power

cables

The location of the equilibrium chimney and the connection to the derivation of Thauti

Nullah

The layout of the outflow tunnel.

13.12. Discharge Works

Discharge works consists of three branches which receive the released flows by the

turbines; and the tailrace tunnel, the structure and outlet channel which return the flows by

the plant to the Kandiah River.

The collector is made up of three branches, each for every turbine which converge to a

collinear branch with the tailrace tunnel. The branches are parallel mutually and

perpendicular to the powerhouse axis, and they cross under transformers cavern. Thecollector has concrete lining. Each branch will have guides to allow installing a gate and

being operated from the transformer cavern floor. The collector will only have a gate in

case of being necessary.

The alignment of tailrace is almost parallel and close to Kandiah River, to be of a shorter

length and with a proper vertical coverage. At the end of tailrace tunnel, in a short length,

the tunnel alignment turns to right to find the Kandiah River.

Structure and outlet channel have been defined with conventional characteristics. The

outlet structure considers a cut and cover tunnel at the end of tailrace tunnel. It is possiblethrough guides to install in case of being necessary, stop-logs which offer protection


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against river levels to allow tunnel inspection; allowing to locate on the top of a mobile

crane to install the stop logs. The outlet channel will be in the form of expansion with angles

12 ; the section will be excavated in rock with trapezoidal pattern, and treatment with

shotcrete and (tentatively) with concrete floor slab.

13.13. Thauti Nullah Derivation and Headrace

The diversion works of the scheme will be two Tyrolean weirs (one by each stream), each

one with a screen bar, a collector channel, a well to deposit gravels, a conduction channel,

a lateral excess weir, a desander with three cells, a control thin wall weir and a stilling well.

The Tyrolean weirs will work as spillway during the floods and at the same time will work

as an intake using the screen bar that will be along the weir and over it. Under this screen

bar there will be a channel to conduct the water to the headrace channel, at the beginning,

it will have a tank where the gravels are going to be deposited. Downstream of the tank,

on the left lateral wall of the channel the lateral excess weir will be located. Downstream

of the lateral excess weir, there will be a trifurcation in the channel that would allow toconduct the water to each one of the desander's cells where the particles in suspension

will be settled. At the end of the desander's cells, there will be a thin wall weir that will

work like an hydraulic control and will allow to cross the water into a stilling well, which is

connected to a Morning Glory structure.

The Thauti Nullah headrace system will consist of a tank and morning glory-spillway, intake

structure, a pressure shaft and headrace tunnel.

14. MECHANICAL EQUIPMENT

Following characteristics of Pelton turbine units have been worked out in Volume-8 of theFeasibility Study Report

Symbol Feature Units Value

Maximum normal Operating Level m.a.s.l 1500

Minimal Operating Level m.a.s.l 1480

Turbine Runner center line m.a.s.l 971.1

Hb Normal Operating Gross Head m 528.9

Conduction losses m 28.8

Total Flow m3/s 125

Number of units Number 3

Hn Net design head m 500

HnmaxMaximum net head (one unit operating at

100%)m 525.25

Qd Turbine rated flow m3/s 41.7

i Number of jets Number 6

Nsj Specific velocity for jet calculated m.kW 18.9

Et Turbine efficiency % 91.0%

Pd Designed power kW 185,829

max Maximum Power (one unit operating) kW 195.174


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N Calculated Rotational Speed min-1 253.7

N' Selected Synchronous Speed min-1 230.77

Nsj' Single Jet Specific speed m.kW 17.2

Jet Maximum Head Velocity m/s 98.9nf Runway Speed min-1 415

Eg Generator Efficiency % 98.3%

Generator Power Factor 0.85

PG Generator Capacity MVA 202.93

Generator Adjusted Capacity KVA 215,000

Etr Transformer Efficiency % 99.50%

C.I. Installed Capacity kW 545,170

Capacity to Bridge, Gordon's criteria kN 3560

Capacity to Bridge, recommended kN 3900

SIZING BY SIERVO Y LUGARESI

Wheel Dimensions

Ku Runner Peripheral Velocity Coefficient 0.48

D2 Wheel Pitch Diameter m 3.9

Dj Jet diameter, Dj< 0,27m m 0.306

D2/Dj Relationship of diameters 12.8

D2/B Relationship Dpitch/B 3.8

D3 Wheel Outer Diameter m 4.95

H1, B Bucket Width m 1.03

H2 Bucket Length m 0.96

Casing Dimensions

L Pelton turbine casing length m 11.2

GDistance between the runner centerline and

top of the casingm 2.1

FHeight between the runner centerline and

the floor channelm 9.0

W Height between the wheel centerline andwater level m 4.0

H Channel height m 6,4

F-HHeight between the wheel centerline and the

metal pitm 2.7

I Discharge channel width m 5.4

Spiral Case Size

v Water velocity at the spiral case inlet m/s 8.83

A Inlet diameter m 2.45

B Distance axis unit to exterior outside input m 8.34


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C Distance axis unit to the entry opposite side m 8.0

D Distance groups axis to spiral end side m 7.6

E Distance groups axis to downstream side m 8.25

15. ELECTRICAL EQUIPMENT STUDIES

During the alternatives evaluation studies, the sizing and budget of the electrical

equipment for the proposed alternatives has been carried out

As a result of the optimization studies, the alternative with three generating units driven by

Pelton turbines, arranged vertically in an underground powerhouse has been selected.

Each generator will be connected through the corresponding circuit breaker to a single-

phase transformer bank, to raise the voltage to 500 kV. From the terminals of thetransformers, it will be run out, through a tunnel, three three-phase circuits on high voltage

insulated cables, to a square on the surface, where it will be installed to a 500 kV

substation receiving the three generator circuits and the lines for interconnection to the

national grid.

Details can be found in Volume-9 of the Feasibility Study Report.

16. POWER TRANSMISSION LINE STUDIES

Volume-11 of the Feasibility Study Report proposes a transmission system for dispersal

of power generated at Kaigah powerhouse to load centres of Mardan and Peshawar.

The Route of the proposed corridor of Option-I for 500KV transmission line from

Basha-1 to Kaigah has been described below:

It is proposed that a 500 KV transmission line emanating from Basha-1 be connected

to Kaigah via In-Out Basha-1 to Mardan S/C at Kaigah.

Kaigah-Mardan New 500 kV D/C (operated as an interim arrangement until the

commissioning of 2nd stage of Basha).

Since there are steep V-shape Mountains on both sides of River, availability and

access to the corridor 50m wide will have to be confirmed before finally designing the

transmission line. It is anticipated that land uses will remain relatively unchanged during

the next few decades. Increase in growth is expected but overall rural character of the

project/corridor area should remain un-changed.

17. TRANSPORTATION STUDY

545 MW Kaigah Hydropower Project is proposed in a difficult terrain in terms of

accessibility and transportation.


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Existing road network does not have capability of improvement or up-gradation and almost

the whole length of approximately 25 km is to be attended within Kandiah valley.

The existing bridge at Kandiah-Indus confluence is the sole connection of the valley with

KKH which will be submerged in the reservoir of proposed Dasu Hydropower Project.

The bridge over River Indus at Shatial will not be affected by the reservoir level of proposed

Dasu Hydropower Project but it is not a feasible option due to its distance of about 35 km

from the existing Kandiah Bridge.

Construction of a new bridge at the same location i.e. confluence of Kandiah River and

Indus River is also not recommended because at the safer elevation, the span of bridge

exceeds 450 meters which is not a feasible option for the required purpose.

The Consultants of proposed Dasu Hydropower Project have proposed the construction

of bridge near Seo village to provide access to the inhabitants of Kandiah valley to KKH.

The Consultants of Dasu Hydropower Project have proposed a road along the right bank

of River Indus which will enter the Kandiah valley upto the proposed Dasu reservoir.


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It is recommended that sharing of proposals and plans with the Owner Agency of Dasu

Hydropower Project be made at an earliest. In order to develop a mutually beneficial and

integrated approach towards the development of access to Kandiah valley from KKH and

road infrastructure within the Kandiah valley as described in Volume-10 in detail.

18. ENVIRONMENTAL STUDIES

Environmental & Social Impact Analysis has been performed and presented in Volume-12

of the Feasibility Study Report. It concludes :

The study of the environmental and social setting of the Kaigah Hydropower Project,

and the implications of the proposed interventions, i.e. construction of a dam,

excavation of tunnels, creation of the reservoir, and construction of underground

powerhouse and so on, do not indicate any significant negative impact of such nature

or magnitude that would suggest the project is environmentally unfriendly.

The study has identified some potential impacts, which are not of serious nature and

can be ameliorated or mitigated within normally acceptable levels through practicable

control and management measures.

The overall findings of the EIA studies show that the Kaigah Hydropower Project is

environmentally and socially viable subject to the development and implementation of

a full Environmental Management Plan.

19. COST ESTIMATES & FINANCIAL ANALYSIS

A detailed Cost Estimate of the Project alongwith Financial and Economical Analysis have

been developed which yields total Project cost as1564.8 Million USD. Whereas, feasibility

level tarrif is calculated as 9.5 cents per KWh.

Cash flows of Project are discounted at the cost of capital (6.79%) and the NPV of the

Project resulted into USD 464.07 million, which passes the NPV test for the acceptance of

Project as a profitable investment.

Details are presented in Volume-13 of the Feasibility Study Report.

Documents

Kaigah HPP -Executive Summary