Site Assessment Report_for Study

FEBRUARY 2015

WAPCOS LIMITED(A Government of India Undertaking-

Ministry of Water Resources, River Development & Ganga Rejuvenation)76-C, Institutional Area, Sector - 18, Gurgaon-122015

Gurgaon - 122015

Proposed Barrage Axis

NORTH KARANPURA SUPER THERMAL POWER PROJECT(3X660MW)

NTPC LIMITED(A Government of India Enterprise)

Engineering Division

North Karanpura Super Thermal Power Project (6x660 MW), Jharkhand

Site Assessment Report 1 | P a g e

1.0 BACKGROUND

For the development of backward areas of Hazaribagh District of Bihar, construction of a

Super Thermal Power Plant was conceived by Govt. of India way back in 1990. The

decision to construct a 2000 MW (4X500 MW) power plant near North Karanpura in the

then Hazaribagh District and later in Chatra District of Bihar (now in Jharkhand State)

was primarily guided by ample availability of coal from Tandwa block of north Karanpura

coal fields and the proximity of the coal demands of the thermal power plant. National

Thermal Power Corporation (NTPC) was entrusted for implementing the proposed power

project.

During September1999, NTPC entrusted the work of preparation of Detailed

Project Report (DPR) for Make-up Water System to WAPCOS, a Govt. of India

Undertaking. The objectivity of DPR as envisaged by NTPC was to identify and

ensure a permanent source of water and to conceive a suitable arrangement for

utilization of water to meet the make-up water requirement throughout the

operational period of the proposed thermal power plant. The DPR for this projectwas prepared by WAPCOS and submitted in 2001.

The Power Potential Studies conducted by WAPCOS estimated the capacity of

the project as 1980 MW against the conceived capacity of 2000 MW. The power

plant was planned to have a closed cycle condenser for cooling and ash handling

system with an estimated uninterrupted water requirement of about 90 cusecs

(2.55 cumecs) by constructing a dam at village Ulrathi across river Garhi. The

proposal envisaged water to be pumped directly from the submergence of Garhi

dam.

NTPC has recently taken up the execution of its coal based power project of

3x660 MW capacity at North Karanpura in Hazaribag district of Jharkhand. The

water for the project is envisaged to be drawn from river Garhi for the purpose of

Water Cooling requirements for the Thermal plant.



2.0 GEOLOGICAL SET-UP OF THE PROJECT AREA

Project area is located on Gondwana Super-group of geo-chronological

sequence. The area falls within North Karanpura Coal-fields. It forms the northern

part of the main Karanpura basin. It is a prominent East-West trending valley

surrounded by Pre-Cambrian metamorphic comprising Hazaribagh Plateau to the

North and the Ranchi Plateau to the South.

The project area in general is a wide country with Plateaus, residual hills and

valleys. The drainage is dendritic to sub-dendritic. The Damodar River and its

tributaries including Garhi Nadi are shallow meandering streams.

The Gondwanas predominantly comprise Mahadevas, Raniganj, Barren

Measures and Barakars. Gondwanas have been deposited on very uneven

Archaean floor. Gondwandas are known habitats for huge coal deposits.

3.0 RESERVOIR TIGHTNESSReservoir rims are made up of Gondwana rocks which on surface are covered with silty

soil and sand derived partly from the Gondwana bed rock and partly from alluvial

deposits. Gondwana bedrock is made up of coarse grained sandstone with interbedded

shale, siltstone and coal and are in general impervious as far as primary permeability is

concerned. Weathered rock mantle and fractures and fissures within the bedrock could,

however, form conduits & passages for the movement of ground water. Open wells in this

type of medium have been reported to show more fluctuation and get dried up very often.

Secondly there is no major adjoining valley in close proximately to the reservoir rim into

which the stored water could leak. However, during initial reservoir filling the reservoir

water may charge the overburden material and fissures and joints in the rim rocks.

4.0 COAL MEASURES

It is pertinent to make a mention of the coal deposits in the project area. Three

bore-holes have earlier been drilled in village Laranga on the right flank of Garhi

River downstream of the proposed dam site. These holes have been drilled to

depth of 300 m, 250 m and 200 m respectively. Coal seams are reported to have

been encountered in holes around 200 m depth. These holes are reported to have



started in Raniganj formation. The coal mines around Piparwar are mostly open

cast.

5.0 INVESTIGATIONS CARRIED OUT AT THE EARLIER DPR STAGE

Geological / Geo-Technical investigationsSince the depth of the bed rock is shallow, sufficient no. of boreholes were

made at DPR stage instead of relying on geophysical investigation. The

boreholes along the dam axis have indicated that foundation rock, which is

generally semi-impervious in nature, is available at shallow depth within 8 m

and the overburden material is mostly pervious in nature. For the purpose of

the earth materials laboratory tests were conducted for the physical and

strength characteristics of the soils from various borrow areas. Borrow area

investigation indicated the sufficient availability of desired quality and quantity

of earth materials for construction purposes.

Hydrological ObservationsNo hydrological observations on the river Garhi was available for arriving at the

hydrological design parameters of the storage dam. A gauge-discharge site

was established by WAPCOS on the river Garhi and daily discharge

measurements were taken from 19.09.1999 to 19.12.1999. This actual

discharge observations were for supplementing the other existing hydrological

/river flow data in the upper Damodar river basin for assessing water availability

and other hydrological studies.

6.0 REVISED PROPOSAL FOR THE REDUCED WATER DEMAND

Due to the changes made in the plant cooling system (from water cooling to air

cooling), the consumptive water requirement of the plant has reduced from 90

cusecs to 20 cusecs (18 MCM approx.). NTPC has accordingly requested

WAPCOS to assess the possibility of constructing a low height weir / barrage for

storage of water and pumping the same to an in-plant storage reservoir for its

revised water requirement of 20 cusecs (18 MCM approx.). The structure is

proposed to be located at a close proximity to the high level road Bridge Site

across River GARHI. Water stored at the proposed barrage location shall be



conveyed thru a buried pipe line to the in-plant reservoir by pumping it from the

pump house envisaged close to the proposed weir/barrage location.

On a request by NTPC, a Team of Experts from WAPCOS along with NTPC

Officers visited the Site on 8th January, 2015 to assess its suitability for the

proposed Barrage. The list of Experts is enclosed as Annexure I.

7.0 OBSERVATIONS DURING SITE VISIT

The proposed location of a low height weir/barrage near the road bridge site is

around 5Kms upstream of the Dam location proposed in the DPR prepared by

WAPCOS. Since no data/ details are available at the proposed location, the

existing reports prepared by RITES Ltd. for the Road Bridge as well as the Data

on the hydrological studies available in the earlier DPR prepared by WAPCOS

Ltd. have been referred for a preliminary assessment.

The Thermal Power Plant requires a sustained water supply and the sources like

Ground Water option and Surface Water through direct pumping or through a

system of infiltration galleries do not appear to provide an uninterrupted source of

supply throughout the project operation period.

The Detailed Hydrological studies earlier conducted by WAPCOS at DPR Stage

confirms the sufficiency of water availability during monsoon season. Since the

discharges available in the Garhi River during monsoon season is considerable,

the option of creating a storage to transform the volume of water available during

monsoon for effective utilization during non-monsoon season appears to be the

Only Feasible Alternative. The reservoir can be impounded only during the

monsoon months viz June to August, as flows during non-monsoon months in the

river Garhi is very small, and will not give the required storage. It is thus

contemplated that the impoundment will be done during the monsoon only.



The team was also apprised that a Connecting road is proposed from the NH to

the Thermal Plant which crosses the river near the Tandwa village about 1.5 km

D/s of the existing road bridge near Surya Mandir. A bridge has already been

proposed at this location to cross the river. The River width at the proposed

location is about 200-250 m. The river alignment is almost straight up to about 1.5

km U/s where the confluence of two rivers converge. The river course at the

proposed location is well defined. The river slope is almost flat as in the plain

area. The Slope of the river appears to be in the range of 1 in 400-500. The

material on the river banks in the vicinity of the proposed structure appears to be

Silty clay type soil. The water level in the river during monsoon period was

observed to be about 3-4 m above the river bed. The river bed material similar to

silty sand type.

It was also informed that the River carries a lot of silt load during the monsoon

period. No sediment inflow data are available in the Garhi catchment. Some data

of adjoining catchment of the Barakar at Maithon reservoir are available. The

average rate of silting at Maithon reservoir is 1.02 mm/year. The Maithon reservoir

also lies in the Damodar river basin as that of Garhi river basin with almost similar

catchment characteristics. A long term average silt rate of 1 mm/year appears

reasonable and is therefore adopted for the present assessment studies.

Accordingly, it is suggested that adequate silt flushing arrangement need to be

explored and provided in the proposed Barrage after detailed investigations.

The Area plan of the Project demarcating the Proposed Barrage location as well

as the earlier Dam location is enclosed as Annexure-II.

8.0 CONCLUSIONS

The river Garhi, a tributary of the Damodar, is a non-perennial river. The flows in

the Garhi River are mainly dependent on monsoon precipitation. The average

annual rainfall in the region is around 1350 mm. The catchment is mostly rocky &

sandy interspersed with jungles & bushes.



Based on the hydrological data furnished in earlier DPR & RITESs reports, it is estimated

(Refer attached Annexure-III) that adequate water can be stored during the monsoon period by

construction of a low height barrage to meet the revised storage requirements of the plant

(i.e 18 MCM approx.). The water after storage at the proposed structure across Garhi

River shall be pumped to an in built reservoir and utilized for the entire life of the project

on a continuous and sustained basis throughout the year including the non-monsoon lean

period.

It was observed at site and also appraised by the NTPC site officers accompanying the

team that sound rock may be available at a depth of around 4-5 meters below the NSL at

the proposed road bridge location. Accordingly, it is opined that a raised crested barrage

adjoining the road bridge would be most suitable proposal for storage of water. The

barrage could be raised over a RCC raft with a u/s and d/s cut off for achieving a safe exit

gradient of seepage flow. Consolidation Grouting below the foundation of the Barrage

need to be adequately planned.

NTPC apprised to provide the guide embankment on either bank of the River as close to

the river course as possible to minimize the submergence area. The river banks on either

side of the river at the proposed Barrage site are proposed to be treated with stone

pitching or boulders in wire crates up to the required height & length for containing the

water within the guide banks. It is preliminary estimated that the embankment length may

be around 1.50 Kms and more on each bank which can be confirmed after detailed

topographical surveys.

The WAPCOS team members are of the view that the Road Bridge can be located on the

proposed Barrages Piers thereby omitting the requirement of Bridge sub-structure (i.e.

deep Pile foundations & Pile cap etc.).

The barrage is planned to be provided with vertical lift fixed wheel type hydraulic gates

electrically operated by means of rope drum hoists for storage of water u/s of barrage.

The rope drum hoists shall be placed on a raised platform over steel trestles. One set of

stop log units operated by means of a monorail crane placed on the extended arm from

the hoist bridge shall suffice for any emergency gate requirements (Refer sketch

enclosed as Annexure-IV.)



Since, the SEDIMENT LOAD of the river appears to be quiet high, it would be desirableto restrict the entry of silt into the pump intake. The River slope is almost flat at the

proposed barrage location, it is apprehended that suspended silt would settle down at a

fast rate after the structure is raised. The heavy suspended silt load shall enter the pump

intake and may choke the suction sump and pipes. Since provision of a de-sander with a

flushing arrangement would be a costlier option, the following alternatives are being

proposed for removal of silt and its flushing so as to optimize the pumping operations.

The structural arrangement as well as all other design details / parameters shall be

worked out after further investigations including the river silt studies, in-plant reservoir

simulation studies etc.

1. Alternative. 1. A raised crest barrage having silt flushing bays with a depressed

invert. The Intake for the pump house shall be located very close to the silt

flushing bays at the right bank of the river towards the thermal plant. A raised

crest with its top level below MDDL and above the Sluice invert is proposed all

around the intake to the pump house for reducing the entry of silt. (Sketch 1

enclosed as Annexure IV)

2. Alternative .2. A deep cunnette of adequate dimensions could be provided

towards the U/s and adjoining the raised crest all around the pump intake. The

invert of the cunnette shall have a steep slope and connected to a pipe having a

control valve for flushing operations towards the d/s of barrage. (Sketch 2

enclosed as Annexure V)

3. Alternative .3. The suction chamber below the riser pipes of the pumps could be a

hopper shaped with provisions of flushing the silt via pipe line equipped with a

control valve. This alternative could be planned in combination with the measures

listed at alternative 1&2 above (Sketch 3 enclosed as Annexure VI)

4. Alternative .4. A geotextile filter membrane could also be installed in the trash rack

units or separately in order to restrict the entry of suspended silt load along with

trash. Or else a system of pipes wrapped in geotextile filter material could be

installed at various levels around an intake well for water diversions. Arrangement

shall be provided to clean the choked geo-filter at regular intervals by back water



pressure slushing system or frequent replacement of the filter textile fixed in

panels .( Sketch 4 enclosed as Annexure VII)

5. Alternative .5 Large diameter deep wells can be raised at the middle of river width

above the available bed rock in place of the proposed barrage structure. The

water can be diverted during monsoon thru intakes sufficiently above the river bed

thru a trash rack supporting structure all around the well at top level .The geo

textile filter could also be installed in panels along with the trash rack units. The

geotextile filters could be cleaned of choking by back water flushing arrangement

or by provision of removable panels .The pumps can also be housed in a pump

room located above these intake wells. (Sketch 5 enclosed as Annexure VIII)

The alternative no. 5 appears to be cost effective option as it does not include the

cost of the barrage and guide embankment at the river banks. However, the

merits and demerits of all the above alternative proposals shall be worked out

after detailed hydrological surveys and studies.

Annexure-I

List of team members during the site visit on 8th January, 2015 to North Karanpura Super ThermalPower Project site

NTPC

Er. Manas Samantray, Sr. Manager

WAPCOS

Er. A.Ahluwalia, Consultant Er. D.C Mathur, Consultant Er. Kh Ashique Akbar, Engineer

ms07733Text BoxANNEXURE-II

A Inputs/AssumptionsDetails Unit Value Refered from

1 River bed level m 433.00 approx. M/s RITES bridge documents2 Barrage U/s Raft top level m 4333 Barrage Crest level m 434.5 assumed4 Undersluice Invert El m 4335 MDDL m 434.56 FRL m 437.5 assumed7 Top El of Gate m 4398 Deck EL of Bridge m 441.00 approx. M/s RITES bridge documents9 Top of Barrage Piers at Crest location m 44410 Width of River at Proposed Barrage axis m 200 assumed as per visual observations during sitevisit11 River bed Slope 1 in 500 assumed as per M/s RITES Document & VisualObservations during Site VisitB Priliminary Assessment1 Volume of 90% dependable flow in Garhi River at OldDam Axis MCM 67.00 As per DPR

2 volume of 90% dependable flow in Garhi River atProposed Barrage Site MCM 53.60assuming the Catchment area of the ProposedBarrage Axis is 80% of the Catchment area of theold dam location

3 Yeraly Revised Water Requirement of the Thermal Plantas reported by NTPC MCM 18.00 Approx.

4 FRL-MDDL m 35 MDDL-River Bed Level m 1.56 Live storage MCM 0.9

1500.00 m FRL Line

3.00 mFlow Barrage Axis

Natural Embankment/Existing river bank (1.5 m ht. assumed) 1.50 m

MDDL Line

C Pumping Requirement

1

2 So, Days of Pumping operations per Year days 60 to be on the safe side (this can be modified asper requirments)3 Quantity of water to be Pumped per day MCM 0.3 based on the requirement of 18 MCM4 Pumping hours per day assumed hrs 165 Total Pumping discharge cumec 5.21

Pumping capacity as per DPR cusec 50.00Pumping capacity as per DPR cumec 1.42

7 Nos. of Pumps required nos. 3.68 say 4.00 nos + required nos standby pumps

Note : The priliminary computaions provided above are based on the observations during Site Visit & limited data. The Computed designparameters may undergoes changes and other Design Parameters shall be assessed after Detail Investigations/Survey

Preliminary Assessment of Water Availability at the Proposed BarrageAnnexure - III

6

Assuming that The in plant Reservoir is filled up with 18 MCM in two months (considering the uncertainty if occurred during any year),although water flow is available for five months

Adequate Water is Avaiable for Pumping to the In plant Reservoir

River Bed slope (1 in 500)

750.00 m

Guide Embankment length (tentative)=1500.00 m

Annexure-IV

Annexure-V

Annexure-V

I

Annexure-V

II

Annexure-V

III

Untitled.pdf (p.1-13)Final COVERPAGE .pdf (p.1)Site Assessment Report Feb 15.pdf (p.2-9)Annexure-I.pdf (p.10)Annexure-II.pdf (p.11)Annexure III _north karampura final.pdf (p.12)Annex- IV_aLTERNATIVE 1.pdf (p.13)

SKETCH 2.pdf (p.14)SKETCH 3.pdf (p.15)SKETCH 4.pdf (p.16)SKETCH 5.pdf (p.17)

Documents

Site Assessment Report_for Study