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Section - I
EXECUTIVE SUMMARY
1.1 THE PROJECT
The Pahumara Small Hydel Project is located on the river of the same name. The
project is located in the Baksa District of Assam near village Laugaon. It is proposed to
have an installed capacity of 2000 Kwe consisting of two (02) units of 1000 Kwe each.
The project has been conceived as a run of the river project with diurnal storage.
The existing Pahumara irrigation barrage is used as the diversion weir.
1.2 PROJECT PURPOSE
The Pahumara SHP has been proposed to be developed for augmenting the
power generation in Bodo Territorial Council area of the State of Assam especially using
renewable energy source and for helping in rural electrification of the State.
After commissioning of the Pahumara Small Hydroelectric Project, the electrical
energy produced shall be utilized for augmenting the energy supply in the local rural
distribution network in the Jalah Block of Baksa District and shall provide electricity to
un-electrified villages. The energy availability will also improve the voltage profile and
reliability of the power system in this remote area in and around Laugaon.
1.3 WATER RESOURCES
Pahumara is a hilly stream and is a tributary of river Brahmaputra. It has its origin
from the southern water shed of Arethumake of Bhutan range of Assam Himalayas.
Pahumara is a perennial stream with a minimum flow of around 2.94 cumec (for 90%
dependable year 1974) after meeting the irrigation requirement and a maximum flow of
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PAHUMARA - SHP
948.32 cumec (33457 cusec). The stream has a catchment area of 440 sq.km at the
Kathalmurighat barrage site. The river flows through mixed jungle.
1.4 GEOLOGY AND GEOTECHNICAL ASPECTS
The small hydropower stations do not require construction of any heavy
structures. The geology along the location of various project components have been
found to be favourable for founding these structures. The location of various structures
including the power plant and alignment of the power channel and the tail race channel
have been made keeping in view the slope and structural stability.
1.5 POWER PLANT
The power plant is proposed to have two (02) turbine – generating units each of
1000 Kwe output at generator terminals. The turbines shall operate under a net head
varying between 7.2 m and 6.315 m. As for this head and variable discharge, Kaplan
turbines are suitable, the same has been proposed. The turbine-generators shall be of
vertical shaft type alignment.
The generation voltage shall be at 3.3 KV which shall be stepped upto 11 KV
through a common step-up transformers of 2500 KVA capacity. There is an existing
11 KV line upto the barrage site which shall be used to evacuate the power generated.
Each of the generators shall be provided with brushless excitation system and all
standard protections for generators and transformers of this capacity shall be provided.
1.6 FINANCIAL ASPECTS
The average annual energy expected to be produced from the proposed project
is 9.34 x 106 kwh and the net energy available for sale is expected to be 8.784 x 106
kwh at 95% plant availability. The plant load factor is 50.64%.
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PAHUMARA - SHP
The design energy of the project is 6.853 x 106 kwh, and the net energy available
for sale i.e. 6.785 x 106 kwh.
The estimated cost of the project is Rs. 1413.00 lacs out of which the cost of the
civil works is Rs. 683.00 lacs and the cost of electro-mechanical works is Rs. 653.00
lacs. There is an existing 11 KV line upto the barrage site which shall be used to
evacuate the power generated.
The cost of generation in the first year of operation is estimated at Rs. 3.49 per
kwh and on levellised cost basis over a 35-year period works out to Rs. 3.12 per kwh.
The gross revenue in 50% dependable year is estimated at Rs. 281.20 lacs with sale
price of energy at Rs. 3.20 per kwh (levellised sale price). The return on equity after
meeting all operating expenses, tax, but including depreciation is estimated at 20.1 %
on levellised cost basis over a 35-year period.
1.7 FINANCING OF THE PROJECT THROUGH CDM
The CDM facility was established in August 2003 to assist Developing Member
Countries (DMCs) to access new development opportunities made possible through the
Clean Development Mechanism (CDM).
Its main objectives are as follows:
Promote projects that contribute to poverty reduction, sustainable development,
and greenhouse gas (GHG) mitigation.
Lower CDM transaction costs by supporting CDM project identification,
development, registration , and implementation.
Help find competitive prices for Emission Reductions (ERs), or carbon credits,
arising from projects.
Facilitate access to underlying-finance by improving project viability.
3.
PAHUMARA - SHP
The CDM facility is applicable to both sustainable development benefits and
GHG mitigation. These include:
Renewable energy
Energy efficiency
Sustainable agriculture,
Forestry.
It is estimated average annual energy production from the Pahumara SHP shall
be 8.873 x 106 KWh (allowing for 5% forced outage) and the energy available for sale
be of the order of 8.784 x 106 kwhr per annum. The coal being used in the thermal
power stations in India not being of very good quality, it may be appropriate to assume
that the carbon dioxide being emitted shall be of the order of 987 gms per kwh. On this
basis the carbon dioxide emission reduced by generating same amount of electrical
energy from Pahumara SHP works out to 8.75 x 106 kg per annum which equivalent to
8750 tonnes per annum. On this basis over the life time of power plant the carbon
dioxide reduction is expected to be of the order 3,06,500 MT. Since the Pahumara SHP
is a renewable energy project and its operation can provide energy for social and
sustainable development without contributing to GHG emissions is eligible for financing
under CDM facility as envisaged in Article 12 of the Kyoto Protocol.
1.8 RECOMMENDATIONS
The project is technically suitable and financially attractive and hence
recommended for execution.
******
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PAHUMARA - SHP
Section - II
SALIENT FEATURES
1. Location :(i) State : Assam (ii) District : Baksa
Bodo Territorial council (BTC)(iii) Block : Jalah(iv) Village : Laugaon (v) Access-road
From nearest air port - Guwahati Nearest rail station - Barpeta road
:
:::
10 kms from NH-31 at Bhawanipur point
148 kms 33 kms
(vi) Geographical Coordinates
LongitudeLatitude
:::
Powerhouse site
910 1 E 260 37 N
(vii) Altitude : 50 m above msl2 River Catchment
(i) Catchment : 440 sq. km.
(ii) Name of River : Pahumara(a tributary of Brahamaputra)
3. Type of Project : Low head, run of the river type with diurnal storage
(a) Diversion Structure (Head works)(i) Type of structure weir/barrage Barrage type weir of RCC(ii) Length of barrage : 172 m (iii) Maximum discharge capacity (cumecs) : 1699 cumec(iv) Number of undersluices (Existing) : 5 bays (v) Number of weir bays (Existing) : 18 (vi) Normal pond level : 49.60 m(vii) Maximum water level ; 49.60 m(viii) Crest level of undersluices (existing) : 44.75 m(ix) Top level of guide bund (existing) ; 52.5 m(x) Top width of crest (existing) : 2.0 m
4. Head Race Channel :(a) Shape : Rectangular(b) Bed width (at the entrance) : 9.5 m
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PAHUMARA - SHP
(c) Length : 43.4 m (d) Bed slope : 0.1 m in 43.4 m (e) Fully supply depth : 4 m (f) Free board : 1 m
(g) Manning’s coefficient : 0.018 (h) Design discharge : 49.7 cumec
5. Forebay :(a) Live storage volume : 350 cum.(b) Dimensions (length x width x depth) : 25 m x (9.5 x to 15) x 10(c) Free board : 1.0 m
6. Power Station :(a) Type : Surface(b) Design head : 6.3 m(c) Power station dimensions :
Length : 23.5 m Width : 9.86 m Height : 27.5 m
(d) Proposed installed capacity : 2 x 1000 Kwe(e) Number of units : 2(f) Design discharge : 38.60 cumecs
(g) Firm power (at 90% dependable discharge)
: 260 kW(4.62 cumec)
(h) Design energy : 6.853 x 106 kwh7. Turbine :
(a) Type : Vertical axis Kaplan(b) Number : Two (c) Capacity : 1063 kw (d) Diameter of runner : 2100 m(e) Rated head : 6.4 m (f) Rated discharge per unit : 19.3 cumec
8. Generator :(a) Type : Synchronous (b) Number of units : 2(c) Number of phases : 3(d) Frequency : 50 (e) Rated output : 1000 KW(f) Rated voltage : 3300 V
(g) Power factor : 0.8 lagging (h) Rated speed : 750 rpm
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PAHUMARA - SHP
9. Power Station Crane : Hand operated bridge crane – 15 tonnes
10. Switchyard :(a) Voltage level : 11000 / 3300 V(b) Number of bays : One + one for auxiliary power
transformer(c) Number of step up transformers : One(d) Transformer capacity : 2500 kVA(e) Transformer mounting : Plinth mounted(f) Auxiliary power transformer
VoltageNumber
:::
125 KVA 11000 V / 433 VOne
11. Tail Race :(a) Shape : Trapezoidal (b) Length : 85.0 m (c) Bed width : 30.0 m (d) Bed slope : 0.1 m in 85 m (e) Full supply depth : 1.2 m (f) Free board : 1.0 m
(g) Manning’s coefficient : 0.0225(h) Design discharge : 40 cumec
12. Estimated cost :(a) Project cost : Rs. 1413 lakhs (b) Cost of electro-mechanical equipment : Rs. 653.0 lakhs (c) Cost of civil works : Rs. 683.00 lakhs (d) Total project cost including IDC : Rs. 1566.33 lakhs (e) Cost per KW installed : Rs. 78320.00
13. Benefits :(a) Design Energy : 6.853 x 106 kwh(b) Average energy available for sale per
annum: 8.784 x 106 kwh
(c) Plant load factor : 50.6 %(d) Cost of Generation per KWh (on
levellised cost basis): Rs. 3.12
(e) Annual revenue at sale price of Rs 3.20 per kwh
: 281.10 lakhs
14. Financial performance indicator :(a) Return on equity (levellised) : 20 %(b) Cumulative cash accrual on equity of
Rs. 437.93 lakhs: Rs. 4269.35 lakhs
*******
7.
PAHUMARA - SHP
Section – III
CHECK LIST
1 NAME OF THE PROJECT PAHUMARA SHP
2. LOCATION
a. State Assam
b. District BaksaBodo Territorial council (BTC)
c. Block Jalah
d. Village Laugaon3. CATEGORY OF THE PROJECT
a. Small Hydel Hydroelectric scheme with a total installed capacity upto 25000 KW
2 x 1000 KW
4. PLANNING Has the overall development of the stream/canal been prepared and stages of development discussed ?
Yes
Have the alternative proposals been studied and their merits and demerits discussed ?
Yes
Have the detailed topographical surveys been carried out for the following items and drawings prepared as per prescribed scales ?
Yes
a. Head work surveys (weir or diversion structure) Yesb. Desilting tank Yesc. Water conductor system Yesd. Forebay Yese. Penstock. Yesf. Power house, Tailrace etc. Yes
5. GEOLOGY 6. FOUNDATION INVESTIGATIONS
Have the general surveys regarding construction materials like pervious and impervious soils, sands, aggregates, etc. been carried out ?
Yes, as applicable and necessary
7. HYDROLOGICAL & METEOROLOGICAL INVESTIGATIONS Have the hydrological investigations been carried out and status of discharge data of stream/canal discussed in reports ?
Yes
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PAHUMARA - SHP
8. HYDROLOGY Have hydrological studies been carried out to establish the availability of water for the benefits envisaged, and what is the dependability of the potential ?
Yes50% Dependability
9. LAND ACQUISITION & RE-SETTLEMENT (Whenever Applicable) Have the provisions for land acquisition and resettlement been considered ? Have the socio-economic problems involved in resettlement been investigated & discussed?
Yes-provision for land acquisition has been made.No - Re-settlement is not involved
10. DESIGN Has the layout of the project area viz., location of diversion structure, powerhouse etc. been finalized ? Have the preliminary designs been prepared for the following components ?
Yes
a. Diversion Weir. Yesb. Penstock and water conductor system, etc. Yesc. Power house etc.
Yes11. POWER BENEFITS
Have the following been discussed ? a. Total energy production and installed capacity of the
system Yesb. How does the scheme fit into overall development of
power of the region ? (as applicable ).Power station being developed for meeting the electrical power requirements especially in rural areas of Assam
c. Energy generation from the project, firm power etc. Saleable energy : 8.784 million kw hrs annually on average
d. Proposal for transmission and/or connecting to the existing system, etc. (wherever applicable).
11 KV single circuit line existing upto the barrage site shall be used for power evacuation
e. Cost of generation per kwh installed as compared to the various micro hydel projects and services in the region of justify the economic viability of the scheme.
Rs. 3.20 per kwh is comparable to the cost of other canal based low head hydropower station in the region. Further, the cost is less than
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PAHUMARA - SHP
the cost of energy purchased by Assam State Electricity Board from Central Generating Stations and Private Generating Stations.
12. CONSTRUCTION PROGRAMME Are the major components of work proposed to be done departmentally of through contractor ? Have the quantities of the following items been worked out for various components of the project ?
Through Contractor
Yes
a. Excavation –soft & hard strata Yesb. Earthwork in filling (wherever applicable) Yesc. Stone for masonry Yesd. Coarse aggregated for concrete Yese. Steel for reinforcement. Yesf. Other materials – P.O.L., Electricity
Yes13. ESTIMATE a. Is the estimate prepared ? Yesb. Have the analysis of rates for various major items and the
components of the project been furnished, with basis of analysis & the price index ? Yes
14. ECONOMICAL & ENVIRONMENTAL ASPECTS Is the area likely to the environmental and ecological problems due to the altered surface water pattern and preventive/corrective measures discussed ? (wherever applicable)
No Environmental and ecological degradation. For environmental preventive and corrective measures a sum of Rs. 0.50 lacs has been provided for in the cost estimates
15. CAMP AND BUILDINGS : Has the planning of the camps/building been done ?
Yes16. SOIL CONSERVATION
Is the need for soil conservation measures in the project discussed ?
Not required
******
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PAHUMARA - SHP
CHAPTER – 1
SCOPE OF THE PROJECT
1.1 PROJECT PLAN AND PURPOSES
It is proposed to harness hydro energy available at the barrage site on the river
Pahumara located near the village Laugaon in the district of Baksa in the State of
Assam. The barrage has been constructed to feed one canal on the right bank. The
Pahumara river, alongwith its numerous tributaries, originate from the southern
watershed of Arethumke peak of Bhutan range of Assam Himalayas and pass through
vast areas of open mixed jungles within the North Kamrup reserved forest before joining
the Brahmaputra.
The discharge in the river is much more than the irrigation requirements. It is
proposed to utilize the head available by ponding the upstream of the barrage and the
surplus water flowing through the barrage (at present after meeting the irrigation
requirements).
The maximum (pond) water level is 49.60 m above msl. The average river bed
level at a distance of above 200 meters downstream of the barrage is 41.8 meters. Thus
a gross difference of 7.8 meters is available between the pond level and the river bed
level.
The maximum and minimum discharge passing through the barrage after
meeting the irrigation demand are 53.35 cumec and 15.73 cumec in a 50% dependable
year and 50.52 cumec and 2.94 cumec in a 90% dependable year respectively as per
the river discharge data available over a period of 6 years. On the basis of this
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PAHUMARA - SHP
discharge data, water power studies have been conducted, which has resulted in the
possibility of establishing a hydropower station on the left bank of the river (barrage). It
is proposed to install a power generating facility comprising of 2 units of 1000 KWe
rating each, aggregating to 2000 KWe installed capacity with a plant load factor of
50.6% on average.
The electrical energy generated from this project would meet the needs of the
villages in the vicinity and in the backward districts of Baksa, Kokrajhar and Barpetta
which will improve the power availability in the region and help accelerate socio-
economic development. Besides, the project would also help reduce the energy
shortage of 5.40% and peak power shortages of 5.80% of the state of Assam (Ref.
2004 – 2005 statistics – source: North – Eastern Region Power Sector Profile, Ministry
of Power, Govt. of India January 2006).
1.2 PROJECT COMPONENTS
The proposed project shall be of ‘run-of-the-river” type for the generation of
hydroelectric energy.
The proposed Pahumara SHP shall consist of the following major system
components:
(1) Head race channel
(2) Road bridge (conforming to IRC Class A) on head race channel.
(3) Intake structure with trash rack and stop-log gates with hoist arrangement.
(4) Vertical axis Kaplan turbines coupled to synchronous generators through
appropriate speed increaser – 2 sets, each of 1000 KWe capacity.
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PAHUMARA - SHP
(5) One (01) 15 tonne capacity bridge crane H.O.T for the turbine generator
room.
(6) One (01) 10 tonne capacity gantry crane for intake gate operation.
(7) One (01) set of generator and turbine control and protection cubicles with
measuring, recording, and indicating instruments, protective relays and
annunciation system.
(8) SCADA system
(9) Pond level controller
(10) Two numbers of drainage pumps.
(11) One number step-up transformer 3.3 KV / 11 KV, 2500 KVA with associated
current and voltage transformers (CTs and PTs) and vaccum circuit breaker.
(12) Draft tube gates – 2 nos.
(13) Monorail with gate hoist (7.5 tonnes) for operating draft tube gates
(14) Tail race channel.
In the event of tripping of the unit / units, the inflow into the upstream of the pond
shall be made of flow to the downstream of the river by opening of the barrage gates as
required. The opening and closing of the gates shall be controlled by a level controller to
be installed on the upstream of the barrage. To avoid overtopping of the banks, the level
controller shall be provided with adequate redundancy.
1.3 PROJECT BENEFITS
It is estimated that on average 8.784 x 106 Kwhrs of electrical energy shall be
available for sale after meeting the energy required for auxiliary power consumption.
13.
PAHUMARA - SHP
The project when completed would result in conservation of 8800 tones of coal
annually thereby providing a cleaner environment for future.
Further, the project since uses renewable resource for power generation would
benefit the global reduction of carbon – dioxide (green house gas) pollution by 8750
tones annually.
1.4 CONSTRUCTION MATERIAL
Fine aggregate and coarse aggregate are available in the river bed nearby and in
u/s reaches . Coarse aggregate boulders are to be collected from the u/s reach river of
and crushed for use in the structures.
Cement from reputed manufactures is available from dealers at Bongaigaon and
Kokrajhar which are within a distanced of about 25 / 30 kms from the project site.
Structural and reinforcement steel can be obtained from the Stockyard of Steel
Authority of India Ltd. (SAIL) located at Guwahati at a distance of 150 kms from the
project site.
1.5 CONSTRUCTION PROGRAM
The construction of the project comprises of the following major activities:
- Excavation of approach channel p.u. pit and tail race channel.
- Power station raft foundation.
- Dewatering
- Construction of head race channel, road bridge, intake and power
house structure, tailrace channel.
- Erection and commissioning of power plant equipment, trashrack,
cranes, gates (intake and draft tube).
- Dismantling of the to upper portion of left side retaining wall u/s of head
regulator of irrigation canal and to construct approach channel to
forebay.
14.
PAHUMARA - SHP
- Construction of 11 KV switchyard and connecting the existing 11KV
line.
The above works can be completed within twenty four (24) months from the date
of technical and financial closure of the project. Preparation of tender specifications,
issue of notice inviting tenders, tender evaluation, and placement of orders can be
completed within six months from the date of start of the project, which is included
within the above mentioned period of twenty – four months. Temporary sheds for
construction storage, and accommodation of construction staff also be constructed
during the first six – month period. The existing building at the barrage site on the left
bank can be used for locating the site office.
1.9 CONSTRUCTION POWER
It is estimated that a maximum of 250 KVA of power would be required at the
project site including power required for dewatering. There is already on existing 11 KV
line upto the barrage site. The construction power shall be drawn from this line.
However, as a standby, it is proposed to install a 100 KVA Diesel Engine driven (DG)
set for taking care of any contingency.
1.10 ENVIRONMENT AND ECOLOGY
Since the power plant is proposed to be set-up adjacent to the existing barrage
and within the land owned by the irrigation department, no adverse effect to
environment and ecology in the vicinity is expected.
Since the water diverted from the upstream of the barrage is again let out into the
same river about 150 metres downstream, the threat to aquatic life in the downstream
stretch of the river is non-existent. Besides, leakage of water through the barrage gate
15.
PAHUMARA - SHP
seals would not dry-up the river in the downstream of the barrage upto the junction of
the tail race channel with it.
There is no wild life habitat including breeding, feeding and migration route within
the project periphery. It is also not a potential site for wild life sanctuary.
There are no rare or endangered species of flora and fauna within the project site.
There are no monuments of cultural, historical, religious or archaeological
importance within the project boundaries.
It is also not a spot used for recreation at present. However, it is likely that after
the site is developed for power generation, by creating a pool upstream of the existing
barrage, the head pool could be developed as a place for recreation by provision of
boating facilities. Further, the upstream pool could be used for developing fishery and
pisciculture, which will increase availability of local and fresh fish in the villages and
towns nearby. It may be worth mentioning here, that fish is the staple food of the state,
and presently fish is being imported from far away places like Andhra Pradesh and Uttar
Pradesh for meeting the growing demand.
There are no trees within the project boundaries. However after completion of the
project, trees with commercial value can be planted along the tail race channel and the
head pool to enhance the environment and ecology of the area. Appropriate provision of
Rs. 0.50 lakhs has been made in the budget estimates for plantation of trees, and land
scaping around the project area.
16.
PAHUMARA - SHP
1.11 LAND ACQUISITION
The entire project is proposed to be aligned within the land owned by the
Government of Assam and hence no difficulty in acquisition of land is envisaged. The
land required for the project area 0.81 hectares.
1.12 PROJECT COST
The total cost of the project is estimated at Rs. 1413.00 lakhs without escalation
in cost and interest during construction, and Rs. 1566.33 lakhs with escalation in cost
and interest during construction. The cost of civil works and electro-mechanical works
are stated as below:
Cost of civil works : Rs. 683.00 lakhs
Cost of electro-mechanical : Rs. 633.00 lakhs
Cost of power evacuation : Rs. 20 lakhs
Cost of land : Rs. 2 lakhs
Expenditure on pre-project Development works : Rs. 75.00 lakhs
It is proposed that the phasing of expenditure shall be as follows with debt to
equity ratio as 70 : 30 :
Ist year(in lakhs)
2nd year (in lakhs)
Promoter’s contribution 437.93 NilExternal borrowing 39.87 981.96
Total 477.80 981.96
The interest during construction on the borrowed capital is Rs. 106.57 lakhs.
1.13 BENEFIT TO THE STATE
As per small hydro power policy of Government of Assam, it has been proposed
to give 0.05paise per unit as water cess to the state.
Keeping this in view, the cost of generation has been worked out.
17.
PAHUMARA - SHP
1.14 COST OF GENERATION
The cost of generation in the first year works out to Rs. 3.49 per kwh at the
station busbars, and Rs. 3.12 per kwh on levellised basis.
As per the figures available for the year 2001 – 2002, Assam State Electricity
Board has been purchasing power from other states and Central Sector Stations with an
average cost of Rs. 1.9041 per kwh. For the same year, (2001 – 2002) the tariff
structure has been as follows:
Domestic : Rs. 1.9981Agriculture irrigation : Rs. 2.8715Industry : Rs. 4.4756Average : Rs. 3.6734
(Source : North Eastern Region Power Sector profile, Ministry of Power Govt. of India, January 2006)
1.15 FINANCIAL RETURN
As per the financial analysis carried out for the project and reported in Chapter
cash accrual is Rs. 4269.35 lakhs over the life time (35 years) of the project. Further,
the return on equity is 20.1 % on levellised basis.
It is thus apparent that generation from this project is competitive with the power
purchased from other states / Central Government stations. Further, whereas the
energy produced from coal, oil and natural gas stations would rise in the future, the cost
of energy produced from this station would not rise with time and would rather reduce in
terms of its real cost, considering the inflation in economy and devaluation in real value
of money.
18.
PAHUMARA - SHP
1.16 RECOMMENDATIONS
The project envisages harnessing of renewable energy source, thereby
conserving non-renewable energy source and reducing environmental pollution by
avoiding carbon – dioxide emission to the atmosphere.
The proposed project being technically feasible, economically desirable,
financially viable and environmentally benign is recommended for execution on the
explicit considerations of long term benefits to the society.
******
19.
PAHUMARA - SHP
CHAPTER – 2
INTRODUCTION
2.1 GENESIS OF THE PROJECT
The State of Assam is located in the North-eastern part of India blessed with
abundant natural resources especially oil, gas, forest and agricultural resources. The
state is located as a strategic corridor to other states like Arunchal Pradesh, Nagaland,
Tripura, Manipur, Meghalaya and Mizoram located on the north-eastern and eastern
frontiers of the country. Assam State Electricity Board (ASEB) has been assigned the
role of bulk purchase of supplying of electricity throughout the State. During the year
2004 – 05 there was a shortage of peak power by 5.80 % and an energy shortage of
5.40%. The state has been also purchasing power to a tune of 2072 million units (2001-
02) from central sector stations and other states. The average purchase price is Rs.
3.03 per kwh (as per the present agreed cost of power procurement from Power Trading
Corporation by ASEB).
The National Electricity Policy of Government of India envisages that peak and
energy shortages should be met completely by 2012. It is further envisaged that the
quality and reliability power should improve. The policy lays emphasis on rationalizing of
tariffs, rural electrification and encouraging higher private sector participation. The policy
also addresses key issues such as hastening the returns process by defining time lines
for critical processes such as open access in each state, metering requirement, energy
audits intra-state transmission tariffs and upgrading technology at regional level
dispatch centers.
20.
PAHUMARA - SHP
The Infrastructure Leasing and Financial Services Limited (IL&FS) is one of
India’s leading infrastructure development and finance companies. IL&FS was promoted
by the Central Bank of India (CBI), Housing Development Finance Corporation Limited
(HDFC) and Unit Trust of India (UTI). Over the years, IL&FS has broad-based its
shareholding and inducted institutional shareholders including State bank of India, Life
Insurance Corporation of India, ORIX Corporation – Japan, HSBC Group and
Government of Singapore. IL&FS has a distinct mandate – catalyst the development of
infrastructure in country. The organization has focused on commercialization and
development infrastructure projects and creation of value added financial services. The
IL&FS group has evolved along routes perfectly configured to business requirements.
Technical support and service routes provide specialized expertise project development
and sectoral companies house the ability to see initiatives and carry than through to
completion. The IL&FS group is active in the development of infrastructures sectors
namely,
* Transportation, * Area Development * Cluster development * .Finance * Power
* Ports * Water and Wastewater * Urban Infrastructure * Environment * Education
* Tourism
The IL&FS has entered into an Memorandum of Understanding (MOU ) with the
Bodo land territorial council for development of small hydro power stations in the Bodo
land area for meeting the local electrical energy requirements as presently electrical
energy availability especially in the rural areas in Assam suffer from unreliable power
supply, low voltage and brown outs. Towards this end, IL&FS has identified the existing
barrage.- sites for power generation purposes by utilizing the head difference between
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PAHUMARA - SHP
the upstream water level of the barrage and the downstream water level and the
discharge which is released through the river as excess over the irrigation requirements.
These irrigation barrages have been constructed by the Assam Irrigation Department for
meeting the irrigation requirements in the adjoining areas by impounding the river flows.
Pahumara is a perennial river flowing from the Bhutan hills through the State of Assam
and draining into the river Brahmaputra.
2.2 GEOGRAPHICAL DISPOSITION
The proposed Pahumara SHP is located at the geographical coordinates latitude
260 37’ N and longitude 910 1’ E near village Laugaon in the district of Baksa.
2.3 ACCESSIBILITY
The Pahumara SHP is connected by all weather road from NH-31 from
Bhawanipur point. The distance is around 10 kms. The nearest railway station is
Barpeta road situated at a distance of 33 kms. The project site is accessible through out
the year from NH-31. The project site is 150 kms from the state capital Guwahati.
2.4 TOPOGRAPHY
The proposed power station is to be located on the right bank of the river
Pahumara, downstream of the existing barrage. The land around the site is almost plain
and flat without much undulations. The land around the site is barren and not used for
any productive purposes.
2.5 CLIMATE
The South West monsoon rains from the end of the early half of April being the
general rainy season. The period from April to September is the monsoon period. The
Pahumara basin receives an average rainfall of 1427 mm.
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The climate is predominantly humid from April to September, the humidity being
very high - more than 90% with an average temperature of 290 C. The humidity
decreases to 60 – 67% from September to March. Normally the dry period is between
February and March. The minimum temperature (during December and January) is
130 C (mid night).
2.6 GEOLOGY
The site is located in the alluvial plain of Assam. As per geological and soil
investigations based on observations of the soil excavations in and around the project
area, the proposed power house site is devoid of rock strata and is entirely covered with
sandy / clay soil.
2.7 NATURAL RESOURCES
There are no mineral resources below the ground level in the vicinity of the
proposed project site.
2.8 SOURCES OF WATER
The river Pahumara originates from the southern water shed of Arethumke of
Bhutan range of Assam Himalayas and runs almost in north - south direction to join river
Brahmputra. The catchment area intercepted at the Pahumara barrage site at
Kathalmuri ghat is 430 sq.km.
From the upstream of the barrage one canal take-off on the right bank. The
design discharge of the right bank canal is 9.92 cumec. Since the barrage is accessible
from the National Highway 31 on the right bank, it has been proposed to locate the
power station on the right bank.
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It is proposed to draw the water to the proposed SHP through an intake to be
constructed upstream of the warped wall adjacent to the right bank canal intake. Water
from the reservoir created by the barrage shall be flowing into the head pond of the
power station through the proposed intake channel and the modified intake of the
existing right bank canal.
2.9 HYDROLOGY
The discharge available in the river is much more than the irrigation requirements
of both the canals. It is proposed to utilize the excess water which is presently flowing
down through the barrage gates for power generation purposes.
The discharge data of the river Pahumara for the years 1965, 1966, 1972, 1973,
1974, 1975 ( 6 years) have been utilized for determining the power and energy for the
proposed SHP.
For estimation of hydro power potential, the hydrological data for the years 1965
- 1966 and from 1972 – 1975 (6 years) have been considered which is considered to be
adequate for planning of small hydro power projects. The discharge data corresponding
to these 06 years have been tabulated in Table 4.1. The irrigation requirements is
stated in Table 4.2. The water available for power generation has been calculated after
deducting the monthly irrigation requirements from the river discharge for all the 6-years
and stated in Table 4.3.
2.10 NECESSITY – NEEDS AND OPPORTUNITIES FOR DEVELOPMENT
Only 21% of the 4.5 million households in the state of Assam have access to
electricity. The per capita consumption of electricity is only 104 kilowatt hours, which is
less than one – third of the national average.
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The shortage of electrical power can be easily gauged from the fact that Assam
State Electricity Board has very recently have invited tenders for supply of off-peak
power of 80 MW (between 0000 hrs to 1700 hrs and from 2300 hrs to 2400 hrs) and
peak power of 100 MW from 1700 hrs to 2300 hrs daily from November 2006 to April
2007. This trend is likely to continue into future no major power project is commissioned
to mitigate the power shortages.
Asian Development Bank has observed that the lack of sufficient and reliable
power is eroding the state’s competitiveness and prevents it from attracting industrial
investments from outside. ADB has also observed that improved power supply at a
removable cost is essential to revive the state’s industry and economy. Further, they
have noted that financial sustainability in power sector is equally important to be
improved so that it is no longer a drain on state finances.
Because of technical and financial constraints, Assam State Electricity Board
operates below capacity and is unable to meet the State’s total power demand. It
depends on power purchased from neighbouring states, and other Central Government
power generating agencies. Due to purchase of power from other agencies, the cost of
power is high. Further poor billing and collection of revenue add to the financial
problems of ASEB.
Consequently, ASEB is heavily dependant upon the State Government’s financial
support for providing electricity in the state. Diversion of state government’s funds for
electricity, naturally, reduces the governments expenditure on meting the more basic
requirements of population like health and education.
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With shortage of electrical energy, depletion of fossil fuel resources, and
increasing awareness against pollution caused by use of coal, oil, natural gases in
generation of power, global attention has been focused on harnessing renewable
sources of energy like small water power, solar, and wind etc., which are non-
exhaustible and non-polluting. Amongst all the renewable energy sources receiving
attention, small hydro power is most promising since the technology having evolved
over a period spanning more than 150 years has reached a stage of maturity.
Small hydropower programme is one of the thrust areas of the Government. The
Ministry of Non-Conventional Energy Sources, Government of India has set a goal of
2000 MW capacity addition from small hydro power projects by the year 2012. The
thrust of SHP development would be mostly through setting up of commercial projects
with private sector participation.
2.10.1 National Policies Supporting the Project
The Ministry of Non-Conventional Energy Sources (MNES) was created in 1992
by upgrading the erstwhile Department of Non-conventional Energy sources. The main
responsibility of the Ministry includes the development and utilization of the entire
spectrum of renewable energy sources from the traditional to the modern technologies,
from draught animal power, improved woodstoves, biogas to hydrogen energy,
including solar, wind, biomass, small hydro power, cogeneration, ocean energy,
geothermal energy and alternate fuels. The main activities include research and
development, development of standards, operation of test facilities, promotion of
manufacturing and development of markets, commercialization of technologies,
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PAHUMARA - SHP
operational programmes, awareness creation information dissemination and
international cooperation.
The Ministry has now moved to a liberalized policy regime, allowing the market
forces to play a major role. Direct cash subsidies are being phased out by a package of
incentives and financing arrangements. A suitable policy environment and support for
market mechanisms have been created which would lead to increased participation of
private sector in the production and utilization of non-conventional energy devices.
Strategy
A three fold strategy has been pursued by the Ministry for the promotion of NRSE
which are outlined below:
* Promoting private investment through fiscal incentives, tax holidays, depreciation
allowance, facilities for wheeling, banking and third party sale of grid power, and
a remunerative price for the power generated.
* Extending institutional finance from Indian Renewable Energy Development
Agency (IREDA), and other financial institutions, for commercially viable projects,
with private sector participation, and external assistance from World bank, Asian
Development Bank (ADB), Global Environment Facility (GEF) and bilateral
programmes.
* Providing budgetary resources of government for selected demonstration
projects.
The implementation of the programmes is being carried out by State
Governments, Electricity Boards, Industry and Non-governmental Organizations etc.
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The Government of India and the State Government have announced a number
of incentives for development of small hydro in the country which are stated below:
(a) The Government has permitted a minimum of 14% return on investment.
(b) The Government has permitted private sector to participate in power generation
through the implementation of the Indian Electricity Act 2003.
(c) The MNES supports SHP development, both in the government and private
sectors. Apart from financial support to new modernization and modernization
(R&M) of existing SHP stations and government projects that have been
languishing for want of funds. A special incentive package has been developed
for the promotion of the SHP programme in the Northern Eastern states, Jammu
and Kashmir, Himachal Pradesh, and Uttaranchal. Key performance parameters
such as cost of the project, capacity utilization factor, and cost of electricity
generation are the guiding factors for grant of subsidy. Emphasis is also laid on
quality of the equipment through insistence upon standards and specifications
that match international levels.
To improve the economic viability of SHP projects and to give impetus to
the programme, the MNES provides a one-time subsidy for commercial SHP
projects. The subsidy is utilized by the promoter towards repayment of the term
loan availed from a financial institution. The subsidy is released after the project
performance parameters are attained as laid down in the MNES scheme. The
subsidy scheme covers projects of capacity up to 25 MW each. The eligibility
conditions and subsidy levels are given in below:
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PAHUMARA - SHP
Eligibility criteria and levels of subsidy for SHP project
Eligibility Special category states (North-Eastern region, Sikkim, Jammu and Kashmir, Himachal Pradesh and Uttaranchal)
Other states
Maximum
permissible installed
cost
Rs. 7 crores / MW Rs. 5 crores / MW
Cost of electricity
generation
Rs. 2.50 – 3.30 / unit -
Minimum
permissible
Capacity utilization
factor
Canal based : 30%
Others : 45%
Standards All projects to conform to relevant international /
national codes of practices and standards
Subsidy Rs. 2.25 crores X(C MW)0.646 Rs. 1.5 crores X
(C MW)0.646
Note : ‘C’ stands for capacity of the project.
(d) Soft loan by Indian Renewable Energy Development Agency.
2.11 CHOICE OF SCHEME – ALTERNATIVE STUDIES
The alternative studies conducted during the course of preparation of the DPR
are stated as below:
(1) Installed capacity
(2) Number of generating units
(3) Type of turbine.
The recommendations in this report is based on the alternative that is technically
appropriate, economically attractive and financially most desirable.
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2.12 RECOMMENDATIONS
The recommendation in the report is for installation of vertical axis axial flow
Kaplan turbine located on the left bank of the river on a by-pass channel across the
Pahumara barrage.
*****
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Fig. 2.1
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CHAPTER – 3
SURVEYS AND INVESTIGATIONS
3.1 TOPOGRAPHIC SURVEY
Topographic survey of the area covering the approach channel, forebay, power
station, tail race pool has been carried out on a scale 1:500 at 1 meter contour intervals.
The area surveyed extends upto 200 meters from the upstream of the barrage center
and upto 250 m downstream. The width of the strip surveyed is 200 m from right bank
of the barrage.
3.2 HYDROLOGICAL SURVEYS
The discharge data of Pahumara river have been collected by the Assam
Irrigation Department at gauging site at the NH crossing about 15 kms. downstream of
the proposed barrage site. The discharge at the barrage site has been considered as
90% of the discharge measured at the bridge site of NH crossing. There is no tributary
meeting the river between the barrage and the gauging site at the NH crossing.
The irrigation project has been designed on the basis of the discharge available
for 11 years from 1972 to 1982.
From the barrage at Kathalmuri ghat, one canal take-off on the right bank. The
design discharge of the right bank is 9.92 cuemc.
Since the inflow at the Kathalmurighat is much more than the irrigation
requirement as mentioned in Table 4.1, the surplus water available at the barrage and
intercepted is proposed to be utilized for power generation.
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The discharge data corresponding to these years have been considered for
power potential evaluation. After accounting for the irrigation requirements the balance
water as available for each of these years for power generation has been calculated
and utilized in the planning of the project installed capacity.
******
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Fig.
3.1 A view of the Pahumara river near the Barrage Site showing the location of principal villages – Laugaon and Kathalmuri
34.
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CHAPTER – 4
WATER RESOURCES (HYDROLOGY)
4.1 RIVER SYSTEM
Assam state comprises of two main river valleys. The northern valley is known
as the Brahmaputra valley and the southern valley is known as Barak valley. The
Brahmaputra valley is an alluvial plain in between the foot hills of Bhutan ranges and
other hill tracts, on North and central ranges of Naga, Karbi, Khasi, Jaintia, Garo hills
etc. This valley approximately covers 56339 sq.km. of riverine area within the strip of
both bank of the river, stretching from Sadiya on the east up to Dhubri on the West. The
Brahmaputra receives a number of tributaries and sub-tributaries throughout its course.
These streams and rivulet originate from southern water shed of Arethumke peak of
Bhutan range of Assam Himalaya and flow in areas characterize by open mixed jungles
within north Kamrup reserved forest. River Pahumara is one of the major tributaries on
the north in the District of Baksa district. The catchment area of Pahumara is about 440
sq.km from its origin upto its existing head works (barrage) site at Kathalmuri ghat.
The area between Bhutan foot hills and about 5 km, north of the NH-31 (C) is
covered by reserve forest and mixed jungles etc.
River Pahumara is a major tributary of the mighty Brahmaputra and this river
along with other two main rivers namely Kaldiya and Moradiya command the Pahumara
basin of the Northern region of Brahmaputra valley. This basis lies between lat. 26.10’N
and long. 91.5’ to Lat. 26.5’ N end long. 91.15’E. Each of the rivers has independent
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PAHUMARA - SHP
source of origin but they come together to drain the water of the whole basin into the
river Brahmaputra.
The river Pahumara originates in Himalayan foot hills of Bhutan between
elevation 1000-15000 metres and flows south to join the rivers Kaldiya and Moradiya.
Actually this river is a combination of some hilly streams and local springs. The main
tributary of this river is Rupahi. The other main stream is Jiapota which itself is a
combination of some streams mainly Bhumki and Thebor. This combined discharge of
Jaipota meets the river Rupahi at Kathalmurighat about 8 miles north of NEF Railway
line and takes the name of Pahumara and flows almost towards south. After crossing
the national highway 31 it flows in south western direction. After traveling about 3 miles
south of NH 31 it allows its whole flow to discharge in to vast low lying area consisting of
many beels. Into this low lying area, two other rivers, namely, Kaldiya and
Morapagladiya also discharge. After this it takes the name Chowlkhowa flowing towards
south west and joins the Brahmaputra river.
River Pahumara flows with bed gradient nearing in 1000 – 15000 in the plains on
Kamrup district. Its bed in this reach consists of medium and fine silt. It has a shallow
and wide but well defined section. In the backwater one of the Brahmaputra, the river
has a very flat gradient of the order of 1 in 16000 ft.
4.2 DISCHARGE IN RIVER PAHUMARA AT BARRAGE SITE
The discharge data of Pahumara river have been collected by the Assam
Irrigation Department at NH-31 bridge site (18 kms downstream of head works site)
from 1964 onwards. The discharge at this site has been reduced by 10% to arrive at the
discharge at Kathalmuri barrage site.
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The maximum observed discharge 948.32 cumec (33457 cusec) on July 17th,
1970 and minimum observed discharge is 2.1 cumec. The discharge data available for
the Kathalmuri barrage head works site for the period from 1972 to 1982 is given in
Table 4.1 which has been extracted from the detail project report for the Pahumara
irrigation project prepared by Assam Irrigation Department.
The irrigation requirements to be catered through the right bank canal is
mentioned in Table 4.2.
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Table 4.1 (one page)
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Table 4.2: Gross irrigation requirement for Pahumara Irrigation Project
Month Ten days period Gross irrigation requirement in cumec
January 1 – 1011-2021-30
0.120.120.45
February 1-1011-2021-28
0.370.460.30
March 1-1011-2021-31
0.301.271.31
April 1-1011-2021-30
1.041.041.04
May 1-1011-2021-31
0.770.770.78
June 1-1011-2021-30
0.850.850.29
July 1-1011-2021-31
0.162.813.07
August 1-1011-2021-31
2.452.442.72
September 1-1011-2021-30
2.762.763.65
October 1-1011-2021-31
2.522.520.00
November 1-1011-2021-30
2.892.150.07
December 1-1011-2021-31
0.120.120.12
4.3 DISCHARGE IN THE IRRIGATION CANALS
From the barrage at Kathalmuri one canal take-off on the right bank and the
other on the right bank. The design discharge the right bank canals is 9.92 cumec.
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PAHUMARA - SHP
4.4 DISCHARGE AVAILABLE FOR POWER GENERATION
Since the inflow at the Pahumara barrage is much more than the irrigation
requirement as mentioned in Table 4.2, the surplus water available at the Pahumara
barrage and intercepted is proposed to be utilized for power generation. The water
available for power generation after accounting for irrigation discharge on 10-daily basis
for the years 1965, 1966 and from 1972 to 1976 is shown in Table 4.3.
4.5 DEPENDABLE DISCHARGE
In Figure 4.1, the year-wise total annual runoff, and determination of 50%
dependable year (1974) have been graphically presented. The flow data available for
power generation (after meeting the irrigation requirements) have been stated in Table
4.4 arranged in descending order.
In Figure 4.2, the discharge – duration curve after accounting for the irrigation
drawals for the power generation has been presented. From figure 4.2, after accounting
for the irrigation discharges, the ninety (90) percent, fifty (50) percent and seventy five
(75) percent dependable discharges available for power generation have been
determined and are stated below based on six -years discharge data.
90% dependable discharge : 4.62 cumec75% dependable discharge : 8.20 cumec50% dependable discharge : 18.39 cumec.
4.6 WATER QUALITY
The silt concentration in this river has been observed to be maximum 700 PPM.
In view of this, no additional measures are required in the design of the power station,
civil works and electromechanical equipment.
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Table 4.3
41.
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Table 4.4 ( one page)
42.
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Fig. 4.1
43.
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Fig. 4.2
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CHAPTER – 5
GEOLOGY
5.1 GEOLOGY
The area comes under the new alluvial zone of Assam on the north of the river
Brahmaputra. The alluvial materials laid in the area very recent in the chronological
sequence of origin. The present material of these alluvial curries with a complex
geology of the Himalayan and the Tibetan plateau.
5.2 SUB-SURFACE INVESTIGATIONS
Sub-surface investigations were carried out by digging 1 pit at the proposed
power house location upto a depth of 8 m below the existing ground level. The soil is
young and immature. The soils comprises of a matrix of river bed material and silt.
The prime object of this investigation work is to find out sub soil profile, important
engineering properties, bearing capacities of subsoil etc. The report includes physical
properties of the subsoil deposit such as grain size distribution, bulk density, specific
gravity, moisture content, calculation of angle of internal friction, cohesion “C".
All works beginning from field investigation, collection of samples, laboratory
testing, interpretation of results was done as per pertinent code of practices.
The results are presented in a tabular or graphical form according to
convenience.
5.2.1 Field Works
The field work involved boring, recording soil profile by visual observation,
collection of disturbed and undisturbed samples for laboratory test, undertaking
standard penetration test etc.
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PAHUMARA - SHP
The sample collection by manual boring (Auger and Hand) including pertinent
field test and other visual observation were done in the month of April 2006.
The investigation shows that the soil in the area predominately found clay, silt
and sand. The boring did not present anything unusual like encountering boulders,
rocky strata etc.
The undisturbed samples were collected in metallic tubes as per IS : 1932 –
1963 specifications. The samples so collected were waxed at either end, labeled and
then forwarded to laboratory for conducting necessary tests.
The disturbed samples were collected from auger heads or from returning wash
water and split spoon sampler. It is then packed in polythene bags after marking in the
packets the depth, borehole number etc.
5.2.2 Standard penetration Test
The standard penetration test is done on undisturbed soil at site by hammering
with a hammer of 65 kg weight falling freely through a height of 75 cm. The number of
blows required to push the samples tube through 45 cm length is countered. The
reading of first 15 cm distance is not counted towards standard penetration values and
this position is called seating. The N values are shown in the borehole logs.
5.2.3 Bore Hole Log
The bore hole log is numbered for identification of location and also shows the
following:
(1) Date of boring.
(2) Ground water table – the reading for the ground water table is taken after
waiting for sufficient time till the water level in the casing become stationary.
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(3) Depth of different strata from ground level.
(4) Graphical representation of N-value.
5.2.4 Laboratory Test
The following laboratory tests were performed as soil samples:
(1) Grain size analysis for classification of soil
(2) Direct shear test
(3) Specific gravity
(4) Field density.
5.2.5 Calculation of Bearing Capacity
(a) Bearing Capacity based on shear failure
IS : 6403 – 1981 recommends the following equation to calculate the net safe
bearing capacity ‘qs’ based on Hansen’s bearing capacity analysis:
Qs = I/F {CNc Sc dc Ic + q (Nq – I) Sq dq Iq + 0.5 B N S d i x W}
Where,
C = cohesion of soil
= saturated density of soil
B = width of footing = 2 m (assumed)
W = water table correction factor = 0.5
Q = effective surcharge at footing level = D
(D = depth of footing)
Nc, Nq, N = bearing capacity factor
Sc = 1.3, Sq = 1.2, S = 0.8 (for square footing)
dc,dq,d = depth factor = 1 (assumed)
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ic, iq, i = inclination factors = 1 (assumed)
F = factor of safety = 3.0
The above equation thus becomes
qs = 1/F {1.3 C Nc + 1.2 D (Nq – 1) + 0.2 B N } for general shear failure and
submerged condition.
Depth = 3.0 m,
C = 0.15 kg/cm2 = 1.5 t/m2
= 180, local shear failure,
Angle of shearing resistance for local failure = m = tan –1 2/3 tan 180 = 12.220 say 120
Nq = 3.05, N = 1.79, Nc = 9.19
Angle of shear for general shear = 310
qs = 1/3 {(2/3 x 1.3 x 1.5 x 9.19 + 1.2 x 0.79 x 3.0 x (3.05-1) + 0.2 x 0.79 x 2.0 x 1.79} t/m+2
= 6.13 t/m2 say 10.0 t/m2.
Bearing Capacity Based on Tolerable Settlement
The maximum allowable bearing pressure is to be found out from the elastic
settlement consideration and is found from the following equation of I.S. Code 8009
(Part-I) 1976.
Sr = (Ht / 1 + eo) Cc log10 (po + p)/po
Sr = Total settlement in m
Ht = Thickness of soil layer in m
eo = Initial void ratio at mid height of layer
Cc = Compression index
Po = Initial effective pressure at mid height of layer
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PAHUMARA - SHP
= Pressure increment
Depth = 3.0 m
The soil below the foundation is divided into three layers of thickness 1 m each
and settlement of these three layers are calculated separately and finally summed up.
First layer of 1 m thick
Here, Cc = 0.09
Po = (3.0 x 0.79 + 4.0 x 0.76) / 2 = 2.70
Let us take allowable bearing capacity = 6.0 t/m2
= (6.0 + 3.6) / 2 = 4.8 t/m2
S11 = 1000/(1+0.64) x 0.09 x log10 (2.70 + 4.8) / 2.70 = 24.28 mm
Second layer of 1 m
Here Cc = 0.09
Po = (4.0 x 0.76 + 5.0 x 0.78) / 2= 3.47
= (4.8 + 1.8)/2 = 3.3 t/m2
S12 = 1000 / (1 + 0.64) x 0.09 x log10 (3.47 + 3.3) / 3.47 = 15.91 mm
Third layer of 1m
Here, Cc = 0.09
Po = (5.0 x 0.78 + 6.0 x 0.78) / 2= 4.29
= (1.8 + 1.2)/2 = 1.5 t/m2
S13 = 1000 / (1 + 0.64) x 0.09 x log10 (4.29 + 1.5) / 4.29 = 7.1 mm
Total settlement S1 = S11 + S12 + S13 = 24.28 + 15.9 + 7.1 = 47.28 mm < 65 mm, Safe
Adopt allowable bearing capacity as 6.0 t/m2
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Design of Pile foundation
Ultimate bearing capacity in compression in sand, QU from IS : 2911 (Part-I)-1981
QU = Qp + Qr
= End bearing resistance + Frictional resistance of pile in sand and clay.
Qu = (1/2
Qp = Ap (1/2
Qis =
Qic = Ca As
Qsafe = QU / FOS = QU / 2.5
Where,
Qu (kg) = ultimate bearing capacity of pile
Ap = Cross sectional area of pile toe in cm2.
= Bearing capacity factors depending upon the angle of internal friction
K = Earth pressure coefficient (usually taken as 1.5 for sandy soils)
Ca(kgf/cm2) = Average cohesion of soil around the pile stem
As (cm2) = Surface area of the stem
= 0.85 t/m2
q = D {D = Depth of foundation}
= reduction factor (usually taken as 0.5 for clays)
= Angle of wall friction between pile and soil.
As = Circumferential area of pile stem =
l = Length of embedment
d = Diameter of the pile.
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Let us consider bored RCC piles (without under – reamed bulb)
df = length of pile from existing ground level = 7.5 m
L = pile cut-off level = 1 metre
D = stem diameter = 30 cm / 40 cm
Diameter of Pile = 30 cm Length = 7.5 m
Ap = 0.070 m2
Average cohesion, Cav (2.0 m to 5.0 m) = (0.3 + 0.15 + 0.25) / 3 = 0.23
Here,
= 300
Nq = 18.40 = 22.40
Qp = 0.0707 [0.5 x 0.3 x 0.85 x 22.4 + 0.85 x 7.5 x 18.40] = 8.49
Qic = 0.5 x 2.3 x (3.14 x 6.5 x 0.3) = 7.04
Qis = 1.5 [{(0+5.0)/2x0.85}x0.5x(3.14x0.3x5.0)]+1.5[{(5.0+7.5)/2x0.85}x0.5x
(3.14x0.3x2.5)]
= 7.50 + 9.38 = 16.88 ton
Ql = 7.04 + 16.88 = 23.92 ton
Qu = 8.49 + 23.92 = 32.41 ton
Safe load, Qs = 3.241/2.5 = 12.96 tonne Say 13.0 ton
Diameter of Pile = 40 cm length = 7.5 m
Ap = 0.126 m2
Qp = 0.126[0.5 x 0.4 x 0.85 x 22.4 + 0.85 x 7.5 x 18.40] = 15.25
Qic = 0.5 x 2.3 x (3.14 x 6.5 x 0.4) = 9.38
Qis =
1.5[((0+5.0)/2x0.85}x0.5x(3.14x0.4x5.0)]+1.5[{(5.0+7.5)/2x0.85}x0.5x(3.14x0.4x2.5)]
= 10.00 + 12.51 = 22.51 ton
Qt = 9.38 + 22.51 = 31.89 ton
Qu = 15.25 + 31.89 = 47.14 ton
Safe load, Qs = 47.14 / 2.5 = 18.85 tonne Say 18.0 ton
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5.3 CONCLUSION AND RECOMMENDATION
All the test results have been presented systematically through different tables and
graphs. Subsoil strata are shown in the bore log profiles.
As seen in the bore logs and particle size distribution curves, it is found that soil mass
of the area predominantly contains clay, silt and sand.
As the soil in the site possesses good bearing capacity we recommend isolated footing
suggested net safe bearing capacity for isolated footing of 3.0 m depth is 10.0 t/m2 (Table
5.1). The load carrying capacity of bored cast in-situ RCC pile (without under reamed) of dia
30.0 cm and 40.0 cm size are shown in Table 5.2. However the safe pile load capacity is to
be verified by pile load test.
Table 5.1 : Net Safe Bearing Capacity
Depth from existing ground level (m)
RL of foundinglevel (m)
Net safe bearing capacity (tonne / metre2)
Suggested net safe bearing capacity (tonne / metre2)
3.0 95.0 10.09 10.0 10.0
Table 5.2 : Safe load carrying capacity of bored RCC pile (without under reamed)Pile dia (cm)
RL of pile terminating level (m)
Length of pile from EGL (m)
Pile cut off length (m)
Safe load carrying capacity from IS 2911-1980 (tonne)
Recommended safe load carrying capacity (tonne)
Compression Uplift Compression Uplift 30 90.50 7.5 1 12.96 9.56 13.0 9.040 1 18.85 12.75 18.0 12.0
EGL = Existing Ground Level
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CHAPTER – 6
CONSTRUCTION MATERIALS
6.1 GENERAL
The various construction material required for the project are available in the
vicinity of the project site. The sources have been identified keeping in view the
technical specifications applicable to each type of construction material and the
quantities required.
The following is lead statement of various construction material.
Material Source Distance (km)Sand, Stone, gravel, boulders
River bed Safekamar quarries
5 km15 km
Cement 25 / 30 kmSteel 25 / 30 km
The sand, stone, gravel and boulders are available in the river bed in sufficient
quantity from where it can be collected for the construction purposes.
6.2 SPECIAL MATERIALS
Materials like CGI sheets for roofing of the power station, fixtures etc. would have
to be procured from Bongaigaon or Guwahati (150 kms).
Generating equipment, electrical and mechanical equipment, gates, hoists, trash
racks etc. would have to be specially manufactured to order and transported to site and
installed as and when required. All the equipment proposed are indigenously
manufactured and no import of equipment is envisaged.
6.3 OTHER MATERIAL
Items like checkered plates for covering cable trenches, glass panes for windows
etc., can be procured from Guwahati (150 kms).
******
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CHAPTER – 7
PROJECT PURPOSES
7.1 GENERAL
Government of India is presently giving top priority to the development of Small,
Mini and Micro Hydro Stations for augmenting electricity generation in the country due
their short gestation period besides being environmentally benign.
7.2 PRESENT STATUS AND PROJECTS OBJECTIVES
Once the project is completed, it will on average supply 8.78 million kwhrs of
electrical energy to the Assam State Electricity Board Grid, which will meet the energy
requirements partially. Further, this power station, being located in the midst of vast
tracts of agricultural and where substantial amount of electrical energy is being used for
pumping ground water for agricultural production, shall meet their requirements and
also will reduce transmission losses in Assam State Electricity Board grid.
Further, the energy so produced shall help in reducing atmospheric pollution by
Carbon dioxide and Flyash by reducing carbon-di-oxide production by 11,100 tones and
3000 tones of flyash from the thermal power stations. This objective is in consonance
with the Kyoto-Protocol on world environment.
******
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CHAPTER – 8
CONSTRUCTION PROGRAMME
8.1 GENERAL
The civil works for the project includes; head race channel, road bridge over
head race channel, intake structure, power house building to house turbine and
generation equipment along with control and protection equipment, draft tube, tail pool,
tailrace channel and switchyard. The head race channel is proposed to take off
diagonally between approaches of barrage and the right bank main canal. The intake
structure is to be constructed on the upstream of the power station structure and
integral with the same. It is proposed to cut a rectangular notch through the retaining
wall upstream of the head regulator for the main canal. The tail race channel joins the
Pahumara river about 150 m downstream of the existing Pahumara barrage.
The power house is proposed to be completed in a period of 24 months which
includes 3 months for preparing tender documents. Tender specification are to be
invited separately for execution of civil works, supplying and installing mechanical
equipment and electrical plant. During the period the tender formalities are being
complied with action for acquisition of required land is envisaged. Accommodation for
residential and non-residential purposes and other ancillary facilities are also required at
the site as no facilities are available at the site. It may perhaps be possible to avail the
facilities available in the irrigation department rest house located nearby, for which
Assam Irrigation Department has to be contacted by the developer.
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8.2 MATERIAL PLANNING
Chapter 6 gives the sources of various construction materials and their
availability.
8.3 CONSTRUCTION POWER
The power supply will be required at the power house site. About 250 KVA will be
required for operating the concrete mixer and vibrators and the dewatering pumps. The
existing 11 KV line of Assam State Electricity Board to the barrage site and located
within the project area can be tapped at a suitable point.
8.4 MANPOWER PLANNING
The construction agency executing the power house will arrange its own
manpower as required.
8.5 DEWATERING
Dewatering shall be required when the foundation is excavated due to proximity
to the river which runs almost continuously. The contractor will have to make his own
arrangement for pumps required for dewatering.
8.6 REQUIREMENT OF CONSTRUCTION EQUIPMENT
For civil works of the power house, the main equipment required will consist of:
(a) Earth excavators like JCB etc.
(b) Concrete mixer and vibrators for producing and compacting plain and
RCC,
(c) Air compressor, rock drills, diesel generating set as a standby, welding
set, chain pulley block and tripod.
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The project estimate does not include provision of these equipment as these
would be arranged by the construction agency. No difficulty is envisaged in arranging
these equipment as these are indigenously available.
8.7 METHOD OF CONSTRUCTION
The work is proposed to be done through contractor.
8.8 SUPERVISORY STAFF
During execution, supervisory staff for both civil and mechanical – electrical
works being carried out will have to be posted by the developer. Provision for
establishment has been made at the rate of 4% of the I-works (details of which are
given in Chapter – 14).
8.9 SERVICES AND UTILITIES
The staff for operation and maintenance would be appointed by developer.
However, it is proposed that the O&M staff be appointed by the time the erection of
electro-mechanical equipment starts so that they get acquainted and are trained in the
process. Residential facilities may be constructed at the site or accommodation on hire
can be taken at the nearest villages / towns of Pathsala and Sarupeta where such
facilities are available.
8.10 BAR CHART
A bar chart showing the construction of works has been included in this report.
The programme includes the civil works, and supply and installation of mechanical and
electrical equipment (Fig. 8.1).
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BAR CHART
(two pages)
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CHAPTER – 9
ENVIRONMENTAL AND ECOLOGICAL ASPECTS
9.1 SITE SELECTION
The site of the power station has been selected on the left bank of the Pahumara
river. The power station will be located on a bypass channel to be constructed from the
Pahumara river upstream of the existing barrage.
9.2 PHYSICAL ASPECTS
The approach channel and the forebay is aligned in an area where there are no
constructions. The land is owned by the Assam Irrigation Department.
The land which to be utilized for the project purposes does not have any tree and
is almost barren with some small bushes, scattered here and there. There are no
plantation with any commercial value.
There is no wild life habitat including breeding, feeding and migration route at the
site. It is also not a potential site for wild life sanctuary. There are no rare or endangered
species of flora and fauna at the proposed site.
There are no monuments of cultural, historical, religious or archaelogical
importance at the proposed site. It is also not a spot used for recreation. However, it is
likely that after the site is developed for power generation, the surrounding area could
be developed into a picnic spot and a place for recreation.
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9.3 RESOURCE LINKAGE ASPECTS
The impact of construction materials on the environment is virtually negligible in
view of very small quantity required for the construction of the power plant and
appurtenant works.
There would also be no impact due to migration of construction workers to the
project site since the number of workers envisaged at the peak of construction is
approximately fifty (50).
9.4 PUBLIC HEALTH ASPECTS
The maximum number of construction workers at the peak period is not likely to
exceed fifty (50) persons. The civil construction work is likely to take not more than six
(06) months. Necessary sanitary and health facilities shall be provided for the workers
by the contractor.
9.5 PREVENTIVE AND CORRECTIVE MEASURES
The project would enhance the aesthetic aspects of the site. To improve the
aesthetics of the site as well as to improve upon the vegetal cover, it has been provided
for in the project estimate for planting of trees around the project site.
9.6 ESTIMATION FOR MEASURES
There is no specific necessity for conducting environmental studies/surveys for
the power station, being exempted under the relevant act of the Government of India.
As there is no virtual impact on the environment, there is no necessity for
initiating any remedial and mitigative measures.
A sum of Rs. 50,000/- has been provided for in the project estimate for meeting
the expenditure on land scaping and plantation around the power station.
******
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CHAPTER – 10
WATER AND POWER STUDIES
10.1 DATA AVAILABLE
The discharge data has been monitored by the Assam irrigation Department from
the years 1965, 1966 and from 1972 to 1975 (6 years) which they have used for the
planning and design of the Pahumara Irrigation Project including the Pahumara barrage.
The discharge data for this period has been taken from the “Revised Project Report for
the Pahumara Irrigation Project” prepared by the Assam Irrigation Department and
presented in Table 4.1.
10.1.1 Discharge for Power Generation
It is envisaged to utilize the surplus discharge available at the Pahumara barrage
at Kathalmuri ghat for power generation purpose. Therefore from the discharges
available at the Kathalmuri ghat barrage site irrigation requirements through the left
bank and the right bank canals have been deducted to arrive at the surplus flow
available at the barrage site to be utilized for the power generation purposes.
For planning of small hydroelectric projects, it is considered adequate to use
three years discharge. However, since the discharge data is available for a longer
period (i.e., for 6 years), it has been considered desirable to analyze the entire six years
data for planning of the proposed Pahumara SHP.
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10.1.2 Head
The gross head is the difference in elevation between the water surface levels in
the upstream of the barrage and the downstream of the barrage.
As the project is a low head development, it is proposed to maintain the barrage
pond level (49.6 m above mean sea level) as the upstream level, in order to maximize
the head availability and the consequent energy productivity.
From the topographical survey of the river downstream of the barrage, at a
distance of about 150 metres from the barrage axis, a suitable site has been identified
where the tail race channel can join the river. This site has been identified on the basis
of the following considerations:
- The length of the head race and the tail race channel is minimum,
- The bed level of the river does not change appreciably, if the length of
the tail race channel is further increased, or in other words, if a lower
river bed level is to be attained (for achieving higher head), a much
longer tail race channel is required which is not economically justified.
At the site of the confluence of the tailrace channel with the river channel, the
river cross section has been plotted and the water level in the river corresponding to the
discharge has been calculated.
Similarly, the bed width of the tail race channel has been taken as 30 metres, so
that when the power discharge flows through this channel, the depth of flow does not
exceed 1.03 m. This has been chosen to achieve a higher available head for power
generation.
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The river bed level at the point of confluence is 41.7 metre (above mSL). With a
slope of 0.1 metre from the tailrace channel with a length of 85 metres, the bed level of
the tailrace channel works out to 41.8 m (mSL). The tail water rating curve has been
prepared for different flows. The tail water rating curve is shown in Fig. 10.6.
10.2 INSTALLED CAPACITY
For deciding the installed capacity, four alternative scenarios have been created
and evaluated. The alternatives are:
Alternative (1) : Installed capacity of 2 x 750 KWe = 1500 KWe
Alternative (2) : Installed capacity of 2 x 1000 KWe = 2000 KWe
Alternative (3) : Installed capacity of 2 x 1250 KWe = 2500 KWe
Alternative (4) : Installed capacity of 2 x 1500 KWe = 3000 KWe
The water power studies have been conducted with the above four alternatives
for the entire six calendar years i.e. for 1965, 1966 and from 1972 to 1975. Thus, the
simulation studies conducted for these years amply reflects the total likely scenario as it
covers a long period of six years.
The energy generated for each of these alternatives, year-wise are shown in
Figures 10.1, 10.2, 10.3 and 10.4.
The comparative performance of these four alternatives are tabulated below in
Tables 10.1, and Table 10.2 and also diagrammatically displayed in Figure 10.5.
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Table 10.1
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Table 10.2 : Utilization of the generating units in the 50% dependable year
Utilization of unit in nos. of days per year Nos. of units 2 x 750 KWe 2 x 1000 KWe 2 x 1250 Kwe 2 x 1500 KWe
One unit 365 365 365 365Two units 150 130 100 60
From the Table 10.1, it is evident that the incremental energy increases when the
installed capacity is increased from 1500 KW (2 x 750 KW) to 2000 KW (2 x 1000 KW),
but decreases when it is increased to 2500 KW (2x 1250 KW). This clearly shows that
the optimum installed capacity for the Pahumara SHP is 2 x 1000 KW. This decision is
also further buttressed by the fact that the plant load factor for an installed capacity of
2 x 1000 KW is 53.3% whereas the same for an installed capacity of 2 x 1250 KW is
45.6% before accounting for forced outage, auxiliary consumption and transformation
losses.
Further, the use of two units is justified as can be seen that with the alternative of
2 x 1000 KWe, the second unit is required to be operated for about 130 days (4.3
months) in a year. This solution gives an opportunity that spare capacity is available for
a reasonable time to take care of annual maintenance and forced outage of one unit in
operation.
If the plant load factor in the 90% dependable year is considered, the plant load
factor with an installed capacity of 2 x 1000 KW is 41.2% whereas the same for the
installed capacity of 2 x 1500 KW is 33% which is considered to be low enough.
In consideration of plant load factor (> 50% on average and > 40% in the 90%
dependable year) flexibility in operation and maintenance, part load operation and
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indigenous manufacturing capability of runner, it is proposed to install two units of 1000
KWe each.
10.3 DESIGN ENERGY
The design energy is the energy likely to be produced in the 90% dependable
year with 95% availability. From the hydrological data for the Pahumara Barrage, 1975
is the 90% dependable year. From the power generation simulation studies conducted
for this year with 2 units of 1000 KWe each, the energy likely to be produced is 7.214 x
106 KWhrs. With 95% availability, the design energy is calculated to be 6.853 x 106
Kwhrs.
********
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Fig. 10.1
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Fig. 10.2
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Fig. 10.3
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Fig. 10.4
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Fig. 10.5
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Fig. 10.6
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CHAPTER – 11
INTAKE AND TAIL RACE WORK
11.1 HEAD RACE CHANNEL
The head race channel takes off from the left bank of the river at a distance of 70
metres from the barrage axis. The bed width of the head race channel is 23 metres. The
head race channel has vertical sides. At 83.0 m downstream of its off-take point of head
race channel (i.e. after crossing the existing left bank main canal alignment), it is
proposed to construct a village road bridge with a width of 6 metres catering to IRC-
Class-I specifications for facilitating the road traffic to the existing barrage and villages
on the right bank of the river.
11.2 INTAKE STRUCTURE
The Intake structure is integral with the upstream face of the power station
structure. The intake structure comprises of a trash rack in the upstream face installed
at an angle of 750 to the horizontal followed by a vertical intake gate. The vertical intake
gate is proposed to be of stop-log type and is to be lowered for facilitating the
maintenance of the turbine and the draft tube.
11.3 TAIL RACE
The tail pool is provided with a reverse bed slope of 1V : 5 H till it meets the bed
level of 65.3 m El of the tail race channel. The width of the tail pool at the exit of draft
tube is 15.0 m, which is same as the combined width of the draft tubes of all the three
units and piers. This splays to 30.0 m in width over a length of 20 metres. The walls of
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the tail pool are warped in both horizontal and vertical. The tail race channel has
trapezoidal section with side slope of 1V: 1.0 H till it meets the Pahumara river, the
length of trapezoidal section is 110.0 metres. The tail race joins the river at a distance of
192 metres downstream of the barrage axis.
**********
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CHAPTER – 12
WATER CONDUCTOR SYSTEM
Water conductor system consists of head race channel, head regulator bridge,
forebay, Intake, power house, draft tubes, tail pool and tail race channel.
1.0 HEAD RACE CHANNEL
As per the surveyed site plan the length of HRC is 43.4 m, with a bed slope of
0.1 in; 43.4 m length, the channel is 9.5 m wide with 5.0 m depth of water.
1.1 Max discharge to be taken by two machines for
Generation of power = 49.7 cumecs
Area of flow = 9.5 x 5.0
= 47.5 sq.m
Velocity of flow
= 1.05 m/sec.
Velocity head =
2.0 Head Regulator
Width of HRC is 9.5 m; at chainage 33 m of HRC, 1.5 m wide pier has been
provided, so there are two bays, each 4.0 m wide and are provided with 5.3 m high
gates and gates hoist arrangement. In case of repair of forebay or P.H, the flow can be
controlled by these gates. Upstream of the gates, coarse trash rock is also provided to
check entry of wooden logs etc. into channel.
3.0 Forebay
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Within the available space and considering he economic aspect the layout of
scheme has been proposed so that it may have 350 m3 of water above MDDL.
Because head race channel is not so long and it is also connected with barrage
pond, so there would not be any difficulty to get water for generation. The width
of forebay is 15.0 m with a sloppy bed, length of forebay including its upstream
transition is 25 m.
4.0 Trash Rack at Intake
Inclined trash rack at intake has been provided at an angle of 700, to stop the
entry of trash etc. to the turbine. The height of opening at trash rack is 5.0 m and
the width of trash rack in each bay is 3.0 m.
No. of bays / openings = 4
Width of opening = 3.0 m
Height of opening / length of inclined trash rack = 5.0 m
through which water will flow
velocity through trash rack =
at trash rack
Velocity head =
5. Entrance Opening to Power House
No. of bays / openings = 4
Width of opening = 3.0 m
Height of opening = 2.8 m
Area of opening for one machine = 2 x 3.0 x 2.8 = 16.8 sq.m.
Area of opening for two machines = 2 x 16.8 = 33.6 sq.m
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velocity of flow at entrance =
Velocity head =
6. Tail Race Channel
Width of channel = 30.0 m
Side slopes = 1.5 H : IV (Boulder pitched)
Mannings coefficient = 0.0225
Longitudinal slope S =
(0.1 m in a length of 85 m) = 0.03443
Maximum design discharge = 38.6 cumecs
Let D = depth of flow
With all above parameters D = 1.03 m
and V = 0.67 m/sec
Velocity head =
For other depth of flows an equation has been written and plotted (Fig. 10.6).
7. Head Losses in Water Conductor System
By considering all the head losses and adding them, average h l comes out to be
K. (where velocity V has been taken at entrance) which is approx. 0.03 m
for Q = 38.6 cumecs; similar head losses can be found out for other discharges.*******
CHAPTER 13
DESIGN CRITERIA OF POWER HOUSE AND POWER PLANT
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13.1 STRUCTURAL DESIGN CRITERIA
Intake Structure
The intake structure proposed consists of a rectangular bellmouth behind the
trashrack.
The intake gate is provided in a separate structure. Grooves shall also be
provided in the intake gate structure for stoplogs. The intake gate is proposed to be
operated by electric motor operated hoist from the control room. The gate shall be of
vertical sliding type.
Trashrack
A trashrack fabricated out of mild steel flats and structural numbers at the inlet to
the bellmouth to prevent the entry of large size debris/floating matter. Trash racks (in 3
pieces) shall be erected between the grooves provided at the nose piers on either side
& bay for easy removal from the top. The trash rack shall be installed at an angle of 75 o
to the horizontal.
The racks are provided from the bottom of the intake structure 1.0 above pond
level. The area of the trashracks is sufficient to ensure a minimum velocity of flow or
0.75 m/s with 50% clogging.
Approach to Service Bay
Access to the power house has been proposed along a 5 m wide road on the
right bank of the channel located at an elevation of 50.5 m.
Power House Building
A surface powerhouse has been proposed to be located on the right bank of
river. The size of the building is 10.6 m (along flow) x 23.5 m (across flow) to
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accommodate two units of Kaplan type turbine along with its respective synchronous
generators and control panels. The layout of the various components is shown in Drg.
No. 05 and 06.
Flow to the turbine is to be regulated by wicket gates. Provision for vertical
sliding stop log type intake gates has been made to take care of maintenance
requirements. The power house proposed is of the indoor type, where all erection and
maintenance of machine is done within the power house itself.
Drainage sump, hydraulic power pack and control panel are placed at suitable
locations to minimize the space requirements and the length of the control cables, etc.
Structural Design
The power house design consists of (a) superstructure and (b) substructure. The
components of the superstructure are :
(1) Roof
(2) Roof supports
(3) Brackets for gantry crane rails
(4) Walls
(5) Floors.
The components of the substructure are :
(1) Draft tube top slab
(2) Draft tube bottom slab.
(3) Turbine and generator foundation.
The superstructure is designed to withstand the following loads :
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(a) Dead loads consisting of self weight of the structure and the permanent
superimposed loads.
(b) Live loads for roof and floor according to IS : 4247.
(c) Wind loads conforming to IS : 875.
(d) Crane loads consisting of the weight of fully loaded crane, its impact, crane
surges or crane braking forces.
(e) Earthquake forces according to IS: 1893.
(f) Water pressure, earth pressure wherever applicable.
The permissible stresses for design of superstructure are as per IS:456 for RCC
and IS:800 for structural steel. The same have been increased for various
combinations of loads as laid down in IS: 4247.
Sl. No. Load Combination Increase in stress by % age
1. D.L. + L.L. + moving crane loaded to half its capacity and normal FWL
8
2. D.L. + L.L. + moving crane loaded to half its capacity + temperature + normal TWL + wind load
25
3. D.L. + L.L. + moving crane loaded to full capacity + temperature + normal TWL
25
4. D.L. + L.L. + unloaded standing crane + temperature + max TWL + earthquake
33.3
5. D.L. + L.L. + moving crane loaded to half capacity + temperature + max TWL
33.3
6. D.L. and temporary construction loads 25
The permissible stresses for rivets, bolts, etc. are increased by 25% only in all cases
from Sl.No. 2 to 6.
Roof
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The power house is proposed to be covered by GCI sheets with the sheets fixed
to the roof truss through purlins. A minimum thickness of 1.25 mm is provided.
The GCI sheets conform to IS:277. It is to be placed directly on the purlins and
held in position by hook bolts of 10 mm dia at 400 mm c/c. At joints of two sheets a
minimum overlap of 150 mm is provided. The joints along the sides of the sheets shall
overlap two corrugations and the screws are provided at 300 mm centers. All holes are
to be made through ridges and curved washers are inserted to avoid leakage. At the
eaves, the hook bolts are placed at 250 mm c/c to prevent the lifting of sheets due to
gales.
Roof Supports
The roof is supported on purlins resting on steel trusses. The spacing of trusses
is governed by the considerations of the load on the roof. The truss is analyzed for
loads and permissible stresses.
Gantry Girders
The gantry girders are of RCC embedded in the concrete columns and walls of
the power house. The girders will be supported on brackets projecting from the RCC
columns on the upstream and downstream sides. Suitable base plates are also
provided for fixing the rails on the girders. The gantry girders are designed for worst
combination of moments, shear force and thrust transmitted to them by the crane in the
loaded conditions.
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Substructure
The power house is designed with a raft foundation. The stability analysis is
done considering:
(a) Dead load and bearing pressure
(b) Shear friction factor.
The analysis is done in two directions, longitudinal and transverse. The loads
considered in the design are :
(a) D.L. of the structure including embedded parts,
(b) Main equipment loads, i.e., turbine, generator, valves, etc.,
(c) Crane loads including surges,
(d) Live loads,
(e) Wind loads,
(f) Penstock thrust including water hammer,
(g) Weight of water acting on the substructure, i.e., draft tube.
(h) Pressure due to tail water level.
(i) Uplift pressure,
(j) Pull of conductor if fixed on building, and
(k) Seismic forces.
Generator Floor
The generator floor which is also the top slab of the draft tube is designed to
carry load of machines, live load and any thrust transferred through turbines, generator
or any other machine. Structurally it is designed as a slab constructed on ground level
with opening at draft tube location where it acts as RCC box combined with draft tube
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piers and the base slab. However, it is checked for concentrated loads and thrust of
machine foundation on generator floor.
The drawing of the power house showing general layout and other details are
enclosed as Drawing No. 05 & 06.
Tail Race Channel
The water from the power house after power generation is proposed to be
channelised to join the Pahumara river downstream of the existing barrage through at
tail race channel provided with a suitable slope. The tail race channel is designed to
pass the maximum discharge at the desired full supply level.
13.2 HEAD RACE CHANNEL
An approach channel shall be constructed just upstream of the existing right
bank canal intake and upstream of barrage. The bed width of the proposed head race
channel shall be 9.5 m. To prevent entry of bed load into the approach channel, it is
proposed to construct the bed of channel sufficiently high at the entry into the mouth of
the approach channel. The entry to head race channel shall be so aligned such that a
smooth flow from the river into the approach channel is ensured and the bed load is
directed towards the under-sluices located in the barrage.
The head race channel shall have a rectangular cross section with a width of 9.5
metres. The length of the head race channel is proposed to be 43.4 meters.
13.3 ROAD BRIDGE
The proposed approach channel has to pass under existing road to barrage
requiring a bridge span of about 9.5 m. To keep the same alignment of road the bridge
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is proposed to be constructed on the transition portion of the approach channel to the
power house. The span of the road bridge at centre line shall be of 9.5 m.
13.4 SPILLWAY
In the event of load throw-off or non-availability of machines for power
generation, the excess water has to be passed over the barrage spill ways after meeting
the primary commitment for irrigation in order to maintain the safety of the canal and the
upstream river bank from breaching due to over topping.
13.5 INTAKE STRUCTURE
The intake structure will be provided with a trash rack downstream of which will
be the intake gates. The two number gates will be operated by a hoist provided on the
upstream deck of the power station.
13.6 POWER STATION
13.6.1 CRITERIA FOR SELECTION OF HYDRO TURBINE
General:
The hydro-turbine is the key element in the hydro power station and all the
ratings and dimensions revolve around that of the turbine. Though theoretically , turbine
can be applied at any head , but on considerations of economy ,and the strength of
materials achieved upto that point of time, the use of hydro-turbine is limited in
application to specified range of head.
The basic factors considered in the selection of the turbine is enumerated below:
(1) Availability of the type of turbine for the applicable head,
(2) Standard runner diameters available,
(3) Suitability of the runner diameter to adapt to runner blade angle control on
account of wide variations in head and discharge,
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(4) Standard outputs (frame sizes) for generator,
(5) Easy availability of equipment indigenously, and
(6) Less number of units to economize on cost while not compromising on
reliability.
Type of Turbine
The following types of turbines are suitable for application up to a head of 25
metres.
(a) Axial flow
(b) Cross flow
(c) Mixed flow (Radial axial)
As per IS 12800 (Part 3) :1991 – “Guidelines for Selection of Hydraulic Turbine ,
Preliminary Dimensioning and Layout of Surface Hydroelectric Power Houses- Part 3 :
Small, Mini , Micro Hydroelectric Power Houses” issued by Bureau of Indian Standards,
the head of application for different types of hydro turbines are given in Table 13.1.
Table 13.1: Turbine Performance CharacteristicTurbine Type Application Head
Minimum (in meter) Maximum (in meter)Vertical fixed blade propeller 2 25Vertical adjustable propeller (Kaplan) 16 40Tubular with adjustable blades and fixed wicket gates (Horizontal Kaplan)
2 25
Tubular fixed blade with wicket gates (Horizontal propeller)
2 25
Bulb(Horizontal Propeller) 2 25Rim (horizontal propeller) 2 25Francis Horizontal 10 250Francis Vertical 10 250Francis Openflume 2 8Cross flow 1 200Turgo Impulse 40 200Pelton 100 500
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The broad performance specifications for reaction type turbines are given in
Table 13.2.
Table 13.2 Turbine Performance Specifications for Small Hydro Power Applications
Type of TurbineApplicable Head Range
Permissible Head variation from Rated Head
Permissible output variation from rated power output
M % %Propeller 2-25 65-140 35-115Semi-Kaplan 2-25 55-140 30-115Kaplan 2-25 50-140 25-115Francis 5-30 60-125 40-115
However many manufacturers are offering Kaplan, semi-Kaplan, Propeller types
of turbines for application upto a minimum head 1.5 metres. Though it is possible,
theoretically, to harness any head, even as low as 0.1 m, but the same is not desirable
on account of economy. It may be worth mentioning here that the lowest head
harnessed so far on the basis of reported literature is 1.05 meter at Ganzhutan hydro
power plant in Guangdong province of People’s Republic of China. This power station
has one (1) unit of 3000 kW rating with a rated discharge of 610 cumec.
On critical perusal of the tables 13.1 and 13.2 stated above , the following types
of turbines are suitable for application to the SHP site under discussion with a design
head of 6.3 meters , and a head range of 6.13 to 7.17 meters :
- Vertical fixed blade propeller (Kaplan and semi Kaplan)
- Tubular with adjustable blades and fixed wicket gates (Horizontal semi- Kaplan)
- Tubular with adjustable blades and adjustable wicket gates (Horizontal - Kaplan)
- Tubular fixed blade with wicket gates (Horizontal propeller)
- Bulb(Horizontal Kaplan/ semi Kaplan)
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- Rim (Horizontal Kaplan / semi Kaplan)
- Francis Open flume
- Cross flow
The cross flow turbines are suitable for a head range 1 metre to 200 metres and
are of predominantly impulse type. This type of turbine has a very good part-load
efficiency but low peak efficiency when compared to the other two types. Further, being
an impulse type has to be placed above the tail water level and there by some head will
be perpetually remain unutilized. This will also result in further energy loss. The un-
utilizable head in the case of low head installations may be a significant quantity.
Therefore, use of cross flow type turbine in this particular case is not recommended.
The Francis open flume type is also not recommended for the following reasons:
(a) The turbine setting is in this case is vertical , which will result in a higher
head loss as compared to a horizontal axis turbine.
(b) The Francis turbine has a low specific speed which will result in a low turbine speed
as compared to a propeller type turbine . Consequently , the runner diameter will be
larger leading to a costlier turbine and associated cost of civil works. Further , the
cost of speed increasing gear box will be also higher due to a larger speed ratio.
(c) The part load efficiency of Francis type turbine is lower than that of Kaplan type of
turbine which will lead to perpetual loss of revenue.
After exclusion of Francis (open flume) and cross-flow types from the ambit of
consideration, the following types of turbines , which are axial type, are left for
consideration . These belong to the generic type – Propeller and are further classified
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as (i) propeller,(ii) Kaplan and (iii) semi – Kaplan depending on the adjustability of
wicket gates and runner blades , separately or both.
The axial flow turbines , as per the configuration of their shaft, are available in
any of the following types :
- Horizontal
- Vertical
- Inclined
The horizontal configuration requires more length in the horizontal direction with
the vertical configuration requiring the minimum. The inclined axis configuration
requires an intermediate value. The vertical axis type has a higher head loss as
compared to horizontal axis lay-out
On the basis of relative placement of turbine and generator, the configuration can
be of any of the following types :
- Tubular
- Bulb
- Stra -flow (Rim type)
The bulb and stra-flow type have horizontal axes whereas the tubular type can
have any of the axis configuration. The bulb and straflow type are generally suitable for
large flows and outputs (normally greater than 1000 KW). Moreover, these type of
turbine generating units are very sophisticated in construction, requiring a higher degree
of skill for installation and maintenance. Further, these types of turbines are susceptible
to erosion damage if the sediment load is heavy. Hence for the project under
consideration, bulb and rim type hydro turbine generator units are not being considered.
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The comparison between alternative types of turbines for this power station is
now limited to –
(1) Propeller type (fixed runner blades and adjustable wicket gates)
(2) Semi Kaplan type (adjustable runner blades and fixed wicket gates)
(3) Kaplan type (adjustable runner blades and adjustable wicket)
with both vertical and horizontal configurations.
The Kaplan type turbines are suitable to large head variation and variation in the
output and has a higher part-load efficiency as compared to those of semi-Kaplan
turbine. Hence Kaplan type of turbine is recommended for application.
The current world wide trend is to use standard runner diameters for
economizing on the cost. Similar practice is also adopted by the Indian manufacturers.
However the Indian manufacturers also agree to manufacture the runner to any exact
diameter when so desired by the customer, and to suit to specific site conditions for
increased efficiency.
Therefore while tendering for the turbine and the generator, it will be desirable to
give the option to the manufacturer to supply the turbine with that diameter as per his
design which suits best to the operating regime. As the responsibility of the basic
hydraulic and mechanical design of the turbine is vested in the manufacturer so also its
performance, the above flexibility in approach shall be in the overall interest of economy
and efficiency of the power plant and thus shall not deviate from the basic philosophy of
the design.
The turbine manufacturers have published the basic layout dimensions of the
power plant as a function of standard runner diameters. In the preparation of this
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project report, standard layout designs have been adopted for effecting economy of
space. The detailed for construction, however, shall be based on actual information
furnished by the suppliers of the equipment.
The basic specifications of the turbine, generator and other equipment have been
outlined in this report. These criteria have been specified on the basis of adequacy of
performance, reliability under the required operating conditions, easy maintainability
keeping in view the location at which the installation is proposed and the level of
availability of technical skill locally and above all simplicity and robustness of the
equipment. These conditions are based on a systematic analysis of experience gained
at different mini and small hydroelectric power stations elsewhere using similar type of
standardised axial flow tubular turbines.
The runner shall be made of 13% Chromium – 4% Nickel stainless steel. If the
bidder offers Aluminium Bronze as a cheaper alternative, the same could be also
accepted. The runner hub shall be of cast steel. The runner chamber shall be made
structural steel. The turbine shaft shall be made of forged carbon steel. The stay ring
shall be fabricated of structural steel, the draft tube elbow piece including the transition
piece shall be fabricated from mild steel plates. After the transition piece, the draft tube
shall be of reinforced concrete construction.
The turbine speed shall be in the range of 100 – 150 rpm depending upon the
specific speed adopted by the manufacturer. To reduce the cost of the generator, it
would be desirable to increase the speed to 500 /600/750 rpm which would be the
normal rpm of the generator. The speed increase shall be accomplished by using a
suitable gear box.
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The power station building shall accommodate the following equipment :
(1) Vertical Kaplan Turbine - 2 nos.
(2) Synchronous Generator (1000 Kw) - 2 nos.
(3) Trash rack and Intake Gate - 2 sets
(4) Draft Tube Gate - 2 sets
(5) Turbine – Generator Room Equipment Handling Crane (1) 15 ton capacity –
Bridge Crane
(6) Gantry crane 5 tonne capacity for handling intake gate and trash rack
The turbines shall broadly conform to the following specifications :
Turbine :
Number of Turbines : Two
Type of Turbine : Kaplan
Rated Output : 1063 kW
Maximum net head : 7.21 mMinimum net head : 6.315 m
Rated Head : 6.4 metersDiameter of Runner : 2100 mm.
13.6.2 Generator
There are two types of generators namely:
1. Synchronous, and
2. Induction.
Induction generators are generally about 20% cheaper than the synchronous
generators of same output. Whereas synchronous generators are self contained in
developing its own excitation power, induction generators require an external source for
providing it with the magnetization power. The synchronous generators require more
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complicated governing and excitation control systems whereas the induction generators
do not operate and being sturdier require less maintenance, and are ideally suitable for
mini hydroelectric stations where economy in capital cost is of prime concern.
Since the unit size is 1000 KW, it would not be possible for the 11 KV local
system to provide the magnetization power required by the generator. Hence it has
been proposed to use synchronous generators.
The generator shall conform to the following broad specifications:
Type : Synchronous
Number of Units : Two
Rated output : 1250 KVA
Rated Voltage : 3300 V
Number of Phase : Three
Frequency : 50 Hz
Power factor : 0.8 lagging
Synchronous speed : 750 rpm
Continuous overload capacity : 10%
Each generator shall be provided with its individual control and protection
equipment and system which are broadly defined as follows:
(a) Water level control
(b) Protective relays
(c) Neutral grounding resistor and isolating switch.
The generator shall be designed with adequate structural strength to withstand
the runway speed of the turbine i.e. about 2.7 times the rated speed for 30 minutes
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without any damage. The factor of safety at maximum runaway speed of the turbine
based on yield point of material shall not be less than 1.5.
The generator shall be designed to continuously deliver 10% overload capacity
without overheating.
The generator shall be provided with four (04) nos. of embedded temperature
detectors for indicating the stator winding temperature on the generator console.
The generator shall be provided with space heaters of adequate rating to
maintain the temperature of the generator at last 5oC above the ambient and avoid
condensation of moisture.
The generator shall be cooled by axial flow centrifugal fans mounted at each end
of the rotor. The generator shall be provided with screen protected enclosures for open
ventilation.
The stator frame shall be manufactured of cast iron/fabricated steel construction.
The frame shall be designed to withstand the bending stresses and deflections due to
its self weight and the weight of the core supported by it.
The stator core shall be built up by segmental punching made of low loss silicon
sheet steel non-oriented type and end plates. Each punching shall be properly debarred
and applied with insulating varnish on both the sides.
The generator speed has been tentatively suggested to be 750 RPM.
The generator shall be designed to have a noise level not exceeding 90 db at a
distance of one (01) metre from the equipment.
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13.6.3 Flywheel
Necessary flywheel effect shall be incorporated into the rotating parts of the
generator and shall be determined in consultation with the turbine manufacturer to limit
the speed rise and pressure rise within permissible limits. In case requisite moment of
inertia is not available from the rotor, a separate flywheel shall be provided to furnish the
additional flywheel effect required.
13.6.4 Speed Increaser
A single stage speed increaser shall be provided connecting the shafts of the
turbine and the generator.
It is proposed that belt drive used as mode of power transmission as well as
increasing the speed of the turbine to that of the generator. In case suitable belt drive is
not available gear type speed increaser can be used.
In case parallel shaft gear types speed increaser is used, it shall have body
manufactured out of cast iron or fabricated steel. The gear shall be made of suitable
hardened alloy steel of chromium-nickel and molybdenum.
13.6.5 Control System & Oil Pressure Unit
The turbine is proposed to have moveable guide vanes to help in switching on
the generator to the system exactly at the synchronous speed.
The guide vanes as well as the adjustable runner blades are proposed to opened
by hydraulically operated servomotor and held in desired position by oil pressure. In the
event of load throw off or when actuated by master tripping relay due to fault or under
command to shut down (normal or emergency), the oil pressure is released by the
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actuation of DC operated solenoid valve and the guide vanes close under counter
weight provided.
An oil pressure unit (OPU) proposed to be provided for the purpose. The OPU
shall be provided with an electrically operated pump and a manual pump. The pressure
in the system shall be continuously maintained at the desired pressure level within a
very narrow band. In the event of pressure falling by say about 5% the electrically
operated pumping shall start to build up the pressure again. Pressure switches shall be
therefore provided for starting the pump (on falling pressure) and stopping the pump (on
reaching set pressure) automatically.
The oil pressure unit shall also be used to operate the runner blades.
13.6.6 Generator Control Board
There shall be one control panel for each of the turbines and the generators
fabricated out of 2 mm thick mild sheet steel. It shall be free standing type with single
front design. The control panel shall be mounted on antivibration pads. The board shall
be applied with synthetic enamel paint on antirust primer after being subjected to sand
blasting and acid pickling.
Each generator cubicle shall contain the following:
- Surge diverter – 3 nos.
- Surge capacitor – 3 nos. with built-in discharge resistor
- Panel space heater with thermostat – 1 no.
- Panel illumination lamp with switch – 1 no.
- Cast resin type current transformer – 3 nos.
- Cast resin dry type double secondary single phase potential transformer – 3 nos.
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- 1200 Amps 415 V, 3 phase, 3 pole, electrically operated drawout type air breaker
with thermo-magnetic release, shunt trip coil under voltage release, auxiliary
contact, 50 KA- - One no.
- Protective relays comprising of the following :
- Voltage restrained over current (IDMT) relays - 2 nos.
- Earth fault relay - 1 no.
- Over voltage relay - 1 no.
- Under voltage relay - 1 no.
- Generator stator earth fault relay - 1 no.
- Auxiliary relay (Master relay) - 1 no.
- Measuring & Indicating instruments comprising of the following :
- Voltmeter with selector switch - 1 no.(R – Y – B - 0)
- Ammeter With selector switch - 1 no.(R – Y – B - 0)
- Kilowatt meter - 1 no.
- Kilovar meter - 1 no.
- Power factor -1 no.
- Frequency meter - 1 no.
- Speed indicator - 1 no.
- Temperature indicator – 6 point for stator temp. - 1 no.
- Kilowatt hour meter – 3 phase balanced/unbalanced - 1 set
- Indicating lamps for breaker on/off - 1 set
- Controls comprising of the following :
- Start control switch with relays - 1 set
- Stop, control switch with relay - 1 set
- Twelve point annunciation facia comprising of the following :
- Oil pressure unit high / low
- Generator winding temperature high
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- Machine shutdown under fault
- D.C. failure
- Cooling water failure to bearing of generator/turbine/generator/shaft seal.
One set of acknowledge, reset and test push buttons
One hooter and blinking relay.
13.6.7 PLC System
It is proposed to provide a programmable logic controller for the following
functions :
- Start/stop of the turbine and generator.
- Monitoring of the temperature inputs from RTD’s.
- Monitoring of the alarm inputs from the turbine and generator protection system.
There shall be also inputs through suitable transducers for monitoring the
following parameters and recording the same.
- Generator KW
- Generator KWH
- Generator current
- Generator voltage
- Frequency
- Power factor
- Trivector meter.
The system shall be provided with independent CPU, MEMORY and POWER
SUPPLY so that failure of one system shall not affect the operation of other system(s).
The system shall have self-checking and self-diagnostic features for all internal
faults and shall be capable of isolating the defective sub-system.
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The system should be suitable for continuously operating without air conditioner
in the power plant environment with temperature upto 45o C and high humidity.
13.6.8 Local Instrumentation
The following instruments shall be mounted locally :
(1) Rotameter to check flow of cooling and sealing water to the bearings, gearbox,
stuffing box as required.
(2) Turbine and gearbox (if provided) bearing temperature.
(3) Oil pressure gauge of the oil pressure unit.
13.6.9 Station Auxiliary Power Board
This board shall also be of single front design conforming to the same
manufacturing standards and dimensions as the unit control board. This power
distribution board shall cater to various auxiliary power requirements in the station.
The power supply to the board shall be obtained from the spillway gate control
room due to its higher reliability. The board shall house the following :
- Incoming 100 Amps MCCB - 1 no.
- Voltmeter with selector switch - 1 no.
- Ammeter with selector switch - 1 no.
- KWhrs meter with CTs - 1 no.
- Aluminium Busbar 4 wire-100 Amps - 1 set
- MCBs with HRC fuses 25 Amps on feeders - 7 nos.
- MCBs with HRC fuses 16 Amps on feeders - 8 nos.
- Terminal blocks for 12 feeder circuits - 15 nos.
13.6.10 Telephone System
One telephone connection shall be provided in the power station from the local
Department of Telecommunication Network.
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13.6.11 Station Drainage System
Since the level of the bottom most floor is below the tail water level, there is
likelihood of seepage water entering into the power station. Besides there is likelihood
of leakage water from gland packing etc.
It is proposed to provide a drain of 250 mm x 250 mm around the outer walls of
the power station entering into a drainage sump whose floor level is fixed at
31.6 m.
It is proposed to install two (02) nos. of sump pumps discharging into the tail race
above the maximum tail water level.
The pumps would be of self priming mono-block type. The motors will be rated at
415 volts, three phase.
13.6.12 Dewatering System
It is proposed to dewater the draft tube by one number portable centrifugal pump
of submersible type. For the purpose of dewatering of the draft tube, a 750 mm dia
opening has been provided on the draft tube deck. The dewatering opening shall be
closed by suitable mild steel cover with bolting facility and shall be flush with the floor
level.
A submersible pump drive by a 6 HP AC three phase, 415 volts motor is
considered to be adequate for the purpose.
13.6.13 Lighting System
The indoor lighting shall comprise of twenty four (24) numbers of twin 40 watt
lamps in industrial type fittings.
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Besides there will be ten (10) number of 60 watts incandescent lamps distributed
around the power station to form the D.C. emergency lighting systems. These lamps will
be connected to the DC system through a suitable inverter 110 Vdc/230 VAC.
The outdoor lighting is proposed to comprise of 8 nos. of 250 watt sodium vapour
lamps mounted on the powerhouse walls – two on each face to illuminate the
transformer yard the draft tube deck, the approach road and the spillway area.
13.6.14 Ventilation System
It is proposed to install six (06) nos. of exhaust fans of 300 m size, 1000 RPM
mounted at a suitable elevation facing towards the tail race.
13.6.15 D.C. System
To meet the requirements of operation under emergency conditions it is
proposed to install a D.C. Battery lead-acid type rated at 120 Ampere-hours, 110 volts.
The cells shall be of tubular positive plate with polypropylene plastic or hard rubber
container.
A suitable battery charger is proposed to be provided to meet the trickle charge
as well as boost charge requirements of the DC battery.
A DC control board is proposed to be provided made out of 2 mm sheet steel of
wall mounting type housing the following :
(1) Four feeder circuits with MCCBs of 10 AMPs each.
(2) Earth leakage indication
(3) Battery healthy condition indication
(4) 0 – 20 amps DC ammeter
(5) 0 – 60 volts DC voltmeter
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(6) Trip and indication fuses
(7) Charger on-off indication
(8) Battery incoming MCCB-20 AMPs.
13.6.16 Station Grounding
Station grounding is proposed to comprise of a suitable earth-mat buried at the
foundation level below the raft. From the grounding mat, six (06) nos. of risers shall
brought upto the machine hall floor. The risers as well as the ground mat shall be made
of mild steel strips with corrosion protection as per standard practice. The risers shall be
of 50 mm x 6 mm mild steel strips.
The earthing of the frames and the neutral shall be as per the relevant provisions
of the Indian Electricity Rules and Indian Standards Specification.
13.6.17 Fire Fighting
It is proposed to provide the following types of portable fire extinguishers :
(1) Dry chemical type fire extinguisher 4 kg capacity - 10 nos(2) Foam type fire extinguisher - 4 nos.
13.6.18 Power House Crane
It is proposed to provide a girder type hand operated crane with a capacity of 15
tons. The hoisting operation shall be done by electric motor operated hoist, which can
be operated from the generator floor level. The HOT crane would facilitate a small group
of erection and maintenance personnel to handle both erection and maintenance
activities.
13.6.19 Draft Tube Gate
Two numbers stop log type gates are proposed as the draft tube gate for each
unit for facilitating maintenance of the turbine.
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The gates shall be operated from a gantry girder provided for the purpose on the
draft tube deck. The lifting and lowering operations shall be possible with a chain pulley
block of requisite capacity.
The gate shall be provided with a suitable lifting beam with grab-clamps.
13.7 TAILRACE CHANNEL
The tail race channel will connect the draft tubes of the power house with the
Pahumara River. The section of the channel would be trapezoidal with a bed width of
30 m. The length of the Tail race channel would be 85 m.
13.8 AUXILIARY POWER SYSTEM
To meet the auxiliary power requirements of the power station, it is proposed to
install one 125 KVA, 3300 /433 V transformer tapped from the 3.3 KV generator bus.
13.9 POWER EVACUATION
It is proposed to install one no. of step-up transformer rated at 2500 KVA, 3.3 /11
KV. The transformers shall be plinth-mounted.
From the high voltage side a single circuit 11 KV overhead line shall be erected
upto the existing 11 KV line near the barrage.
The power is to be evacuated through the existing 11 KV single circuit line upto
the Pahumara barrage site.
**********
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CHAPTER – 14
ABSTRACT OF COST ESTIMATES.
No.ITEM
AMOUNTREMARK
CIVIL E/M TOTAL(1) (2) (3) (4) (5) (6)
I Works 1. A-Preliminary 75.00 75.00 2 B-Land 2.00 2.00 3. C-Works 3.1 Head Race Channel 47.42 Annex. C-1 3.2 Regulator & Bridge 60.43 Annex. C-2 3.3 Forebay 47.96 Annex. C-3 3.4 Intake & Power Station Structure 319.66 Annex. C-4 3.5 Tail Pool & Tailrace Channel 109.77 Annex. C-5 Total C-Works 585.24 585.24 4. K-Building 25.00 25.00 5. M-Plantation 0.50 0.50 6. O-Miscellaneous 15.00 15.00 7. P-Maintenance @ 1% of items C-works & K-buildings 6.10 6.10 8. Q-Special tools & plants 4.00 4.00 9. R-Communication 20.00 20.00 10. S-Power Plant & Accessories 600.00 6000.00 11. Y-Losses on stock @ 0.25% on item 3 to 7 & 9 to 10 1.64 1.64 Total : I – works 734.48 600.00 1334.46 II ESTABLISHMENT @ 4% of I-Works 29.38 24.00 53.38
III ORDINARY TOOLS & PLANTS @ 0.5% of I-Works 3.67 3.00 6.67
IV RECEIPT & RECOVERIES At the rate of 75% of Q-spl. T&P -15.00 -15.00 Total of Direct Charges 1379.53 V INDIRECT CHARGES 1. Audit & Account @ 1% of I-Works 7.35 6.00 13.35 VI TRANSMISSION SYSTEM
1.Strengthening of the existing 11KV Single circuit line upto 33/11 KV Substation at Sarupeta (15 kms) . 20.00 20.00
GRAND TOTAL 759.88 653.00 1413.88
**********
EXPLANATORY NOTES ON COSTS ESTIMATES
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In the following paragraphs explanatory notes on cost estimates of various items
of work are stated:
1. A-Preliminary: In this estimate, the expenditure on investigations like
reconnaissance survey, topographical survey, geological and geotechnical
investigations are included. The cost estimates also include the expenditure
on preparation of detailed project report and also the expenditure likely to be
incurred on detailed design, tendering and tender evaluation etc. Expenditure
on this account is estimated at Rs. 75.00 lacs.
2. B-Land: The land required for the proposed power plant including the
appurtenant works are within the government owned land. It is therefore
presumed that the project activity being an activity aimed at economic and
social development of the un-developed area around the project, the land
required shall be transferred to the project developer at no-cost. However, a
token amount of Rs. 2,00,000.00 is provided for meeting any likely
eventuality.
3. C-Works: The estimates for the following works have been included:
(i) approach channel, (ii) head regulator for approach channel and coarse
screening, (iii) intake and power station structure and (iv) tail-race. The cost
estimates have been based on the designs prepared for each of the
structures and the schedule of rates of Public Works Department of Assam
Government with due consideration towards lead distances for steel, cement,
coarse and fine aggregates and other materials and cost escalation.
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A bridge is to be constructed across the head race channel. To prevent
entry of trash, logs and other foreign materials to the forebay, it is proposed to
provide a coarse trash rack in front of the bridge structure. It is also proposed
to provide two vertical lift gates operated by a gate hoist so that the approach
channel to the forebay could be closed whenever necessary so as to facilitate
cleaning of the channel as well as the forebay. The cost estimates for the
RCC bridge of 10 m long and 6 m wide complying to IRC Class-A and the
cost of the structure for the coarse track rack and the gate hoist and a 1 m
wide operating platform is Rs. 60.43 lakhs (Annexure C-2). The cost of the
head race channel is estimated at Rs. 47.42 lakhs (Annex.C-1); that of
forebay is Rs. 47.96 lakhs (Annex-C3); that for intake and power station
structures is Rs. 319.66 lakhs (Annex-C-4) and that for tail pool and tail race
channel is Rs. 109.77 lakhs (Annex-C). The total cost of civil works is
estimated at Rs.585.24 lakhs.
4. K-Building: The cost for temporary buildings and residential buildings for the
operating staff has been estimated at Rs. 25,00,000/- and including in the
budget estimates.
5. M-Plantation: A sum of Rs. 50,000/- has been provided for plantation in the
project area. Since the project area is very small, the expenditure proposed is
considered adequate.
6. O-Miscellaneous: For miscellaneous expenditures for which no specific item-
wise cost could not be estimated, an expenditure estimated at Rs. 15 lakhs
has been provided for.
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7. P-Maintenance: A provision for expenditure @ 1% of the estimated cost for
C-Works and K-Buildings is proposed to meet the maintenance of these
works during the construction period which is in line with the prescribed
norms of the Central Electricity Authority.
8. Q-Special Tools & Plants: A provision for expenditure amounting to Rs.
20,00,000/- has been provided for special tools and plants like: concrete
mixtures, pneumatic vibrators, portable air-compressors etc. However, since
the works is to be executed through the contractors, expenditure on this head
shall be included by the contractor in the civil works estimates.
9. R-Communications: A provision of Rs. 4,00,000/- has been made in the cost
estimates to meet the probable expenditure on construction of connecting
road from the PWD road upto the power plant entry.
Under this head expenditure on telephone connections to the project
office is also included.
10. S-Power Plant and Accessories: A provision of Rs. 600,00,000/- has been
made in the cost estimates towards design, engineering, manufacture, supply
(including transport upto the project site), handling, erection, commissioning
and testing of two units of 1000 KW turbine and generating units along with
all auxiliary equipment including the cost of 2500 KVA step-up transformer
and 11 KV switchyard with circuit breaker, isolators, and earthing system etc.
The cost estimates are based on budgetary prices receive from a few reputed
indigenous manufacturers and suppliers of similar equipment.
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11. Y-Losses on Stock: In accordance with the prescribed norms of framing
estimates for hydro power projects towards losses on stock @ 0.25% on C-
works, K-buildings, O-miscellaneous, Q-special tools and plants, R-
communication and S-power plant accessories has been provided for.
12. Establishment: Towards expenditure on establishment for supervising the
construction, a provision @ 4% of I-works has been made in the cost
estimates which is in tune with the practice adopted by private power
producers.
13. Ordinary Tools and Plants: A provision has been made @ 0.5% of the I-
works towards the cost of ordinary tools and plants in line with the prescribed
norms by Central Electricity Authority (CEA).
14. Receipts and Recoveries: In accordance with prescribed norms, 75% of the
cost of tools and plants has been provided for under this head amounting to
Rs. 15,00,000/- This is based on the assumptions that on the completion of
the construction of the project, the special tools and plants procured for the
project shall be disposed off at a depreciated cost.
15. Indirect Charges – Audit and Accounts: In accordance with the prescribed
norms of Central Electricity Authority, a provision towards expenditure on
audit and accounts @ 1% of I-works has been provided for.
16. Transmission System: The power is to be evacuated through the existing 11
KV single circuit line upto the Pahumara barrage site. There is an existing 11
KV line upto the barrage site from the 33 x 11 KV, 2 x 5 MVA Pathsala Sub-
station. The length of the existing line is approximately 30 kms. It is
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understood that a 33 x 11 KV sub-station with a capacity of 1 x 2.5 MVA has
been proposed at Sarupeta which is located at a distance of 15 kms. from
the proposed SHP. It is understood that the 11 KV line from Pathsala has a
connected load of about 500 KVA. It is proposed that the existing 11 KV line
shall be strengthened by changing the conductor to ACSR Weasel. On this
account an expenditure estimated at Rs. 20,00,000/- has been provided for in
the cost estimates.
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Annex. C-1
COST ESTIMATE FOR HRC
Sl. No. ITEM OF WORK QTY UNIT RATE, Rs AMOUNT, Rs
1 Excavation 8947.20 cum 74.13 663,256
2 EW in filling in forebay 2236.80 cum 41.58 93,006.14
3 CC 1:4:8 253.80 cum 2338.17 593,427.55
4 CC M15 251.20 cum 3434.20 862,671.04
5 Stone Masonry 1225.00 cum 2016.00 2,469,600.00
6 Shuttering 384.00 sqm 156.85 60,230.40
TOTAL 4,742,191.07
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Annex. C-2
COST ESTIMATE FOR RAGULATOR & BRIDGE
Sl. No. ITEM OF WORK QTY UNIT RATE, Rs AMOUNT, Rs
1 Excavation 100.00 cum 74.13 7,413.00
2 EW in filling 25.00 cum 41.58 1,039.50
3 CC M15 100.00 cum 3434.20 343,420.00
4CC M20 in deck slab, raft slab & piers 176.80 cum 3878.08 685,644.54
5
Steel Reinforcement (Fe 415)
in M20 concrete15.27 MT 36379.35 555,391.90
6 M S Coarse Screen 38.70 sqm 15000.00 580,500.00
7
MS gates including hoisting
arrangement38.70 sqm 100000.00 3,870,000.00
TOTAL 6,043,408.94
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Annex. C-3
COST ESTIMATE FOR FOREBAY
Sl. No. ITEM OF WORK QTY UNIT RATE, Rs AMOUNT, Rs
1 Excavation 7261.50 cum 74.13 538,295
2 EW in filling in forebay 1815.38 cum 41.58 75,483.29
3 CC 1:4:8 204.30 cum 2338.17 477,688.13
4 CC M15 317.64 cum 3434.20 1,090,839.29
5 Stone Masonry 1235.72 cum 2016.00 2,491,211.52
6 Shuttering 784.00 sqm 156.85 122,970.40
TOTAL 4,796,487.63
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Annex. C-4
COST ESTIMATE FOR INTAKE & POWER HOUSE
Sl. No. ITEM OF WORK QTY UNIT RATE, Rs AMOUNT, Rs1 Excavation 12612.00 cum 74.13 934,927.562 EW in filling near runner chamber 3153.00 cum 41.58 131,101.74
3CC 1:4:8 in base course for raft below turbine chamber
110.00 cum 2338.17 257,198.70
4 CC M20 2695.00 cum 3878.08 10,451,425.605 CC M20 in superstructure 248.00 cum 3878.08 961,763.846 B/W in PH Walls 168.70 cum 2763.60 466,219.327 Dewatering LS 500,000.008 Steel Reinforcement (Fe 415) in M20 168.40 MT 36379.35 6,126,359.85
9M S intake gates including hoisting arrangement
48.00 sqm 100000.00 4,800,000.00
10 M S trash rack 50.00 sqm 35000.00 1,750,000.0011 Draft tube gates & hoist 56.00 sqm 100000.00 5,600,000.0012 P/F pressed steel door frames
aSingle rebate 30.00 RM 322.77 9,683.10bDouble rebate 7.00 RM 371.39 2,599.73
13 P/F steel door/windows 26.00 sqm 1612.80 41,932.8014 CP 10 mm th 1:6 1778.00 sqm 57.07 101,470.4615 Cement Pointing in 1:3 CM 100.00 sqm 42.13 4,213.0016 P/F Glass strip 25x4 mm 120.00 RM 16.00 1,920.0017 P/F alluminium strip 50x6 mm 180.00 RM 65.00 11,700.0018 CC floor 25 mm th 232.80 sqm 128.94 30,017.2319 CC floor 50 mm th 67.90 sqm 303.22 20,588.6420 P/F ceramic tiles 140.00 sqm 613.73 85,922.2021 P/F 30 mm th flush door shutters 19.00 sqm 1244.25 23,640.7522 P/F MS sliding doors 17.00 sqm 1735.86 29,509.6223 P/F alluminium partitions 25.00 sqm 2609.90 65,247.5024 P/F 6mm th false ceiling 100.00 sqm 530.00 53,000.0025 White washing 1420.00 sqm 11.35 16,117.0026 Synthetic Enamel painting 750.00 sqm 60.00 45,000.0027 P/F Pavement tiles 103.00 sqm 436.00 44,908.0028 Electrification work of the PH area 1 Job NA 100,000.0029 Sanitary & water supply 1 Job NA 100,000.0030 Switch Yard (Civil works) 1 Job LS 50,000.00 TOTAL 31,493,238.64 Contingency @ 1.5% 472,398.58 TOTAL 31,965,637.22
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Annex. C – 5
COST ESTIMATE FOR TAIL POOL & TAIL RACE CHANNEL
Sl. No. ITEM OF WORK QTY UNIT RATE, Rs AMOUNT, Rs
1 Excavation in TRC 29611.00 cum 74.13 2,195,063.43
2 EW in filling near TRC 7402.75 cum 41.58 307,806.35
3 CC 1:4:8 in base course below
floor of TRC 392.60 cum 2338.17 917,965.54
4 CC M15 1178.70 cum 3434.20 4,047,891.54
5 Stone Masonry 1410.00 cum 2016.00 2,842,560.00
6 Boulder Pitching 620.40 cum 864.15 536,118.66
7 Launching apron LS 130,000.00
TOTAL 10,977,405.52
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CHAPTER – 15
FINANCIAL EVALUATION
15.1 BASIC PARAMETERS
(1) Project Cost: Cost of the project has been worked out in detail in chapter of cost
estimates:
(2) Operation and Maintenance Cost : This cost includes : (i) the employee cost, (ii)
repair and maintenance cost and (iii) administrative expenses inclusive of
insurance cost. This cost has been assumed @ of 2% of the project cost
escalating @ of 4% per annum.
(3) Interest on Working Capital: The working capital has been worked out on the basis
of the following assumptions in accordance with the regulations of the
Assam State Electricity Regulatory Commission:
(a) Operation and maintenance expenses for one month
(b) Cost of maintenance and spares @ 1% of the historical cost
escalated @ 6% per annum.
(c) Receivable equivalent to two months fixed charges for sale of
electricity.
The interest rate has been taken as 11% per annum on the working capital. The
working capital and the annual interest due on it for the 35-year period of
operation has been calculated and presented in Sl. No. 7 of Table 15.2 (Page
3/3).
(4) Energy : Generated energy has been calculated as per detail under power studies.
It has been done on the basis of 95% plant availability factor.
Losses:- Auxiliary consumption - 0.5%
Transformation Losses - 0.5%
Total - 1%
Transmission losses have not been considered as it is proposed to sale the
energy produced to the Assam State Electricity Board at the Power Station bus bars.
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The average energy produced considering the river discharges for the period
from 1965 to 1965 and 1972 to 1975 is 9.34 x 106 Kwhrs. Allowing for 5% towards
outages, the likely energy to be produced is 8.873 x 106 Kwhrs. After accounting for
auxiliary consumption, transformation and transmission losses (totaling to 1%), the net
energy available for sale is 8.784 x 106 Kwhrs.
(5) Free Energy to State:
It has been agreed between the IL&FS and the Bodoland Territorial Council that
from the sixteenth year of operation the power producer shall provide free power to the
state to the extent of 7.5% of the energy available at the bus-bars i.e. after accounting
for the auxiliary power consumption and transformation losses.
(6) Financing: Equity 30%
Loan 70%
Rate of interest 10.%
Loan repayment period 10 years
(7) Taxation: As per Govt. of India policy Income Tax holiday for first ten (10) years of
operation is available. However Minimum Alternate Tax is leviable @
11.2% per annum which has been considered for the first ten (10) years of
operation. Thereafter corporate tax @ 33.6% has been considered.
15.2 FINANCIAL ANALYSIS
The financial evaluation of the project has been carried out and presented in the
following annexures.
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Annexure No.
Title of Annexure Remarks
17.117.2
17.317.4
Input data sheetProject cost and calculation of Interest during construction Cost of generationFinancial evaluation and profitability analysis
Basic input
15.3 SUMMARY & CONCLUSIONS
The scheme would generate 9.34 million kwhrs on average year and it is
projected that the net energy available for sale after meeting auxiliary power,
transformation and transmission losses and accounting for forced outages shall be
8.873 million kwh. The cost of generation is estimated as follows :
Year 1 2 3 4 5 10 15 20 25 30 35Genera-tion cost per kwh
3.49 3.38 3.27 3.17 3.06 2.54 2.79 2.98 3.22 3.51 3.87
The cost of the project is estimated at Rs. 1413.00 lakhs and cost including
escalation and interest during the construction is Rs. 1566.33 lakhs. The per kilowatt
cost is Rs. 7.832 crores per MW. The cumulative cash accrual at the end of 35 – year
operating period is Rs. 4269.35 lakhs on an equity of Rs. 437.93 lakhs which is 9.75
times the equity.
The project benefits do not include the carbon credit i.e. likely to be available
under “Clean Development Mechanism (CDM)” which will enhance the profitability of
the project. The equivalent carbon dioxide remission shall be 8,750 tonnes per annum
which shall qualify for CO2 trading under CDM regime. With a notional trading value of
US $ 12 per tonne of carbon, additional annual revenue on this account is estimated at
Rs. 52,50,000.00 (assuming US $ 1 = Indian Rupees 50).
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It is also to point out that the financial evaluation has been made on the basis of
escalation in cost of operation and maintenance @ 4% per annum whereas the sale
rate of energy has been considered constant at Rs. 3.20 per kwh for all the 35 – years
which is unlikely to happen due to inflation and depreciation in the value of rupee. In the
event of increase in cost of generation, the profitability of the project shall further
improve.
********
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Annexure 15.1
INPUT DATA SHEET
Total Project Cost Rs. 1413.00 lacs Cost of land Rs. 2.00 lacsPreliminary Development works Rs. 75.00 lacsEstimated cost of Civil work Rs. 683.00 lacsEstimated cost of E/M works including Rs. 653.00 lacstransmission works Escalation in cost per year 5%Construction period (proposed in year) 2 years
Phasing of expenditure Ist Year 30%IInd Year 70%
Energy (i) Generated in 90% dependable year 7.214 x 106 Kwh
Less 5% towards forced outage 0.36 x 106 kwhAuxiliary consumption @0.5%Loss during transformation @ 0.5% 0.072 x 106 kwhNet available energy for sale 6.782 x 106 Kwh
(ii) Water cess to the state @ 0.05 paise/unit 3.39 laks
(iii) Generated on average in a year 9.34 x 106 kwhLess 5% towards forced outage 0.467 x 106 kwhAuxiliary consumption @ 0.5%Loss during transformation @ 0.5% 0.088 x 106 kwhNet available energy 8.784 x 106 kwh
DepreciationSalvage value 10%Depreciation has been calculated on an useful life span of 35 years by straight line method.
Interest rate Interest rate on term loan 10%Interest rate on working capital 11%Period of repayment of term loan (in years) 10 years
125.
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126.
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127.
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128.
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129.
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130.
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131.
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132.
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133.
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CHAPTER – 16
FINANCING OF THE PROJECT THROUGH CLEAN DEVELOPMENT MECHANISM
16.1 INTRODUCTION
Gases like carbon dioxide, nitrous oxide, methane etc. are termed as green
house gases (GHGs) as they absorb and re-emit some of the infrared radiation warming
the earth’s surface and the atmosphere. Any change in the quantity of these gases in
the earth’s atmosphere can change the earth’s temperature and climate. Between 1860
AD and 2000AD, the average global surface temperature has increased by about 0.30C
to 0.60C. The warming has been significant since 1970. The warming is more prominent
in the continental land mass lying between 400 N and 700 N. the increase in
concentration of green house gases in the atmosphere has been attributed to the
human activities like burning of fossil fuels, deforestation, agricultural practices and
manufacturing of industrial products. The enhanced green house effect are likely to
change precipitation patterns, increase in frequency and intensity of storms, hurricanes,
change in vegetation and rise in sea level. Developing countries especially the poor
ones are more vulnerable to these changes due to their high dependence on natural
resources and their limited capacity – human, financial and institutional – to adapt to
extreme events. Climate changes can also affect the health and the livelihood of the
poor adversely. Extreme climate conditions accentuated by green house effect are likely
to cause diversion of scarce resources from poverty reduction to disaster recovery.
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Keeping in view the adverse effects of the increase in green house gas
emissions to the atmosphere, the developed countries and economies in transition
(referred to as Annexure B countries as they are listed in Annexure B of the Kyoto
Protocol) at the Third Conference of the Parties of the United Nations Framework
Convention on Climate Change (UNFCC) in Kyoto, agreed to reduce the GHG
emissions. This agreement is known globally as the Kyoto Protocol.
The Kyoto Protocol outlines a framework for three cooperative implementation
mechanisms: joint implementation, CDM, and emissions trading. Of the three
mechanisms CDM is the only one in which developing countries can participate.
16.2 CLEAN DEVELOPMENT MECHANISM
The CDM is a financing instrument defined in Article 12 of the Kyoto Protocol. A
project in a developing country that reduces GHG emissions, relative to a baseline
project, generates emissions reduction (ER), CDM enables the project owner to sell the
ER credits, once they are certified, to an interested buyer. The project owner or seller
may be a DMC government or a DMC-based company and the buyer could be an
Annex. B country or an Annex B-based company with responsibility to reduce emissions
at home or through the Kyoto mechanisms or any company that might be interested in
buying emission credits for investment, resale, or enhancement of its green image. The
benefits of CDM for the developing country are new financial resources, better
technology, and achievement of its sustainable development objectives, while the
benefit for developed countries is access to less expensive ER opportunities in a
developing country. As emissions have the same global effect irrespective of their
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PAHUMARA - SHP
geographical origin, CDM provides a cost-effective way of addressing the adverse
effects of global warming.
A CDM project produces a new commodity, ER credits, which can be traded to
generate revenue for the project owner. However, as the ER credits are invisible and
intangible, their existence needs to be established and verified. For example, a small
hydro power station generates electricity without emissions of GHGs, while an
alternative thermal power plant (base line) would have produced GHG emissions. The
avoided emissions or ER credits once quantified and verified by independent
operational entities and certified by the CDM Executive Board have a financial value
and can be sold to generate a revenue stream for the project owner. The CDM project
would normally also result in improved local environmental conditions and lowering of
pollution – related health problems compared with the baseline. The CDM facility works
with projects aimed at both sustainable development benefits and GHG mitigation.
These include:
Renewable energy
Energy efficiency
Sustainable agriculture
Forestry.
16.3 THE CDM PROCESS
The CDM process is quite complex and includes five major steps as follows:
(i) Project Identification: the CDM facility will assist the operations departments
to undertake a preliminary assessment of projects and identify projects with
GHG abatement potential. Necessary government or other clearances will be
obtained to proceed further. If the seller is interested in the CDM project
activity, a brief project identification note will be prepared. Next, potential
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PAHUMARA - SHP
buyers will be invited to express interest in offering a commitment to pay for
the development costs of the CDM and for purchasing an agreed quantity of
ERs. Alternatively, the seller might want to pay for the development costs of
the CDM and later approach buyers.
(ii) Project development : The second step relates to project development. This
entails demonstrating and estimating the GHG abatement potential of the
project using an appropriate baseline, developing a monitoring and
verification plan that will be implemented during the operation of the project to
determine actual ER credits generated by the project, and development of the
project design document.
(iii) Validation and registration : The project design document developed in (ii) is
validated by an independent accredited entity or designated operational entity
and submitted for registration to the CDM Executive Board.
(iv) Monitoring verification, and certification of ER credits : During the operation of
the project, the ERs generated are measured according to the monitoring and
verification plan and verified by an independent and accredited designated
operational entity.
(v) Issuance of ER credits: The CDM Executive Board certifies the verified ERs
that can be transferred to the buyer in case of an existing purchase
agreement or traded in the ER market at prevailing prices.
The CDM process is explained through the flow chart enclosed as Annexure-16.1.
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16.4 CARBON DIOXIDE EMISSION REDUCTION FROM PAHUMARA SHP
From the report of the International Agency, “Benign Energy” The Environmental
Implications of Renewables” (1998) the Life Cycle Emission from various energy
sources are reproduced below:
Energy sources
Green House Gas Emission
CO2
G/kwh
SO2
g/kwh
NOx
g/kwh
Coal (best practice) 955 11.8 4.3
Coal (NO2)& FGD 987 1.5 2.9
Oil (best practice) 818 14.2 4.0
Natural gas (CCGT) 430 - 0.5
Small Hydro 9 0.03 0.07
Large Hydro 3.6 – 11.6 0.009 – 0.024 0.003-0.006
It is estimated the annual energy production from the Pahumara SHP shall be
8.873 x 106 on KWh and the energy available for sale be of the order of 8.784 x 106
kwhr per annum. The coal being used in the thermal power stations in India not being of
very good quality, it may be appropriate to assume that the carbon dioxide being
emitted shall be of the order of 987 gms per kwh. On this basis the carbon dioxide
emission reduced by generating same amount of electrical energy from Pahumara SHP
works out to 8750 tonnes per annum. On this basis over the life time of power plant the
carbon dioxide reduction is expected to be of the order 306500 MT. Since the
Pahumara SHP is a renewable energy project and its operation can provide energy for
social and sustainable development without contributing to GHG emissions is eligible for
financing under CDM facility as envisaged in Article 12 of the Kyoto Protocol.
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16.5 Benefits from MNES
The Ministry of Non Conventional Energy Sources (MNES), Govt. of India, provides
a one time subsidy to improve the economic viability of Small Hydro Electric Projects
up to 25 MW installed capacity under certain eligibity criteria. The subsidy is
generally calculated in accordance with the following formula in the North Eastern
Region
Subsidy = Rs. 2.25 cores X C 0.646
Where C stands for capacity of the project in MW.
Since the installed capacity of the project is 2.0 MW, the likely amount of one time
subsidy may be about Rs. 3.52 cores
******
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ACKNOWLEDGEMENT
140.
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The Detailed Project Report for the proposed Pahumara Small Hydroelectric
Project, (2 x 1000 KW capacity) has been prepared under the sponsorship of
Infrastructure Leasing & Financial Services Limited. The contributors to this report
acknowledge gratefully the support and help extended by Sri D.K. Mittal, Managing
Director, IIDC Sri G.K. Pharlia, Advisor and Sri Pradeep Agrawal, Senior Manager
without whose encouragement and cooperation this report could not have been
prepared.
The authors also acknowledge the technical support provided by Sri D.K.
Agarwal, Retired Engineer-in-Chief, and Sri G.P.S. Bhati, Retired Executive Engineer,
U.P. Irrigation Department in preparation of this report.
This work has been undertaken as a part of the institute’s forward looking policy
towards establishing a coherent industry – institute partnership with a view to furthering
the national development activity.
Devadutta Das Principal Investigator and
Professor, Department of Water Resources Development & Management,
CoordinatorScience and Technology Entrepreneurship Park
Indian Institute of Technology, RoorkeeTelephone No. 01332: 285774 (O), 285822 (O), 285773 (R)
Fax No. 01332 – 285774, 273967
141.
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CONTENTS
CHAPTERS DESCRIPTION PAGE NO.
ACKNOWLEDGEMENT (i)
Section-I Executive Summary 1-4
Section-II Salient Features 5-7
Section-III Check List 8-10
Section-IV PROJECT REPORT
1 SCOPE OF THE PROJECT 11-19
2. INTRODUCTION 20-31
3. SURVEYS AND INVESTIGATIONS 32-34
4. WATER RESOURCES (HYDROLOGY) 35-44
5. GEOLOGY 45-58
6. CONSTRUCTION MATERIALS 59
7. PROJECT PURPOSES 60
8. CONSTRUCTION PROGRAMME 61-65
9. ENVIRONMENTAL AND ECOLOGICAL ASPECTS 66-67
10. WATER AND POWER STUDIES 68-79
11. INTAKE AND TAIL RACE WORK 80-81
12. WATER CONDUCTOR SYSTEM 82-84
13 DESIGN CRITERIA OF MAJOR COMPONENTS OF SCHEME
85-109
14 ESTIMATES OF COSTS 110-120
15 FINANCIAL ASPECTS 121-133
16. FINANCING OF THE PROJECT THROUGH CLEAN DEVELOPMENT MECHANISM
134-139
ANNEXURES 140-163
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LIST OF ABBREVIATIONS
AC Alternating currentACSR Aluminium conductor steel reinforcedAh Ampere-hourAERC Assam Electricity Regulatory Commission ASEB Assam State Electricity Board AVR Automatic voltage regulatorBCR Benefit/cost ratioBTC Bodo Land Territorial Councilc/c Center to centerCB Circuit breakerCEA Central Electricity AuthorityCh Chainagecm/s Centimeter per secondCumec Cubic metre per secondCWC Central Water CommissionDC Direct currentDG Diesel generatorDia DiameterDSCR Debt Service Coverage RatioDPR Detailed Project ReportDSI Detailed Surveys & InvestigationsE&M Electro-MechanicalFRL Full Reservoir levelFSL Full Supply Level FY Financial yearGI Galvanised IronGOI Government of IndiaGRP Glass Reinforced Polyester GWh Giga Watt hour (one million unit of power)HDPE High Density PolyethyleneHFL High Flood LevelHGL Hydraulic Grade LineHV High VoltageHz HertzICR Interest Coverage RatioID Internal diameterIDC Interest During ConstructionIL&FS Infrastructure Leasing and Financial Services LimitedINR Indian National RupeeIREDA Indian Renewable Energy Development AgencyKg KilogramKm Kilo-meterkN Kilo-Newton
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kV Kilo-voltkVA Kilo-volt-amperekW KilowattkWh Kilo-watt-hourLS Lump-sumLV Low Voltagem MetreM15 Concrete of characteristic strength 15 N/mm2
m2 Square metreM20 Concrete of characteristic strength 20 N/mm2
M25 Concrete of characteristic strength 25 N/mm2
m3/s Cubic metre per secondmA Milli-ampmasl Meters above sea levelmin Minutemm Millimeter MAT Minimum Alternate Tax MDDL Minimum Draw Down Level MNES Ministry of Non-Conventional Energy and Sources Ltd.MoU Memorandum of Understandingmsl Mean Sea LevelMVAr Mega-Volt-Ampere reactiveMW Mega-WattMWL Maximum Water Level No. NumberNPV Net Present ValueNWL Normal Water LevelO&M Operation & MaintenanceOD Outside DiameterOGL Original Ground LevelPLC Programmable Logic ControllerPMG Permanent Magnet GeneratorPPA Power Purchase AgreementR RadiusRC Run-of-riverrpm Revolutions per minuteRs Indian rupeesSCADA System Control and Data AcquisitionSHP Small Hydropower ProjectTWL Tail Water level V VoltV:H Vertical to HorizontalVAT Value Added TaxYr Year
144.
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LIST OF DRAWINGS
LIST OF DRAWINGS
Sl.
No.Title of Drawings Drg. No.
1. Layout Plan of Scheme marked on Contour Map 01
2. Layout of Project 02
3. Plan of Power House 03
4. Cross-Section of Power House 04
5. Head Race Channel – Plan & Sections 05
6. Tail Pool & Tail Race Channel – Plan & Sections 06
7. Main Electrical Single Line Diagram 07
8. Switch Yard 08
9. Land Area Required for the Scheme 09
10. Topographic Survey of Scheme 10
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ANNEXURESA1-6, B1-6, C1-6, D1-6
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Table 5.2 : Plate Load Test
Plate size =30 cm x 30 cm Size of Pit = 1.5M x1.5MDepth of pit : 2.0
M
Observations Date of testing :30-03-06
Date LoadTime in
Hr Load intensitySettlement of Plate
(mm) Mean(mm)
Applied(ton)
applied(ton/sqm) A B
30/3/200
6 0 0 0 0.00
0.5 9.30 5.50 0.97 0.93 0.95
9.45 2.34 2.67 2.51
10.00 3.40 3.32 3.36
10.30 3.44 3.40 3.42
1 10.30 11.00 4.22 4.45 4.34
10.45 5.42 5.36 5.39
11.00 6.88 6.83 6.86
11.30 7.12 6.92 7.02
1.5 11.30 16.60 3.05 3.12 3.09
12.00 3.18 3.22 3.20
12.30 11.38 11.50 11.44
2.00 12.30 22.20 12.43 12.56 12.50
13.00 15.11 15.20 15.16
13.30 15.18 15.24 15.21
2.5 13.30 27.70 19.45 19.76 19.61
14.00 21.34 21.40 21.37
14.30 21.37 21.45 21.41
3.00 14.30 33.30 23.32 23.54 23.43
15.00 27.51 27.60 27.56
15.30 27.60 27.65 27.63
147.
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