Water Power and Dam Construction. Issue April 2010

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WWW.WATERPOWERMAGAZINE.COM APRIL 2010 29

OPERATION & MAINTENANCE

When the design of the runner and other components are hydrauli-

cally validated by CFD, a mechanical check is performed based on a

structural analysis with the use of a ﬁnite element model (FEM). This

point is considered during the design development through hydraulic

and mechanical optimisation.

The runner design is optimised using Navier Stokes computations

to deliver the best characteristics in term of efﬁciency and cavita-

tion behaviour in both pump and turbine modes. For the cavitation

behaviour, speciﬁcally in pump mode, the pressure level at the blade’s

leading edge is calculated in order to guarantee a cavitation-free pit-

ting area over the operating range. To avoid any risk of cavitation

pitting in pump mode, the most appropriate hydraulic shape during

the runner design must be found.

MECHANICAL DESIGN

A typical arrangement of a pumped storage unit involves a shaft-line

resting on three bearings: two for the motor-generator and one for the

pump turbine. The thrust bearing is generally supported by the lower

bracket, but in some cases it can be mounted on a cone transmitting

the thrust load directly to the headcover [7]. A spherical valve is used

to isolate from the upstream penstock pressure.

Dismantling of high-head pump turbine components is done either

through the generator motor stator bore or at the pump turbine pit

level. The bottom ring and the draft-tube cone are in such a case

embedded into the concrete.

As a PSP is likely to operate several cycles a day in both pump and

turbine modes, implying many starts and stops, the inlet and covers of

the hydraulic machine are repeatedly submitted to high static pressure

variation. A robust design is necessary.

The inlet spiral case and stay ring are made of high strength steel

plates and castings; elements are fabricated and stress relieved in a

workshop to be assembled on site. It is pressure tested before con-

creting and is concreted with partial water pressure inside in order to

ensure a stiff anchorage to the civil works.

The main components are carefully checked by FEM calculations.

Static, dynamic and fatigue analyses are performed to take into

account the speciﬁcities of the pump turbines in terms of dynamic

solicitations, especially at the interaction between the runner, guide

vanes and head cover. The runner is a critical component which

requires simultaneous hydraulic and mechanical optimisation at

an early design stage. Alstom developed in-house automated proce-

dures to directly link wall pressure ﬁelds issued from CFD results to

mechanical FEM. The complex 3D shape of the blades is precisely

reproduced using a ﬁve-axis numerical control milling machining

process. Accessibility for welding the runner blades to the crown and

band may require fabrication with segmented circular elements.

MOTOR GENERATORS

Alstom has built more than 20 motor-generators for up to 300MW

for differing speeds. These include the very high speed units at Afourer

in Morocco (190MVA, 750rpm), Beni Haroun in Algeria (90MVA,

1000rpm) and Feldsee in Austria (75MVA, 1000rpm).

In order to follow the design requirements for peak-load units and

to guarantee high availability of the machines, Alstom applies the fol-

lowing design concepts to its motor-generators: structural design with

oblique elements; permanent pre-stressed stator core; VPI insulation

system and slot ripple spring; self ventilated rotor rim; redundancy

on auxiliaries.

STRUCTURAL DESIGN WITH OBLIQUE ELEMENTS

High cycled machines are very sensitive to thermal expansion, cen-

trifugal forces, and forces involved in fault disturbances such as short

circuits. The concept of oblique elements is designed to meet require-

ments like roundness, concentricity and stability of the motor-gen-

erator in all operation conditions and to minimise the impact of the

above-mentioned forces.

The stator frames are welded structures designed and dimensioned

to withstand all possible stresses. Evenly distributed around the stator

frame circumference, steel plates are oblique welded to the radial

direction. The bottom ends of these steel plates are bolted to the base

plate and act as frame feet. These oblique plates also act as springs

between the stator frame and the foundation. This arrangement pro-

vides a rigid connection against eccentric displacement movements.

Radial displacements are thus prevented but free concentric thermal

expansion is allowed. Buckling of the stator laminations, which

occurs in rigid frames with non-ﬂexible connections to the founda-

tion, is not possible with this arrangement. This ﬁrm connection is

totally maintenance-free, and no regular inspection of the connection

frame to the base is required.

Above, top left: Figure 1 – Manufacturing of a PSP runner;

Bottom left: Figure 2 – Structural design with oblique elements on stator and

bracket; Right: Figure 3 – Micadur® stator bar insulation.

30 APRIL 2010 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

OPERATION & MAINTENANCE

STATOR C ORE PRESSIN G SYSTEM

Independent from the core clamping system, the laminations are

compressed by hydraulic jacks using clamping bolts through the

core. The permanent pre-stress in the clamping bolts is maintained

even after any settling of the stator core due to heat and vibration.

Clamping ﬁngers transfer the pressure to the stator core teeth. The

location of the clamping bolts along the midline of the stator seg-

ments ensures uniform distribution of the core pressure. Additional

spring elements in the clamping bolts ensure that the compressive

force exerted on the laminations due to the pre-stressing of the bolts

remains present even after a long service period of the generators.

With this system, buckling of the core is avoided, and it is required

for pumped storage schemes with high thermal dilatations.

VPI INSU LATIO N SYST EM AND SLO T RIPPLE S PRING

The reliability of the stator winding is determined primarily by the

quality of its insulation. The Micadur insulation system has been used

by Alstom for more than 40 years. The system has been continuously

investigated and further developed, producing excellent results on all

machines even under severe conditions.

The Micadur system consists of a continuous tape insulation

impregnated with synthetic resin in a vacuum which is subsequently

cured. A glass fabric strip is used as a carrier material for the high-

grade mica ﬂeece and a specially developed solvent-free epoxy resin

is the impregnating agent. The uniform production process ensures

high quality insulation.

To facilitate insertion of the bars, to ensure a good ﬁt, and good

heat transfer between the insulation surface and the stator core, the

straight portions are supplied with a ‘round-packing’ consisting of a

double-folded conductive polyester foil ﬁlled with a curable rubber

compound. This system also warrants an excellent grounding after

installation due to the gap free installation (no discharge effects on

the outer part of the bar).

SELF VEN TILAT ED ROT OR RIM

Depending on the machine dimensions, Alstom applies one of two

standard cooling philosophies with self-ventilated rotors:

U Standard rim-cooled ventilation design which has been thoroughly

tested in the past and provides a secure and stable cooling system.

U High-speed PSP-generator ventilation design, which was speciﬁcally

adjusted to overcome the high-speed generator constraints such as

the small ventilation relevant entry diameters.

In the classical design, the air coming from the heat exchangers ﬂows

into the spider, it passes through the rim, the poles and enters the

stator core before passing through the heat exchanger again. A small

part of the air leaves the pole gap and the air gap axially and after

cooling the winding heads and connectors, merges with the stator

cooling air before entering the heat exchangers.

The high-speed solution uses the advantage of additional straight,

radial blade fans on the top and bottom side of the rim to provide an

additional volume ﬂow. This is required because the small available

air passage dimensions in the spider and rim limit the volume ﬂow in

a way that the required volume ﬂow cannot be met. In the pole gap

the parallel ﬂows (rim and fans) merge together and continue in the

same way as the standard rim-cooled solution. To ensure a homoge-

neous pole coil cooling, this cooling design has two additional fea-

tures. Firstly, it guides the air coming from the rim to the axial pole

coil centre and secondly, a speciﬁc air ﬂow passes between the pole

coils and the pole bodies thus cooling the coils from the rear.

HV SWITCHYARD

EXCIT.

POWER EVACUATION

HV LINES

HV LINK

POWER

TRANSFORMER

UNIT 1

UNIT CIRCUIT

BREAKER

UNIT AUXILIAR

TRANSFORMER

EXCITATION

TRANSFO.

NEUTRAL

CELL

Table 1

Project SHAHE BAILIANHE HEIMIFENG PUSHIHE ZHANGHEWAN LAM TA

KHONG

YECHEON HUIZHOU BAOQUAN HOH HOT YANG

YANG

Country China China China China China Thailand Korea China China China Korea

Rotational speed

(rpm)

300 250 300 333.3 333.3 428.6 400 500 500 500 600

PUMP

Delivery head (m)

Max/min

125 217 335 335 345 408.5 491 565 575 595 832.4

104.4 194 275 295 295 346.5 446 529 500 505 782.5

TURBINE

Rated net

head (m)

97.7 195 295 308 305 360 450 517.4 510 521 798.4

TURBINE

Rated Output

(MW)

51.1 306 306 306 255 260 408 306 306 306 258

Frequency range

(Hz)

Max/Min

49.5 49.5 49.5 49.8 48 49.8 59.8 49.5 49.5 49.8 58.8

50.5 50.5 50.5 50.2 50.4 52 60.2 50.5 50.5 50.4 60.9

Speciﬁc speed

(Nq)

54 51 40 43 38 40 37 33 32 30 23 (38 per

stage)

Left: Figure 4 – HPP Unit single line diagram

WWW.WATERPOWERMAGAZINE.COM APRIL 2010 31

OPERATION & MAINTENANCE

PLANT IN TEGRA TION

Alstom Hydro is a plant integrator and provides a complete range of

pumped storage electromechanical equipment. This includes pump

turbines, motor-generators, control systems and optimised hydro

mechanical and balance of plant (BOP) equipment.

Depending on the customer’s preferences, Alstom can provide an

integrated turnkey PSP or various separate lots. For turnkey projects,

specialised Alstom Hydro teams have developed speciﬁc skills for

optimising the complete plant conﬁguration to help ensure highest

global water-to-wire performance.

As the runner of a high head pump turbine needs to be located

under the normal pool level of the lower reservoir, this type of

machine has to be installed in a cavern.

A dedicated cavern is also designed in order to arrange the genera-

tor step-up transformers, the starting equipment (SFC) and some-

times, an underground substation (GIS). One gallery per unit is

excavated between the powerhouse cavern and transformer cavern

to arrange the insulated phase bus and related equipment.

Moreover, a downstream gate cavern is created in order to install

the draft gates or tailrace emergency gates. Sometimes, a dedicated

upstream gate cavern is needed to install one spherical valve per unit

if the powerhouse width is not sufﬁcient due to a large generator. This

is the case for low rated speed such as Balianhe project in China.

If we consider the access tunnel, the HV cable tunnels, the pen-

stocks with bifurcations, the draft tube and tailrace tunnels, the surge

tanks and other galleries for drainage, ventilation and construction,

the excavation cost is very important and the civil work design is

considerable at a pumped storage plant.

The power evacuation design is particularly sensitive for PSPs and

more complex in comparison with a hydro power plant (HPP). For

an HPP, the insulated phase bus (IPB) is generally associated with a

generator circuit-breaker (GCB) only. For a PSP the IPB is moreover

associated with a phase reversal disconnector (PRD), a back-to-back

disconnector (BBD), a starting disconnector (SD), a neutral discon-

nector (ND), an electrical braking disconnector (EBD) or electrical

braking circuit-breaker (EBCB) and a starting circuit.

The last one is mainly constituted by the static frequency converter

(SFC), the dedicated input and output transformers, the AC reactors,

the DC reactors, the related circuit breakers, the by-pass disconnector

and the starting bus which link all the units.

Consequently, the power evacuation circuit is more complex and

delicate for a PSP. The number of daily average starting and stopping

cycles varies for each project (one cycle means one starting and one

stopping sequence). For example at Huizhou PSP, it is ten cycles per

unit and per day. This means equipment is more stressed for a PSP

than for a HPP.

Seven operating modes are generally used at a pumped storage

plant: generating; spinning reserve; synchronous condenser in gener-

ating direction; pumping; synchronous condenser in pumping direc-

tion; standstill; black start.

Twenty-three mode transition schemes are issued in operating

modes with a dedicated time for each.

The authors are Jean-Bernard Houdeline, Jean-Bernard

Harnay and Gérard Vuillerod from Alstom Hydro France,

and Thomas Kunz from Alstom Switzerland

This article is based on a paper originally

presented at the Waterpower XVI conference

held in July 2009 in Spokane, Washington. The

conference technical papers are available on CD from

PennWell’s Hydro Group.

www.waterpowerconference.com

IWP& DC

POWER EVACUATION

HV LINES

ALSTOM HYDRO CONTROL SYSTEM

HV SWITCHYARD

HV LINK

POWER

TRANSFORMER

AC REACTORS

UNIT 1

TO UNIT 2

BACK TO BACK START

DISCONNECTOR

EXCITATION

TRANSFO.

UNIT CIRCUIT

BREAKER

EXCIT.

ELECTRICAL

BRAKING SWITCH

PHASE REVERSING

DISCONNECTOR

UNIT AUXILIARY

TRANSFORMER

G M

SFC INPUT

TRANSFORMER

DC REACTORS

NETWORK

SIDE

MACHINE

SIDE

AC REACTORS

THYRISTORS

NETWORK BRIDGE

THYRISTORS

MACHINE BRIDGE

SFC OUTPUT

TRANSFORMER

LOW FREQUENCY

DISCONNECTOR

(BY-PASS)

STARTING

DISCONNECTOR

NEUTRAL DISCONNECTOR

(FOR BACK TO BACK)

References

1. J.B. Houdeline, JM. Verzeroli, J. Clerin, “DERIAZ Pump turbine for the

NAUSSAC 2 plant in France”, Hydropower & Dams, Gmunden (Austria), 1999

2. J. Kirejczyk, JM. Verzeroli, JP. Taulan, “Non-polluting Pump turbine :

Naussac 2”, Hydrovision 2000, Charlotte (USA), 2000

3. JB. Houdeline, Y. Bouvet, D. Bazin, M.Couston, M.François, J.M. Verzeroli,

“Double-stage Regulated and Reversible Pump turbines of YangYang Power

Station in Korea”, 23rd IAHR Symposium, Yokohama (Japan), 2006

4. S. Lee, J.M. Henry, “Yang Yang Pumped Storage Power Plants in Korea

under 817m net head : Selection of Double-stage Regulated Pump Turbines

Technology”, Hydro 2007, Granada (Spain), 2007

5. J.B. Houdeline, J.M. Verzeroli, T. Kunz, A. Schwery, Reversible Pump

turbine and Generator-Motor Design -The Last PSP Achievements Experience

in Asia, Asia 2008, Danang (Viet Nam), 2008

6. JB. Houdeline, S.Lavigne, P.Mora, M.Couston, M.François, Single-stage

reversible Pump turbine – From design to experience, Waterpower XIV,

Austin (USA), 2005

7. J.Brémond, M.Verger, P.Marin, G.Vuillerod ALSTOM’s long experience

in thrust bearings resting on headcover, 23rd IAHR Symposium, Yokohama

(Japan), 2006

8. F.Mazzouji, C.Ségouﬁn, PY.Lowys, JL.Deniau, Investigation of

unsteadiness in hydraulic turbines, 23rd IAHR Symposium, Yokohama

(Japan), 2006

9. C. Boireau, G.Vuillerod, Non-linear modeling of a hydraulic generating

unit – Application to stabilizing pump-turbines in speed-no-load turbine mode,

21st IAHR Symposium, Lausanne (Switzerland), 2002

Hydro control systems

Alstom Hydro Control System (HCS) concept is designed to control and

supervise hydro power plants. It is based on Alspa Digital Control System

(DCS). Alspa is a system designed, developed and maintained by Alstom and it

is designed speciﬁcally for power generation applications.

This Alstom HCS is named CONTROPLANT. Its newest release, the Series 7

has standardised architecture is constituted with :

CONTROBLOC – automation cell composed of multifunction controllers

interconnected to each other through data networks (lower

control levels).

CONTROLOG – the supervision system.

CONTROCAD – engineering software tool for maintenance and conﬁguration

of Alspa Controplant.

Below: Figure 5 – PSP Unit single line diagram

32 APRIL 2010 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

TUNNELLING

HE Grand Poubara project is located approximately

20km from the town of Franceville, at Poubara Falls

on the Ogooue River (Figure 1). The main structure is a

37m high rockﬁll roller compacted concrete dam and the

project will include a 160MW hydro plant, equipped with four

40MW Francis units with a designed discharge of 196m

/sec. The

crest is 300m long with a stepped spillway with a discharge capac-

ity of 1100m

/sec. A bottom outlet is designed as an environmen-

tal measure to provide permanent downstream water releases of

25m

/sec, a further 108m

/sec is released for energy production at

the existing Poubara 1 and 2 hydro stations. Other characteristics

include an intake tunnel and a 3.4km long pressure tunnel, with

a 7m-diameter horseshoe section, a surge tank of 25m diameter,

powerhouse, switchyard and two transmission lines. The dam will

impound a reservoir with a surface area of 60km

and will provide

a storage volume of 800 x 10

with live storage of 560 x 10

for normal daily operation. The annual average energy production

has been estimated to be around 1200GWh, taking advantage of

a head of 94m. The hydraulic layout of the project is presented in

Figure 2. The project is implemented under an EPC-FIDIC contract

with a total investment cost of approximately US$400 x 10

GEOLOGI CAL CONDIT IO NS

The evaluation of rock mass and its support after excavation for a

tunnelling project requires sections to be deﬁned which exhibit equal

rock mass characteristics and behaviour. According to geological

data, four rock types are expected during excavation for the Grand

Poubara project. The sedimentary series is moderately inclined at an

angle of 8 to 10º to the northwest.

For the deﬁnition of homogeneous sections, data about the various

states of decomposition was taken into consideration, as well as drill

hole data (RQD) and the expected ground water inﬂow.

As a result, three different sections were deﬁned for the Grand

Poubara project. Section 1 represents the siltstones and pelites, with

intercalations of ampelites including all states of decomposition with

a total length of about 1500m. Section 2 represents the fresh sand-

stones with good rock properties and a total length of about 700m.

Section 3 is represented by sandstones of medium to high state of

decomposition with a total length of about 1200m.

ROCK SUP PORT ESTIM AT ION

Tunnels constructed by the drill and blast method are efﬁciently

upported by any combination of rock bolts, shotcrete, steel rod mats,

steel arches and, if necessary, face support. In areas where full section

concrete support is not needed, the rock surface or the shotcreted sur-

face is sufﬁcient for a long term support system. The GSI (Geological

Strength Index) provided by Hoek and Brown [1997] was used for

calculations and modelling of the tunnel excavation and support.

Tunnel support requirements, tunnel excavation and rock supports

were assessed by a mandatory rock mass classiﬁcation system. This

system takes into account both the geotechnical parameters and the

geological conditions to assess the rock mass behaviour. Under the

rock mass rating system (RMR) there are ﬁve rock classes correspond-

ing to different support and excavation guidelines (see Table 1).

The applica tion of these excavation and support guidelines can be

used to estimate the cost of tunnel support. In Figures 3 and 4, an esti-

mation of the rock mass and the support class is presented, according

to the RMR-system. It is to be anticipated that the identiﬁed fault

Tunnelling at Grand Poubara

Currently under construction on the Ogooue River in Gabon, the 160MW Grand Poubara

hydroelectric project is being developed to help provide adequate power supplies in the

country. Cesar Alvarado-Ancieta, Uwe Wackwitz, Maximiliam Riehl and Yalis Ongalla present

details on the project and the tunnelling aspects likely to be encountered during construction

Figure 1 – Project view

Grand Poubara

Reservoir

Phase 1

Poubara 1+2 Weir

PH Poubara 1+2

38 MW

PH Grand Poubara

160 MW

max

are only for full energy

production in order to achieve

full installed power capacity

Legend

Grand Poubara works

Existing works

Poubara Falls

PFalls

= 25 m

/sQ

Out max

= 133 m

/s Q

Out max

= 133 m

P1+2 max

=108 m

Power tunnel, Q

GP max

= 196 m

River Ogooue

ut max

= 133

Poubara

Fal

lls

= 25 m

nel,

P ma

P1+2 max

=10

133 m

Figure 2 – Hydraulic scheme

WWW.WATERPOWERMAGAZINE.COM APRIL 2010 33

TUNNELLING

and shear zones along the tunnel line are zones that are designated to

require the maximum support class.

EXCAVAT IO N AND OVE RBREAKAGE

The tunnel passes through four rock types which are each only mod-

erately inclined, at an angle of 8 to 10°, against the horizontal plane.

The working face of the tunnel is approximately parallel to bedding

of the rock mass. During the excavation process, this near-horizontal

bedding can cause overbreakage in the crown. The spacing, orienta-

tion and frequency of discontinuities are crucial parameters.

Constructional overbreakage – This is most often caused from inex-

perienced work by the blasting team and such type of overbreakage is,

to a certain degree, often accepted. An ‘A-line’ is an economic indicator

used to deﬁne the margins of extra costs attributable to the construc-

tor. Detailed documentation of tunnelling progress is deﬁned by the

parameters for the expected conditions and unexpected conditions.

Geological overbreakage – This is caused by disadvantageous geologi-

cal conditions such as parallel bedding to the tunnel axis, small-spaced

cleavage or an unfavourable system of joints. In cases where unstable

pieces of rock become stuck in the crown and do not fall away immedi-

ately after blasting, instant intervention is required. The falling of unsta-

ble rock pieces into the area behind the working face represents a danger

to the workforce. Such unstable areas must be identiﬁed and secured

with single rock bolts of at least 6m length in addition to whatever regu-

lar systematic support is required. Documentation of geological over-

breakage serves as an indicator for poor rock conditions.

SUPPORT DIMENSION IN G

The RMi rock support chart for discontinuous ground with plots of

three geological sections is shown in Figure 7.

Rock bolts – The installation of rock bolts as propping agents rep-

resents an effective and economical method for the support of rock

mass. There are two methods of application in modern tunnelling.

Single rock bolts are used to secure small areas of unstable conditions

while the use of a systematic rock bolt grid allows the transfer of loads

from the degraded tunnel lining to the interior of the stable rock mass.

The use of both rock bolt systems was recommended for Poubara.

U Single rock bolts: The use of single rock bolt anchorage for secur-

ing small areas with unstable geological condition was recommended

during the advance tunnel process. A length no less than 6m was pro-

posed to ensure sufﬁcient traction, mass and strength of the rock bolt.

U Systematic rock bolts: A systematic rock bolt arrangement is required

in almost all sections where both soft and hard rocks are anticipated.

Spacing and dimensions of the rock bolts are dependant on the prevail-

ing geological conditions. For the systematic bolts systems, either grouted

(resin) or Swellex bolts were recommended. Swellex rock bolts are

used

in hard rocks with a low possibility of fracturing, while the use of grouted

rock bolts is recommended for soft rocks and highly fractured areas.

Individual rock bolts and the rock bolt system will be tested at the

construction site to ensure appropriate characteristics. The same on-

site testing also applies for the rock bolt grouting material.

Shotcrete – To re-enforce the excavated space, shotcrete is applied pneumati-

cally through a hose at constant pressure, directly after the blast. There are

two common types of modern shotcrete application; dry mix and wet mix.

Shotcrete is reinforced by conventional steel rods, steel mesh, and/or fibres.

Fibre reinforced (steel or synthetic) shotcrete is more frequently used for stabi-

lization in modern tunnelling and its use was considered for those project areas

where special properties are assigned to the shotcrete, such as fault zones.

WATER MA NA GEMENT

Water inﬂow in the tunnel – The Lugeon permeability tests per-

formed on drill holes along the line of the tunnel have values of

5 to 10m/sec, indicating low rates of water inﬂow. Water inﬂow

rates through hard rock are dependant on the spacing and orienta-

tion of discontinuities. The geological condition along the course of

the tunnel is bedded lithology of siltstone/pelites with intercalation

of ampelite and sandstones. Water inﬂow will circulate along the

discontinuities and fractures of the rocks as well as along the strati-

ﬁcation horizons. Taking into account the geological conditions,

an anisotropic and inhomogeneous groundwater situation for the

course of the tunnel was conceived.

The inﬂow of water is also highly dependant on the time of the

year at the Poubara project site. Calculated using the mean pluviom-

eter values of the last 50 years, the months of March, April, May,

October, November and December were identiﬁed as having high

precipitation, with an average of more than 180 mm. Water inﬂow in

the tunnel will be increased during times of intense rainfall.

290.00

340.00

390.00

440.00

490.00

540.00

-0+200 0+000 0+200 0+400 0+600 0+800 1+000 1+200 1+400 1+600 1+800 2+000 2+200 2+400 2+600 2+800 3+000 3+200 3+400

Chainage [km]

Elevation [m asl]

1.5%

Intake

Tunnel

Surge

Tank

Shaft

Powerhouse

Powertunnel

RQD 45 85 74 60 81 >10 60

Drill hole

111

121

122

124

132

131

151

Fault zone F6 F3 F5

Rock type

Siltstone/pelite + interbedded

ampelite horizons

Sandstone + ampelite

horizons

Sandstone +

ampelite horizons

Sandstone + ampelite

horizons, quat.

SandstoneDolerite

Weathering/

Decomposition

high to

medium

high to mediumlow low low lowmedium high high

Rock mass classification

GSI

Geological

Strength

Index (estimated)

Section 1:

siltstone/ampelite

GSI:40

Section 3:

sandstone,

strong alterated

GSI:40

Section 3:

sandstone

GSI:60

Section 2:

sandstone,

fresh

GSI:55

Section 2:

sandstone,

fresh

GSI:55

Section 3:

GSI:60

Water inlet (est.) medium

high to

medium

low to mediumlow low lowhigh high

Above: Figure 3 - Rock mass classiﬁcation

34 APRIL 2010 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

TUNNELLING

Figure 4

Estimation of excavation mode and support measures

290.00

340.00

390.00

440.00

490.00

540.00

-0+200 0+000 0+200 0+400 0+600 0+800 1+000 1+200 1+400 1+600 1+800 2+000 2+200 2+400 2+600 2+800 3+000 3+200 3+400

Chainage [km]

Elevation [m asl]

Rock type

RQD

RMR

Rock mass rating

GSI

Geological Strength

Index (Sinohydra)

Siltstone/pelite + interbedded ampelite horizons

Fault zone

Estimation of excavation mode and support measures

Sandstone +

ampelite horizons

Sst + ampelite

horiz., quat.

Sandstone + ampelite horizons

Section 1: siltstone/ampelite

GSI:40

F6 F5F3

85 74 60 81 >1045

RMR: 65

Section 2: sandstone,

fresh GSI:55

Section 2:

sandstone,

fresh GSI:55

Section 3: sandstone,

strong alterated GSI:60

Sect. 3

GSI:60

RMR: 45, in fault zone RMR: <20

Dolerite

RMR: 45 RMR: 65 RMR: 45

1.5-2 m

30 mm

crown

none

1.5%

GSI = RMR-5 for rocks of very good to fair quality.

For very poor quality rock masses, the value of RMR is very difficult to estimate and the correlation between RMR and GSI is no longer reliable.

Categories below fair are estimates only.

Sandstone

Section 3:

sandstone

GSI: 60

RMR: 45

Excavation

Support

Complete support 10 m from face, in fault:

install shotcrete support concurrently with blasting

Rock bolts

Spacing

compl. 20 m from face

10 m from face

compl. 20 m

from face

Top heading and bench, 1.5-1.0 m in advance,

fault: multiple drifts 0.5-1 m

Full face, 1.5-3 m

in advance

Top heading and bench,

1.5-1.0 m in advance

Full face,

1.5-3 m in

advance

Top head.

+ bench

Length

Shotcrete

Crown

Sides

Wire mesh

Steel arch

Systematic rock bolts in crown and walls

1.5-2.0 m, fault: 1.0-1.5 2.5 m 1.5-2.0 m 2.5 m

1.5-2.0 m, fault: 1.0-1.5 2.5 m 2.5 m 1.5-2.0 m

allover

50-100 mm

30 mm, fault: 150 mm in sides and 50 mm on face

50 mm 50-100 mm 50 mm

50-100 mm

- 30 mm

crown when required crown when required

None, fault:heavy ribs spaced 0.75 m with steel

lagging and forepoling if required. Close invert

none nonenone

10 m from

face

Open

pit

Top heading and

bench, 1.5-1.0 m

in advance

10 m from face

1.5-2.0 m

30 mm

50-100 mm

crown

none

Intake

Tunnel

Surge

Tank

Shaft

Powerhouse

Powertunnel

Above: Figure 5 – Guidelines for excavation and support, RMR / Class I + II (left side) and Class III (right side); after Bieniawski (1989)

Above: Figure 4 – Estimation for excavation mode and support measures

WWW.WATERPOWERMAGAZINE.COM APRIL 2010 35

TUNNELLING

RISKS

Fault zones / decomposed zones – There are possible areas susceptible

to higher rates of water inﬂow. First, the identiﬁed major fault zone ‘F5’

represents a brittle zone that permits groundwater to ﬂow more con-

stantly and at higher rates. The same applies in the vicinity of the minor

fault zones ‘F3 ‘and ‘F6’. Secondly, zones of strongly decomposed rock

also represent brittle areas where water inﬂow might be increased in

comparison to normal conditions. The surface of weathered rock is

dependant on the morphology of terrain and lithology. Whenever the

excavation of the tunnel is carried out in decomposed rocks, special

attention is drawn to appropriate water management. The decomposi-

tion of parent rock material leads to the formation of clay minerals and

these minerals are capable of blocking and trapping water from circu-

lating along ﬁssures. The result is small-scale conﬁned aquifers which

will burst into the tunnel or drill holes when penetrated.

Invert water conditions

– The invert of the tunnel is often not specially

prepared and consists of extracted loose material. The invert is the base

of the machinery and provides work force for the excavation process and

is, therefore, subject to changing load conditions. The siltstones, pelites

and ampelites may change their consistency and tend to deform after

contact with water. The result is a local reduction of the load capacity

and interference to the working process due to softening of the invert.

Water management during excavation – A water management

system has been foreseen and supports the excavation process. In

the event that the water inﬂow becomes excessive and when it is

necessary to reduce water inﬂow, a grouting programme has been

Table 1: Guidelines for excavation and support 10m span rock tunnels in

accordance with the RMR system (after Bieniawski, 1989)

Rock mass class Excavation Rock bolts (20mm, fully grouted) Shotcrete Steel arch

I - Very good rock

RMR: 100-81

Full face, 3m in advance. Spot bolting. – –

II - Good rock

RMR: 80-61

Full face 1.5m in advance, Complete

support 20m from face.

Locally bolts in crown, 4m long,

2.5m spaced with occasional

mesh wire.

5mm in crown, in walls

where required.

–

III - Fair rock

RMR: 60-41

Top heading and bench, 3-1.5m

advance in top heading. Commence

support after each blast. Complete

support 10m from face.

Systematic bolts 4m long, 1.5m

spaced in crown and walls, with

mesh wire in crown.

50-100mm in crown,

30mm in walls.

–

IV - Poor rock

RMR: 40-21

Top heading and bench, 1.5 -1m in

advance in top heading. Install support

concurrently with excavation. Complete

support max. 10 from face.

Systematic bolts

4-5m long,

1.5-1m spaced in crown and walls

with mesh wire.

100-150mm in crown,

100mm in walls.

Light to medium rips,

1.5m spaced where

required.

V - Very poor rock

RMR: <20

Multiple drifts, 0.5 - 1.5m advance

in top heading. Install support

concurrently with excavation. Shotcrete

as soon as possible after blasting.

Systematic bolts,

5-6 m long, 1.5-1m spaced in

crown and walls with mesh wire,

additional bolts in invert.

150-200 mm in crown,

150mm in walls and

50mm in front.

Medium to heavy ribs,

0.75m spaced, with steel

lagging and fore poling if

required, close invert.

Figure 6 - Guidelines for excavation and support, RMR / Class IV (left side) and Class V (right side); after Bieniawski (1989).

36 APRIL 2010 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

TUNNELLING

planned. Grouting can be used to seal off the water before excava-

tion. During grouting operations, in front of the excavation chamber

and during the curing process, it is necessary to suspended the tunnel

advance. This is a disruptive event, as grouting long lengths of tunnel

can require numerous weeks of extra effort.

Areas where it may be necessary to grout prior to tunnel excavation

include the fault zones ‘F5’, ‘F3’ and ‘F6’ as well as areas of highly

decomposed rock mass. Grouting will be initiated at least 10m in

advance of the identiﬁed brittle zone to assure effective stabilizing.

Surface effect – The construction phase of a tunnel excavated into a

complete rock mass system can be regarded as similar to a large drain-

age system. The discharge of water in near-to-surface tunnels will lead

to subsidence at the surface. The impact of this depends on the total

discharge of water and on the properties of the lithology. When tunnel-

ling in undeveloped areas, this effect can be neglected.

The crossing of existing developments represents an additional chal-

lenge for tunnelling construction. Provisions to minimize surface subsid-

ence must be taken both in advance and during excavation. Preventive

Surface monitoring

Extensometer

Inclinometer and

Extensometer

2 3

4 5

100

600

400

200

0.01

0.02 0.04 0.06

0.1

0.2 0.4 0.6

2 4 6

20 40 60 600

100

200400

Ground condition factor

Gc = , x JP x SL x C

RMi rock support chart for discontinuous ground

for blocky ground and many weakness zones

Section

roof

roof Plot symbol Note

1 0.20 1409.92

plot out of diagram

Sr-value >> 600

2 7.93 18.76 -

3 0.91 40.11 -

Section

wall

wall Plot symbol Note

1 0.99 634.47 -

2 39.61 33.78 -

3 4.55 72.19 -

Size ratio

Sr = (Dt / Vb) (Co / Nj)

{For weakness zones with thickness Tz , Dt: Sr = (Tz/Db) (Co/Nj)}

Limit

Shotcrete thickness (mm)

Rock

olt

Rock bolt sp

cing in shotcreted area

1x1

Limit

ING

Short blast round,

shotcrete quickly

after blast, plu

CONCRETE LINING

Special designed Shotcrete

or concrete lining

150 mm

100 mm

200 mm

Only Rock Bolts

40 mm

Fibre reinforcement

50 mm

60 mm

Time estimation for tunnelling

Excavation excavation from 3 sides and counter heading: 1) 0+000 – 0.900m, 2) +670 – 0+900m, 3)2+670 – 1+800m, 4) 3+380 – 3+000m and shaft at approx. 3+000m

orking condition 2 shifts per day of 8 hours, 7 days a week, including drilling, blasting, mucking, scaling, rock support and concrete lining

Progress Tunnel: 21 m/w, Shaft 7.0 m/w Tunnel: 28 m/w, Shaft: 10.5 m/w

Section 1.0+000 – 0+900 2.1+800–0+900 3.2+670–1+800 Shaft 3+000 4.3+380 – 3+000 1.0+000 – 0+900 2.0+900 – 1+800 3.2+670 – 1+800 Shaft 3+000 4.3+380 – 3+000 1.0+000 – 0+900 2.0+900 – 1+800 3.2+670 – 1+800 Shaft 3+000 4.3+380 – 3+000

ccess port.[w] 12-16 12-16 12-16 12 12-16 12-14 12-14 12-14 12 12-14 10-12 10-12 10-12 12 10-12

Excav., muck, supp, shotc [y] Tunnel 0.83+/- 0.1 (+42.9w), Shaft 0.11 (=5.7w) Tunnel: 0.49 +/- 0.1 (=25.7w), Shaft0.06 +/- 0.1 (=2.9w)

Excav. [w] 14.3 14.3 13.8 1.9 6.0 10.7 10.7 10.4 1.3 4.5 8.6 8.6 8.3 1.0 3.6

Mucking [w] 9.5 9.5 9.2 1.3 4.0 7.1 7.1 6.9 0.8 3.0 5.7 5.7 5.5 0.6 2.4

Rocksup. [w] 14.3 14.3 13.8 1.9 6.0 10.7 10.7 10.4 1.3 4.5 8.6 8.6 8.3 1.0 3.6

Shotcrete [w] 4.8 4.8 4.6 0.6 2.0 3.6 3.6 3.5 0.4 1.5 2.9 2.9 2.8 0.3 1.2

Concrete lining [w] 89.0 4.0 12.7 89.0 4.0 12.7 89.0 4.0 12.7

Tunnelling [y] 3.01 +/- 0.1 (=156.6 w) 2.80 +/- 0.1 (=145.8 w) 2.68 +/-0.1 (=139.4w)

Parameter for calculation:

ork force: scaling of loose blocks and fragments: 0.5 h, drilling and loading (45m2 cross section: 2.5 h, installation of ventilation duct: 0.5 h, mucking out of blasted material: 2.0 h, installation of support 3.0 h. Time calculating does not take into account possible downtimes of machinery and change in tunnel progress due to geological conditions. Geotechnic: constant, work progress of 21/28/35m per week even in the identified fault zones. Concrete lining: 30 m/w (estimated). No delay with support installation, no support in advance like probe drilling and pregrouting. In case of problematic condition, an extra progress time of at least 20-30% must be added to each value. All parameters given, this estimation is a best case scenario.

Parameter for calculation:

Work force: scaling of loose blocks and fragments: 0.5 h, drilling and loading (45m2 cross section: 2.5 h, installation of ventilation duct: 0.5 h, mucking out of blasted material: 2.0 h,

installation of support 3.0 h. Time calculating does not take into account possible downtimes of machinery and change in tunnel progress due to geological conditions. Geotechnic: constant,

work progress of 21/28/35m per week even in the identified fault zones. Concrete lining: 30 m/w (estimated). No delay with support installation, no support in advance like probe drilling and

pregrouting. In case of problematic condition, an extra progress time of at least 20-30% must be added to each value. All parameters given, this estimation is a best case scenario.

Tunnelling [y] 3.01 0.1 (=156.6 w) 2.80 0.1 (=145.8 w) 2.68 0.1 (=139.4w)

Concrete lining [w] 89.0 4.0 12.7 89.0 4.0 12.7 89.0 4.0 12.7

Shotcrete [w] 4.8 4.8 4.6 3.6 3.60.6 2.0 3.5 0.4 1.5 2.9 2.9 2.8 0.3 1.2

Mucking [w] 9.5 9.5 9.2 1.3 2.44.0 7.1 7.1 6.9 0.8 0.63.0 5.7 5.7 5.5

Excav. [w] 1.9 10.7 10.7 10.46.013.814.3 14.3 3.61.08.38.68.64.51.3

Rocksup. [w] 14.3 14.3 13.8 1.9 6.0 10.7 10.7 3.61.08.38.68.610.4 4.51.3

Excav., muck,

supp, shotc [y]

Tunnel: 0.83 0.1 (=42.9w),

Shaft 0.11 (=5.7w)

Tunnel: 0.62 0.1 (=32.1w),

Shaft 0.07 0.1 (=3.8w)

Tunnel: 0.49 0.1 (=25.7w),

Shaft 0.06 0.1 (=2.9w)

Access port.[w] 12-16 12-16 12-16 12 1212-16 12-14 12-14 12-14 12-1412 10-12 10-12 10-12 10-12

Shaft

3+000

4.3+380 –

3+000

1.0+000 –

0+900

2.0+900 –

1+800

3.2+670 –

1+800

Shaft

3+000

4.3+380 –

3+000

1.0+000 –

0+900

2.0+900 –

1+800

Shaft

3+000

4.3+380 –

3+000

3.2+670 –

1+800

2.1+800 –

0+900

3.2+670 –

1+800

Section

1.0+000 –

0+900

Tunnel: 28 m/w, Shaft: 10.5 m/w Tunnel: 35 m/w, Shaft: 14.0 m/wTunnel: 21 m/w, Shaft 7.0 m/w

Progress

2 shifts per day of 8 hours, 7 days a week, including drilling, blasting, mucking, scaling, rock support and concrete lining

Working condition

Excavation excavation from 3 sides and counter heading: 1) 0+000 – 0.900m, 2) +670 – 0+900m, 3)2+670 – 1+800m, 4) 3+380 – 3+000m and shaft at approx. 3+000m

Time estimation for tunnelling

0.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

160.0

180.0

200.0

220.0

240.0

260.0

280.0

300.0

-0+200 0+000 0+200 0+400 0+600 0+800 1+000 1+200 1+400 1+600 1+800 2+000 2+200 2+400 2+600 2+800 3+000 3+200 3+400

0.00

100.00

200.00

300.00

400.00

500.00

21m/w

28m/w

35m/w

1.5%

Intake

Tunnel

Powertunnel

Surge

Tank

Shaft

Power-

house

21m/w

28m/w

35m/w

14 / 10,5 / 7 m/w

21m/w

28m/w

35m/w

Excav., muck.,supp.,shotc.

Concrete lining

Excav., muck.,supp.,shotc.

Chainage [km]

Time (weeks)

Elevation (m asl)

Above: Figure 7 – RMi rock support chart for discontinuous ground,

after Palmström (2000); Left: Figure 8 – Schematic conﬁguration of

convergence, extensometer and inclinometer measurements

Figure 9 – Time estimation for tunneling, best-case scenario for an excavation with three heading faces and counter heading

WWW.WATERPOWERMAGAZINE.COM APRIL 2010 37

TUNNELLING

measures will include grouting and icing of soft grounds. To evaluate

the effect of surface subsidence, extensometer grid systems in combina-

tion with a groundwater monitoring system will be installed.

CONVERG ENCE MEASU RE MENTS

During excavation of the tunnel, convergence measurements have been

taken and monitoring of deformation to the excavation chamber was

undertaken. Deformation of the excavation chamber is a result of stress

redistribution leading to increased stress in some parts and a reduction

of stress in other areas. Monitoring of this redistribution is necessary to

ensure stability of the construction. Convergence monitoring includes

in-situ measurements of the excavation chamber, but can sometimes

also require surface levelling and the use of surface installations such as

extensometer and inclinometer units along the axis of the tunnel.

Arrangement and installation – A standard cross-section for correct

data acquisition has been deﬁned for the levelling of the crown and

sidewalls to monitor and record deformations. The distance between

the single convergence measurement stations must be under 10m.

Additional installation of pressure cells in the seam between rock

and shotcrete was also recommended to evaluate rock pressure. An

additional radial load cell to measure the concrete pressure was also

recommended every 50m. A standard cross-section for convergence

measurements must be comprised of at least ﬁve reading points to

ensure complete data acquisition of the crown, the sides and the base

of the tunnel cross section (Figure 8). The installation of the reading

points must be carried out directly after the installation of the support

so as to capture the initial deformation. An early reference measure-

ment must be carried out to assess the later data.

Interval of measurements – The time of the reference measurements

has been documented on the Poubara project. The following conver-

gence measurements are carried out quickly and must be executed on

a daily basis until the deformation has settled to an acceptable level.

The level of tolerance is dependent on the behaviour of the rock mass.

Deformations of 5 to 10cm are already critical for a brittle rock mass

and might be enough to produce a rock failure while deformations up

to 15cm in a ductile rock mass are still non-critical. An evaluation of

the fracture behaviour must be assessed to deﬁne a tolerable limit of

deformation. Once deformation is assessed to be below the tolerance

level, convergence measurements can be carried out on a weekly or

monthly basis. The time taken for one standard cross-section conver-

gent measurement is typically 10 minutes.

ESTIMAT IN G THE TUN NE LLING CO NS TRUCTIO N TIME

General – The main parameters guiding an estimation of tunnelling

progress include the available work force (teams, shifts), the machinery

and the maximum size of the construction site and its access routes.

The normal construction method is from one side only and represents

the slowest mode of excavation. The fastest progress can be made by

adopting simultaneous excavation from multiple tunnel endings. The

geological conditions in the project area favour a two- sided or even a

simultaneous excavation from three sides. The main parameter used for

the estimation of tunnelling progress is the weekly excavation progress.

This parameter was set at 21, 28 and 35m per week corresponding to

a daily progress of 3, 4 and 5m.

Construction time estimations – Excavation with one heading face

Daily progress is estimated using the parameters of work force and

machinery available for the main tunnelling construction. A constant

progress of 3, 4 and 5m per day is expected.

This constant progress can be achieved by two to three shifts per day,

with eight to ten hours per shift. The main tunnelling works include the

drilling and loading of blasts, scaling of loose material after blasting,

mucking, installation of ventilation and drainage units, and the installa-

tion of rock supports. The time for completion of the main excavation

works for this single sided excavation ranges from 2.52 (3m/day), 1.89

(4m/day) and 1.51 (5m/day) years depending on the daily progress.

Excavation with two heading faces – The time required for tunnelling

can be shortened substantially by a simultaneous excavation using

two heading faces. The following estimations were made by adopting

the same parameters mentioned above. Excavations using two portals

can yield time-savings of approximately 50 per cent. The two head-

ing faces are situated at the two tunnel endings with equal sections of

approximately 1600 m. The time for completion of the main excava-

tion works for the two sided excavation ranges from 1.46 years (3m/

day), 1.09 years (4m/day) and 0.87 years (5m/day).

Excavation with three heading faces – The fastest completion of the

tunnel can be achieved by a three-sided excavation. This involves

an intensive planning of the construction site taking into account

an economic evaluation of the available workforce, machinery and

access routes. Two portals are located at the end of tunnel and one

additional heading can be installed at the fault, 1800 m from the dam.

Each section consists of equal parts of 900 m. Time for completion

of the main excavation works for the three sided excavation ranges

from 1.05 year (3m/day), 0.84 year (4m/day) and 0.67 year (5m/day)

for each heading operation.

Estimation of quantities – Finally, Figure 10 provides estimations of

the consumption of different support materials.

Cesar Adolfo Alvarado-Ancieta (Peru), Civil Engineer,

Dipl.- Ing., M. Sc., Director of Project, Head Hydropower

Uwe Wackwitz, Maximiliam Riehl (Germany), Dipl.-

Geologists, GAUFF GmbH & Co. Engineering KG,

Patrick Yalis Ongalla (Gabon), Ing. Electrical - Deputy

Coordinator / Resident Engineer, Direction Générale de

l’Energie et des Ressources Hydrauliques, Republic of

Gabon, Franceville

IWP& DC

References

Hoek, E. and Brown, E.T. (1997): Practical estimates of rock mass strength. - Int.

J. Rock Mech. & Mining Sci & Geomechanic Absracts, Vol. 34(8), pp. 1165-1186.

Bieniawski, Z.T. (1989): Engineering rock mass classiﬁcations. - New York: Wiley.

Petterson, S-A, Molin, Hans (1999): Grouting & Drilling for Grouting. Purpose,

application, methods and equipment with emphasis on dam and tunnel projects -

Atlas Copco.

Palmström, A (2000): Recent developments in rock support estimates by the

RMI. - in: Journal of Rock Mechanics and Tunneling Technology, Vol. 6, No. 1, pp

1 - 19; ISRMTT.

Palmström, A. (1995): RMi - a rock mass characterization system for rock

engineering purposes. - Dissertation at the Departement of Geology, Faculty of

Mathematics and Natural Sciences, University of Oslo.

Norwegian rock and soil engineering association (2000): Engineering Geology and

Rock Engineering, Handbook No. 2. - Oslo: NRSEA.

U.S. Army Corps of Engineers (1997): Tunnels and shafts in rock, engineering and

design. - Engineer Manual No. 1110-2-2901; Washington, DC: USACE.

Rock bolts

0 1000 2000 3000 4000 5000

Shot-

crete

Mesh wire

Steel archbase lock

Steel arch

Shotcrete = [m

] / Other[t]

Material(s)

Figure 10 – Estimation for total material consumption: shotcrete, rock bolts,

mesh wire, steel arch and steel arch base lock

38 APRIL 2010 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

PUBLIC ACCEPTANCE

NE of the key elements to integrated water resource

management (IWRM) is that water development

and management should be based on a participatory

approach, involving users, planners and policymakers

at all levels. This was again highlighted at the World Water Forum

V held in Istanbul in 2009.

Some of the outcomes highlighted in sessions that covered this sub-

ject showed the beneﬁts of a ‘bottom up’ approach when planning

and implementing IWRM. Governments need to ensure that mean-

ingful stakeholder participation is a statutory requirement at all levels

and phases of IWRM.

It was also suggested that donor organisations, when dealing with

governments in the developing world, need to be aware of the needs

of the beneﬁciaries of development projects at a local level. Problems

were highlighted where the intentions of projects were well meaning,

but the ongoing costs and charges to local beneﬁciaries were unsus-

tainable. It was considered local stakeholder consultation would be

beneﬁcial to measure and assess the real needs and impacts of ongo-

ing costs relating to such projects.

The inclusion of consultation with affected stakeholders and local

NGOs, and the involvement of environmental experts in project

design, is now generally part of any large water project - no matter

what stage of development a county has reached. Rightly or wrongly,

in recent years these processes have been driven by the expectations of

the international public which in turn has been reﬂected in the policies

of lending institutions such as the World Bank.

It is predicted that public awareness and acceptance will play a

signiﬁcant role in future water development proposals. There is

no one size ﬁts all approach. One must be aware of the govern-

ance structures and cultures that are unique to different countries

and audiences.

When formulating strategies one must be conscious that water

development projects are long term and have a life that can stretch

over many human generations. There are many examples in New

Zealand where during the development process for the sake of

progress and ‘national good’, the rights of local stakeholders have

been ignored. I am not questioning the correctness of these decisions

or approaches as they were made in the context of a different era than

exists today. However many of these grievances have been passed

from generation to generation and are causing problems and resist-

ance to development today.

There are also examples in New Zealand where projects have

been promoted and a signiﬁcant degree of agreement has been

reached with stakeholders through a consultation and negotiation

process. Others have achieved the same result through using the

regulatory planning framework and a protracted litigation proc-

ess. Both methods appear to have achieved the same short term

outcome. However, I would suggest that the consultative approach

will achieve a more positive and sustainable long term solution in

the eyes of the stakeholders and public. In using this approach one

ensures a degree of ownership of the outcomes by stakeholders. I

believe this can result in signiﬁcant long term beneﬁts. I also think

this approach will result in reduced long term cost to the project

owner and a smoother path for achieving re-consenting or altera-

tions to the project in the future.

For many projects there is a signiﬁcant focus on public awareness

to gain initial approval but less emphasis on ongoing public aware-

ness programmes and enhancing the long term image of the project.

As one speaker described the situation, it is a matter of building up

and maintaining a ‘bank account’ of goodwill or positive image. This

bank account can be very helpful to ‘draw down’ when embarking

on a new project or alteration to an existing project, and can also

soften the impact on public perception when things go wrong or not

quite as planned.

As part of developing the bank account, ongoing credibility is the

most vital element. To achieve this one’s approach to delivering infor-

mation and promoting the project must in my opinion be honest

and transparent. Apart from a professional moral obligation to the

stakeholders in any project there are a number of other reasons to

support this approach.

In the past there are a number of instances where public relation

campaigns have successfully used ‘spin’ or an advocacy stance when

promoting a project. This approach in today’s information loaded

society is fraught with risk especially to the long term credibility of

any project proponent.

With wide access to communication mediums in both the

developed and developing world it is very hard to hide the facts

for any length of time. As an example, in my travels with ICOLD

through many developing countries, despite varying levels of

standards of living and technology, many communities have

access to a satellite dish along with information and the views of

the outside world.

In putting forward consistent messages and being prepared

to address both the positive and negative aspects of any project,

while not necessarily gaining agreement from all stakeholders, a

project proponent does build credibility and a degree of tolerance

from those with opposing views. This also has the advantage of

avoiding any myths being created in the media by groups opposed

to the project.

It is true in the past that the public have not been given balanced

information by opponents to some water development projects. In

countering this situation I think we must be careful of falling into the

trap of either promoting balance using the opponent’s tactics, (ie pub-

lishing unbalanced arguments) or trying to indoctrinate any target

groups. We must try and establish the high ground and credibility in

the initial stages of any public relations exercise.

When promoting water development projects we should present

all alternatives in an holistic approach. All alternatives to meet-

ing the world’s water and energy problems have both positive and

negative environmental and social impacts. It should be accepted

Enhancing the image of water

development schemes

Public awareness and acceptance will play signiﬁcant roles in future water development

projects. Peter Mulvihill believes that we should be working towards a long term

commitment to enhance the lifelong image of water development schemes. It should not

just be a quick ﬁx obtained for project approval