14.5 MW MAI HYDROPOWER PROJECT
FEASIBILITY STUDY

Submitted by :
Alish Bamanu
Kumud Adhikari
Akash mahat
Bishal Shrestha
Kumar Jeeva Tamang

Submitted to :
Yalam vaidya
Kings College

Table of Contents:
SUMMARY ....................................................................................................................................... 1
SALIENT FEATURES ...................................................................................................................... 2
1. PROJECT BACKGROUND .................................................................................................... 4
2. THE PROJECT AREA ............................................................................................................ 4
3. REPORT INVESTIGATIONS ...................................................................................................... 5
4. BASIC STUDIES ................................................................................................................. ... 7
4.1 HYDROLOGY AND SEDIMENT STUDY .................................................................................... 7
4.2 POWER MARKET ................................................................................................................. 8
4.3 GOVERNMENT POLICY ......................................................................................................... 8
4.4 GEOLOGICAL AND GEOTECHNICAL STUDIES ........................................................................ 9
4.5 SEISMICITY ........................................................................................................................ 12
4.6 MASS WASTING STUDY ..................................................................................................... 12
5. PROJECT LAYOUT ............................................................................................................. 12
6. OPTIMIZATION .................................................................................................................... 13
7. PHYSICAL DESCRIPTION OF THE PROJECT ................................................................. 14
8. ENVIRONMENTAL IMPACTS AND MITIGATION .............................................................. 18
9. CONSTRUCTION SCHEDULE AND COST ........................................................................ 19
9.1 ACCESS ROAD .................................................................................................................. 19
9.2 CAMPS AND FACILITIES ..................................................................................................... 19
9.3 CONSTRUCTION POWER .................................................................................................... 20
9.4 CONTRACT PACKAGE ........................................................................................................ 20
9.5 PROJECT IMPLEMENTATION SCHEDULE ............................................................................. 20
9.6 COST ESTIMATE ................................................................................................................ 20
9.7 DISBURSEMENT SCHEDULE ............................................................................................... 22
10. PROJECT OUTPUTS AND BENEFITS ............................................................................... 22
11. PROJECT EVALUATION ..................................................................................................... 23
12. CONCLUSION AND RECOMMENDATIONS ...................................................................... 24
12.1 CONCLUSIONS................................................................................................................... 24
12.2 RECOMMENDATIONS ......................................................................................................... 25

List of figures :

Figure 1: Project Location Map
Figure 2: Project Area Map
Figure 3: Project Layout
Figure 4: Headworks General Arrangement
Figure 5: Powerhouse General Arrangement
Figure 6: Tailrace General Arrangement
Figure 7: Single Line Diagram at Delivery Point
Figure 8: Implementation Schedule

SUMMARY
Mai Hydropower Project (MHP) was identified by Sanima Hydropower (P.) Ltd. following a reconnaissance study under taken by the company in 2004. After obtaining the survey licence from Government of Nepal (GoN) a detail study was carried out to determine the feasibility of the project. This feasibility report is the out come of the continuous and untiring efforts put up by the staff of the company spanning several years of experience.

The project site is located at a distance of 30 km north from Birtamod in East-West Highway.
Headworks of the project is located on t he Mai Khola between the boarder of two Village
Development Committees (VDCs) namely Chisapani and Soyak in Ilam District. Right bank of the diversion dam lies in Soyak VDC of Ilam district. The powerhouse site is located at
Musekhop village approximately 4.5 km upstream from the confluence of the Lodhiya Khola and Mai Khola in Danabari VDC of Ilam district.

Initially, in June 2006, MHP was proposed as a daily peaking run of river project with installed capacity of 20.1 MW (2x10.05 MW) with design discharge of 21.4 m3/s and net head of 108.9 m.
As the NEA’s requirement on peaking hour supply Project is of no significance at present (when the base dement is not met) and there is no adequate exercise neither from the Government nor from NEA side to propose the peak hour energy pr ice, NEA side asked to propose the simple run-of-river plant. The optimization study carried out by the company showed that the least cost option for the simple run-of-river scheme at the proposed Mai Khola location is the 14.5 MW run-of-river Project. This report summarizes the out come of the study for the 14.5 MW simple run-of-river scheme and further addresses the settled technical parameters, the cost and energy finalized by both NEA and SHPL side during the technical review of NEA and has been the basis for negotiating the energy rates for Po wer Purchase Agreement (PPA) with NEA.

The 14.5MW MHP is technically feasible and po sses characteristics very desirable for the
INPS system by serving to reduce technical lo ss, improve the voltage profile and power supply scenario in the region. In addition, this Project will help to reduce the operation of the expensive thermal power to some extent and dependency on Indian system for the Eastern
Nepal. The Project’s proximity to the power-hungry Eastern load center of Nepal will be the biggest attraction of NEA.

Headworks of MHP on the Mai river, located just downstream of the Soktim Tea State diverts water through a 2172 m long headrace tunnel and 474 m long exposed penstock pipe to the semi-surface powerhouse and generates 14.5 MW through two vertical axis Francis turbines then water will be discharged to Lodhiya khola through 1370 m long stone masonry tailrace canal and 225 m long tailrace pipe.

The project cost on the basis of unit rates as applicable on March 2006 is NPR 1941.8 million before interest during construction. The gr oss energy production is 98.53GWh (Poush to
Chaitra = 20.98 GWh and Baisakh to Marg = 77.55 GWh). At the delivery point of NEA’s
Anarmani substation, the net energy to be supplied is 88.440 GWh per annum with double circuit 33kV transmission line.

The project is financially viable at an average energy rate of 4.48NPR/kWh (lower rates as compared to the existing energy rates of the priv ate sector power plants with simple run-of-river schemes of this range) in base year of 2006 and the escalation as described below.

Base case financial evaluation shows that the NPV of the Project is 1283 million NPR, the internal rate of return is 17.52% and Benefit to Cost ratio is 1.54. Further, the NPV of government takes (as a royalty and tax takes) is also as high as NPR 761 million. The return on equity is 24.58%. These parameters are as presented below:

Financial Parameters | Base-Case | At 110% cost and 90% revenue | NPV, MNPR | 1,283 | 862 | IRR% | 17.52% | 14.87% | B/C-ratio | 1.54 | 1.36 | RoE, % | 24.58% | 19.30% | NPV-Govt takes, MNPR | 761 | 641 |

Since the hydropower project involv es many risk factors, return on equity less than 20% will be very risky for the investor to invest into hydropower projects. The above financial parameters are resulted from the average energy price as tabulated below:

Year2006 ‘07 ‘08 ‘09 ’10 ’11 ’12 ’13 ‘14 ‘15 ’16 ‘17 ‘ 18 ‘19 ‘20 ‘21
NPR4.48/kWh 4.75 5.02 5.29 5.56 5.82 5.97 6.12 6.26 6.41 6.55 6.70 6.84 6.99 7.13 7.28
Commercial operation is envisioned in the end of year 2010.

SALIENT FEATURES
Location: Danabari and Chisapani VDC, Ilam District, Eastern Development Region of Nepal
Purpose of Project: To supply for domestic use by connecting to national grid
Hydrology:
Catchment Area 589.0 km2
Average Flow 32.66 m3/s (minimum monthly flow 7.22 m3/s)
Design Flow 15.40 m3/s (50.31% ecceedance flow)
90% Exceedance flow 7.48 m3/s
Design Flood (Q100) 3590 m3/s

Diversion Dam:
Type :Concrete gravity dam
Slope: Ogee-profile
Crest Elevation : 316.0 m above msl
Crest Length :133.0 m
Maximum height :7.0 m
River Diversion During Construction:
Alignment : Along the river channel
Diversion flow: 250 m3/s
Coffer dams : Two cofferdams facilitating stage1 and stage2 concreting : (Total coffer dam length=660m)
Spillway:
Type: Over-flow weir with under-sluice (2x8m width)
Crest Elevation : 316.0 m above msl (undersluice 311.0 m above msl)
Maximum Flood Level: 322.5 m above msl
Length: 133.0 m
Design Discharge: 3590 m3/s
Intake:
Type: Side Intake, submerged orifice
Number of Orifices: 4
Bottom Elevation of Orifice : 313.5 m above msl
Top Elevation of Orifice: 315.5 m above msl
Length of Orifices: 3.0 m

Gravel Trap:
Type: Convensional flushing, Single chamber
Top elevation: 317.75 m above msl
Average Height: 6.2 m
Average Width: 14.0 m
Side spillway crest elevation: 316.0 m above msl
Spillway length: 20 m
Settling Basin:
Type: Convensional flushing
Number of Chamber: 3 (Three)
Top elevation: 316.30 m above msl
Normal Operation elvation: 315.80 m above msl
Length of the basin: 70.3 m
Average Height: 5.25 m
Average Width per Chamber: 8.25 m
Headrace Canal:
Type: Trapezoidal, Stone masonary with concrete lining
Length: 775 m
Height: 2.5 m
Bottom width: 2.5 m
Longitudinal slope: 1:1500 (V ertical:Horizontal)
Side slopes: 1:1 (Vertical:Horizontal)
Headrace Tunnel:
Length: 2172.0 m
Dimensions Inverted: D 3.8x3.8m, (13 m2-finish)
Discharge: 15.40 m3/s
Surge Tank dimensions:
Type: Vertical, circular section
Height: 28.0m
Diameter: 6.0m (finish)
Penstock
Length: 474m
Diameter/thickness: 2.35 m internal dimeter/10 mm to 28 mm thickness
Power Facilities:
Powerhouse Type: Semi-surface
Dimensions : 27.0 m x 22 m
Gross Head: 117.0 m (316.0 – 199.0 m above msl)
Net Head: 109.58 m
Installed capacity : 14.5 MW (2x7.25MW)
Annual Net Energy Output: 88.44 GWh
Tailrace Canal:
Type: Trapezoidal, Stone masonary with concrete lining and steel pipe
Length: 1370 m canal and 1.5 dia pipe 225 m
Height: 1.5 m
Bottom width: 1.5 m
Longitudinal slope: 1:100 (Vertical:Horizontal)
Side slopes: 1:1 (Vertical:Horizontal)
Transmission Facilities:
Transmission line length: 24 km
Voltage level: 33 kV, double circuit
Project Cost: 2,125 million NPR (29.52 million USD),
Economic and Financial Indicators:
Benefit cost ratio (B/C Ratio): 1.54
Internal Rate of Return: 17.52%
NPV Government takes (as a tax and royalty): 761 million NPR
Net Present Worth: 1283 million NPR
Cost per kW installed Capacity: 2,036 USD/kW

1. PROJECT BACKGROUND

On 14 May 2005 Sanima Hydropower (P) Ltd. (SHPL) obtained feasibility study licence for Mai
Hydropower Project (MHP) from the Department of Electricity De velopment (DoED) of Ministry of Water Resources (MOWR), Government of N epal. This study was then focused to assess the feasibility of the 13.4 MW Run-of-River project optimizing possibi lity for daily peaking arrangement to contribute to acute peak-load cris is in the National Grid during dry months.

SHPL has submitted the complete techno-economic feasibility study of 20.1 MW daily peaking
RoR to NEA on June 2006. The presentation of the feasibility study proposal to NEA was made on July 2006 at the NEA office, Ratnapark, Kathmandu. NEA side then responded that at present when NEA is facing difficulties to supply base load, adding the project with daily peaking capacity in the system wi ll not be beneficial to NEA. Therefore, in accordance with the
NEA’s view, SHPL has made this revision for the simple run-of-river scheme with 14.5 MW installed capacity.

2. THE PROJECT AREA

The project’s headworks is situated on the Mai Khola between the boarder of two Village
Development Committees (VDCs) namely Chisapani and Soyak in Ilam District. Right bank of the diversion dam lies in Soyak VDC of Ilam district. The powerhouse site is located at
Musekhop approximately 4.5 km upstream from the confluence of the Lodhiya Khola and Mai
Khola in Danabari VDC of Ilam district. The intake structures, gravel excluder, headrace canal, settling basin and balancing pond are placed on the left bank of the river at Gunmune village just downstream of the Soktim Tea Garden of Chisapani VDCs. From Gunmune, headrace tunnel starts and runs across the hill passing the boarder of Chisapani and Danabari VDC. The surge shaft area, penstock, powerhouse and outdoor switchyard are located in Danabari VDC.
Tailrace canal is placed along right bank of Muse Kholsa and water will be discharged into
Mai river is one of the tributaries of the Kankai Mai River. The proposed intake of the project lies at approximately 87º53’33.64” E longitude and 26º 49’ 11.9” N latitude and at an elevation of 315 m. The powerhouse is located at appr oximately 87º 53' 2.01” E Longitude and 26º 47’
30.0” N Latitude and at an elevation of 200 m. The catchments area of this project is 589 sq. km. The major tributaries of Mai river upto the location of headworks are Mai, Jog Mai and
Puwa Mai. Deo Mai is also one of the major tributaries which meets Mai river at approximately
8 km downstream of the proposed headworks area. After the confluence of Deo Mai, Mai river is named as Kankaimai Nadi.

The area lies in the Siwalik Zone, immediately south from the boundary with the Lesser
Himalaya. The predominant rock types are sandstone, siltstone and mudstone. The area is mostly covered with forest and cultivated land and tea gardens in the surrounding. The weathered depth of Siwalik rock provides necessary environment for forest and plants.

The proposed MHP lies in sub-tropical & temperate climate zone. The average annual temperature varies from 5.5°C in winter to 29°C in summer. The average annual rainfall in this region is about 1545 mm.
The main access point to the area is at Birtamod of Jhapa district along the East-West
Highway. District headquarters are located in Ilam Municipality, some 77 km north-east from
Birtamod along the Mechi Highway. The primary m eans of access to MHP site is the fair weather road from Birtamod (Jhapa), via Sanischare, khudunabari, Shukhani jungle, Garuwa
Sukrabare, Sitali to Musekhop (Danabari VDC) at powerhouseabout 25 km long. This road is black-topped up to Khudunabari (approximately 9 km) and rest of the portion is earthen. The access to headworks site is along the same road up to Soktim Village and another 1.5 km downhill along the existing road.

There are two tea processing industries in the project area. One is located at Soktim, the other is at Chilinkot. No electricity supply system ex ist in the area. But at some places of project surrounding, an 11 KV transmission li ne from Phikkal Bazar of Ilam district comes primarily to provide energy for tea processing factory. Regulated and well managed system of infrastructures for water supply has not been noted in the area.

The area is relatively accessible. No comm unication system does exist in the area. The nearest town with communication facility is Khudunabari. However, the mobile telephones provided by the Nepal Telecommunications Co rporation do work in the project area.

Most families in the project area are subsistence farmers, gr owing crops and rearing mostly pigs, goats, chickens, cows and buffaloes. Some people specially living in Soktim, Kanchhi
Kaman, Lebartol and Chilingkot work as unskilled and semi skilled workers in the tea estates around the project area. In the recent a large number of young people from the project area are going to the overseas, specially Malasiya and Arab nations searching for employment opportunities. Settlements in the project area are mostly clustered. Banana, broomgrass (Amriso), gingers
(Aduwa) are the most common agro-products which are widely collected in the area and supplied to Silgadi, India. Kerosene, rice, sugar, soap, cloth, medicine, stationary goods, iron products, fast food (Chau-chau / biscuits), spices, cigarettes, chewing tobacco and Gutkha are the major commodities being imported into the vi llages of the area from Birtamod. The average literacy of the area is 50% out of whic h around 60% are male and 40% are female.

3. REPORT INVESTIGATIONS
Surveying
The topographic survey work covering headworks area, tunnel por tal and surge tank area, penstock pipe alignment, powerhouse and switch yard locations, tailrace and approximately
4km length of the tail-water escape co rridor upto Mai Khola was performed.

Hydrological Investigations
The daily climatological/precipitation data as well as hydrological data (daily flow records and sediment data) were collected from the exis ting stations of Department of Hydrology and
Meteorology, GoN. Rajduwali and Mainachuli (Gauging Station no. 728 and 795) were used for the hydrological analysis. Further to this Revision A, the mean monthly flow was derived from the direct catchment correlation of Rajduw ali station. This was adopted because of the following two reasons:
• The catchment area at Rajduwali station is 377 km2 (Elev. Approx. 350m amsl) and that of Puwa Khola at Puwa intake is 107 km2 which is together 484 km2 and is more by 80% of the catchment area at proposed Mai intake at Elevation 310m amsl,
• The proposed intake is close to and at lower elevation and has similar catchment characteristics.

A staff-gauge was installed at the intake location and gauge height readings are taken continuously from May 2005. The established gauging station at the intake site is being calibrated by using current meter to derive the rating curve of this location. Being the short measurement period, the observed data were not interpreted. Observed data are in the lower side.

Sediment Investigations
Available data and sediment records were coll ected. The data were compared with other similar catchments and river basin. No major mass-wasting and big land slides were observed.
Field sediment gauging program was carried out to supplement the available information on sediment. The sediment samples were collec ted from May 2005. The sediment analysis has been carried out for the collected samples in laboratories in Kathmandu.

Geological and Geotechnical Investigations
Geological and geotechnical investigations were carried out to establish geological settings, determine detailed geological and geotechnical conditions of the project area as well as foundation conditions of the weir and the powerhouse area. The tunnel support and tunnel construction cost is highly dependable on geological conditions of the proposed alignment. To predict the costs and support works the investi gations along the tunnel portal area, surge shaft and critical tunnel section area were also carried out.

The data and maps were collected to initiate geological and geotechnical investigations. The surface geological mapping was first carried out and two dimensional Electrical Resistivity
Tomography (ERT) survey was carried out to assess the depth, extent and quality of subsurface material types present in the project area. A total of 13 nos. of 2D ERT profiles summing to approximately 3 km length were investigated.
Electrical resistivity using mise-a-la-masse method was employed to find out the velocity and flow direction of the ground water around two boreholes in diversion weir.
All together 8 test pits were dug at the location of proposed structures. In-situ condition of the materials was logged, samples were collected and analysed to assess material property for foundation and construction suitability. The assessment of rock types found in the ar ea were made in relation to their strength and mineral contents. For this several samples of sandstone, mudstone and siltstone were collected from the field and tested in the laboratories in Kathmandu.

Surveys for Coarse Aggregate, Sand and Impervious Materials
The construction material investigation included identification of borrow areas, test pitting, sample collection and laboratory testing.

Different locations for construction materials such as cohesive soil (red clay), fine and coarse aggregates were identified within the permissible haulage distance from the project area. There are vast alluvial plains of Mai Khola and Lodhiya Khola. Several patches of red clay are also found within reasonable lead distance. The quantity of available material far exceeds than actually needed for MHP implementation. The collected materials were checked at laboratory in Kathmandu and satisfactory results were obtained.

4. BASIC STUDIES
4.1 Hydrology and Sediment Study
The flow duration data has been correlated from the Rajduwali station-Station No. 728 of DHM in Kankaimai River. The design discharge of 15.4 m3/s falls on 50.31% exceedance flow and is presented in the flow duration curve below:

The mean monthly flow was derived from the Rajduwali station-Station No. 728 of DHM in Mai
River. The average long-term mean monthly flow is as follows: Month | Jan | Feb | Mar | Apr | May | June | July | Aug | Sept | Oct | Nov | Dec | Discharge, m3/s | 8.95 | 7.26 | 7.22 | 9.16 | 15.64 | 38.14 | 85.16 | 80.90 | 76.94 | 33.14 | 16.20 | 10.86 |

The average minimum monthly flow is 7.22 m3/s.
The flood frequency analysis gives the following magnitude of floods with corresponding return period: Return period: years 5 10 50 100 1000
Maximum Floods, m3/s 1411 1932 3100 3598 5247

90% exceedance flow = 7.48 m3/s
65% exceedance flow = 10.69 m3/s
50.31% exceedance flow = 15.40 m3/s
Daily Maximum Discharge (October to May) =248.83 m3/s
The design discharge has been adopted as 15.4 m3/s which is 50.31 percentile exceedance flow. The construction flood fo r coffer dam has been adopted as 250m3/s which is maximum daily flow during the period of October to May for the recorded interval. The design flood has been taken as
3590m3/s.The ecological flow release from diversion dam to preserve the ecosystem of Mai Khola is determined to be 0.722 m3/sec (10% of the minimum monthly flow (the minimum monthly flow shall be verified by observing the low flow in the coming years at this intake location). This is considered satisfactory because it is augmented by the discharge of Deomai river after 8 kmfrom the intake, which is about 1.2 m3/sec in dry season.
This will keep the project eco-friendly. This flow has been deducted from the mean monthly flows for power and energyestimation when the flow in the river is less in t he dry months to ensure this flow at all the time through the river.

The specific sediment yield val ue adopted for Mai Khola is 2670 tonnes/Km2/year.
The annualsediment transportation through the weir is 1566740 tonnes. The average sediment concentration is around 5600 ppm. The sediment concentration adopted for the design of the settling basin is 8,000 ppm. Field sediment gauging program was carried out to supplement the available information on sediment. The s ediment sampling result shows that maximum sediment concentration observed was 1052 ppm in August 2005 for this study year. The distribution is such that the sediment is consisted about 90% of silt and 10% of silty clay. The specific gravity of sediment is about 2.73 and the percentage of hard mineral is 57%. Further sediment study is being carried out in year 2006, results have not yet been adjusted.

4.2 Power Market

In Nepal, the growth in electricity gener ation capacity has not been adequate enough to meet the ever increasing demand. The gap betw een demand and supply is widened even further during the dry season of each year when flow of rivers plummet down to the lowest level giving rise to desperate measures of long hours of load shedding as is the case at this time. The demand for electricity is fueled by rapid urbanization particularly in the Terai belt and lower hills, expansion of distribution network, enhancem ent in living standard catalyzed by flow of remittance, and other factors.

On the other hand, the ongoing political instability coupled with financing and other problems has hindered the development of hydropower so that hardly few Mega Watts gets added per 2-3 years period, whereas, about 60-70 MW addition is required each year to keep pace with the demand. According to load forecast of NEA, the capacity demand is expected to grow by about
8% each year. With the changes in political situation and approaching peaceful environment ahead, the demand of electricity will rise even by 100MW per year.

The Eastern region has many promising load centers. Ilam is a burgeoning town with tea estates and bright prospects for tourism industry. The district headquarters of Eastern zone have already been connected to the grid with 33 kV lines. Rural distribution lines are being expanded to the hinterlands each year thereby in creasing the electricity demand of the region.
The network size already developed in the region supports additions in generating capacity in the region without requiring the power to be transported to farther load centers for consumption. That means Mai Project is very desirable also from the perspective of loss reduction for NEA. This Project will replace the expensive thermal power to some extent and even reduce dependency on Indian system for t he Eastern Nepal. Realization of Mai hydropower project will help rapid industrialization of the power hungry eastern Terai belt of
Nepal. Hence this project is very important for the national economy as well.

4.3 Government Policy
Export of hydropower has been stated to be one of the objectives of development in the
Hydropower Development Policy 2001 of Nepal. The Policy provides for both the bilateral and regional cooperation in such development efforts wi th a view to lend support to the growth of the region's economy. The private sector is hi ghly encouraged to participate in such regional projects. The approach paper of the current Tent h Plan (Fiscal Year 2003 -2007) reiterates the above policies of developing regional projects and encouraging private sector in such efforts.
The Water Resources Development Strategy 2002 projects that by 2027 under high growth scenario the country will have developed a to tal hydropower capacity of 22000 MW including
15000 MW for export.

Repatriation Facility
As per the Foreign Investment and Technology Transfer Act,1992, a foreign investor making investment in foreign currency shall be entit led to repatriate the following amounts outside
Nepal:
• The amount received by the sale of the share of foreign investment as a whole or any part thereof,
• The amount received as profit or dividend from foreign investment,
• The amount received as the payment of pr incipal and interest on any foreign loan,
• The foreign investor or a foreign technology supplier is also entitled to repatriate the amount received under the agreement for the technology transfer in such currency as set forth in the concerned agreement as approv ed by the Department of Industries of
HMGN.

Concession (License) Period
The license is provided to the hydropower developer on BOOT (Build, Own, Operate and
Transfer) basis. Study License is provided firs t (if the developer intends to carry out the feasibility study) for maximum 5 years period then the generation licence is issued after the developer concludes the Financial Closing of the Project. The license peri od for BOOT projects is as follows:
• For hydropower projects supplying the in ternal demand, the concession period is 35 years, • For export-oriented hydropower projects, t he concession period is 30 years from the date of issuance of the generation license,
• For storage projects, the term of the generation license may be extended for a maximum period of five years on the basis of the construction period.

Royalties
The government royalty-take for this scale of project to connect to national grid for domestic supply is NPR 150.00 per year per kW instal led capacity and 2% on energy sales up to 15 years of operation. After 15 years of operation these values are NPR 1200.00 and 10% respectively. Taxes
The prevailing taxes are 20% on the net inco me earned. The taxes imposed on hydropower projects from the start of the operation has limi ted the attractiveness of such power plants from the financing point of view. In most of the cases, since royalty takes and tax-takes of the government are high, with the existing energy tariff, the net takes of the developers are very low to make the project financially viable.

4.4 Geological and Geotechnical Studies

The project area consists of sedimentary rocks of the Siwalik locally named as Soktim
Formation. It comprises loosely cemented, m edium bedded to massive, medium to coarse grained, irregular blocky, strong, mica ceous, grey 'salt and pepper' sandstone with intercalation of mudstone, siltstone and calcrete beds. The siltstones are blue, fine grained, medium bedded, medium strong to strong, irregular blocky. The mudstones are light brown, fine grained, medium bedded, medium strong, i rregular blocky with botroidal weathering pattern. In general all rock types are slightly to moderately weathered. Sandstone covers about
40% whereas mudstone and siltstone cover 30% and 30% in the project area.

The MBT is present at about 400 m upstream from the weir axis. The MBT is characterized by about 25-30 m wide zone of alternate of s heared/jointed rock and fault gauge/breccias.
However, shearing effects were not observed in and around the proposed weir axis area.
Hence, the effect of MBT is likely to be less in the weir site. In addition two major shear zones are present in the area; one downstream of the headworks and the other near powerhouse area. They are characterised by crushed rock and fault breccias with seepage. The shear zone in powerhouse site is more active than that of the headworks’. Apart from major shear zone six minor shear/weak zones of 10 to 25 m thic k were identified along tunnel alignment.

The weir axis and sluice structure areas are pr oposed on alluvial deposit consisting of rounded to well rounded boulders, cobbles, pebbles and grav els (60%) in sand matrix (40%). The slope of the area is stable but clay lining is proposed to stop water leaking through the weir.

Rock outcrop was not observed in and around the proposed Inlet tunnel portal. The geophysical survey shows that the thickness of alluvial is less than 10 m. Therefore open excavation is necessary to construct the tunnel portal.

In general, tunnel alignment is almost per pendicular to the bedding plane with moderately dipping (60º-35º) which is favourable exca vation condition. The proposed headrace tunnel alignment will pass through the sandstone (34% ), siltstone (26%), mudstone (36%) and shear zones (4%).
The rock mass along the tunnel alignment is rated and classified both by Q system and RMR.
The observations were taken along and around the proposed tunnel alignment in the area though difficult topographical features, soil cover, and dense vegetation as well as very poor rock outcrop. The rated parameters of Q value and RMR in the field is given in Volume 4
Appendix C1. According to the surface observation the quality of rock mass distribution at the level of the proposed tunnel alignment was estima ted (Table below). This estimated quality of rock mass distribution is mainly based on rock mass rating at different rock exposures. The rock mass is divided according to ro ck support class (next Table below).

Rock mass distribution along the headrace tunnel Rock class | Q- value | Percentages | I Fair to very good rock | >2 | 51% | II Very poor to poor rock | 0.6 – 2 | 29% | III Very poor rock | 0.2 – 0.6 | 14 % | IV Very poor to Extremely poor rock | 0.04 – 0.2 | 1 % | V Extremely poor rock | 0.04 – 0.01 | 1 % | VI Exceptionally poor rock | < 0.01 | 4 % |
Hence in the tunnel about 51% is expected to fair to very good rock and about 49% is expected to very poor to exceptionally poor rock. The rock support design is carried out by empirical design criteria based on rock mass classifica tion system entirely depending on previous case studies in similar ground conditions. The rock support design is mainly based on the NGI Q-system rock support chart and experience taken from similar diameter tunnels of different hydroelectric projects of Nepal.

According to the rock mass properties and size of a tunnel the rock support is divided into six classes to optimise rock support. A combination of grouted rock bolts in different spacing and fibre reinforced shotcrete in varying thickne ss are recommended from class I to VI. Reinforced ribs of shotcrete with pattern of bolting and conc rete lining are also included in VI specially in squeezing section. Shotcrete is recommended throughout tunnel due to slaking nature of rock.
A 2.3 m long, 25 mm diameter grouted rock bolt of tor steel is recommended. Invert concrete lining is included in class I to VI throughout headrace tunnel due to slaking nature of rock.
Isolated wedge failures will not be significant and this designed rock support will control the failure. Wedge failure will be more prominent in Class II & III. This support design also covers for rock squeezing. Squeezing sections need heavy rock support. Therefore concrete lining or reinforced ribs of shotcrete are recommended in rock squeezing section. However, for rock squeezing excavation method and support should hav e to be modified according to the rock behaviour and existing ground condition during course of construction. This proposed rock support classes require modification during tunnel excavation according to local ground condition. Recommended rock support for the headrace tunnel, (Width = 4.25 m, ESR = 1.6)

For the purpose of cost calculation of the headrace tunnel, the above basis and the recommendation of the experts view of NEA has been integrated. 100% length of the tunnel invert has been recommended for concrete lini ng (150mm to 300mm thickness), The wall and crown has been lined with rock-bolting of size 25mm dia. 2.4 to 4m length tore steel in a pattern of 1x1m to 2x2m spacing, plain s hotcrete and fibre-shotcrete of 50mm to 200mm thickness. It is suggested that the fibre shotcrete lining with appropriate thickness recommended above is both strengthwise and time wise suitable for the rock-support. In addition to this 4% length of the tunnel (weak-zo nes) is suggested for concrete lining over the shotcreted surface of wall and crown with steel ribs.
A surge shaft is proposed in about 20 m deep from the outlet portal in mudstone. The thickness of residual soil ranges from 3 to 5 m and weathering depth of mudstone varies from
5 to 7m. The shaft axis will be vertically down to the bedding plane, which is favourable condition for tunnel excavation. Expected rock mass quality is fair to good condition. A 4 m long grouted rock bolts in pattern and 10 cm th ick fibre reinforced shotcrete is adequate for temporary support in the surge shaft.

The penstock alignment is proposed along the moderately dipping ridges. The area is covered mainly by residual soil. The expected thickness of residual soil ranges from 5 to 6 m and weathering depth of mudstone varies from 5 to 15 m. The anchor block of penstock pipe is proposed about 20 m upslope from the shear zone in the bent of pipe to avoid the shear zones. The surface powerhouse site is proposed on the right bank of Muse Khola on the flat alluvial terrace. The deposit is non-cohesive, low to medium compact and pervious in nature. It contains about 30-40% sub rounded to rounded gravels, pebbles, cobbles and boulders of siltstone, mudstone and supported in 60-70% sand matrix. The fine material is non-cohesive and contains sand. The shear zone is present near to powerhouse and follows towards slope of powerhouse. There is no evidence of slope failure however activenes s of the shear zone during construction phase might induce slope failure. Ther efore powerhouse is proposed further downstream from the location of shear zone to minimise effect.

4.5 Seismicity

The seismicity study of other hydroelectric pr ojects in Nepal is based on seismic-technonic features of the project area and data on historic al earthquakes of the region. The specific project related seismic studies were not carried out so far. The records of seismic activities are limited in the Nepal Himalayas and hence correl ation of seismic events with adjacent
Himalayan Region would be a useful source of information for designing the major components of project. Seismic coefficient for Mai Hydropower project is evaluated based on Nepalese and
Indian Standards and compare and derived from Tamur-Mew project at this stage. Seismic coefficient evaluated by Nepalese and Indian Standards is 0.10. Similarly recommended OBE of Tamur-Mewa project is 0.16 g – 0.15 g. Hence, it is recommended that OBE value of 0.16 g and MDE value of 0.2 g be used for the Mai project (MHP is far from the epicentres of the historic past earthquake events in Nepal and the project is a simple low-height structure run-of-river scheme).

4.6 Mass Wasting Study

Only two landslides are observed in the upstream vicinity of Mai Khola. One is located near
Malbase village at about 200m downstream from the confluence of Thade Khola and Mai
Khola, which is about 3 km upstream from the h eadworks site. The landslide is shallow, with planar failure mechanism in green phyllite. The estimated average length, breadth and height of the slide is about 60m × 50m × 100m respectively. The landslide is located above Mai Khola and debris were not found to reach the Mai Khola. According to local people, this landslide is more than 5 years old and is still active. The other landslide is situated at Ragapani village. It is located at about 4 km upstream from the hea dworks site and 200m downstream from the confluence of Thade Khola and Mai Khola. The estimated size of the landslide is 350 m x 125 m x 260 m. The slide is active though feeding very little amount of debris to Mai Khola. It can be concluded that chances of debr is flow is very low from the field evidences and geological condition. 5. PROJECT LAYOUT
The project configuration has been selected after a study of alternatives. The alternatives for the arrangement of the headworks were limited because of the site condition and topographic constraints. The alternatives for both water conveyance and powerhouse locations were thoroughly analyzed with respect to geological, topographical and power benefit analysis. The adopted layout is as follows:

Headworks
The arrangement of headworks location was best selected some 200m downstream from the
Soktim Tea Garden. The diversion weir height was selected in a way to allow the 100 year flood without any damage to the Tea Garden in consideration with the flushing head requirement. This is the best location allo wing accommodation space for other headworks structures. Similarly this location provides the shortest possible water conveyance length with the maximum head gain on the other side of the watershed area (powerhouse area).

Tunnel and Penstock Pipe
The headrace tunnel starts from the Gunmune village and ends at Muse Kholsa at elevation of
300 metres above msl. It is 2172 m long. At the end of the headrace tunnel a surge shaft will be made. After the surge shaft about 474 m long exposed penstock pipe will convey water to the power house. It passes along the ridge of the area. Geology of this alignment is favourable for the exposed penstock alignment.
Powerhouse
The powerhouse is located on the right bank of the Muse Kholsa just upstream of the confluence of the Dhade and Muse Kholsa. The powerhouse will be a semi surface type. The generator floor elevation in the Powerhouse will be 203 meters above msl and Tailrace water level for normal operation will be 199.0 metres above msl. This location avoids the shear-zone extending from Muse kholsa towards Dhade kholsa.

Tailrace
The Muse Kholsa is not wide and deep enough to accomodate the design discharge of the project if water is discharged in to it. Therefore about a 1600 m tailrace system will be required from powerhouse to the Lodiya Khola for safe release of designed discharge of the project.
Some river training works will be required to protect the agriculture land along Lodiya Khola.
The open canal from powerhouse to Lodiaya khol a along the left bank is considered as the one alternative to discharge the designed flow. Buried concrete pipe is considered as the second alternative.The preliminary cost estimate of both options suggests that the choice of stone masonry open canal option is more feas ible. Hence the stone masonry trapezoidal open canal option has been recommended for detail study.

Transmission Line
The route follows from the powerhouse to Danabari-3 upstream of Sukhani Khola and passes through Danabari-1, Khudanabari-7 and Khudanabari-8. Then it crosses near the boarder of
Khudanabari-8 and Arjundhara-5 and enters Arjundhara VDC via Danabari-1, Khudanabari-7,
Khudanabari-8. It crosses the Birin Khola near the boarder of Arjundhara-5 and Arjundhara-6.
The line crosses the district road near the boarder of Arjundhara-6 and Arjundhara-3 and joins at Charpani-3, Jhapa to the proposed route as described above. The total length of this route is 24 km.
Access Road
The existing motor-able roads from Lodiya Khola to the powerhouse area and from Soktim tea garden to Gunmune, with upgrading shall be used for the Project.

6. OPTIMIZATION
The optimized dimensions of the majo r project components are as follows:
Tunnel cross section area(m2): 13 m2
Penstock diameter (mm): 2350 mm
Installed Capacity(MW): 14.5 MW
Design Discharge(m3/s): 15.4 m3/s
Number of generating units: 2 (Francis)
The average energy benefit rates for the optimization of the waterway was adopted USD 0.06/ kWh. The installed capacity was optimized on t he basis of levelized s pecific energy cost.
The head-water level was determined on the basis of flushing requirements during normal floods. The weir crest height was not optimized due to its very little cushion on head to pass the 100 year flood without causing damage to Soktim Tea Garden. The normal water level at tailrace was determined to avoid submer gence due to proposed future Kankai Mai
Multipurpose Project and fixed at 199.0m above msl. The gross head thus obtained is 117 m.

7. PHYSICAL DESCRIPTION OF THE PROJECT

The general arrangement of MHP is shown in figure 3 The arrangement comprises of
Headworks on the Mai river, located just downstream of the Soktim Tea State. The headworks diverts water through a 2172 m long headrace tunnel and a 474 m long exposed penstock pipe to the semi-surface powerhouse and generates 14. 5 MW through two vertical axis turbines.
Then water will be discharged to Lodhiya khola through a 1370 m long stone masonry tailrace canal and a 225 m long tailrace pipe.
Headworks
The headworks of MHP comprises of a 7.0 m high and a 133.0 m long free overflow weir, which diverts water into a 70.30 m long three chambered settling basin through orifice intake and gravel trap. Sediment deposited in the settling basin will be flushed back to the river through a 2.0 m wide, 2.0 m high and 225 m long flushing culvert. Then water from settling basin will be conveyed to tunnel intake by a 775 m long trapezoidal headrace canal. Further refinement of geometry and design of the headworks components shall be finalised during detail design stage after conducting th e physical hydraulic model test.

Weir
The location of the weir is selected at t he rock outcrop about 20 m upstream from the open large barren flat field area. The overflow weir is 133 m long and 7.0 m high from the foundation level. The weir is Ogee shaped and crest level is 316.0 m above msl.

The calculated water elevation for 100 and 1000 years flood are 321.150 m and 322.75 m above msl respectively. Adopted top level of flood and head wall is 322.75 m above msl with free board of 1.6 m for 100 yrs flood.

Stilling Basin
The stilling basin consists of three stilling ponds and two baffle walls. The length of the first stilling basin is 17.8 m and the invert level is 311.50 m above msl. The first baffle wall is 2.0 m high and the top level of the wall is 313.50 m above msl. The second and third stilling ponds are 14 and 12.65 metres long respectively. And their floor levels are 309.75 m and 309.00 m above msl respectively. The calculated water level at the end of the stilling basin is 314.73 m and 316.0 m above msl for 100 years and 1000 years flood respectively.

Undersluice
About 100 m long and 17.5 m width at weir axis (width gently increases in the upstream) approach canal is designed to maintain a clear and well defined river channel towards the intake and to flush the bedload build up in front of the intake. The invert surface are lined with hardstone and the wall up to 1.0 m high are lined with 16 mm thick steel lining to protect their separates the weir area and the undersluice. Two radial gates of 8 m wide and 5.5 m high are proposed to flush the bedload sediments which will be accumulated in front of the Intake. A fish ladder is placed along the side of the left wall of the undersluice. The fish ladder passes from the intake area to the stilling basin area along the undersluice’s left wall.

Intake
The side orifice intake is located about 5 m upstream of the weir crest axis on the left bank of the river. A low concrete sill, with a structur e to prevent passage of large boulders, will allow water to enter the intake area. The intake consis ts of 4 orifices of 3.0 m wide by 2.0 m high to draw the water from river in the intake headwall. It is aligned parallel to river flow. The invert level of opening is set at an elevation of 313.5 m above msl. Bedload up to 100 mm diameter and suspended sediment will pass through intake orifice and will be conveyed to gravel flushing arrangement along the intake culvert. Inta ke gate will be fixed at inner side of the intake headwall to control the flow into the intake culvert during high flood. An intake platform will be designed for the gate operation. The level is fixed at 322.75 m above msl for 1000 years flood without free board and 1.6 m free board for 100 years flood. The water level inside the intake will be 317.50 m above msl for 20 years flood. The wall level inside the intake is adopted at 317.75 m with a free board of 25 cm. When flood is higher than that, the intake stoplog gates will be closed.
A coarse trash-rack of 100mm opening shall be provided at the intake. Details of trash-rack and cleaning arrangements shall be decided during detail design and model testing.

Gravel Trap
A gravel trap is located about 15 m downstream of the Intake and designed with a single hopper bottom for conventional hydraulic flushing. The size of the gravel trap is designed to settle the particle size of 5 mm. The gravel trap is 10 m long, 14 m wide and 6 m high. The longitudinal slope is 1 in 60. The most vulnerable areas in gravel trap as well as in flushing channel exposed to wear and tear due to high ve locity should be lined with dressed hard stone and steel lining. At the end of parallel section and just before the outlet, a coarse trash rack of
14 m wide and 4 m high with vertical angle of 10.6 degree is located to prevent passing of debris. The stacked debris should be removed mechanically.

The water level at the gravel trap for the designed discharge will be 315.87 m above msl and the adopted wall level is 317.75 m above mean sea level. A 25 m long spillway with crest level
316.00 m above msl is provided at the right wall of the gravel trap to spill excess water which will be entered to intake during high floods. The spilled water will be discharged back to river via stilling basin.
Sediment deposited in the gravel trap will be flushed through a flushing culvert. The flushing culvert is 43 m long, 1.5 m wide and 2.5 m high with longitudinal slope 1 in 60. The bottom slab lined with hardstone and the wall up to 1.0 m high are lined with 15 mm thick steel lining to protect their surface from erosion and abrasion. A 1.5 m wide and 2.5 m high flushing gate will be operated to allow for necessary flushing discharge only so that production can go on
Settling Basin
The settling basin is located 25.0 m downstream of the gravel trap with 25 m transition length.
The settling basin is designed to trap 90% of 0.2 mm particle size. The maximum flow velocity in settling zone will be 0.2 m/s. The discharge to the settling basin duri ng flushing is controlled by three gates of size 4.25 m wide by 2.25 m high which are located just upstream of the inlet transition to the settling basin. The settling basin consists of three chambers with 8 m width and 70.3 m long each. The average depth of the settling basin is 5.25 m. The water level at the settling basin for the designed discharge will be 315.80 m above msl and the adopted top wall level is 316.3 m above mean sea level with freeboard 50 cm. The middle wall levels are adopted only at 315.90 metres above msl. The bottom slab of the settling basin will have a slope of 1 in 100. The less sediment content wa ter from the settling basin will be discharged through 8.0 m width weir to the headrace canal. There are three stoplog gates 20 m downstream from the weir to stop the entry of water to the settling basin from the canal during the flushing period. The size of the stoplog gat e is 2.77 m wide and 2.6 m high. The sediment flushing system will be conven tional hydraulic flushing.

The sediment flushing is controlled by 2 m by 2.5 m gates for each chambers. Stoplogs are provided for each gate for the gate maintenance pur pose. The gates are located adjacent to the right wall of the settling basin outlet. About 225 m long 2.0 m by 2.0 m rectangular section flushing culvert is proposed for sediment flus hing purpose. The culvert bed slope will be 1 in
500. The bed slope is adopted flatter so that the flushing culvert should not be submerged during high floods(1 in 5 years flood).

Headrace Canal and Balancing Pond
Less sediment content water from settling bas in will be conveyed by a 775 m long trapezoidal headrace canal to balancing pond. The longitudinal slope of the canal is 1 in 1500 with side slopes 1 in 1. The canal is constructed with 0.5 m thick stone masonry with 1 in 4 cement sand mortar and 10 cm thick concrete lining with nominal reinforcement for thermal crack control. The pond is located at Gunmune Bagar. The main purpose of the pond is to balance the water supply to start the powerplant for short period. The average length and width of the balancing pond is about 100 m and 100 m respecti vely. The embankmet of balancing pond is of the earthfill type. The water level at the pond area will be 315.3 m above msl and the top level of the embankment is adopted at 316.0 m above msl.

Tunnel Inlet
The tunnel intake is located at the end of headrace canal and the balancing pond. The entry to the tunnel intake from the headrace canal c onsists of a 10 m long transition part from trapezoidal section to the rectangular section, a fine trash rack before the sloping glacis, 7.5 m long and 4.4 m high sloping glacis and funnel type t unnel intake. Sloping starts from elevation
313.15 m above msl to 310.0 m above msl. The funnel starts at an elevation of 310.0 m with a diameter of 10.2 m and ends at 3.3 m length with a diameter of 4.25 m. Vertical drop of the
4.25 m shaft is 1.9 m and the shaft is connected with headrace tunnel by a bend of the same diameter with central radius of 3.0 m. Invert level at the beginning point of the headrace tunnel is 300.00 m above msl. The transition length between the circular shape to the invert “D” shape is 8 m.

Headrace tunnel
The headrace tunnel starts at the Gunmune vi llage and ends at the Dhade Kholsa Gaon just upstream of the confluence between Musse K holsa and Dhade Khosa at an elevation of
297.00 m above msl. The headrace tunnel is 2172 m long. At the end of the headrace tunnel and before the surge tank a rocktrap of 80 m long 3 m wide and 1.5 deep has been provided.

The cross section of the tunnel is inverted “D” shaped with base width and height being 3.80 m each and crown radius 1.9 m. According to the geological conditions 4 types of tunnel supports have been considered. About 70% of the tunnel length where the rock is fair to good quality will be supported with 50 mm thick plain shotcrete and 25 mm dia 2.3 m long rock bolts at 2 metre centre to centre provided in staggered. About 23% of the tunnel area consists of poor to very poor rock. Tunnel support in this area wi ll be 50 mm thick fibre reinforced shotcrete and
25 mm dia 2.3 m long rock bolts at 1.6 m centre to centre provided in staggered. About 3% tunnel length will be in very poor rock, support in this area will be 50 mm thick on wall and 80 mm thick on crown fibre reinforced shotcrete and 25 mm dia 2.3 m long rock bolts at 1.4 metre centre to centre provided in staggered. Remaining part of the tunnel will be in extremely poor rock, support in this area will be 70 mm th ick on wall and 100 mm thick on crown fibre reinforced shotcrete and 25 mm dia 2.3 m long rock bolts at 1.2 m centre to centre provided in staggered. The base of the tunnel will be concreted with 10 cm for first and second type tunnel,
15 cm thick for third and forth type tunnel.

Surge-Tank
The surge shaft proposed at the end of the t unnel and immediately downstream of the rock trap is located at about 400 m upslope from the powerhouse area. The shaft consists of 6.0 m finished diameter with concrete lining of 0. 6, 0.4 and 0.25 m thickness at lower, middle and upper part of the shaft respectively. Each part of the shaft is 9.0 m high. The surge shaft is connected to the tunnel by a 4.0 m diameter and 0.8 m thick orifice. The shaft is covered with a
8 m diameter corrugated roof truss.

Penstock Pipe
The penstock pipe comprises three sections: a 84 m long horizontal steel lined tunnel, a 265.5 m long inclined exposed steel pipe and 66.5 m long buried steel pipe before it bifurcates. The internal diameter of the pipe is 2.35 m and the thickness varies from 10 mm to 32 mm. After the inclination part the penstock crosses the Muse Kholsa. The penstock pipe at the Kholsa crossing will be protected by a 30 cm thick concrete casing. Before entering the powerhouse the penstock pipe is bifurcated symmetrical ly to the penstock alignment at 36.870 and 15.8 m long. After bifurcation a 10 m long penstock pipe conveys water to the powerhouse. The thickness and the diameter of the pipe after bifurcation is 25 mm and 1.5 m respectively.

Support Piers, Anchors and Thrust Blocks
There are five anchor blocks for four ve rtical bends and one combined bend. The anchor block is to be constructed of C15 concrete with 40 % plums and nominal reinforcement. Hoof reinforcement is required around t he pipe. The size of the anchor block is about 4.5 m long,
3.8 m wide and 4.0 m high.
There are four thrust blocks. The first thrust block is for the horizontal bend immediately after the Muse Kholsa crossing, the second is for t he bifurcation and the third and fourth thrust blocks are for the smaller pipes after the bifurcati on. Thrust blocks are also constructed of C15 concrete with 40 % plums and normal reinforcement.

Support piers are required along the straight section of exposed penstock between anchor blocks. Spacing of the piers is kept 3 m center to center to avoid overstressing of the pipe. The support piers will be constructed with C25 reinforced concrete.

Powerhouse
The powerhouse is located at the right bank of the Muse Kholsa just upstream of the confluence of Muse Kholsa and Lodiya Khola. The powerhouse is a surface structure to accommodate two generating units of capacity 7.25 MW each. The powerhouse consists of a
R.C.C structure that houses the machine floor and control building. Machine floors are inlet valve floor, turbine floor, generator floor, maintenance and unloading bay. An overhead traveling crane is installed in the powerhouse to facilitate installation and maintenance of powerhouse equipment. The superstructure of pow erhouse will be constructed from R.C.C columns, walls and block masonry walls. Series of windows will be provided for proper lighting and ventilation in the powerhouse. One small ac cess door and one large shutter door will be arranged in the powerhouse. The sm all access will be mainly used for the entrance of people and small size materials and equipm ent and will be located at the stair case area. The large shutter access will be mainly used for the transportation of large equipment and heavy equipment during installation and repair and maintenance of the power plant. This shutter access will be located at the erection bay of the powerhouse. The roof of the powerhouse is arranged with steel truss structures on R. C.C columns covered with corrugated coloured galvanized iron sheets.

Tailrace
After the generation water will be discharged to the tailrace canal via draft tube. Stoplogs are provided at the end of the draft tube. Water level immediately after the draft tube will be 199.0 m above msl during normal operation period. The tailrace is designed for the maximum 202.75 m above msl considering the maximum flood leve l of Kankai Mai Multipurpose Project. The tailrace conduit is connected with the draft tube by a 13.5m long transition section. The first 8 m portion has horizontal bottom slab, while the other 5.5 m part has sloped bottom slab to connect the tailrace conduit. A stoplog is provided at the beginning of the tailrace conduit. A stoplog is also provided at the end of the tail race at Musse Kholsa. This stoplog will be operated during tailrace conduit maintenance peri od.The tailrace conduit consists of a 15 m long C25 concrete culvert, 20 m long C25 tr ansition, 1370 m long trapezoidal section stone masonry canal, 225 m long 8 mm thick and 1.5 m dia steel pipe and 15 m long outlet structure.

The tailrace canal begins with invert level 195.60 m above msl to maintain minimum tailrace water level of 197.00 m. The tailrace canal is trapezoidal in section of stone masonry with 1 in
4 cement sand mortar. Bottom width and height of the canal are 1.5 and 1.5 respectively. The longitudinal and the side slope of the canal are 1 in 100 and 1 in 1 respectively.

Generating Equipment
Two generating units are placed with Francis turbine. The installed capacity is 14.5MW (2x
7.25 MW). The selected turbine is two sets of vertical Francis turbine with 7.75 MW capacity each, at the net head of 108.89 m and design discharge of 15.40 m3/s (7.7 m3/s per unit). The speed is 600 rpm. Vertical synchronous generator, N=7250 kW, 50 Hz, 10.5 kV, 0.85 p. f. lag, class “F” insulation with temperature rise limited to class “B” have been used.

Two sets of main transformers with 8530 kVA- 33/6.3 kV shall be used. The adopted standards shall be: GB1094.3.5-85, GB/T6451-1995, GB1094.1.2-1996, JB/T3837-1996 equivalent to
IEC standards.

One overhead traveling crane shall be of electrical operated, cabin controlled type, suitable for three-phase 220/380 V-50 Hz power supply, and s hall be equipped with a single trolley having both main and auxiliary hoists. The maximum load to be lifted by the crane shall be 35 ton.

Transmission Line
24 km long 33 kV double circuit transmission line from powerhouse switchyard to connect to the NEA sub-station at Anarmani of Jhapa district is proposed.

8. ENVIRONMENTAL IMPACTS AND MITIGATION

The environmental impact to the size and type of the project are moderate. The major impact shall be the ecosystem of the river downstream of the weir up to 8 km length where Deo Mai discharges approximately 1.2 m3/s of water in the driest month (March). The continuous environmental release of 10% of minimum monthly flow which is equivalent to 722 l/s will compensate the adverse effect to this reach. A fish-ladder has also been proposed for migratory fish-movement.

The key social issues in the area are rural electrification and upgrading of the access road to this area. Electricity is a must for the pr ospective growth of small scale industries and upgrading of the road will facilitate trade and commerce of the area. With the launching of the project some budgetary provisions are made to c ooperate with the local people for these works which will provide better environment for the local area.

There is existing irrigation system in Kankai river which is approxim ately 16 km downstream from the powerhouse. Adoption of 14.5 MW simple run-of-river scheme will have no effect to the existing Kankai irrigation system.

There shall be permanent loss of forest land and trees as in the case of other similar type of projects. However, the loss is minimal in the main project area and higher in the transmission line route. The re-plantation progr am shall address this issue to the extent of acceptibality.

Two species of animals are found in the area Salak (Manis crassicaudeta) and Sun Gohoro
( Varanus flavescens ) which are protected by the government under the National Park and
Wildlife Conservation Act 1973. During the project construction, contractual provisions shall be made for restricting hunting and entering into the forest by the project people.

Three river systems namely Mai Khola, Muse Kholsa and Lodhiya Khola pass through the project area. Mai river system provides habitat for fishes such as Sahar ( Tor tor) and Asala
( Schizothorax plagiostomus). Other fishes locally called as Gardi, Thend, Buduna, Raj bam,
Katle, Jhinge etc. are also available in the Mai river.

Environmental Management Plan for impacts after designing and implementing them shall be monitored to check effectiveness of design and implementation plan (mit igation requirements).
For this compliance monitoring and impact monitoring shall be done. To facilitate
Environmental Management Plan (EMP), an Environmental Management Unit (EMU) working under Project Manager will be established.

9. CONSTRUCTION SCHEDULE AND COST

9.1 Access Road

The access to the site is through the existi ng road from East-West Highway at Birtamod of
Jhapa district to Soktim via Sanischare, Khudunabari and Garuwa Sukrabare. The road needs to be upgraded for the purpose of supply to t he project. The upgrading of the road shall be started at least 3 months before the main cont ractor mobilizes to the site. The duration to correct geometry of the road including descending reach to the headworks si te from Soktim has been estimated about month. Thus the access to the site shall be completed in four months including one month at the start to the main civil contractor.

All local supplies shall be carried out through the East-West Highway at Birtamod and locally transported through the access road up to the si te. Location of local construction materials such as gravel, sand and red-clay is nearby the access road and the project area and hence is easily accessible.

9.2 Camps and Facilities

The peak time labour (from outside the Projec t area) is estimated to be around 300 persons.
There is a village Gunmune at the headworks site and Musetar village at the powerhouse site.
In addition there is a small Bazar at Sitali whic h is at a distance of 2 km from the powerhouse and another village Soktim which is at a distance of 1 km from the headworks site. One third of the peak labour can be accommodated in the near by villages. However, it has been planned to construct temporary camps for the labour at the adjacent areas. Headworks camp shall be placed aside of the Gunmune village and powerhouse camp shall be c onstructed downstream of the powerhouse in the plain area of Muse Kholsa. Tunnel muck for the tunnel length to be excavated from intake portal side shall be dis posed into the left bank of Mai river in the headworks (settling basin, canal ) area whereas the tunnel muck from tunnel and surge shaft area including excavated material from pensto ck foundation shall be dumped along the Muse
Kholsa bagar in a controlled manner.

Drinking water to the camp shall be provided from the source at Soktim by constructing a reservoir to collect water during night. T he water supply shall be done via pipe line of approximately 1.5 km upto the headworks. Other al ternative for water supply shall be using the water of Mai Khola with purification.

9.3 Construction Power

The existing 11kV line at the Soktim village is approximately 1.6 km fr om the headworks site and then another 3.0km from headworks to powerhous e site. Another option is to build a new
33 kV transmission line from Puwa Power Plant located at a distance of 8 km from the headworks site. Construction power requirement for tunnelling is at least 500 kW at the time when single tunnel-boomer is working. To work from two faces with this power, the sequence of drilling and support work shoul d be altered. With this arrangement, 750 KW power shall be sufficient to work in tunnel and concreting.The tentative time for the erection of this line is assumed to be 4 months.

9.4 Contract Package

It is aimed that the main civil contractor shall perform the execution of all civil works including tunnel and powerhouse. The preparatory works such as upgrading of access road, owner’s camp facilities and construction power supply shall be executed by the owner with sub-contractors before and during the full mobilization of the main civil construction contractor. This will provide additional time cushion to the project for accelerating construction works.

The 33 kV power evacuation transmission line shall be a separate contract and be started in such a way that the erection of the line is ready before testing/commissioning date of the project. This work does not fall under critical path.

All hydro-mechanical works such as gates, tr ash-racks, steel penstock pipe and other steel works will be another contract package. This package is fitted in the construction schedule so that the works are easily carried out parallel to all civil constr uction activities.

Powerhouse equipment from the end of penstock until the start of 132 kV power evacuation line will be a single package including des ign, drawings, fabrication & supply, erection/installation plus testing and commissioning.

Engineering design and construction supervision of the project will be conducted by in-house engineering department of the Owner. This will fa cilitate close monitoring and coordination with different contractors and suppliers for integrated work harmony to achieve set target date for completion of the project.

9.5 Project implementation Schedule

The project implementation schedule has been derived on the basis of calculated quantities of works to be done and the duration that is r equired for design, fabrication, supply and installation of major project components. Time for further investigations recommended in this report to incorporate in detail design and prepar ation time for contract and tendering including negotiations and contract awards have been considered appropriately while preparing implementation schedule. The critical path observ ed is tunneling which is estimated to be 34 months (including portals and surge shaft) and the total duration of the project completion including testing and commissioning is estimated to be 4 years from the date of power
Purchase Arrangement. The Implementation Schedule is attached with this summary.

9.6 Cost Estimate

The total Project cost is NPR 2125 million . local market rates for similar nature civil construction and hydro-mechanical works have been used, royalties and taxes were applied as per provisions in the corresponding HMGN’s regulations. Royalties or costs associated with construction materials and borrow area have not been considered and it was assumed that the local contractors shall bi d for civil and hydro-mechanical installations.
Powerhouse equipment supply shall be through inte rnational suppliers by inviting proposals and negotiating with them.

The capital cost of the project were derived from the unit costs of the major civil work items.
The eletro-mechanical equipment cost were adopted by comparing the quotations received from the suppliers. The hydro-mechanical installations were compared to the prices in existing market as well as quotations received. The env ironmental mitigation costs and land costs were derived by direct interaction with the local people and the environmental provisions for such mitigations. The physical contingencies adopted for the capital cost estimate of the project are:
(a) Tunneling work (15%), Civil construction (10%), Electrom echanical equipment (5%), Others
(10%). An allowance of 10% of the project cost was applied for engineering management and administrative costs of the projec t to cover further site investigations
(geological investigations and physical modeling, environmental assessment, preparation of tender stage design and documentations and detailed engineering design of the project, contract and tendering, construction supervision, testing and commissioning of the project, project administration, reviewing and approving contractor’s submittals, and cost of owner’s/consultant’s equipment, supplies, communication and transport. The summary of the cost estimates are presented in Table :

9.7 Disbursement Schedule
The summary of the cash-flow is as shown in the Table below. The cash-flow is based on the implementation schedule and the corresponding co sts of the project components.The yearly distribution of costs is as follows:
Yearly cash-flow (transmission line cost included)
Year-1 Year-2 Year-3 Year-4
15.88% 27.63% 46.77% 9.71%
10. PROJECT OUTPUTS AND BENEFITS
Energy Production and average Energy Rates

The energy production is carried out on the basis of daily data of Rajduwali station with catchment coorelation. These data were then tr ansferred into Nepali calander months. Below is the Monthly average Power and energy summary Table:

The average energy rate considered for the computation of the benefits is NPR 4.48/kWh in the year 2006 (Base Year). These rates were then escalated for 15 years from base year at the rate of 6% for first 5 years and 2.5% for the rest of the period.
The energy benefit shall be by the sales of energy to the grid and the government-takes shall be the royalty on installed capacity and energy production as well as the taxes on energy sales. Energy Consumption
The estimated energy produced by MHP is assum ed to be consumed by the local market in the National Grid. This project situated at t he eastern region will be the added benefit to the national grid because all other existing plants ar e far from this load centre and the nearest is the multi-fuel diesel plant in Duhabi. At present demand supply scenario, more power plants need to be added in this region for better supply of the energy. Hence the energy produced by the project is considered to be consumed fully by the grid.

Emission Benefit
The benefit stream for the project is based on the sale of power and quantification of the benefit from reducing emissions from an equivalent thermal generat ion alternative. The project located in the eastern region shall directly r educe the operation of existing multi-fuel diesel plant located in this region to the extent of its capacity at least during dry season (mid
November to mid May) as well as the import of power from Indian system during this period
(sometimes even during wet period).

Benefit Evaluation for MHP has thus been calculated at least for dry season generation of 32.2
GWh energy (mid November to mid May) as shown in table below:
Description External Cost
(USc/kWh)
Reduced kWh Emission Credit
(USD)
CO2 : Multi Fuel Diesel 0.6 32.20*10
6
193,200
SO2 : Multi Fuel Diesel 0.14 32.20*10
6
45,080
NOx
: Multi Fuel Diesel 0.0075 32.20*10
6
2,415

Total Emission Credit in USD 240,695
The emission credit has been estimated for the dry-season energy when operation of the multi fuel diesel plant is must.

Capacity Benefit
The long run marginal cost analysis from the report entitled "Size and Number of Units
Optimization of Upper Arun Project" which was carried out for the World Bank in 1991 suggests the capacity benefit of USD 108.4 /kW per annum. The capacity benefit has not been applied in the financial analysis since the projec t is intended to be developed through private sector and the benefit shall be reflected through the agreed energy tariff between NEA and the private party.

11. PROJECT EVALUATION

The evaluation of the project has been performed from the financing point of view. The analysis has been preformed for the total project deve lopment cost of 2125 million Nepali Rupees including transmission line. Operation and mainte nance costs were considered as 2% of project development cost. NPV were calculated at 10% discount rate for 25 (34) years. The interest on bank loan on 70% debt has been considered as 11% during construction per iod (including bank commissions and loan management fee) and then at the rate of 10% per annum during loan repayment years.

The base case results of financial evaluation for average energy rate of 4.48 NPR/kWh at the discount rate of 10% and escalation as m entioned above is presented in Table below.

Base-Case Results
Net Present Value of Cashflow at 10% discount rate, NPV 1,283 Cost Revenue
Internal Rate of Return (IRR) 17.52% 100% 100%
Benefit Cost-ratio (BC-ratio) 1.54
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Summary Report, Revision A (NEA’s comments incorporated)-24
Return on Equity (RoE) 24.58%
NPV Govt-takes (as royalty and tax takes) 761

The increase in the cost is likely due to international market with ever increasing price of fuel and that climatic change may result in longer dr oughts resulting into losses of revenue of the hydropower projects. In addition a hydrological risk is always bound to be with hydropower projects. This risk always exists and therefore there must be some margins in the benefit streams to safe-guard the investments. The normal practice shall be to test the project at 10% cost over-run and 10% revenue losses. The results of this test are as shown in the table below:

Results of Sensitivity Test (cost over-run by 10% and revenue loss by 10%)
Net Present Value of Cashflow at 10% discount rate, NPV 862 Cost Revenue
Internal Rate of Return (IRR) 14.87% 110% 90%
Benefit Cost-ratio (BC-ratio) 1.36
Return on Equity (RoE) 19.30%
NPV Govt-takes (as royalty and tax takes) 641

Since the hydropower projects involves many risk factors, return on equity less than 20% will be very risky for investors to invest into hydropower projects.

It is further tested on its sensitivity to evaluate the attractiveness of the project at the average energy rates of 4.25NPR/kWh and escalation as before (NPR 4.25/kWh in Year 2006 with 6% escalation for 5 years and then 2.5% for the ne xt 10 years). The results are as shown in the
Table below:
Net Present Value of Cashflow at 10% discount rate, NPV 729 Cost Revenue
Internal Rate of Return (IRR) 14.19% 110% 90%
Benefit Cost-ratio (BC-ratio) 1.31
Return on Equity (RoE) 17.95% (17.7% in 25Yrs)
NPV Govt-takes (as royalty and tax takes) 595

Since the return on equity is as low as 17.7%, further test on lower rates has not been performed.
It is the negotiation process between NEA and SH PL where the energy rates shall be fixed on the basis of sharing of risks between both parties.

CONCLUSIONS
The evaluation shows that the project is financ ially viable and attractive at the average energy rate of NPR 4.48/kWh in year 2006 and still shows the viability at an average rate of 4.25/kWh.
These rates are then to be escalated at the rate of 6% for first five years and then at the rate of
2.5% for another 10 years.

Further, it is recommended to enter into negotiation for the PPA with NEA on the basis of the results of this Summary Report. The analysis performed herein above provides sufficient background to enter into the negotiations for Po wer Purchase Agreement with NEA. The energy rates proposed for the evaluation are attractive to NEA compared to the existing energy rates of the most of the private sector power plants of this range.

12. CONCLUSION AND RECOMMENDATIONS

12.1 Conclusions
The following conclusions were made from the feasibility study of Mai Hydropower Project:
1. The 14.5 MW MHP is technically feasib le and possesses the importance in the INPS system mainly for the following reason:
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Summary Report, Revision A (NEA’s comments incorporated)-25
− MHP is very desirable from the perspective of loss reduction for NEA being nearer to load center of eastern region,
− For the improvement of voltage and power supply scenario in the region,
− This project will replace to some ext ent the operation of expensive thermal power plant and even reduce dependency on Indian system for the Eastern Nepal.
− Realization of MHP will help rapid indust rialization of the power hungry eastern Terai belt of Nepal.
− Many Nepali skilled, semiskilled and unskilled workers will have an opportunity to get employment during construction and to some extent post construction period that strengthens the local economy.
− The project is therefore very important for the national economy as well.
2. Installed capacity and energy: The installed capacity of the plant is 14.5 MW (2x 7.25
MW) with design discharge of 15.4 m
3
/s and net head of 109.58 m. The gross energy production is 98.53 GWh (dry energy 20. 98 GWh and wet energy 77.55 GWh delivering
88.440GWh per annum of net energy at delivery point).

3. The project is financially viable with an average energy rate of NPR 4.48/kWh (in the
Base year 2006). The base year energy rates were escalated at the rate of 6% for first five years and then at the rate of 2.5% for another 10 years.
4. The environmental Impact Assessment (EIA) is being prepared as a separate report. The environmental and social impacts are moderate to low typical for the run-of-river project.
5. The major environmental issue would be downstream release of design discharge through Lodhiya Khola (approximately 3 km), which may cause damages to the adjacent rice-field and also cause trouble to dry-seas on movement of vehicles along the Khola.
6. The headworks diversion structures are designed for 100 year flood. At 1000 year floods, the structures are allowed to pass the flood without free board. Minor damages are expected during these floods.
7. To evacuate generated power a 33 kV double ci rcuit transmission line (24 km long) is proposed to connect to the NEA sub-stat ion at Anarmani of Jhapa district.
8. Existing access road is considered with upgradi ng (approx 30 km length).
9. The construction period of 4 years has been considered from the date of PPA.

12.2 Recommendations
The following recommendations were made for t he implementation of Mai Hydropower Project:
Further Geological and Geotechnical Investigations
1. Boreholes shall be drilled in weir axis (10 m), tunnel inlet portal (30 m), surge shaft
(20 m), Penstock alignment (10 m) and
2. Lugeon or leakage tests shall be carried out in lateral low cover area of tunnel alignment to estimate water leakage through the tunnel.
3. Slack durability test of rock sample (to test durability of rock with water flow) to be carried out.
4. Swelling Test of mudstone should be done.
Physical hydraulic modelling and modification of weir structures
The major cost component is headworks. Therefore it is recommended to perform physical modelling to assess flushing requirement and down-stream protection requirement as well as to
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Feasibility Study: Executive Summary (Revision-A)

Summary Report, Revision A (NEA’s comments incorporated)-26 check flood levels and weir geometry to adopt during detail design phase. The hydraulic modelling is also required to size and confirm the geometry of the stilling basin.
Hydrology and Sediment study
It is recommended to continue the flow measurement and sediment sampling.
Transmission line
It is recommended that the 132 kV transmission line should be erected by the government as a separate project and link it as one of the major transverse power evacuation transmission line in this region to connect to the up coming projects in this region (Kabeli, Tamur-Mewa, Hewa etc.) including this Project although the 33 kV double circuit transmission line is proposed for this project. Tax Holidays
To come with reasonable energy rates and encourage private sector to invest in hydropower projects it is recommended that the tax holidays should be provided to the developers for the period of at least 10-15 years or loan repayment period.