MTKVARI - Caucasus Energy and Infrastructurecei.ge/data/file_db/Technical Documentation/Mtkvari...

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Project no.: 2008.0310 August 2009

MTKVARI HYDROELECTRIC PROJECT

FEASIBILITY REPORT

Mtkvari HEP Feasibility Study

K:\2008.03\10\skyrsl\Feasibility_Report\SK-2009-08-06-Feasibility.doc

a

Project summary The Mtkvari river, which originates in north east Turkey, flows into Georgia at about elevation 1200 m a.s.l. It meanders through the country and finally flows into the Caspian sea. The project comprises harnessment of the potential of the Mtkvari river essentially existing between the villages Rustavi and Sakuneti. The rated discharge is 55 m³/s, the gross head 102 m, installed Power 43 MW, and the yearly energy production about 245 GWh/a. The layout in general comprises: Upper works: The Mtkvari river will be dammed a few km upstream from the village Rustavi and diverted into an approx. 9,6 km long headrace tunnel. About 300 m long earth-rockfill dam with a central impervious core will be constructed on the river to retain the intake pond with a normal water level at El. 1012,0 m a.s.l. The max. dam height will be about 25 m. A concrete intake structure complete with trashracks and provisions for bulkhead gates will be provided at the portal of the headrace tunnel. The horseshoe shaped 32 m², headrace tunnel will convey the harnessed water to the lower works. Lower works: At the downstream end of the headrace tunnel the water will enter into the penstocks and from these to the powerhouse housing the two 21,5 MW power generating units. The powerhouse will be on four levels from EL. 901,65 m a.s.l. at the bottom of the draft tubes to El. 931,1 at the arch of the roof. A 90 m high surge shaft is foreseen in excess of 100 m upstream of the penstocks, surfacing at approx. El. 1025. The pressure tunnel will be split into two steel lined distributor tunnel branches, which convey the water to two 21,5 MW Francis type power generating units. A butterfly valve between distributor and turbine will allow independent shut down of each unit. The harnessed water will flow from the turbines into the draft tubes at El. 907,5 m a.s.l. and from these into the horseshoe shaped 32 m² tailrace tunnel, 120 m long, which empties into a 150 m long tailrace canal which again opens into the Mtkvari riverbed at elevation 910 m a.s.l. The powerhouse cavern will be about 51 m long, 13 m wide and max. 29,5 m high. Access to the powerhouse cavern will be through a 100 m long tunnel. Alternatively an access is through the adjacent cable tunnel that will lead the high voltage cables from the power generating units to the power transformers situated in the switchyard. The switchyard is located in the powerhouse yard along with the control building. From the high voltage substation the transmission line will extend some 8 km westwards to the town of Akhaltsikhe. The execution of the Project will include construction of the road at the upper works and construction of new road and bridge at the lower works.


b

Table of significant data Hydrological data: Mean river flow at intake 52,8 m3/s Rated turbine discharge 55 m3/s Average discharge through station 34,3 m3/s Preliminary design flood 1.500 m3/s Max. recorded flow (April 18th 1968) 1.110 m3/s

Intake pond: Highest regulated water level (HRL) 1.012 m a.s.l. Minimum operating level (MOL) 1.010 m a.s.l. Highest flood water level (FWL) 1.015,2 m a.s.l. Empty pond 991 m a.s.l. Total volume 4,9 106m3 Regulated volume 1,0 106m3

Headrace tunnel intake: Sill level 1000 m a.s.l. Bulkhead 5,2×6,1 m2 Trashrack 6×9,5 m2

Spillway: Crest elevation 1.012 m a.s.l. Length of concrete overflow weir 120 m Capacity at water level 1015,2 m a.s.l 1.500 m3/s

Main dam: Crest elevation 1.016 m a.s.l. Length 300 m Volume 152.000 m3 Max height 25 m

Headrace tunnel: Headrace tunnel, length 9,6 km Diameter, horseshoe 6,0 m Inclination variable Water velocity (rated) 1,71 m/s

Adits: Pending excavation Adit 1, length 600 m method. Adit 1, inclination 10 % Adit 2, length 550 m Adit 2, inclination 10 % Diameter, horseshoe 6,0 m

Surge shaft: Diameter of shaft 3,5 m Basin bottom level ( 200m2) 990 m a.s.l. Basin surface level (875m2) 1020 m a.s.l. Total height of shaft and basin 93 m

Pressure tunnel: Steel lining, length 30 m Steel lining, diameter 3,4/2,3 m



c

Powerhouse: Units and installed capacity 2×21,5 MW Type Vertical Francis Rated speed 333,3 rpm Rated generator capacity 2×24 MVA Size of powerhouse (w×l) 13×51 m

Tailrace: Tunnel length 120 m Tunnel diameter, horseshoe 6,0 m Length of canal 150 m Bottom width of canal 6,0/5,0/var. m Minimum tailwater elevation 909 m a.s.l. Average tailwater elevation 910 m a.s.l. Maximum tailwater elevation 915 m a.s.l.

Transmission line Length 8 km Voltage 110 kV

Power & energy: Gross head 102 m Total headloss at rated discharge 14,5 m Net head at rated discharge 87,5 m Mean annual output 245 GWh Nominal max. power 43 MW

Implementation: Total construction time 3 years



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Table of Contents Project summary .............................................................................................................................. a Table of significant data .................................................................................................................. b Table of Contents ............................................................................................................................. i List of tables ................................................................................................................................... iii List of figures ................................................................................................................................. iii 1 Introduction ............................................................................................................................ 1

1.1 Background ....................................................................................................................... 1 1.2 Prevailing conditions ......................................................................................................... 1 1.3 Alternatives ....................................................................................................................... 1 1.4 Proposed further investigations and studies ...................................................................... 2

2 Topography ............................................................................................................................ 3 2.1 Previous investigations ..................................................................................................... 3 2.2 Present investigations ........................................................................................................ 3

3 Geology .................................................................................................................................. 5 3.1 Introduction ....................................................................................................................... 5 3.2 Geology of the area ........................................................................................................... 5 3.3 Tectonics and jointing ....................................................................................................... 6 3.4 Rock types ......................................................................................................................... 6 3.5 Site investigations ............................................................................................................. 6 3.6 Construction materials ...................................................................................................... 6

4 Seismology ............................................................................................................................. 7 4.1 General .............................................................................................................................. 7 4.2 Mapping of faults & fissures ............................................................................................. 7 4.3 Peak ground acceleration .................................................................................................. 7

4.3.1 Deterministic approach ....................................................................................................... 7 4.3.2 Probabilistic approach ......................................................................................................... 7

4.4 Design response spectrum ................................................................................................. 7 5 Hydrology .............................................................................................................................. 9

5.1 Climate .............................................................................................................................. 9 5.2 Hydrological records ......................................................................................................... 9

5.2.1 Discharge to powerstation ................................................................................................... 9 5.2.2 Tailwater level ................................................................................................................... 11

5.3 Flood study ...................................................................................................................... 12 5.4 Groundwater .................................................................................................................... 13

6 Ice regime ............................................................................................................................ 15 7 Sediment regime .................................................................................................................. 17 8 Conceptual design ................................................................................................................ 19

8.1 General ............................................................................................................................ 19 8.2 Headworks ...................................................................................................................... 19

8.2.1 Intake Pond ........................................................................................................................ 19 8.2.2 Diversion canal .................................................................................................................. 20 8.2.3 Main dam .......................................................................................................................... 20 8.2.4 Cofferdam ......................................................................................................................... 20 8.2.5 Spillway ............................................................................................................................. 21


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8.2.6 Roads ................................................................................................................................. 21 8.2.7 Intake ................................................................................................................................. 21

8.3 Headrace tunnel ............................................................................................................... 22 8.3.1 TBM versus D&B (drill and blast) and/or roadheader ...................................................... 22 8.3.2 Optimization of tunnel diameter ....................................................................................... 23 8.3.3 Headlosses ......................................................................................................................... 24

8.4 Pressure tunnel ................................................................................................................ 25 8.4.1 Distributor ......................................................................................................................... 25 8.4.2 Valves ................................................................................................................................ 25 8.4.3 Steel liner .......................................................................................................................... 25

8.5 Surge shaft ....................................................................................................................... 25 8.6 Powerhouse ..................................................................................................................... 26

8.6.1 Underground vs. surface powerhouse ............................................................................... 26 8.6.2 Layout ............................................................................................................................... 27 8.6.3 Fire safety .......................................................................................................................... 27 8.6.4 Draft tube gates ................................................................................................................. 27 8.6.5 Adit steel door ................................................................................................................... 27

8.7 Tailrace ............................................................................................................................ 28 8.8 Switchyard ...................................................................................................................... 28 8.9 Control building and access area .................................................................................... 28 8.10 Transmission line ............................................................................................................ 28 8.11 Electromechanical equipment ......................................................................................... 29

8.11.1 Introduction ....................................................................................................................... 29 8.11.2 Standards and regulations .................................................................................................. 29 8.11.3 Turbines ............................................................................................................................. 29 8.11.4 Governors and shut-off valves .......................................................................................... 29 8.11.5 Cooling system .................................................................................................................. 29 8.11.6 Sump pump system ........................................................................................................... 29 8.11.7 Fire extinguishing systems ................................................................................................ 30 8.11.8 Ventilation system ............................................................................................................. 30 8.11.9 Domestic piping ................................................................................................................ 30 8.11.10 Generators and excitation systems ................................................................................ 30 8.11.11 Generator terminal equipment ...................................................................................... 31 8.11.12 Power transformers ....................................................................................................... 31 8.11.13 High voltage substation equipment ............................................................................... 31 8.11.14 Medium voltage power cables ...................................................................................... 31 8.11.15 Control- and protection systems ................................................................................... 31 8.11.16 Station power supply systems ....................................................................................... 32 8.11.17 Cabling .......................................................................................................................... 32

9 Construction methodology ................................................................................................... 33 9.1 General ............................................................................................................................ 33 9.2 Construction methodology .............................................................................................. 33 9.3 Construction schedule ..................................................................................................... 34

10 Cost estimate & energy generation ...................................................................................... 35 10.1 Introduction ..................................................................................................................... 35 10.2 Basis for the cost estimate ............................................................................................... 35

10.2.1 Scope description .............................................................................................................. 35 10.2.2 Contingency ...................................................................................................................... 35 10.2.3 Exclusions ......................................................................................................................... 35 10.2.4 Pricing Methods ................................................................................................................ 35 10.2.5 Estimation methods ........................................................................................................... 36

10.3 Final cost estimate ........................................................................................................... 36



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10.4 Cash flow and man power schedule ................................................................................ 37 10.5 Energy generation ........................................................................................................... 39

11 Conclusions and recommendations ..................................................................................... 41 11.1 Main conclusions ............................................................................................................ 41 11.2 Conceptual design ........................................................................................................... 41 11.3 Further studies and investigations ................................................................................... 42

12 References ............................................................................................................................ 43 APPENDICES

APPENDIX A Average monthly flow in Mtkvari river at headworks of Mtkvari HEP APPENDIX B Monthly flow in tributary rivers Uraveli and Pokhof 1976 to 1980 APPENDIX C Assumed monthly average discharge to the headworks of Mtkvari in m3/s APPENDIX D Bill of quantities and cost estimate APPENDIX E Construction schedule

DRAWINGS

List of tables Table 5-1 Average discharge at tailwater and estimated average tailwater level ......................................... 12 Table 8-1 The present worth factor (the inverse of the capital recovery factor) as a function of the

interest rate and depreciation time in years .................................................................................. 24 Table 8-2 Comparison on powerhouse alternatives, surface vs. underground ............................................. 26 Table 10-1 Cost estimate summary ................................................................................................................ 36 Table 11-1 Average energy cost as a function of interest rates ...................................................................... 42

List of figures Figure 5-1 Discharge to the intake pond and its statistical distribution through the year evaluated

from historical records from the years 1934 to 1985 ................................................................... 10 Figure 5-2 Duration curve for the discharge to the intake pond .................................................................... 11 Figure 5-3 Result of preliminary calculations of elevation of waterlevel in the river where the tailrace

canal will enter this. ..................................................................................................................... 12 Figure 8-1 Area and volume of intake pond .................................................................................................. 19 Figure 8-2 Optimization of diameter in D&B tunnel .................................................................................... 23 Figure 10-1 Project cost probability distribution ............................................................................................. 37 Figure 10-2 Man power curve ......................................................................................................................... 38 Figure 10-3 Cash flow curve ........................................................................................................................... 38 Figure 10-4 Energy generation and value of produced energy according to historical discharge for

different years .............................................................................................................................. 39


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1 Introduction

1.1 Background JSC Caucasus Energy and Infrastructure (CEI), Tbilisi, Georgia has initiated studies to prepare harnessing of the hydropower potential in the river Mtkvari near the city of Akhaltsikhe, between the elevation somewhat over 1000 m above sea level and 900 m a.s.l. In December 2008 the Icelandic consulting company Verkis hf. prepared a conceptual design study of the scheme which was finalised and the pertinent report submitted in the beginning of January 2009. This study was mostly based on rather limited information, especially regarding geology. However topographical mapping had recently been done in the main two areas, around the headworks on one hand and the powerhouse and tailrace area on the other. The next step in the project design development was to undertake geological investigation, including core drilling in the main two areas and in the tunnel route area itself. The geological investigations were conducted by the Georgian company Geoengineering Ltd. in Tbilisi from January to June 2009. In January 2009 Verkis hf. was retained by CEI to prepare a feasibility study for the project, based on the conceptual design and the results from the geological investigation program performed by Geoengineering Ltd. Drawing 2.001 shows the location of the proposed Mtkvari hydroelectric project in South West Georgia.

1.2 Prevailing conditions The river Mtkvari originates in the northern Turkey highlands above El. 1200 m a.s.l. and flows towards south west into Georgia at elevation above 1100 m a.s.l. The river turns east near the city Akhaltsikhe at about elevation 950 m a.s.l. and flows onwards through the capital Tbilisi into neighbouring country Azerbaijan and to the Caspian Sea. The river discharge at the project location is estimated 52,8 m3/s on average. No reservoir is foreseen upstream of the proposed intake, except a relatively small intake pond approximately 0,5 km2.

1.3 Alternatives There are generally three different alternatives taken into consideration in this study: -Option 1 and 2 of the headrace tunnel, respectively 7,5 km and 9,6 km long. -Three different tunnelling methods; TBM method (Tunnel Boring Machine), Roadheader method and D&B method (conventional drill and blast). -Underground versus surface type powerhouse. In the earlier conceptual study, comparison was made between the two options for the headrace tunnel. In option 1, the intake was located downstream of the village Rustavi, where the elevation of the river is approx. 973 m a.s.l. The headrace tunnel length was estimated 7,5 km. Option 2 with headworks further upstream where the river is at approx. 992 m a.s.l., was selected as more cost effective and recommended for further studies. Consequently, the geological investigations were focused on that alternative. The headrace tunnel was originally presumed to be made by either the TBM method, bored full-face from the downstream end or alternatively with a roadheader or D&B. After more detailed studies, the latter has become somewhat more attractive and the site investigation program has been revised accordingly although excavating the tunnel with a roadheader is still under consideration and may prove to be the most cost effective alternative. The D&B implies that apart from the upstream and downstream tunnel openings two adits are foreseen for construction access, one some 2,7 km from the downstream end of the tunnel and another some 2,5 km from the upstream end. Therefore geological studies considering that these two adits be realised have been added to the program, including mapping of the two potential portal sites. However, it is acknowledged that this will require further


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studies e.g. based on added geological investigations. As for the roadheader driving method, this also hinges on a number of uncertainties, not the least the extent of high strength rock existing along the proposed tunnel alignment. In case of the roadheader we should still recommend providing an adit in the mountain as the execution safety of having two adits can hardly be overemphasised. In the conceptual report, the powerhouse was selected as a surface type solution, but after a comparative study, an underground powerhouse proved to be slightly more economical (about 10% difference). By taking advantage of the prevailing rock stresses around the headrace tunnel adjacent to the powerhouse, the needed steel liner section of the waterways will be much shorter resulting in considerable savings. This, however, is subjected to uncertainties in steel prices and will have to be further studied during next phases of the Project.

1.4 Proposed further investigations and studies In addition to this detailed under 11.3 the following should be considered:

• A comprehensive investigation and testing of construction materials. • More detailed review of the hydrological data (daily discharge and floods) is recommended. • Further geological information, including added boreholes on the headrace tunnel route and the

powerhouse cavern, along with assessment of the prevailing seismicity. • Specific studies on TBM versus roadheader or D&B execution of the headrace tunnel.


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2 Topography As expected, the prevailing topography seems in many aspects favourable for harnessing the potential of the Mtkvari river with a relatively large head difference over a rather short distance, considering this being achieved with a tunnel. In the former conceptual report pertinent source of information was noted. Presently, we have added some to this earlier received from the Owner and i.a. acquired maps from the internet. The site comprises in general a mountain range extending between the proposed upper and lower sections of the Project. Some valleys cut into the mountain range which between the two extremes seemingly comprises a relatively flat plateau at an elevation of 1150 to 1200 m, however with a 2 km long lower middle section at about elevation 1050 to 1100 m a.s.l. It is further assumed that in general the stability of the slopes adjoining the proposed Project structures is adequate. Still, this will need to be re-evaluated i.a. in view of changes brought by the Project and relevant to this. This is further discussed in the Geotechnical Investigation report (Geoengineering 2009). Furthermore, potential avalanches in the Project area which might affect the pertinent structures should be further assessed. The upper Project section where the headrace works, dams and power intake with appurtenances will be located seems to favour the construction of a rockfill dam with a central impervious core.

2.1 Previous investigations Our information on previous investigations in the respect of harnessing the hydropower potential at this site is rather limited. Still, we understand that some site investigation at the presumed location of both the upper and lower works has been performed.

2.2 Present investigations Recently a fairly comprehensive geotechnical investigation was performed by Geoengineering Ltd. in Tbilisi, including field investigation, laboratory tests and desktop studies. The results are described in a special report issued in English in June 2009 (Geoengineering 2009). The investigations include core drilling with sampling and core logging along with excavation of test pits. This was aimed at logging the rock formations and their pertinent properties along the tunnel alignment, along with the location of the groundwater table here and testing the permeability of the rock. Furthermore however, it is important to acquire information on potential sources for construction materials, comprising concrete aggregate, fills for the dams; i.e. silty sand or the like for the impervious core, gravel for the relevant filters, and rock for the shells and the armour zones, (wave and slope protection).


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3 Geology

3.1 Introduction As deduced from the report; General assessment of engineering-geological conditions of building territory of Mtkvari- HES (Geoengineering a) it is concluded from visual inspections and data from geologic literature that from geological standpoint the site is in general favorable for construction of the relevant structures i.e.; whether underground or on the surface. Consequently, we here presume that geological uncertainties in the construction will neither be excessive nor unsurmountable, or conversely be as are common during such construction. However, in the Geotechnical Investigation report (Geoengineering 2009) some warnings are presented regarding the prevailing geology comprising different units of variable strength, both soft and hard, implying i.a. that difficulties due to fault zones and water ingress should be expected in the execution of the tunnel as well as such in the case that the tunnel will be excavated by the roadheader method. In view of all this it seems favorable that the tunnel excavation should be by either drill and blast (D&B) or with a roadheader, rather than by TBM. This, however, should be further analyzed with added boreholes and geotechnical investigations on the tunnel route and further optimization on the tunnel boring techniques. Admittedly, the rock supposedly prevailing along the tunnel route generally seems to consist of types in which appreciable TBM advance rates may be expected, but such may presumably also be achieved with a roadheader. Still it should be realized that the existence and accompanied uncertainties regarding the fault zones with adjoining fault breccias and very soft rock types (argillite) are less favorable for a TBM execution of the tunnel.

3.2 Geology of the area The geology of the area is in general considered favourable, yet variable, for construction of the structures relevant to the hydropower project. Still, some geologic features such as faults and lineaments exist at the pertinent sites, albeit not to such an extent as to render the sites unsuitable for the intended development. Admittedly however, some of the loose overburden may be of questionable properties for use in the various structures as well as for the founding of these. In the above secondly referenced report from Geoengineering Ltd (2009) such faults are listed. Still, the general area is transversed by faults and lineaments of different age and origin and will thus necessitate further site investigations. According to Geoengineering Ltd (2009), numerous faults exist on the proposed tunnel route. Some of these transect the proposed tunnel alignment under a favourable angle while the angle between the proposed tunnel alignment and some other faults seems to be less favourable. The different geological units are mostly slightly inclined with a generally horizontal strike. All this may lead to some difficulties in the execution necessitating added rock support measures both as regards short- and long term stability of the tunnel. It should be noted that information in general on the prevailing geohydrology, not the least the permeability of the rock mass, the location of the groundwater level and the chemistry (PH-value, possible toxicity, aggressive ingredients, as may apply gas content etc.) may need to be further established. Thus, acquiring additional information on this is important in order to allow estimating to an adequate degree of accuracy, the leakage pertinent to the various Project features, as well as may apply possible countermeasures, especially at the dam, the tunnel and the powerhouse.


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3.3 Tectonics and jointing Although Georgia is globally considered located in a highly earthquake prone area the geodynamic conditions in the territory are considered relatively favourable. Further studies in this respect may be required prior to the realisation of the Project. Still, information on possible movement on existing lineaments in the Project area and within a time frame to be reckoned with, needs to be further established and confirmed as well as the potential of such in the future within the operational lifetime of the project. Furthermore, information on the relevant prevailing seismicity in the Project area, inclusive max. ground acceleration and time histories needs to be acquired.

3.4 Rock types The rock formations predominant in the area comprise volcanic, tuffaceous breccias, sandstone, mudstone and some intrusions of harder basalt-andesite rock. Additionally however and somewhat regrettably, softer type formations, s.a. argillite exist in the area and presumably on the tunnel route. In general though, we presume that the prevailing geology on the tunnel alignment essentially comprises relatively strong rock, yet somewhat dissected by faults, lineaments and fissures, coupled with other geologic anomalies some of which may be accompanied by weakness zones and potential high ingress of groundwater. Some 80 to 85 % of the rock, considering the total volume of layers, are classified as VII-XI group in the respect of drilling and blasting with some 15 to 20 % classifying as group VI-VII (Geoengineering 2009). We presume that the first implies very favourable drill and blast conditions requiring but limited supporting measures, yet pending water ingress, while the latter may be somewhat less favourable for such. Both cases may favour excavation by a roadheader although this may be marginal as regards the hard rock.

3.5 Site investigations The importance of existing boreholes, especially cored holes, the location of the boreholes and the core from these cannot be over-emphasised. Limited core drilling on the tunnel route has already been conducted. This will need to be markedly extended, presumably by no less than one core hole every 2 km, yet pending results. Additionally however, the drilling of such holes in the upstream portal and dam areas and the powerhouse area should be instigated at the earliest opportunity. Further to this, a relevant issue may be the existence and thus encountering and logging of geothermal activity in the area, specifically along the tunnel alignment.

3.6 Construction materials The economy of the Project is highly dependent on the availability of the various relevant construction materials within a relatively short hauling distance from the different construction areas. Regarding the upper area, these materials comprise; concrete aggregates and materials for fill in the dams and as may apply other structures, while regarding the tunnel and the lower area this predominantly refers to concrete aggregates. In the case that the properties of these have not already been thoroughly tested and their applicability ascertained, further testing might be necessary at the earliest opportunity, especially such of the concrete aggregates as the proper and exhaustive testing of these is quite time consuming. As noted in chapter 8, the fills in question comprise such for the impervious core, the filters, the shells and the protection zones. However, in the case that material for the impervious core is not available within an economic hauling distance a different type of impervious element, be this concrete or asphalt concrete, may need to be considered.


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4 Seismology

4.1 General Our pertinent knowledge is based on information provided in the report on seismic hazard at the construction sites for the HEP on the river Mtkvari, by the Institute of Geophysics by the name of M.Z. Nodia (M.Z. Nodia Institute of Geophysics 2009). Additional information from the US geological survey website was studied (http://www.usgs.gov/). The project is located in the central part of South Georgia. It comprises seismically active zones of the central part of the Ajara-Trialeti infolded-faulted mountain belt, which has a a high seismic potential, and the western part of the seismically very active Javakheti Upland. The largest earthquake in the area in historic time has been categorised of 9 point intensity (the Samtskhe earthquake of 1283), or a maximum magnitude of approximately M7. Additionally numerous average sized earthquakes have been recorded, among them an earthquake of magnitude M4,7 in 1970 (Borjomi).

4.2 Mapping of faults & fissures A prerequisite for the final pertinent seismic design will be a thorough mapping of smaller-scale faults, lineaments and fissures, active or non-active in the project area, in addition to the major seismically active faults shown in the seismic hazard report. If such a pertinent document exists, this may need to be updated.

4.3 Peak ground acceleration

4.3.1 Deterministic approach In a deterministic approach, a worst case scenario is studied, based on active faults and probable source zones, but independent of time. The maximum size of an earthquake in the area has been estimated of magnitude M7 with a corresponding horizontal peak ground acceleration of 0,32 g and 0,39 g for stiff and soft soils, respectively.

4.3.2 Probabilistic approach In a probabilistic approach, an estimate of seismic hazard is calculated based on values of maximum predicted tremors for a given probability of exceedance during a given period of time. A seismic hazard curve for peak ground acceleration is provided in the seismic hazard report (M.Z. Nodia Institute of Geophysics 2009). The derived horizontal and vertical peak ground acceleration in the area are 0,26 g and 0,13 g, respectively for stiff soils and 0,31 g and 0,15 g, respectively for soft soils, with a 10 % probability of exceedance over a period of 50 years (return period of 475 years). Additionally, the main structures of the HEP should be designed to resist events with a 3000 – 10 000 year return period. The exact values of the peak ground acceleration depend on distances of the areas under consideration from the different source zones.

4.4 Design response spectrum It is assumed that the European Earthquake Standard, Eurocode 8 (FS ENV 1998:1994) can be applied as guidance for the definition of a design spectrum for the project. However, no specific design earthquake calculations will be applied at this stage of the design.


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5 Hydrology

5.1 Climate Georgia´s climate is affected by subtropical influences from the west and Mediterranean influences from the east. The greater Caucasus range moderates local climate by forming a barrier against cold air from the north. Climate zones are governed by distance from the Black Sea and by altitude. Along the Black Sea coast from Abkhazia to the Turkish border, the dominant subtropical climate features high humidity and heavy precipitation (1000 to 2000 mm per year). The midwinter average temperature is 5 °C and the midsummer average is 22 °C. The plains of eastern Georgia are shielded from the influence of the Black Sea by mountains that provide more continental climate. Summer temperatures average 20 to 24 °C, winter temperatures 2 to 4 °C. Humidity is lower, and rain averages 500 to 800 mm per year. Alpine and highland regions have distinct microclimates. At higher elevations, precipitation is sometimes twice as large as in the eastern plains. In the west, the climate is subtropical to up about 650 m, above that altitude is a band of moist and moderately warm weather, then a band of cool and wet conditions. Alpine conditions begin at about 2000 m and above 3500 m snow and ice prevail year-round. Reference is made to the report Geotechnical Investigation by Geoengineering Ltd. (2009), for further information on the climate and weather data.

5.2 Hydrological records

5.2.1 Discharge to powerstation Flow in the river Mtkvari (formerly known by its Azerbaijani name Kura) has been recorded at several gauging stations during the period 1933-1986. The most relevant gauging station for the project is located at the village Minadze, just downstream of the confluence of the tributary river Uraveli some distance downstream of the intake pond for the project. The discharge data available during the study was:

1. Average flow (1933-1986) for each of the 12 months at the headworks of Mtkvari HPP as estimated by HydroProject Ltd. (Table 3-2 in E-mail from 20. May, 2009, see Appendix A)

2. Average monthly flow of the tributary river Uraveli and Pokhop for the years 1976-1980. (See Appendix B)

3. A scanned photographs of the books that contain the daily flow values at river Mtkvari at the village Minadze (Kura at Minadze) for the years 1933 to 1975.

4. Average flow every month for the years 1933- 1985 in Kura at Minadze available at the UNESCO web: (http://webworld.unesco.org/water/ihp/db/shiklomanov/part%274/former%20ussr/GEORGIA/georgia.html)

The only data available at the headworks of Mtkvari HPP is item 1 above. It contains only 12 values, one average value for each month, which is not considered sufficient for energy calculations in a feasibility study. Daily discharge values are the required data for calculating the expected energy production of a hydropower project at that stage, especially as the regulated volume of the intake pond is very small compared to the daily water usage. However, as the discharge of Mtkvari is rather stable within each month, monthly discharge values for many years are considered acceptable in this case. The monthly discharge data from item 4 above is therefore used as the basis for energy calculations. Some months are missing during the year 1933 so the data from the 52 complete years from 1934 to 1985 are used as the basis for the energy studies. A better approach would have been to use the daily discharge data from item 3, but as the data was not available in digital form it was not considered


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feasible to computerize the data for this purpose. This daily data should however be used for further studies of this project. Some random checks of the daily data from item 3 and the monthly data from the net (item 4) indicate that these data are consistent. The monthly discharge data from the web (Mtkvari at Minadze) has to be corrected to give the discharge at the headworks. To get the discharge at the headworks, the discharge of the tributary river Uraveli has to be subtracted from the measured values for Mtkvari at Minadze. The correction is done by multiplying the measured monthly discharge data from item 4 by the same constant each month. The constants are selected so as the monthly average discharge at the headworks in the new series will be the same as has been estimated by HydroProject Ltd (see appendix A). The multiplying constants are between 0,91 and 0,96. The ratio is lowest during the low flow months but highest in the high flow months April, May and June. As the ratio is close to one this approach is considered acceptable and the Consultant has based the current studies on this data but recommends it to be reviewed in more detail during further studies. The corrected monthly discharge data is presented in Appendix C. The average discharge is 52,8 m3/s, just as estimated in Appendix A. The statistical distribution for the discharge for the months is shown on Figure 5-1 and the duration curve on Figure 5-2.

0

50

100

150

200

250

300

350

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Dis

char

ge in

m3 /s

max

0,90

0,75

0,50

Average

0,25

0,10

min

Probability of smaller values

Figure 5-1 Discharge to the intake pond and its statistical distribution through the year evaluated from

historical records from the years 1934 to 1985


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0

10

20

30

40

50

60

70

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1

Dis

char

ge in

m3 /s

Fraction of time with higher discharge

Max. discharge to station 55 m3/s

Figure 5-2 Duration curve for the discharge to the intake pond

By looking at the two figures it is apparent that the discharge is highly depended on the time of year. The low flow season is from August through February with average discharge of 26 m3/s. The high flow season is during the months April, May and June, when the average discharge is 126 m3/s or five times higher than during the low flow season. During those three months about 60% of the yearly discharge volume is obtained. A storage reservoir upstream of the project in the main river or some of its tributary rivers would therefore be very valuable and increase the energy production of this project and all other possible hydro projects further downstream. The monthly average measured discharge for the month of July 1949 is only 17,9 m3/s or 16% lower than the third lowest discharge value for all the months in the 52 years long series. This might indicate some error or inaccuracy in the measurements during that month. The daily discharge data (from item 3) supports that as the 1st of August the daily discharge value jumps almost 4 times from the low values in July and is thereafter constant during the next days. This low value was therefore increased by some 20% so it would be more similar to the other low values.

5.2.2 Tailwater level Some slope of the water surface seems to be present in the river course immediately outside of the tailrace tunnel portal. Consequently it will be cost effective to turn the tailrace canal to the right and enter the river course some 100 m downstream from the tunnel portal. Some limited measurements of the water level in the river just outside of the tailrace tunnel as well as some distance downstream of this are available. According to information received from the Owner the discharge in the river was about 26 m3/s when the surveying was carried out. Figure 5-3 shows the result of calculations of the water level where the tailrace canal enters the river course as a function of the total discharge in the river downstream of the tailrace canal (the sum of the discharge through the station and in the river upstream of the tailrace canal). The calculations are based on actual cross section above the water level, and assuming uniform river depth, that matches the measured point of 909,1 m a.s.l for 26 m3/s discharge. The calculations should be repeated when more data become available and further supported by actual measurements at higher discharge.


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908

909

910

911

912

913

914

915

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300

Ele

vatio

n of

wat

er le

vel i

n m

a.s

.l

Total discharge in river downstream of station in m3/s

Figure 5-3 Result of preliminary calculations of elevation of waterlevel in the river where the tailrace canal will enter this.

The average discharge at the tailrace for each month can be estimated as the sum of the discharge at the gauging station in Mtkvari at Minadze and that of the tributary river Pokhop. The results are presented in Table 5-1 together with the average tailwater level according to the relationship in Figure 5-3. Table 5-1 Average discharge at tailwater and estimated average tailwater level

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Average

r.Kura at Minatze m3/s 26 27 35 138 178 85 42 31 29 29 30 27 56

Tributary r.Pokhop m3/s 7 7 14 54 73 35 15 9 9 13 12 8 21

Total flow at tailrace canal m3/s 34 34 49 191 251 120 57 41 38 42 42 36 78

Average tailrace level m a.s.l 909,2 909,2 909,4 910,9 911,3 910,4 909,5 909,3 909,2 909,3 909,3 909,2 909,7

The average tailwater level is estimated 909,7 m a.s.l. but varies by months by more than 2 m from 909,2 to 911,3 m a.s.l. During the estimated design flood of 1500 m³/s the tailwater level may reach up to El. 915 m a.s.l.

5.3 Flood study The largest monthly peak discharge value can be obtained from the scanned photographs of daily flow data from the years 1938 to 1975. The largest measured peak value is 1110 m3/s, which occurred the 18th of April 1968. All other flood peaks were lower than 800 m3/s. A preliminary statistical analysis indicate that a flood with a return period of 1000 years is around 1500 m3/s, that is the same value as had been estimated by the Owner as a design flood. Until further floods studies have been conducted this value will be used as the design flood.


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5.4 Groundwater Information on the groundwater in the project area is fairly well established and detailed in the report of Geoengineering Ltd (2009). Consequently we here venture to refer to the pertinent chapters in the report s.a.; Chapter 5 - Hydrogeological Conditions. In general however we deduce from this information that the construction activities may be presumed to be affected, albeit to a varying degree, by the existence of groundwater. Further, that the permeability varies markedly and that the pertinent aquifers are at least partly confined. Thus the appropriate countermeasures to ensure short term as well as long term safety will be necessary. We further deduce from the above referenced report (Geoengineering 2009) that the springs encountered are mostly small with a discharge ranging from approx. 1 l/s up to 12 l/s, and that these contain some, yet limited amounts of chemicals, s.a. hydrocarbonate-calcium or calcium-sodium. The groundwater regime prevailing in the powerhouse area, along the tunnel alignment and in the down area may however need to be further detailed.


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6 Ice regime Georgia´s climate is affected by subtropical influences from east and Mediterranean influences from west. Precipitation and humidity are higher in west Georgia as the region is affected by the Black Sea. Alpine and highland conditions start at over El. 2000 m a.s.l. which is higher than most of the catchment area of the Mtkvari project. Ice conditions in the project area, i.a. in the Mtkvari river upstream of the intake pond are not considered to be of any concern, especially since the headrace tunnel intake is submerged by more than 3 meters measured from the top of the trashrack panels. Further, the entire waterways are underground protecting the water flow from any ice formation. Consequently, ice is not expected to be a problem for safe operation of the plant. Reference is made to the report Geotechnical Investigation by Geoengineering Ltd. (2009), for further information on the climate and weather data.


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7 Sediment regime As detailed earlier in this report the Mtkvari river originates in the north-eastern Turkey and flows into the south-western highlands of Georgia. No glacier exists in the catchment area of Mtkvari. Information on sediment such as sampling or analyses is not available but generally the river is considered to be rather clean in respect to sediments. Sediment transport is normally divided into suspended sediments and bed load transport. Analyses of suspended sediments are to be recommended as a basis for the turbine design criteria in the detail design phase. The intake pond is rather limited in size but considering that the bottom elevation of the headrace tunnel intake is some 5 m above the riverbed here allows trapping of considerable amount of sediments without affecting the flow in the intake. Still, the amount of bed load transport should be evaluated as a part of the final investigation program.


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8 Conceptual design

8.1 General The conceptual design has been reviewed and the general features are described in the following chapters. The current Project layout comprises; the upper works, the headrace tunnel and the lower works. At this stage in the design, certain essential project features with appurtenances are foreseen. However, to locating these in a cost effective manner, while facilitating construction, remains to a certain degree to be optimised.

8.2 Headworks

8.2.1 Intake Pond The intake pond is formed by a dam across the river course. Generally, the size of the intake pond and the associated head water level should be chosen as high as economical, taking into account the cost of various structures, such as spillway, main dam, intake, road and diversion works. However the existing highway road and the surroundings adjacent to the intake pond restrict the possible heightening of the water level. Therefore an economical optimisation is not considered relevant in this case. Consequently, 1012 m a.s.l. will be the crest level of the spillway and the highest regulating level (HRL), but during floods the water level can reach up to 1015,2 m a.s.l (MFL). The intake pond is some 3 km long but the maximum width about 0,6 km. The lowest regulating level (MOL) is selected 1010 m a.s.l. Figure 8-1 provides information about the pond surface area and volume.

990

995

1000

1005

1010

1015

1020

0 1 000 000 2 000 000 3 000 000 4 000 000 5 000 000 6 000 000

Ele

vatio

n in

m a

.s.l

Area in m2 and total volume of water in m3

Area in m² Volume in m³

Min. operating water level (MOL) 1010 m a.s.l

Flood water level (FWL) 1015,2 m a.s.l

Highest regulated water level (HRL) 1012 m a.s.l

Figure 8-1 Area and volume of intake pond


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The usable volume between 1012 m a.s.l. and 1010 m a.s.l. is only 900 000 m3. This is equivalent to the amount of water that the plant uses during 5 hours at full load. The pond can therefore only be used for limited regulation within the day.

8.2.2 Diversion canal In order to be able to execute the headworks i.e. the main dam and the power intake in dry, the river must be diverted from the pertinent area throughout the construction period. This will be achieved on one hand by excavating a diversion canal through the promontory the river flows around and on the other by constructing a cofferdam and thus raise the water level to an elevation which ensures that the considered maximum flood in the construction period, tentatively amounting 600 m³/s, a flood peak with estimated 10 years return period will pass through the diversion canal without the upstream water level overflowing the cofferdam. The canal will be about 220 m long, 12 m wide at the bottom with the sides inclined 1 vertical to 0,25 horizontal. The canal bottom will slope from El 1000 at the upstream end to El 998 at the downstream opening. The diversion canal will be permanently closed with a rockfill dam (Refill) at the end of construction.

8.2.3 Main dam The main dam, located slightly downstream of the tunnel intake, will be about 300 m long with a maximum height of 25 m or so, pending elevation of the bedrock in the river course, rising from about El. 991 up to 1016 m a.s.l. The foundation presumably comprises fairly sound rock which in the abutments is expected to be overlain by some m thick loose overburden while essentially bare in the river course. It is foreseen that the dam will be a conventional type earth-rockfill structure, however pending availability of suitable material for the core and the adjoining filters. The tentatively proposed cross section is enclosed on drawing no 2.008. In the case that suitable fill for the impervious core is available within an economic hauling distance the dam will be as shown; a rockfill structure with a central impervious core adjoined by a filter zone on each side and coarser fill further out from the core. Approved filter criteria between adjoining zones shall prevail. Both dam slopes will be provided with a protection layer of stone. Additionally, at the downstream dam toe a specific fill bench of relatively large size rock is foreseen. The dam footprint will be stripped of all loose overburden down to sound rock. Measures, such as grouting, will be taken in the core foundation to ensure that leakage under the core will be within acceptable limits as well as to ascertain adequate safety of the dam. In the case that material for the impervious core is not readily available within economic distance from the dam site, rockfill type dam with an asphalt concrete type impervious core, will probably proof cost effective. Monitoring leakage in the area downstream of the dam will be an integral part of the operation of the power plant.

8.2.4 Cofferdam This will be constructed from rockfill and as may apply other readily available fill. It is presumed that the construction of the cofferdam shall take place during a low flow period in the river. Initially, loose overburden will be removed from the dam footprint and set aside to be used in the cofferdam to the extent practicable. Subsequently, rock will be dumped from one bank into the river course. In order to achieve a final closure relatively large blocks may be required. In this initial stage of the construction of the cofferdam its height will just suffice to divert the flow into the diversion canal. Then appreciable leakage will presumably be through the rockfill. This will be reduced to acceptable levels by placing first gravel fill and then finer grained fill on the upstream slope. Once this has been achieved the cofferdam can be raised up to the design level. A sketch of a tentative cross section of the cofferdam is shown on drawing 2.008.


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8.2.5 Spillway This will be a relatively low and long overflowing weir, extending between the diversion canal and the main dam. It will be 120 m long ogee formed concrete structure. A typical cross section is shown on drawing 2.005. A self supported retaining wall will be provided at each end of the spillway to connect this on one hand to the main dam and to the closure dam in the diversion canal on the other. As the water head at the spillway will normally be limited, only minimum grouting of the foundation rock will be required. Rock anchors connected to the reinforcement of the spillway will be provided close to the upstream toe in order to enhance stability and as may apply ensure adequate connection to the underlying rock.

8.2.6 Roads Considerable work on both new permanent roads, relocation of existing roads and construction roads will be required in the execution of the Project. Apart from these noted in the following it is presumed that a road system will be required to connect the work areas on the mountain to the existing roads. These however will solely serve in the construction period as no or very limited access is foreseen to be needed to these Project features in the future.

Upper works The existing road which winds along the north river bank will be inundated when the intake pond is filled and thus needs to be relocated. Two or even three possibilities seem to exist i.e.; constructing a new road higher up in the slope, excavating a tunnel into the mountain and thus circumpass the pond, constructing a new bridge on the river a certain distance downstream of the dam and reconstruct the existing bridge upstream of the dam. The first one may create future difficulties due to the potential rock falls and avalanches from the overlying slope as well as to cross the construction site. In the case of a bypass tunnel a drawback may be that the general traffic in this may interfere with the construction activities. In the third alternative neither of the two rather negative issues will occur, but this will possibly be the most expensive alternative. At this stage in the design we choose to estimate the cost of constructing a road higher up in the slope as shown on the drawings but suggest that the other two be further evaluated in the future.

Lower works In order to ensure safe and independent passage to the power station a short road needs to be constructed from the main road on the other side of the river instead of using the existing road and bridge which leads to the village Sakuneti. It follows that this will necessitate a bridge there. This connection will serve the traffic in the construction period.

8.2.7 Intake The headrace tunnel intake comprising a portal structure, a square bellmouth inlet section with trashracks and bulkhead slots will convey the harnessed water from the intake pond into the headrace tunnel. The intake itself will be a concrete structure connected to the trashrack slots and a bulkhead lifting platform foreseen at El.1016,0 m a.s.l. The inlet section will connect the intake pond and the intake. This will mainly be excavated in rock. The bottom will be about 1 m lower than the intake sill to avert debris entering into the tunnel. The square bellmouth inlet section directs the water across the trashracks to the overall tunnel cross-section. A filling pipe with a valve bypasses the bulkhead slot. This will be used for controlled filling of the headrace tunnel. Aeration steel pipes will be inserted into the intake structure downstream of the bulkhead slot extending up to the platform at El. 1016,0. Equipment to monitor pressures and temperatures will be provided at the intake. One set at the bellmouth inlet just outside and above the trashracks and another set located in the bellmouth 2,0 m inside of the trashracks. The measured pressure difference between these two sets of monitors will


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show the headloss through the trashracks and will thus alert of potential blockage of the trashracks by ice or other means.

Trashracks Trashracks are foreseen to be provided at the inlet to prevent trash or debris (e.g. stones carried by ice) from entering into the waterways. The trashracks will consist of three panels in total. The height of each panel will be approx. 3,4 m while these will be 6,0 m wide. The velocity through the trashracks is about 1,0 m/s at rated discharge; 55 m³/s. The trashrack vertical grill bars will be spaced c/c 250 mm. The trashracks will be designed for 9,0 m water pressure difference considering normal loading. Sill elevation will be at 999,7 m a.s.l. The embedded trashrack frames and guides will be of stainless steel. Occasionally, especially in the early years of operation, the trashracks will be removed for inspection and maintenance. For such the sections will be handled individually by a semi-automatic lifting beam and a mobile crane from the platform at elevation 1016,0 m a.s.l.

Bulkheads The function of the intake bulkheads is to enable servicing the headrace tunnel. The foreseen bulkhead will consist of two panels with the bulkhead slot located approx. 5 m downstream of the trashracks. The bulkhead must be operated in still water by the use of a mobile crane and a semiautomatic lifting beam. The bulkhead panels and the lifting beam will normally be stored on storing guides at the top of the bulkhead slot. The foreseen net dimensions of the opening for the bulkhead will be W x H = 5,2 x 6,1 m. The bulkhead is designed for external water pressure from a pond elevation at up to 1012,0 m a.s.l. considering normal loading and 1015,2 m a.s.l. for overloading. Earthquake is in this context considered overload. Sill will be at El. 1000,0 m a.s.l. The embedded gate frames and guides will be of stainless steel.

8.3 Headrace tunnel

8.3.1 TBM versus D&B (drill and blast) and/or roadheader The most cost effective method to excavate the tunnel i.e. which method to apply, depends on a number of parameters such as; the tunnel alignment, the diameter, the prevailing geology, the hydrogeology, the availability of construction equipment, the construction time available, to mention but a few. It is i.a. noted in the Geotechnical Investigation report (Geoengineering 2009), that the prevailing geology is in many respects rather complex inasmuch that number of fracture zones exist along the selected tunnel route as well as relatively soft geologic type units, especially argillite. Additionally, that quite hard rock exists along the proposed tunnel alignment. The permeability tests indicate rather moderate such, implying that overall leakage into the different excavations will presumably be limited. However, with the existence of lineaments and faults on the proposed tunnel alignment the pertinent contractor(s) will have to be prepared to handle in an appropriate manner the occurrence of such in the construction period. A TBM excavation should in some respects be preferable and may given certain conditions be both cost and time effective. Still in our opinion, considering the possible implications in the driving of the TBM such as these caused by ingress of water, soft, potentially squeezing soils, difficult fault zones to cross, possible spalling rock conditions etc. it seems to be more prudent at this stage to presume the tunnel to be executed by drill and blast or roadheader. Admittedly, different types of TBM´s exist and as has been noted by the Owner, a specifically applicable such TBM might be available for the work. It should further be noted that during the conceptual design stage some special tunnel design consultants (Pöyry of Switzerland) were consulted for applicability of TBM for the work and the pertinent pricing. Their results were that driving the tunnel with D&B rather than TBM should be safer, whereas a TBM driven tunnel should most likely be cost effective, albeit not unconditionally so. Another possibility in the respect of the tunnel excavation exists i.e. the roadheader. The application of this in tunnel excavation has increased markedly in the last decades or two resulting in improvements that have added to the versatility of the roadheader in tunnel excavation. The rate of excavation


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applying such a method should essentially be comparable to that of a TBM. However, this is not on the critical line in the construction and thus at this stage it is fairly inconclusive whether the tunnel should be excavated by a roadheader or D&B. Further investigations will be required in order to determine which method will be the most cost effective. Consequently, it is recommended that this be studied in more detail in the subsequent design work. As for the available time for execution, this seems to allow ample time for such by D&B based on information from contractors in Tbilisi. Thus at this stage, we have presumed in our work schedule excavating the tunnel by D&B and foreseen this mostly to be driven on four headings from two adits as shown on drawing 2.013.

8.3.2 Optimization of tunnel diameter Calculations were carried out to optimise the diameter of the D&B tunnel. The construction costs for different size of tunnel were estimated in the cost model and the annual energy generation calculated by simulations by the same method as described in Chapter 5.2 Hydrological records. The headlosses in the tunnels for different diameters were evaluated applying the same assumptions as in Chapter 8.3.3 Headlosses. The value of the produced energy is as estimated by the Owner, 4 US¢/kWh from April through September but 50% higher, or 6 US¢/kWh, during the colder and dryer months, October through March. The energy production is the average annual production for the years 1934-1985 based on the historical data as explained in Chapter 5.2 Hydrological records. Other assumptions and the results of the calculations are presented in Figure 8-2.

0

10

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4,0 4,5 5,0 5,5 6,0 6,5

Con

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ctio

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st in

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SD a

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omes

in

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SD/a

and

the i

ncre

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tal r

atio

bet

wee

n th

ose v

alue

s

Nominal diameter (D) of D&B tunnel in m

Construction cost of D&B tunnel in MUSD

Annual income from energy production in MUSD/a

Ratio between incremental construction cost and annual incomes

Main assumptions;

Rated discharge, 55 m3/s. Headloss according to assumed roughness and overbreak"D" shaped tunnel with vertical walls and the width the same as the heightUnit price of excavation and rock support according to cost model.Quantities of rock support increased in direct relation with D1,5

Total construction cost assumed 30% higher than scheduled cost. Energy value assumed 0,04 to 0,06 $/kWh depending on months.No value to increased power.Energy production based on monthly discharge values for 52 years (1934-1985)Average discharge at headworks 52,8 m3/s, and through station 34,3 m3/s.

Recommended minumum tunnel diameter of 6,0 m according to the ratio between incremental construction cost and annual income of ca 9.

Figure 8-2 Optimization of diameter in D&B tunnel The figure presents the total construction cost for tunnel of different size and the corresponding annual income from the energy production. The third line shows the ratio of incremental difference between those two values, or the years it takes for the annual incomes of the increased energy production to pay back the additional construction cost. The optimum diameter depends on the assumed interest rate as well as the assumed number of years of depreciation for the project (the time allowed for pay back of the loans for the construction). Table 8 – 1 shows the relationship between those variables.


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It should be noted that both a TBM driven tunnel and one driven with a roadheader will have a somewhat smaller diameter in order to achieve similar headlosses. Otherwise the approach will be the same in the respect of optimisation and thus will not be included at this stage in the design.

Table 8-1 The present worth factor (the inverse of the capital recovery factor) as a function of the interest rate and depreciation time in years

Interest rate

Depreciation time in years

% 25 40 3 17,4 23,1 4 15,6 19,8 5 14,1 17,2 6 12,8 15,0 7 11,7 13,3 8 10,7 11,9 9 9,8 10,8

10 9,1 9,8

From the table it may be seen that the present worth factor will be highly dependent on the interest rate on the loans taken for financing the project. Assuming interest rate of some 10% and payback time of 25 years gives a factor of about 9 that results in 6,0 m optimum diameter as can been obtained from Figure 8-2. This must be considered a minimum diameter. Conversely lower interest rates (5%) should result in a diameter of up to 6,5 m.

8.3.3 Headlosses The waterways of the project are relatively long considering the head so the headlosses are significant and have considerable influences on the energy production. Largest part of the headlosses, almost 90%, originates from friction between the water and the tunnel walls. An accurate estimate can be difficult and even questionable to obtain, as the headlosses will depend on the prevailing geological conditions, and in the case of D&B the drilling pattern, the workmanship etc. In the case of roadheader the crew and various geological factors relevant to the execution of the tunnel certainly weigh heavily in this regard. Friction head losses in the tunnel are calculated from the Darcy-Weisbach equation, with the friction coefficient assessed according to the Colebrook-White formula. Assumed roughness values and average overbreak in excess of the theoretical tunnel excavation diameter (Dn) is as follows: Type of waterway Overbreak Roughness Unlined D&B tunnel D=Dn+0,3m 0,3m Shotcrete lined D&B tunnel D=Dn+0,2m 0,2m Concrete lined section no 0,01m Steel penstocks no 0,0003m When calculating the friction headlosses it is assumed that 50% of the tunnel roof and walls are shotcreted. The result of the headloss calculations are as follows: Total headlosses for the waterways for Q=55 m3/s:


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Intake, headrace tunnel and penstocks 14,2 Draft tube, tailrace tunnel and canal 0,3m Total headlosses 14,5m

8.4 Pressure tunnel The pressure tunnel branches from the headrace tunnel some 100 upstream from the powerstation. The tunnel diameter will be a 6 m horseshoe section for about 70 m or where this otherwise distributes onto each power generating unit. The pressure tunnel, extending from the headrace tunnel down to the distributor will be inclined about 10%. At the downstream end of this part a 20 or so m long rock trap is foreseen. Close to the downstream end of the rock trap will be a downward bend in the tunnel. From here to the ensuing distributor the penstock will be steel lined.

8.4.1 Distributor From the pressure tunnel the harnessed water enters a short transition stretch immediately upstream of the distributor. The upstream portion of this will be a concrete embedded steel pipe 3,4 m in dia. which forks out into two also concrete embedded steel sections each of 2,3 m dia. As the diameter of the steel liner decreases the excavation area will be reduced to a 4 x 4 m horseshoe shaped tunnel section for both branches. The distributor will be altogether about 30 m long.

8.4.2 Valves In order to allow a separate shut down of each turbine a conventional butterfly valve will be provided at the end of each distributor fork. The valves will be located immediately upstream of the turbine. The foreseen diameter of each valve is 2,2 m. See also Chapter 8.11.4 Governors and shut-off valves.

8.4.3 Steel liner The last part of waterway from the headrace tunnel, just above the bifurcation, to the powerhouse will be steel lined. The steel liners will be all welded steel structures without expansion joints, complete with straight pipes, bends, stiffening rings, supports, seepage rings, thrust rings, anchor bands and bars and all other necessary components. The steel liners will meet all requirements of and be designed and calculated according to internationally accepted standards. The steel liners will be designed to withstand independently internal and external pressures.

8.5 Surge shaft The dimensions of the surge facilities are based on the presumed shut down time of the turbines, the pertinent size of the waterways and other relevant issues. The surge shaft and overlying basin will be located some 200 m upstream of the powerhouse cavern at invert El. 927 in the headrace tunnel. It is located as close to the powerhouse as possible where the topographical surface elevation is higher than 1020 m a.s.l. A minimum area of some 10 m2 is recommended on the lower sections of the shaft. At elevation 990 m a.s.l the horizontal area is increased to about 200 m2. Assuming maximum slopes of the cut in the rock wall, 1H:0,25V, result in over 800 m2 horizontal area at elevation 1020 m a.s.l The volume of the surge basin will thus be some 16.000 m³. It is further presumed that the shaft will be raise bored and the final diameter, i.e. this following the required rock support measures, will be 3,5 m. The widening at the top will be done by D&B after the narrow shaft has been excavated. The form of the widening can be circular or square depending on what is most suitable for the construction providing the horizontal areas as large as assumed.


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For safety, a circular concrete wall will surround the shaft opening which will be provided with a graded steel cover. Furthermore the entire basin will be surrounded by a safety fence. During operation, the water level will always be within the elevation range of the surge basin. At sudden complete stop of the turbines the water level can rise up to 1017 m a.s.l and up to 1019 m a.s.l if the water level in the intake pond is simultaneously at flood water level. During sudden start-up of both turbines at minimum operating water level in the intake pond the water level in the surge basin can be drawn down to 992 m a.s.l. The two adits to the headrace tunnel will function as additional surge facilities if left open as planned (without a concrete plug). The reduction in the extreme surge levels in the surge basin are on the other hand rather insignificant so its effect is not taken into account in the aforementioned values. The narrow part of the shaft is only about 60 m high and the cost of bringing in a special raise bore equipment might be high for such a short shaft. Alternatively the shaft might be excavated by D&B method, either vertical, steep sloping or gently sloping. If the longitudinal slope is some 15% the length of the gently sloping tunnel will be about 400 m when this reaches the elevation of the surge basin bottom. In that case the surge basin could be replaced by open canal with bottom elevation extending from elevation 990 up to 1020 m a.s.l. The canal would be ca 200 m long if the slope is also 15%. By this way an additional drivable access would be created into the headrace tunnel both during construction and for maintenance. This surge facility could be excavated either down from above or up from the headrace tunnel or both. This alternative should be studied further in the next design phase.

8.6 Powerhouse

8.6.1 Underground vs. surface powerhouse In the Conceptual Report, issued by Verkís hf. in January 2009, a surface type powerhouse was presumed as the initial alternative. During the first stages of the feasibility study it was recognized that with an underground powerhouse it should be possible to reduce costs by shortening the steel lining and the concreting of the pressure tunnel. Subsequently, a comparative study was performed regarding the two pertinent options. In the conceptual project phase a 12,7×32,7 m surface powerhouse was foreseen, with 9 m between the units’ centreline. The pressure tunnel was estimated 170 m long comprising a 90 m concreted section followed by an 80 m long steel lining. In the present study the former bill of quantities was revised. Some inaccuracies were found, mostly related to the pressure tunnel, so the cost increased minutely. The layout of the underground powerhouse is described in subsequent chapters. The contingencies during the conceptual phase are naturally higher than in the feasibility stage. Thus to sum up the comparison it is necessary to take them into account. This is applicable for i.e. that in the conceptual study (Verkís hf. 2009) the distance between the units’ centerline was assumed 9 m but with a more detailed design it is recognized that this was underestimated. In the present study the distance is 14 m. This will obviously be further studied during the next stage of the Project. The cost comparison concludes with the sum of the pertinent features for both alternatives; i.e. features included for the surface powerhouse is the pressure tunnel, powerhouse and tailrace. For the underground powerhouse the comparative features are the pressure tunnel, powerhouse, tailrace, control building and access area. Table 8-2 Comparison on powerhouse alternatives, surface vs. underground

Alternatives Contingency Subtotal (USD) Grand total (USD)

Surface powerhouse 20 % 6.499.580 7.799.500 Underground powerhouse 15,7 % 6.214.070 7.189.680 Cost difference: 609.820


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According to the comparative study it will be cost effective to choose an underground powerhouse. However, the cost difference is relatively minor about 10% of the total costs involved, or US$600.000, which is just a fraction of the grand total of the Project. It should be noted that steel prices continue to be uncertain. Thus if appropriate prices are to be claimed for the construction of the hydropower station this significally affects both alternatives. Furthermore, the Owner’s preferences certainly weigh heavily in the selection of an underground vs. a surface powerhouse. This has to be further assessed during the progress of the Project. Construction of an underground powerhouse is presumed in this study.

8.6.2 Layout The Mtkvari hydroelectric project powerhouse will to be of conventional underground type located some 120 m in from the present surface at about El. 925. The underground selection is based on cost comparison with due consideration of steel and concrete prices. Access to the powerhouse cavern will be provided through a 90 or so m long tunnel lying perpendicular to the powerhouse axis. The access road tunnel will be horseshoe shaped; 6,5 m wide and about equally high. The cavern will house two Francis type generating units with appurtenances. Connection to the transformers, switchyard and other ancillary electrical equipment located at the surface at El. 916,5 m a.s.l. outside of the powerhouse, will be provided through a cable tunnel. The powerhouse cavern will be max. 51 m long at the entrance floor level El. 918,3 m a.s.l., 13 m wide and max. approx. 30,5 m high from about El. 900,5 up to 931,0. The generator floor is foreseen at El. 914,3 m a.s.l. The erection bay will be located on the generator floor as well as on the powerhouse entrance floor that connects directly to the access tunnel. Draft tube gates will be located at the downstream wall of the powerhouse. The power cables, laid on steel brackets provided along the tunnel wall will extend through a dedicated cable tunnel to the outdoor transformers and adjoining AIS switchgear.

8.6.3 Fire safety One of the aspects that need to be considered when designing underground power plants (powerhouses) is fire safety. This comprises the design of emergency routes & exits, smoke ventilation, compartmentation and fire suppression & detection systems as well as the scientific aspects of thermal loading and heat release rates. These aspects have been taken into account and must be further considered in the final design.

8.6.4 Draft tube gates The underground station will house two identical generating units with appurtenances. Each unit will be furnished with a draft tube gate to facilitate turbine maintenance which may only be operated at a balanced pressure over the gates, using a semiautomatic lifting beam and a crane in the powerhouse. The net dimension of the opening for the draft tube gate is foreseen W x H = 5,8 x 2,8 m. The gates are designed for outside water pressure up to 909,0 m a.s.l. considering normal loading and 914,0 m a.s.l. for overloading. Earthquake is considered as overload. Sill elevation for the gates will be 901,65 m a.s.l. The embedded gate frames and guides will be of stainless steel.

8.6.5 Adit steel door The concrete plug in the access tunnel will be provided with a steel door for maintenance purposes. Net door opening will be w x h = 2,5 x 3,0 m. Sill elevation is at 918,0 m a.s.l. The door will be designed for normal loading considering inside water pressure up to 1012,0 m a.s.l. and the applied surge pressure. Additionally, the door will as overloading be designed to sustain an inside pressure from water level at 1015,0 m a.s.l. as well as for earthquake load. The embedded door frames will be of stainless steel. One set of valves and piping for emptying the headrace tunnel will be provided in the concrete plug. Evidently the manually operated valves are normally to be kept closed.


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8.7 Tailrace The harnessed water will flow from the draft tubes onward into the tailrace. From each draft tube will be two about 20 m long tailrace tunnel branches that merge into some 100 m long tailrace tunnel with the same size and form as the headrace tunnel. The tunnel is followed by an about equally long canal which is foreseen to extend somewhat into the present Mtkvari river course. Some slope of the water level seems to be present in the river course immediately outside of the tailrace tunnel portal. Consequently, it will be cost effective to turn the tailrace canal to the right and enter the river course some 100 m downstream from the tunnel portal. The elevation of the tunnel invert and the canal bottom is 904,2 m a.s.l. where this is excavated in rock. Closer to the river when the rock surface becomes lower than the canal bottom the bottom elevation is elevated to 907 m a.s.l. and the canal width gradually widens to about 20 m, where the canal meets the river. The maximum water velocity where the canal is fully in rock is about 1,5 m/s and about 1 m/s where the canal is in loose material. The loose material cut at the canal banks will be protected by riprap. A low ca. 30 m long training dike is foreseen alongside the left bank of the tailrace canal from the yard into the floodway of the river to protect the deepest part of the canal from mud and debris in case of large flood in the river.

8.8 Switchyard The switchyard will be located on the riverbank within the powerhouse yard area, parallel to the tailrace canal, and guarded by a 40 x 26 m safety fence. The layout of the switchyard area includes two power transformers along with the necessary substation equipment, further discussed in Chapter 8.11 Electromechanical equipment. The transformers are located outside, close to the powerhouse access. This is more cost beneficial considering fire – and safety measures. Negligible losses in the cables will be in the cable tunnel. A concrete transformer pit will be constructed for each transformer unit to receive the oil volume in the transformers in the case of damage.

8.9 Control building and access area The control building is located between the switchyard and underground powerhouse access tunnel portal. The 130 m2 building will comprise control equipment along with the necessary personnel facilities including i.e. coffee room, toilets, locker room. Considerable excavation will be needed for the powerhouse access area proposed at EL. 916,5. The existing loose overburden can presumably be dozed out and graded. The access area will be about 7500 m2. Separate portals will be for the cable tunnel and the access tunnel, respectively. The cable tunnel portal will only provide for an access door, 3 x 3 m whereas the access tunnel portal will include a 5,5 x 6 m wide access door.

8.10 Transmission line The power from the Mtkvari power plant will be transmitted via 110 kV transmission line from the high voltage substation at the power plant to the substation of Akhaltsikhe some 8 km away. The line location is expected to be as indicated on drawing no. 2.002. The laying route has not been studied at the site, but indicated as shortest possible route from the power plant to the Akhaltsikhe substation. According to the Owner another substation is located some 2,2 km from the powerhouse that might be a preferable option. This has to be evaluated in the next phases of the Project. The supporting poles are presumed to be galvanized steel structures either tubular pole type or girder structure type. The number of poles is expected to be about 40 with mean length between poles 200 m. The mean height of the poles is expected to be 16 m. The transmission capacity is expected to be 100 MVA and the insulating voltage 123 kV.


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8.11 Electromechanical equipment

8.11.1 Introduction This chapter contains a short description of the main electromechanical systems of the powerstation.

8.11.2 Standards and regulations The design, manufacturing and testing of electromechanical equipment will be based on the latest applicable CENELEC, IEC and CEN standards. If the respective object is not covered by standards from these organizations standards from other organizations such as ISO, ANSI, DIN and NEMA will be applied. Standards from IEEE will be used as guidelines in the design work if such guidelines do not exist from CENELEC or IEC. Reports from international institutes and organizations in the field of the respective systems and equipment will also be used for reference in the design phase.

8.11.3 Turbines The turbine-generator unit will have one turbine guide bearing, a combined thrust and guide bearing below the generator rotor and one guide bearing above the rotor. For a net head of 90 m and 27,5 m3/s flow the generator output of each unit will be 21,5 MW at full load. The hydraulic conditions at site are suitable for Francis type turbines. The most probable synchronous unit speed will be 333,3 rpm and a safe setting of the turbine runner to avoid cavitation is 1,5 m below the tailrace surface. The turbine runner, guide vanes and wearing surfaces on head covers will be of martensitic stainless steel. All linkage and guide vane stem bearings will be of self-lubricating type, maintenance free.

8.11.4 Governors and shut-off valves Digital PID governors will be provided. The hydraulic system will be a high pressure system with double pumps and piston accumulators, with capacity to secure a controlled stop of the units in case of electric power failure. Consideration will be given to redundant electronics to enhance reliability. Each turbine will be furnished with a butterfly inlet valve. The valves will have double disc seals, an upstream maintenance seal and a downstream operation seal. The valves will be closed by a torque from counterweights, but opened and kept in open position by hydraulic actuators, connected to the governor hydraulic power units.

8.11.5 Cooling system Each turbine generator unit will be provided with a separate cooling system. The system shall be a closed circuit primary/secondary circulation system. On the primary side raw water shall be taken from the penstock, through an automatic self-cleaning duplex strainer, heat exchanger, flow meter and delivered to the draft tube. On the secondary side of the system treated cooling water will flow to the generator air coolers, bearing oil coolers and the governor oil sump cooler if required.

8.11.6 Sump pump system One wet drain sump will be provided in the powerhouse. The station drainage system will drain water from various locations in the powerhouse to the wet sump by gravity. The sump will be furnished with sump pumps from which a discharge pipe shall convey the drainage water to above tail water level. For dewatering of the turbines, pumps and valves shall be installed in the sump. Dual-purpose pipes for draining and filling of the draft tubes shall be connected to the draft tube drain and fill box at the bottom of the sidewall of each draft tube and extended to the pump sump.


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8.11.7 Fire extinguishing systems Fire extinguishing system will be installed for main oil containing equipment and other accumulations of flammable materials. Risk analysis and assessment will be used to aid the design of the extinguishing systems. A certain quantity of oil will be in the unit bearings, the governor hydraulic systems and the unit transformers. High pressure water droplet or fog sprinkler systems suitable for oil fires will be considered as well as inert gas systems.

8.11.8 Ventilation system Ventilation and smoke exhaust systems are very important in the underground station. The ventilation system will be designed to ensure sufficiently high air quality in the caverns and tunnels. Smoke exhaust must be sufficient to ensure safe evacuation in case of fire and necessary access for fire fighting. Fresh-air intake is located above the entrance to the access tunnel. The main ventilation unit will be located in the ventilation room in the powerhouse. The unit will draw the fresh air through the access tunnel and heat or cool the air before blowing it through ducts to the generator hall, turbine floor and the valve floor. The air will flow from the valve floor and the turbine floor back to the generator hall. An exhaust fan will be located in the cable tunnel and will draw air from the generator floor through the cable tunnel and blow it to the outside. One exhaust fan and one smoke exhaust fan will be located in the entrance to the access tunnel. The exhaust fan is used for regular exhaust from the generator hall, oil room and sump. The smoke exhaust system will draw air from the generator floor through large ducts located in the center of the ceiling. The smoke exhaust duct will then continue through the access tunnel to the exhaust fan at the access tunnel entrance. Both the exhaust fan and the smoke exhaust fan will use the same duct to blow polluted air to the outside.

8.11.9 Domestic piping The main piping systems are for potable water, drainage (incl. sewage), compressed air and water for shaft seal, air-cooling and fire fighting. Potable water system will be connected to the local water distribution network. None-polluted drainage will be led directly to the wet sump by gravity and sewage will be led through sewage-treating before entering wet sump. Compressed air will be supplied by a compressor and a receiver in the powerhouse. Water for shaft seal, air-cooling and fire-fighting will either be taken from pressure shaft with a pressure-reducer to regulate pressure for the systems or by pumping from tailrace.

8.11.10 Generators and excitation systems The turbine/generator units will be vertical shaft type. The generators will be the conventional semi-umbrella type with combined trust and guide bearing below the generator and guide bearing above. In addition the turbine will have one guide bearing. The rotor will be designed to withstand safely all overloads and stresses encountered during abnormal operating or runaway speed conditions. The stator windings will be with class F insulation but temperature rise limited according to class B. The windings will be star connected with the neutral resistance earthed. The generator voltage is expected to be 10 kV The generators will be air cooled with the air cooled in water-cooled air coolers. The generators will be equipped with inert gas or water mist fire extinguishing system. The bearing oil is the main source for fire within the generator house. Minimizing of the risk of fire in oil within the generator housing will be an aspect in the design of the bearings, the oil systems for the bearings and the supervision system for the generators. The excitation system is expected to be of the brushless type. The static excitation has better time response and faster de-excitation but in this case brushless type expected to be sufficient as the power station is not a demanding station in the power system. The main advantage of using brushless


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excitation is the elimination of brushes and rings and therefore reducing maintenance. The price of brushless excitation is expected to considerably lower than the static excitation.

8.11.11 Generator terminal equipment Current transformers are expected to be in the neutral end and line end terminals of the generators. The generator circuit breaker, the generator neutral end equipment and the generator cable connection facility will be located at side to the generator housing in a cubicle assembly. The generator neutral end will be connected to earth through a neutral point resistor to limit the earth fault currents in certain time.

8.11.12 Power transformers There will be separate step-up transformers for each unit, from generator voltage to 110 kV. The transformers will be located outside the cavern at the switchyard area. The transformers will be three-phase, oil-immersed and with ONAF cooling. The transformers will be of the three winding type with one winding 10 kV facilitated with on-load tap changer for regulation of the station power voltage. Under each transformer will be an oil sump with connection to a common oil separation tank. The station service transformers will be of the dry type located in the cavern aside to the 400 V distribution cubicles. Alternative solution is to use only one power transformer for connection to both of the unit generators. The transformer would be with three windings, one for each generator unit and one for the high voltage winding. The station supply would be performed with one 10/10 kV transformer facilitated with on load tap changer. The back-up power supply is expected to be with connection from rural 10 kV power supply system. The price of one power transformer and one station supply transformer in relation to two power transformers is about 70 %. The calculated availability of the powerstation with the alternative solution is however a little lower.

8.11.13 High voltage substation equipment The high voltage substation is located in the switchyard outside the cavern. The substation consist of the unit power transformers, air insulated (AIS) switchgear with circuit breaks and disconnecting switches, instrument transformers, surge arresters and steel structure. There are two circuit breakers, one for each transformer. These two circuit breakers serve together also as line circuit breakers as indicated on the drawings.

8.11.14 Medium voltage power cables The connection between the generator circuit breakers and the respective unit transformers in the switchyard will be by medium voltage cables. The cables will be XLPE insulated. The cable route will be in cable and ventilation tunnel between the cavern and the outside switchyard. A part of the tunnel will be used as a part of the air ducts in the ventilation system for the powerhouse.

8.11.15 Control- and protection systems The control systems will be based on distributed architecture. The main structure of the control of the power plant will be divided onto four levels, i.e. control from load dispatch centre, SCADA system on station control level, from local control consoles on individual control system and control of individual equipment on emergency control level. The control equipment will be divided in the following individual control systems:

• Control system for each generating unit • Control system for common station equipment

• Control system for the high voltage switchgear • Overall SCADA system on station control level


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The individual control system and the SCADA system will be interconnected on redundant station network. The operator consoles of the SCADA system will be located in a control room in the entrance building. Each control system will be built up with a central redundant PLC with data links to distributed redundant PLC input/output units and data links to PLC's in local control systems of individual equipment. The operator MMI will be at each local control level with touch panel and keyboard. Fiber optic links will be used to the extent possible. The connection to the load dispatch centre is expected to be through redundant gateways, connected to the station network. The protection systems will be divided into protection groups and subgroups to ensure good protection of the relevant systems. The protection relays will be the numerical, solid-state type with data link connection to the control systems. Accurate time tagging of events will be in the control- and protection systems.

8.11.16 Station power supply systems Separate Motor Control Centre (MCC) will be for each generating unit, one separate MCC for common station equipment and one in the entrance building. The MCC for the unit will be directly connected to the station transformers and also connected to the common station MCC as indicated on the drawings. The MCC´s in the powerhouse will have two incoming feeders, each from a separate source. The equipment will be conventional, compartmented metal enclosed switchgear in cubicles for indoor installation. There will be a double 110 V direct current system in the powerhouse. Both systems will consist of a dry type battery-bank, charger and distribution. A 110 V DC distribution will be located in the entrance building, serving the high voltage equipment. This distribution will be connected to both of the DC systems in the power house. All equipment in the process that need direct current feeding will be connected to both direct current systems.

8.11.17 Cabling All cables will be flame retardant, self-extinguishing and non-flame propagating. The cables in the underground station will be of the low-smoke type and halogen free. The cable routes will be along cable ladders, cable trays and cable ducts as applicable. Cable entrance to cubicles will generally be from below. The cable route between the powerhouse and the Control building will be in cable ladders in the cable and ventilation tunnel. Power cables and control cables will be separated in cable routes as far as possible.


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9 Construction methodology

9.1 General An overall target of the construction schedule is to minimise the total construction time and bring the power plant into full commercial operation in about three years. Generally the critical path for such hydro scheme lies through the powerhouse with installation and testing of the hydromechanical equipment. Here, the 9,6 km long headrace tunnel can also be critical, depending on the construction methodology. In the previous conceptual report (Verkís hf. 2009), a TBM driven tunnel was considered the most feasible method. Conversely in this report, either a conventional drill and blast or a roadheader method is recommended as the most favourable approach. Still, it is acknowledged that this needs to be studied further in the future design stages and then in due consideration of the results of added geological investigations.

9.2 Construction methodology Access to the site is already available through existing roads, which connects the area to the main highways in Georgia. The distance from the capital Tbilisi to the proposed powerhouse site is approx. 160 km. The main potential harbours for import of equipment and machinery lie on the east coast of the Black Sea (Batumi or Poli), with transport distance of some 150 km to the site. A new bridge connection crossing the Mtkvari river is foreseen some hundreds of metres upstream of the powerhouse, connected to the existing road on the northern river bank. This same road leads to the city Akhaltsikhe and further upstream along the right river bank when it comes to the headworks site continuing to the rural areas in the direction of the Turkish border some 50 km away. Construction roads required by the contractor to execute his work will be planned and constructed by himself. These roads are required for access to the surge shaft, the two proposed adits to the headrace tunnel, disposal of excavated material and for transport of construction material. The project comprises work activities at mainly three different locations. Firstly, the headworks area near the Mtkvari river at elevation between 1000 and 1020 m a.s.l. Secondly the powerhouse and tailrace area which is on the right bank of Mtkvari at elevation 910 m a.s.l. and finally in the case of D&B execution the two more adits, one with access along a valley from downstream of the powerhouse to approx. elevation 1020 m a.s.l. and other from the road some two km downstream from the intake area, at elevation about 1055 m a.s.l. Conversely, in the case of a roadheader driven tunnel this would most likely be driven from both ends, in which case measures, such as an extra adit, should have to be taken at the upstream end to facilitate this. However as noted earlier in this report an extra adit at a favourable location on the mountain should be considered as such should greatly enhance the safety of the entire construction. Spoil areas are foreseen near all the above mentioned adits, along with such at the downstream construction site. Excavated material from the headworks area will be as may apply used for the pertinent constructions such as dams and road works. Additional material from required excavation will be placed at designated spoil areas, possibly within the intake pond. The exact location of the spoil areas has not been determined as presumably the Owner will have to negotiate this with the local landowners. The same applies for the exact location of other facilities needed during construction. These facilities will be located at each end of the headrace tunnel, i.e. at the headworks construction site as well as at the downstream powerhouse area. This includes installation of two separate concrete factories, workshops, warehouses and camps. A rough estimate of the area is that approx. 4 hm2 of land will be needed in the powerhouse area and 3 hm2 in the headworks area. As for such on the mountain in the case that adit(s) be provided there, this will be considerably smaller. The construction power is expected to be provided from local 10 kV distribution stations in the project area. Power supply for the powerhouse area and as may apply Adit 1 is foreseen to be with 10 kV cables or overhead line from a distribution station in the village Sakuneti whereas supply for the


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headrace intake and the possible Adit 2 is foreseen to be with 10 kV cables or overhead line from a distribution station in the town Rustavi. Compact 10 kV switchgear is foreseen at each construction area along with step- down transformers and distribution from there onto 400V. The power supply for the tunnelling work is foreseen to be on 10 kV into the tunnels with transformers moved as the tunnelling work advances. A water supply system will be required for the concrete plants at each main construction site; the headworks and powerhouse area, respectively. Each water supply system will consist of 1 or 2 water wells, submergible well pump(s), water storage tank, pumping station and distribution pipelines. Wells, pipelines and equipment (incl. tank and pumping station) will be furnished for year-round use. If necessary, potable water system for camp area will be equipped with a disinfection system.

9.3 Construction schedule A construction schedule was composed for the project. The schedule is divided into several areas according to the cost estimate and all major activities and milestones are listed. The schedule is resource loaded based on durations defined by quantities developed in the cost estimate and labour productivity. According to the construction schedule shown in Appendix E it is concluded that the indicated sequence of activities, from decision to proceed to commissioning of the first unit is 36 months. Some basic criteria must be met to achieve this schedule:

• Continuous progress of the work. • Underground excavation must in the case of D&B be planned with four drillrigs (jumbos)

working simultaneously, whereas in the case of a roadheader driven tunnel the use of two or even three such should be considered.

• Design and manufacturing of the hydromechanical and electromechanical equipment must be planned so as to ensure timely installation synchronized with the powerhouse construction.

• The headrace tunnel is if D&B driven assumed to progress at the rate of 40 m per week per heading, whereas appreciably faster construction, amounting on the average some 50 or more m per week may be expected, given favourable conditions.


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10 Cost estimate & energy generation

10.1 Introduction The construction cost is estimated for all major items of the project. To these are added probable Owner’s costs, design and supervision costs.

10.2 Basis for the cost estimate

10.2.1 Scope description The estimate is for a 43 MW Hydroelectric Power Plant in the Mtkvari River in Georgia consisting of a diversion canal, cofferdam, spillway, main dam, road works, intake structure, a 9,6 km long headrace tunnel, surge facilities, underground powerstation, tailrace tunnel and tailrace canal, switchyard and a 8 km long transmission line to Akhaltsikhe.

10.2.2 Contingency The estimate is presented as a central estimate with equal probability of over/underrun, a P50 estimate. Contingency is included to account for non-identified items and unforeseen but normally expected events or effects leading to a cost increase. This cost is estimated as a necessary addition to identified cost items in order to bring the estimate up to a central estimate with an equal probability of over/underrun. For each section of the project, upper and lower limits of a triangular distribution representing the quantities are estimated. An additional triangular distribution is estimated for the prices used in the estimate. A Monte Carlo simulation is then performed to establish the Project Cost Probability Distribution. The contingency is then set as the value needed to add to the estimated value to reach the central estimate.

10.2.3 Exclusions The cost estimate does neither include escalation nor effects of currency fluctuation but is set at a firm price level (May 2009). Exclusions also include VAT, customs and duties, cost of capital (interests during construction), cost of land and water rights and other Owner’s cost.

10.2.4 Pricing Methods General Civil work pricing is based production rates obtained from Landsvirkjun (the National Power Company of Iceland) hydro power cost model, adjusted to the local market by comparing to cost information received from local contractors. The cost of turbines, governors and generators is based on a vendor informal budgetary quotations. Other electromechanical equipment is based on experience from the Consultant’s previous projects.

Price Level The estimate is carried out at a price level of May 2009.

Currencey The estimate is published in United States Dollars (USD). The exchange rate between the USD and EUR is set at 1 USD = 0,76 EUR.

Cost of Labor The cost of labor is estimated using information from local contractors as regards hourly rates and productivity as obtained from the Landsvirkjun cost model

Import Duties The estimate does not include any import duties or customs.


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Freight and logistics The cost of freight is included in the direct cost.

EPCM EPCM (Engineering, Procurement and Construction Management) cost is estimated as 14 % of the contractor’s cost.

10.2.5 Estimation methods Quantities are established by material takeoff from preliminary design of dams, waterways and structures. Man hours are estimated using the Landsvirkjun hydro power cost model.

10.3 Final cost estimate A summary of the final cost estimate is presented in the table below. Table 10-1 Cost estimate summary

Cost estimate summary Cost base 2009-05 1 USD = 0,76 EUR

Description Scheduled cost

USD

10 Site installation - mobilisation 3.241.000 20 Diversion canal 800.000 30 Cofferdam 375.000 40 Spillway 1.048.120 50 Main dam 1.528.960 60 Road work 1.437.480 70 Headrace tunnel intake 1.403.317 80 Headrace tunnel 23.487.000 90 Adit plug 318.233 100 Surge facilities 956.160 110 Pressure tunnel 875.000 120 Powerhouse 4.782.206 130 Tailrace tunnel 226.020 140 Tailrace canal 201.150 150 Switchyard 333.100 160 Control Building and access area 647.720 170 Electromechanical equipment 25.840.632 180 Transmission lines 2.400.000

Scheduled cost 69.901.098

Initial studies and EIA (2%) 1.398.022

EPCM cost (14%) *) 9.786.154

Estimated value 81.085.274

Contingencies (15,7%) 12.730.388 Project cost exl. VAT 93.815.662


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Exclusions: VAT Customs and duties Interests during construction (cost of capital) Escalation during construction FOREX variations Other owner's cost

*) EPCM cost includes design, procurement and construction management

78 81 94 110

P10 P90P50

Estimated value 15.7%

-16.3% 17.8%

MUSD

Figure 10-1 Project cost probability distribution The contingency is estimated at 15,7 % and the accuracy at -16,3%/+17,8% (P10/P90), i.e. there is an estimated 90 % probability of cost below 110 MUSD and 90 % probability of cost above 78 MUSD.

10.4 Cash flow and man power schedule The Schedule is combined with the cost estimate to generate a man power curve (see Figure 10-2) and a cash flow curve (see Figure 10-3). The cash flow curve represents the foreseen movement of cash for the project during the work. The man power curve simulates the work force needed each month during the work period.


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Figure 10-2 Man power curve

Figure 10-3 Cash flow curve


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10.5 Energy generation The energy generation is calculated as the average energy generated according to the discharge estimate for each month presented in Chapter 5.2.1 Discharge to powerstation for the years 1934-1985. Other assumptions are as follows:

Maximum discharge through turbines 55 m3/s Average headwater elevation 1011 m a.s.l Tailwater elevation see Figure 5-3 Total headlosses at maximum discharge 14,5 m Average efficiency of turbine and generator 90 % Reduction of energy production due to lack of daily data 1 %

The usable volume of the intake pond is only about 106 m3. It is the same volume as the station utilises every 5 hours at full load. The pond can therefore be used for flow regulations within the day but not longer periods. As the discharge is never lower than about 20 m3/s (Figure 5-2) the units can, with some help of the small pond, be assumed to operate always at close to the peak efficiency resulting in the average efficiency being assumed relatively high or 92%. Based on those assumptions the result is as follows:

Average energy generation 245 GWh/a

The value of the produced energy is as estimated by the Owner, 4 US¢/kWh from April through September but 50% higher, or 6 US¢/kWh, during the colder and dryer months, October through March. According to that energy price and that all the energy that can be produced can be sold results in following incomes:

Annual average incomes from energy production 11,8 MUSD/a

The energy production varies in accordance with the flow during the historical years between 212 GWh/a and 306 GWh/a with the income varying between 10,1 MUSD/a and 14,7 MUSD/a as can be seen on Figure 10-4 below.

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Figure 10-4 Energy generation and value of produced energy according to historical discharge for different years


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11 Conclusions and recommendations

11.1 Main conclusions The development of Mtkvari hydroelectric project, as shown in this Feasibility report is considered both technically and economically viable. Admittedly, there exist a number of uncertainties as i.a. reflected in the implied contingencies which may be reduced with further pertinent studies. Although such may affect the cost, this will only be to limited amount and certainly not to the extent as to jeopardise the viability of the project. It is recommended that the Project is brought to the next step of preparation, i.e. Tender design or EPCM stage (Engineering, procurement and construction management).

11.2 Conceptual design A conceptual design has been developed, based i.a. on the following key parameters and what the Owner considers satisfactory income:

• Full intake pond level 1.012 m a.s.l. • Design discharge 55 m2/s • Installed capacity 2x21,5 MW

The proposed design discharge is based on evaluation of discharge data, provided by the Owner, resulting in estimated annual energy production 245 GWh/a which corresponds to some 5.700 h/a utility action. This corresponds to 65 % efficiency of the installed capacity, implying that a reservoir storage should be very beneficial for the project. The layout as described in Chapter 8 and consists of:

• A 300 m long intake dam with maximum height of about 25 m • A 120 m long overflow spillway • An intake equipped with trashracks and bulkhead • 9,6 km long headrace tunnel, 32 m2 in cross section • A surge shaft close to the powerhouse • A pressure tunnel and two embedded penstocks conveying water to an underground

powerhouse • Two vertical Francis turbine units of 21,5 MW each • Two generators 23 MVA each, 10 kV • A 32 m2 tailrace tunnel and 140 m long tailrace canal • 8 km long, 110 kV transmission line

The total construction time is estimated three years. The total project cost is estimated as follows: Scheduled cost 69,9 MUSD Initial studies and EIA (2 %) 1,4 EPCM cost (14%) 9,8 Contingencies (15,7%) 12,7 Project cost exl. VAT 93,8 MUSD The estimated average energy production is 245 GWh/a, implying a cost per annual kWh of 0,38 USD/kWh which is well within the presumed selling cost of the energy. The estimated cost per installed kW is thus approximately 2.200 USD.


42

As outlined in the Conceptual report (Verkís hf. 2009), the energy cost is to a great extend governed by the interest rate (cost of capital). As an example, 6% annual interest rate, 1% annual O&M cost (operation and maintenance) and 40 years plant operation, this would give 2,8 US¢/kWh, as shown in the table below, compared to estimated current energy prices 4 to 6 US¢/kWh (Chapter 10.5 – Energy generation) . See also Table 3 in the Conceptual report (Verkís hf. 2009) for effect of different interest rates of the capital. Table 11-1 Average energy cost as a function of interest rates

Annual interest rate % pa

Average energy cost US¢/kWh

5 2,55 6 2,84 7 3,15 8 3,46 9 3,78

10 4,09

Note, the following is excluded (cf. Appendix D): - VAT - Customs and duties - Interest rates during construction (cost of capital) - Escalation - FOREX variations - Other Owner’s cost

11.3 Further studies and investigations Further development of the Mtkvari hydroelectric project should consider the following principles and specific design criteria:

• Additional geological investigations should be carried out on the proposed headrace tunnel area, including core-drilled boreholes, down to or below the tunnel alignment, along with establishing further the existing groundwater regime.

• Discharge evaluation (measurement and modelling), both as regards harnessed discharge and potential floods.

• Investigation, sampling and testing of construction materials • Establishment of earthquake design spectrum • Planning of roads and bridges • Further mapping and evaluation of avalanche and rockfall potentials in the project area. • Specific studies on TBM versus roadheader or D&B execution of the headrace tunnel. • Evaluation of the potential connection to a substation nearer than the town Akhaltsikhe.


43

12 References Balassanian, S; Ashirov, T.; Chelidze, T. et al. 1999. Seismic hazard assessment for the Caucasus test area. Annals of Geophysics, vol. 42, N. 6. Geoengineering Ltd a. (Mr. G. Seturidze). General assessment of engineering-geological conditions of building territory of Mtkvari HES. Geoengineering Ltd b. Topographical survey. Headworks and lower works area (Cad files). Geoengineering Ltd. 2009. Mtkvari Hydroelectric Power Station (HPS) on the River Mtkvari in Georgia – Geotechnical Investigations. Tblisi. Hydroproject Ltd. Hydrological data (provided by the Owner). M.Z. Nodia Institute of Geophysics. 2009. Seismic Hazard on the Construction Sites for Hydro electrical Power Plants on the r. Mtkvari. Verkís/Landsvirkjun Power. December 2008. Site visit report. Verkís hf. 2009. Mtkvari Hydroelectric Project - Conceptual Report. Reykjavík, Iceland.


Appendices APPENDIX A Average monthly flow in Mtkvari river at headworks of Mtkvari HEP APPENDIX B Monthly flow in tributary rivers Uraveli and Pokhof 1976 to 1980 APPENDIX C Assumed monthly average discharge to the headworks of Mtkvari in m3/s APPENDIX D Bill of quantities and cost estimate APPENDIX E Construction schedule


APPENDIX A

Average monthly flow in Mtkvari river at headworks of the Mtkvari HEP (Estimated by HydroProject Ltd., provided by the Owner)


APPENDIX B

Monthly flow in tributary rivers Uraveli and Pokhof 1976 to 1980 (provided by the Owner)


APPENDIX C Assumed monthly average discharge to the headworks of Mtkvari in m3/s This data was obtained from the International Hydrological Programme – UNESCO’S intergovernmental scientific programme in water resources. In a joint SHI/UNESCO product prepared by Prof. Igor A. Shiklomanov of the State Hydrological Institude (SHI), they present a ,Discharge of selected rivers of the world’ (web: http://webworld.unesco.org/water/ihp/db/shiklomanov/). It includes publication of measured river discharge of numerous rivers in Georgia, including the river Mtkvari.


Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual

1934 23,3 27,4 33,9 66,9 131,3 65,9 34,6 26,5 21,6 23,9 25,3 23,1 42,1 1935 23,7 25,4 28,3 133,9 149,2 46,9 27,3 27,8 23,2 23,2 24,1 24,1 46,5 1936 24,3 23,8 26,1 109,0 208,3 116,9 51,1 32,4 29,0 32,5 34,5 27,3 59,8 1937 24,5 23,8 47,3 165,4 215,8 108,4 35,4 28,5 26,5 28,1 27,3 24,6 63,1 1938 25,7 28,4 31,0 152,0 168,9 83,1 30,4 27,6 27,4 26,9 23,3 22,0 53,9 1939 22,6 23,3 28,2 132,0 163,2 58,6 67,1 94,4 68,0 49,5 46,9 35,4 66,0 1940 32,6 31,9 32,9 340,4 187,6 87,6 58,0 29,6 28,6 31,7 31,8 30,0 76,8 1941 28,9 32,8 39,8 178,8 180,1 45,2 30,2 24,8 24,7 27,3 32,4 26,6 56,0 1942 26,0 26,2 28,7 126,2 254,3 79,7 36,0 27,8 26,7 28,1 26,1 21,1 59,1 1943 21,1 21,2 22,1 84,3 123,8 45,1 26,5 22,3 20,1 20,2 21,5 21,1 37,5 1944 20,9 21,7 39,0 97,5 238,3 64,7 35,8 23,1 19,9 19,9 28,6 19,8 52,7 1945 20,9 19,7 21,4 109,0 151,1 82,6 38,2 23,8 22,9 23,6 23,4 22,2 46,6 1946 20,8 21,7 24,8 89,3 167,9 107,4 50,3 32,9 24,6 28,7 28,4 24,6 51,9 1947 23,1 23,0 39,2 65,5 45,0 32,7 22,7 19,9 20,2 20,8 23,4 21,0 29,7 1948 25,1 25,0 26,2 135,8 166,1 101,8 26,3 24,6 25,1 25,1 25,4 24,1 52,5 1949 24,2 23,6 26,3 62,5 218,6 63,0 16,7 25,9 21,7 22,5 21,0 19,7 45,7 1950 20,6 22,2 23,5 174,0 208,3 65,0 30,2 21,8 21,4 26,3 25,1 22,1 55,1 1951 22,2 22,6 55,7 86,3 88,2 78,6 49,8 29,4 30,7 56,9 51,2 28,1 50,1 1952 28,1 28,9 34,8 249,6 175,4 83,4 38,6 22,3 21,8 21,9 22,7 23,8 62,5 1953 23,0 24,3 26,1 87,1 135,1 80,4 42,9 28,5 22,9 24,0 24,6 22,8 45,2 1954 21,6 22,8 25,8 109,0 256,1 147,0 89,9 26,0 24,2 24,2 23,5 22,7 66,3 1955 22,5 23,9 27,2 62,7 93,8 42,5 20,1 19,0 21,9 21,6 21,4 20,9 33,2 1956 20,1 22,1 22,6 141,5 159,5 111,2 38,7 23,1 26,0 27,5 25,6 24,4 53,5 1957 24,3 23,6 37,5 135,8 112,6 53,0 31,6 24,6 27,6 24,9 25,2 24,1 45,4 1958 24,9 25,2 28,6 81,6 156,7 84,4 32,9 26,1 27,7 27,3 25,7 25,3 47,3 1959 25,7 25,8 28,6 181,7 199,8 131,0 43,1 31,9 29,2 25,8 27,0 23,5 64,4 1960 22,3 24,0 25,9 181,7 147,3 48,4 37,3 26,9 22,8 21,9 21,5 21,5 50,1


1961 23,8 27,9 31,6 78,9 112,6 45,0 29,8 25,5 25,8 26,2 26,5 26,4 40,1 1962 26,1 26,8 44,7 110,9 170,8 68,0 34,3 28,6 28,8 29,4 29,6 30,0 52,5 1963 30,2 30,2 30,0 137,7 228,0 173,4 136,9 77,2 34,5 34,2 32,5 30,5 81,6 1964 21,5 22,7 46,8 165,4 235,5 155,5 38,0 23,3 23,4 23,3 23,2 21,8 66,8 1965 23,3 24,1 30,3 172,1 246,7 108,4 42,7 30,0 22,4 26,1 25,4 24,6 64,8 1966 25,0 24,7 29,6 99,4 163,2 63,2 34,9 24,6 26,6 27,1 27,0 27,3 47,9 1967 22,7 22,3 24,7 49,9 144,5 69,9 48,3 51,9 35,6 28,7 29,3 29,5 46,7 1968 29,5 30,7 33,8 321,3 237,4 96,1 50,7 33,0 32,9 30,6 30,1 28,3 79,5 1969 32,5 33,4 41,2 131,0 144,5 31,8 20,7 20,9 21,9 23,3 22,4 22,8 45,5 1970 22,7 22,7 35,4 138,6 70,2 37,6 29,1 29,0 29,9 30,8 29,0 26,7 41,8 1971 26,3 26,6 51,2 96,6 172,6 81,0 30,0 34,1 27,6 27,3 27,8 26,1 52,4 1972 27,6 28,3 29,9 185,5 143,5 99,9 44,7 31,9 38,5 33,3 28,9 26,8 59,9 1973 26,8 27,1 29,4 161,6 168,9 95,2 43,8 23,0 22,5 23,1 23,5 23,1 55,7 1974 23,9 23,2 50,2 59,3 174,5 59,1 23,9 21,2 29,0 22,9 23,1 23,1 44,7 1975 23,2 23,2 29,4 155,9 126,7 73,8 30,0 22,1 22,6 25,0 23,9 22,3 48,1 1976 22,7 23,0 26,4 140,6 253,3 99,9 51,3 25,3 24,6 26,8 25,4 24,6 62,2 1977 23,6 24,4 29,4 110,0 157,6 90,7 41,6 23,7 24,9 25,6 25,4 23,7 50,1 1978 23,4 25,1 34,0 151,1 223,3 85,2 31,0 24,0 22,0 23,0 23,1 23,0 57,5 1979 23,3 24,0 33,7 102,3 160,4 107,4 61,1 24,1 21,4 24,0 28,0 23,6 52,9 1980 24,2 23,4 44,7 170,2 140,7 40,1 23,4 25,3 22,5 25,0 25,7 25,3 49,3 1981 25,0 25,5 34,8 66,1 124,8 101,8 37,6 24,7 23,6 24,3 25,6 25,0 45,0 1982 24,0 24,6 26,1 147,3 151,1 66,4 30,9 22,0 22,8 23,1 23,1 22,0 48,6 1983 22,0 22,1 28,7 73,3 103,2 72,6 27,2 20,1 24,8 24,4 32,3 26,2 39,8 1984 23,1 22,7 54,7 154,9 201,7 81,6 35,8 23,8 21,3 21,4 22,4 21,7 57,2 1985 21,9 22,2 24,9 139,6 120,1 51,6 25,1 20,9 22,9 26,6 27,3 26,6 44,1

Average 24,3 24,9 32,8 131,9 166,9 80,2 39,3 28,5 26,1 26,7 26,9 24,6 52,84


APPENDIX D

Bill of quantities and cost estimate

Cost estimate summary Cost base 2009-05

1 USD = 0,76 EUR

Scheduled cost

USD

10 Site installation - mobilisation 3.241.000

20 Diversion canal 800.000

30 Cofferdam 375.000

40 Spillway 1.048.120

50 Main dam 1.528.960

60 Road work 1.437.480

70 Headrace tunnel intake 1.403.317

80 Headrace tunnel 23.487.000

90 Adit plug 318.233

100 Surge facilities 956.160

110 Pressure tunnel 875.000

120 Powerhouse 4.782.206

130 Tailrace tunnel 226.020

140 Tailrace canal 201.150

150 Switchyard 333.100

160 Control Building and access area 647.720

170 Electromechanical equipment 25.840.632

180 Transmission lines 2.400.000

Scheduled cost 69.901.098

Initial studies and EIA (2%) 1.398.022

EPCM cost (14%) *) 9.786.154

Estimated value 81.085.274

Contingencies (15,7%) 12.730.388

Project cost exl. VAT 93.815.662

Exclusions:

VAT

Customs and duties

Interests during construction (cost of capital)

Escalation during construction

FOREX variations

Other owner's cost

*) EPCM cost includes design, procurement and construction management

Description

K:\2008.03\10\aaetl\kost\BoQ\Mtkvari_BoQ_2009-07-06.xls D1

Bill of Quantities - Feasibility Report Cost base 2009-05

excl. VAT

USD/unit USD

10 Site installation - mobilisationTemporary buildings ls 1 1.665.000

Temporary electricity ls 1 73.000

Temporary roads ls 1 207.000

Mobilization ls 1 1.296.000

-10 Subtotal 3.241.000

20 Diversion canalLoose excavation m³ 110.000 4 440.000

Rock excavation m³ 40.000 9 360.000

-20 Subtotal 800.000

30 CofferdamFills m³ 75.000 5 375.000


40 SpillwayLoose excavation m³ 172.000 4 688.000


Drilling for grout m 1.000 13 13.000

Grouting m³ 30 996 29.880

Concrete m³ 400 238 95.200

Forms, straight m2 200 121 24.200

Forms, curved m2 370 232 85.840

Reinforcing steel kg 20.000 2 40.000

-40 Subtotal 1.048.120

50 Main damLoose excavation m³ 28.000 3 84.000

Drilling for grout connections m 1.100 13 14.300

Grouting m³ 35 996 34.860

Foundation treatment m² 3.100 6 18.600

Fills m³ 143.600 8 1.148.800

Wave protection m³ 4.400 35 154.000

Slope protection m³ 3.100 24 74.400

-50 Subtotal 1.528.960

60 Road workLoose excavation m³ 13.500 4 54.000


Road fill m³ 81.000 10 810.000

Pavement m2 12.900 17 219.300

PriceDescription Unit

Estimated

quantity



excl. VAT

USD/unit USD


Estimated

quantity

Crash barrier m 2.100 89 186.900

Culvert, ø6 m m 20 2.064 41.280

-60 Subtotal 1.437.480

70 Headrace tunnel intakeLoose excavation m³ 900 3 2.700

Rock excavation m³ 900 9 8.100

Rip rap m³ 340 35 11.900

Concrete m³ 840 238 199.920

Forms, straight m2 1.700 121 205.700

Forms, curved m2 100 232 23.200


Miscellaneous steel kg 2.500 8 20.000

Trashrack (7 × 8 m) ea 1 472.969 472.969

Bulkhead (6×6×17 m) (b×h×H) ea 1 324.428 324.428

-70 Subtotal 1.403.317

80 Headrace tunnelCare of water ls 1 1.089.000

D&B excavation, Drive I m³ 64.000 32 2.048.000

D&B excavation, Drive A1 m³ 17.600 31 545.600

D&B excavation, Drive A1.1 m³ 19.200 32 614.400

D&B excavation, Drive A1.2 m³ 72.000 35 2.520.000

D&B excavation, Drive A2 m³ 19.200 32 614.400

D&B excavation, Drive A2.1 m³ 72.000 35 2.520.000

D&B excavation, Drive A2.2 m³ 16.000 32 512.000

D&B excavation, Drive 2 m³ 64.000 32 2.048.000

Shotcrete, at face m³ 4.600 696 3.201.600

Shotcrete m³ 10.000 449 4.490.000

Rock bolts m 72.500 41 2.972.500

Concrete m³ 400 238 95.200


Forms, straight m2 300 121 36.300

Forms, curved m2 500 232 116.000

-80 Subtotal 23.487.000

90 Adit plug

Drilling for grout m 200 13 2.600

Grouting m³ 5 994 4.970

Concrete m³ 230 238 54.740

Forms m2 200 121 24.200


Access door & accessories (2,5 × 3,0 m) ea 1 204.123 204.123




excl. VAT

USD/unit USD


Estimated

quantity

100 Surge facilitiesLoose excavation m³ 1.700 3 5.100


Shaft excavation m³ 550 618 339.900

Shotcrete m³ 400 449 179.600

Rock bolts m 2.200 41 90.200

Metalwork ls 1 116.000

Fence m 180 307 55.260

-100 Subtotal 956.160

110 Pressure tunnel

D&B excavation w/ steel liner ø3,4 m³ 2.200 35 77.000

D&B excavation w/ steel liner ø2,3 m³ 700 48 33.600

Drilling for grout m 200 13 2.600

Grouting m³ 5 994 4.970

Shotcrete m³ 180 449 80.820

Rock bolts m 1.500 41 61.500

Concrete m³ 570 238 135.660

Forms m2 50 121 6.050


Steel lining kg 50.000 9 450.000

-110 Subtotal 875.000

120 PowerhouseCavern excavation m³ 12.100 17 205.700

Cavern excavation, roof m³ 3.500 21 73.500

Draft tube excavation m³ 1.100 31 34.100

D&B cable tunnel excavation m³ 1.500 75 112.500

Shotcrete m³ 900 449 404.100

Rock bolts m 5.000 41 205.000

Concrete m³ 2.500 238 595.000

Forms m2 3.900 121 471.900


Architectural & finishing ls 1 669.000

Powerhouse Building systems electrical ls 1 403.000

Powerhouse Building systems HVAC ls 1 387.000

Powerhouse Building systems piping ls 1 355.000

Metalwork ls 1 69.000

Draft tube gates ( 2 pieces 3,5 × 5,8 m) ea 2 259.103 518.206

-120 Subtotal 4.782.206

130 Tailrace tunnelD&B excavation m³ 3.200 30 96.000

Shotcrete m³ 180 449 80.820

Rock bolts m 1.200 41 49.200



excl. VAT

USD/unit USD


Estimated

quantity

-130 Subtotal 226.020

140 Tailrace canalLoose excavation m³ 28.050 3 84.150


Slope protection m³ 3.900 24 93.600

-140 Subtotal 201.150

150 SwitchyardLoose excavation m³ 800 3 2.400

Concrete m³ 230 238 54.740

Forms m2 450 121 54.450


Steel structure ls 1 154.000

Fence m 130 307 39.910

-150 Subtotal 333.100

160 Control Building and access areaLoose excavation m³ 10.500 3 31.500


Concrete m³ 110 238 26.180

Forms m2 560 121 67.760


Finishing, A 130 m2

m² 130 836 108.680

Bridge & access road ls 1 302.000

-160 Subtotal 647.720

170 Electromechanical equipmentTurbines, governors, auxiliaries, inlet valves ls 1 11.125.400

Generators with auxiliaries (2 pieces) ls 1 12.202.400

Overhead crane (80 tons) ls 1 252.000

Transformers (2 pieces) ls 1 1.448.832

Switchyard equipment ls 1 812.000

-170 Subtotal 25.840.632

180 Transmission lines110kV line, all in km 8 300.000 2.400.000

-180 Subtotal 2.400.000

GRAND TOTAL 69.901.098



APPENDIX E

Construction schedule

Activity Name OriginalDuration

Start Finish

00 General 208 05-Jan-09 A 04-Nov-09

Feasibility study 118 05-Jan-09 A 29-Jun-09

Contracting (EPCM) 96 15-May-09 A 04-Nov-09

Decision to proceed 0 04-Nov-09

10 Mobilisation & Site Installation 59 04-Nov-09 01-Feb-10

Mobilization, construction power plants & workshops 59 04-Nov-09 01-Feb-10

20 Diversion Canal 60 01-Feb-10 30-Apr-10

Diversion Canal - Excavation 60 01-Feb-10 30-Apr-10

30 Cofferdam 124 29-Mar-10 01-Oct-10

Cofferdam - Fill of cofferdam 124 29-Mar-10 01-Oct-10

40 Spillway 140 08-Apr-11 01-Nov-11

Spillway - Excavation 56 08-Apr-11 05-Jul-11

Spillway - Concrete work 84 05-Jul-11 01-Nov-11

50 Main dam 336 10-Feb-11 15-Jun-12

Main dam 336 10-Feb-11 15-Jun-12

60 Road works 461 02-Dec-09 14-Oct-11

Access road - Bridge 62 02-Dec-09 04-Mar-10

Access road - Road to powerhouse 65 04-Mar-10 11-Jun-10

Road work - Excavation and fill 62 08-Apr-11 13-Jul-11

Road work - Pavement 60 21-Jul-11 14-Oct-11

70 Headrace tunnel intake 137 28-Mar-11 14-Oct-11

Power intake - Excavation 40 28-Mar-11 26-May-11

Power intake - Concrete work 43 26-May-11 29-Jul-11

Power intake - Installation of equipment 54 29-Jul-11 14-Oct-11

80 Headrace tunnel D=6,0m 588 01-Feb-10 15-Jun-12

Adit 1, excavation 61 01-Feb-10 03-May-10

Adit 2, excavation 81 01-Feb-10 02-Jun-10

Drive A 1.1 95 04-May-10 21-Sep-10

Drive A 1.2 294 04-May-10 13-Jul-11

Drive A 2.1 293 02-Jun-10 09-Aug-11

Drive A 2.2 66 02-Jun-10 07-Sep-10

Drive I 268 10-Sep-10 06-Oct-11

Drive II 269 15-Nov-10 13-Dec-11

Support and finishing 225 25-Jul-11 15-Jun-12

90 Adit plug 32 18-Jun-12 01-Aug-12

Adit plug 32 18-Jun-12 01-Aug-12

100 Surge shaft 52 01-Jun-11 18-Aug-11

Surge shaft 52 01-Jun-11 18-Aug-11

110 Pressure tunnel 179 09-Mar-11 23-Nov-11

Pressure tunnel excavation 44 09-Mar-11 13-May-11

Steel lining - Installation 72 13-May-11 26-Aug-11

Steel lining - Embedment 63 29-Aug-11 23-Nov-11

120 Powerhouse 499 14-Jun-10 14-Jun-12

Power house - Surface excavation 60 14-Jun-10 09-Sep-10

Power house - Access tunnel excavation 55 10-Sep-10 26-Nov-10

Power house - Cable tunnel excavation 53 16-Dec-10 04-Mar-11

J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F2009 2010 2011 2012 2013

Decision to proceed

MTKVARI HEP GEORGIA - CONSTRUCTION SCHEDULE

Remaining Work

Critical Remaining Work

Milestone

% Complete

Page 1 of 2

01-Jul-09

© Primavera Systems, Inc.

Activity Name OriginalDuration

Start Finish

Power house - Powerhouse excavation 55 16-Dec-10 09-Mar-11

Power house - Concreting, Power house superstructure 65 09-Mar-11 15-Jun-11

Power house - Architectural & Finishing work 66 15-Jun-11 19-Sep-11

Power house - Draft tube gates erection 40 15-Jun-11 11-Aug-11

Power house - Overhead crane installation 20 14-Jul-11 12-Aug-11

Power house - Turbine erection 122 12-Aug-11 01-Feb-12

Power house - Generator erection and auxiliaries 89 02-Feb-12 14-Jun-12

130 Tailrace tunnel 69 20-Jun-11 26-Sep-11

Tailrace - Open cut excavation 33 20-Jun-11 04-Aug-11

Tailrace - Tunnel excavation 36 05-Aug-11 26-Sep-11

140 Tailrace canal 31 26-Sep-11 07-Nov-11

Tailrace canal 31 26-Sep-11 07-Nov-11

150 Switchyard 72 08-Nov-11 17-Feb-12

Switchyard - Foundations 30 08-Nov-11 20-Dec-11

Switchyard - Equipment Installation 42 21-Dec-11 17-Feb-12

160 Control building and access area 167 08-Nov-11 10-Jul-12

Control house - Building 117 08-Nov-11 26-Apr-12

Control house - Installation of equipment 50 27-Apr-12 10-Jul-12

170 Electromechanical equipment 223 30-May-11 18-Apr-12

Electromechanical equipment 223 30-May-11 18-Apr-12

180 Transmission lines 180 09-Nov-11 31-Jul-12

Transmission line - Foundations 60 09-Nov-11 03-Feb-12

Transmission line - Master erection 60 03-Feb-12 04-May-12

Transmission line - Lines installation 60 04-May-12 31-Jul-12

Testing and commissioning 80 01-Aug-12 22-Nov-12

Unit 1 40 01-Aug-12 27-Sep-12

Unit 2 40 27-Sep-12 22-Nov-12

J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F2009 2010 2011 2012 2013

MTKVARI HEP GEORGIA - CONSTRUCTION SCHEDULE

Remaining Work

Critical Remaining Work

Milestone

% Complete

Page 2 of 2

01-Jul-09

© Primavera Systems, Inc.


List of Drawings No. Description

2.001 Project location map 2.002 Project plan, General layout 2.003 Headwork area, Overview 2.004 Diversion canal, Plan and sections 2.005 Spillway, Plan and sections 2.006 Main dam, Plan and longitudinal section 2.007 Cofferdam, Plan and longitudinal section 2.008 Main dam and cofferdam, Typical cross sections 2.009 Permanent road 1/2, Layout and sections 2.010 Permanent road 2/2, Layout and sections 2.011 Headrace tunnel intake, Plan El. 1000,0 and section 2.012 Headrace tunnel intake, Plan El. 1016,0 2.013 Headrace tunnel and adits, Plan and sections 2.014 Surge facilities, Plan and section 2.015 Powerhouse area, overview 2.016 Adit plug and tunnels, overview and sections 2.017 Powerhouse, Valve & turbine floor 2.018 Powerhouse, Generator & entrance floor 2.019 Powerhouse, Cross sections 2.020 Powerhouse, Longitudinal section 2.022 Tailrace tunnel and canal, Plan and sections 2.023 Switchyard and control building, Layout 2.024 Switchyard and control building, Facade and sections 2.025 High voltage, Single line diagram 2.026 Protection system, Schematic diagram 2.027 Control system, Schematic diagram 2.028 Turbines, Schematic diagram 2.029 Cooling water system, Schematic diagram 2.030 Drainage system, Schematic diagram 2.031 Ventilation system, Schematic diagram

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