Journal of Civil Engineering and Architecture 13 (2019) 151-177 doi: 10.17265/1934-7359/2019.03.001

Mosul Dam: Geology and Safety Concerns

Nasrat Adamo1, Nadhir Al-Ansari2, Varoujan Sissakian3, Jan Laue2 and Sven Knutsson2

1. Private Consultant Engineering, Sågaregränd 3 lgh 100260358 Norrköping, Sweden

2. Lulea University of Technology, Lulea 97187, Sweden

3. University of Kurdistan, Howler, KRG, Iraq and Private Consultant Geologist, Erbil 44001, Iraq

Abstract: Mosul Dam is an earth fill dam located on the River Tigris northern part of Iraq. The capacity of its reservoir is 11.11 billion cubic meters which makes it the fourth biggest dam in the Middle East. From geological perspective, the dam is located on double plunging anticlines. The rocks of the site are mainly composed of highly jointed and karistified alternating beds of limestones, gysum and marls, since the impoundment of the reservoir seepage of water was recognized under the foundation of the dam. To stop or minimize the seepage, intensive grouting operations were conducted. Recent investigations and evaluation of the conditions of the dam indicate that it is in a critical situation. In this paper, consequences of the dam failure are discussed and possible solutions are given. Key words: Mosul Dam, karst, infiltration, dam foundation, dam failure.

1. Introduction

Mosul Dam, the largest dam in Iraq, is also one of

the large dams in the world and the fourth largest

reservoir in the Middle East. It is located on the Tigris

river in northern Iraq approximately 50 kilometers

north west of Mosul city and 80 kilometers from the

Syrian and Turkish borders.

Although the dam is about 500 km on a straight line

distance to the north from Baghdad a flood wave study

showed that such wave resulting from the dam collapse

could reach Baghdad within 48 hours causing

devastating results for the whole reach and its

population.

The maps in Figs. 1 and 2 show the location of this

dam.

2. History

Mosul dam site was first investigated in 1952 by an

American firm, after which four investigation

campaigns were conducted in the sixties and seventies.

The first three reports prepared by American, Finish

and Soviet consultants agreed on the difficulties

Corresponding author: Nadhir A. Al-Ansari, professor,

research fields: water resources and environment.

involved in the site for the construction of a high dam

based on the conditions of foundations due to the

presence of gypsum, gypsum anhydride and gypsum

breccias. The fourth study report prepared by Swiss

consultants concluded that the dam can be built and

that the foundation can be sealed by intensive blanket

grouting together with a deep grout curtain. A

conclusion which proved later on to be very short

sighted. The construction of the dam was initiated in

1980 and completed in 1985. The first sign of trouble

appeared at the first filling in the spring of 1986 [1].

Maintenance foundation treatment by continuous

massive grouting program was envisaged as a solution,

but the problem persisted and mass grouting continued

ever since as a maintenance measure with no signs of

an end in the future. Moreover sinkholes which had

started to form since the filling of reservoir evolved

into common phenomena [2, 3].

3. Dams Features

Mosul Dam scheme consists of three parts:

(1) Mosul 1, which is the main embankment dam

and main power station.

(2) Mosul 2, the re-regulating dam and power station

located 9.1 km downstream of the main dam; distance

D DAVID PUBLISHING

152

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Fig. 2 Map o

ul Dam location

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153

of the dam is

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4. Regiona

The geol

Pleistocene

rocks of the

Group (Fath

karstified la

followed by

limestone fo

dam area is

low mounta

NW-SE dire

Fig. 5 is a G

area.

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is karstificat

Typical diss

the dam sit

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during and

were discov

Fig. 10 [7].

Fig. 5 Goog[5].

al Geology

logy of the

to recent age

Lower to Mi

ha Formation

ayers of lim

y Oligocene t

formation. Th

characterized

ainous area. T

ection and cha

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significant mo

tion in the ar

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after operat

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e alluvial dep

iddle Miocene

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ange to almo

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orphological

rea and in the

tification phe

oles are show

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reservoir later

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osul Dam: Ge

belongs to

posits overlay

e age Lower

formed of hig

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ocene age Je

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enomena clos

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close to the

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ying

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se to

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The main ge

ety are give

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1) The karsts

ervoir area.

2) The ex

mations in d

rl layers and

ddings.

3) The prese

led Der Wadi

Figs. 9 and 1

karsts phe

stream area of

The continual

en new conn

ning below a

solution prob

The existenc

estone layers

utma east Anti

rns

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ological fact

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xistence of

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s at the Dam

tors influenc

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in the dam si

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the form o

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the groundw

he dam site c

y karstified

oundations ga

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155

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ing the dam

ects will be

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ng with soft

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water aquifer

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the extent of

of sinkholes

voir.

inkholes will

water aquifer

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ave rise to the

, FI = flat iron

5

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156

Fig. 6 Karst

Fig. 7 Karst

tified gypsum i

tified gypsum w

Mo

in the upper m

within the Fath

osul Dam: Ge

member of the F

ha formation a

eology and S

Fatha formatio

at Atshan antic

Safety Concer

on [6].

cline, South of

rns

Mosul Dam [66].

Fig. 8 Karst

Fig. 9 Enlardam site [5].

tified gypsum w

rged Google Ea

Mo

within the Fath

arth image sho

osul Dam: Ge

ha formation a

owing many sin

eology and S

at Atshan antic

nkholes (dark

Safety Concer

cline, south of

spots encircled

rns

Mosul Dam [6

d by red color)

6].

), in the upstre

157

am area of the

7

e

158

Fig. 10 Resu

formation o

which form

and the res

dissolution

present abov

dynamics ha

of clayey

underneath c

particles and

clayey matr

during the

termed as t

thickness ran

first layer wa

section and

three layers

GB3 was d

chute ski ju

dangerous d

grouting of t

11 shows th

ults of bathyme

of highly dev

easy passage

ervoir water

of gypsum a

ve and below

ad caused th

marls and

cavities form

d anhydride b

rix. Four su

geological in

the Gypsum

nging betwee

as found at a

it was marke

were at high

discovered at

ump. The G

due to their

the deep grou

he geological

Mo

etric survey of

veloped cond

es to the flow

r. This had c

and gypsum

these limesto

he collapsing

gypsum anh

ming beds of b

blocks embed

uch layers w

nvestigations

m-Breccias la

en 8 meters an

depth of 80 m

d as the GB0

her levels. Th

t the founda

GB layers pro

erratic beha

ut curtain und

cross section

osul Dam: Ge

f Mosul Dam r

duits and cav

w of ground w

caused exten

anhydrite ro

one layers. Th

of whole la

hydrite into

brecciaed gyp

dded into a lo

where discov

s and they w

ayers which

nd 16 meters.

meters in the r

0 layer. The o

e last one i.e

ation of spill

oved to be v

avior during

der the dam.

n under the d

eology and S

reservoir carrie

verns

water

nsive

ocks

hese

ayers

the

psum

oose

vered

were

had

The

river

other

. the

lway

very

the

Fig.

dam.

Fig

Dam

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and

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are

I

dev

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bor

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mor

exte

The

wor

Safety Concer

ed out in 2011

. 12 gives the

m central part

During the ex

d flip bucket

ctacular cavi

shown in the

n Fig. 14 the

velopment in

blematic are

imation of th

ing and field

his figure ind

e. Below th

gment karsts

fine the end o

eria of the

ending the c

re safety. In

ended below t

e design crit

rks are given

rns

by a Luleå uni

e lithological

t.

xcavation wo

the GB3 lay

ties and open

e photographs

dotted line is

n sections 69

a as visualiz

his line was

d permeability

dicate some of

his line acco

cease to ex

of the deep g

grout curta

curtain 20 m

actual fact

this line after

eria and full

in Ref. [8].

iversity PhD st

l column und

orks of the sp

yer was expo

n joints and c

s in Fig. 13.

s the estimate

9-87 which

zed by the d

based on th

y testing. The

f the points o

ording to th

xist and this d

grout curtain

ain, however

meters below

the depth o

r impounding

l details of

tudent [7].

der the Mosul

pillway chute

osed showing

cracks. These

ed karsts line

is the most

designers, the

he results of

e black spots

f major grout

he designer’s

depth should

n. The design

r, called for

this line for

f dissolution

the reservoir.

the grouting

l

e

g

e

e

t

e

f

s

t

s

d

n

r

r

n

.

g

Fig. 11 Geoeast to west w

ological long sewhich are stack

Mo

ection under dked together in

osul Dam: Ge

am axis (the lon the above figu

eology and S

ong extending ure) [4].

Safety Concer

from east to w

rns

west shown has

s been divided

159

d in parts from

9

m

160

Fig. 12 The lithological co

Mo

olumn under th

osul Dam: Ge

he Mosul Dam

eology and S

central part (r

Safety Concer

red rectangles

rns

indicate the GGypsum Bresci

a layers) [4].

Fig. 13 Crac

cks and cavitie

Mo

es in the GB3 l

osul Dam: Ge

ayer below spi

eology and S

illway’s chute

Safety Concer

and flip bucke

rns

et [9].

161

1

162

Fig. 14 Estimtake locations

The sch

mechanism

Groundwate

wash the Ma

formed in g

collapse of m

forming con

The grou

during const

construction

cavern struc

amount of

excavation

performing

caverns in t

protection sh

drainage tun

amounts o

intake/tailrac

the excavati

quality of se

river water

concentratio

water throug

Further stud

very large W

from long d

below and i

mated karsts ls) [9].

hematic diag

of the gypsu

er flowing thr

arley clay fro

gypsum/anhy

more gypsum

ntinuous layer

undwater reg

truction espe

n of the pump

ctures and th

seepage flow

of the cave

extensive gro

the form of b

hells around

nnels all round

f seepage

ce tunnel wa

ion face ahe

eepage water

quality and

on of sulfate

gh gypsum a

dies showed th

Wadi Der Ma

distance upstr

independently

Mo

ine in the prob

gram Fig.

um/breccias

ough caverno

om above into

ydrite layers

m/anhydrite in

rs of the brecc

gime was s

ecially in con

p storage sche

he intake/tailr

w was trem

rns was onl

outing work

boxes which

theme, in ad

d the caverns

flow the

as only possib

ead of excav

r was much d

it contained

es indicating

and gypsum a

hat this wate

alih aquifer w

ream and wh

y from the ri

osul Dam: Ge

blem area (sect

15 shows

layer format

ous limestone

o cavities alre

and causing

nto these cav

cias.

studied caref

nnection with

eme undergro

race tunnel.

mendous and

ly possible a

all around th

also served

ddition to driv

. Due to the l

driving of

ble after grou

vation work.

different from

d a much hig

the passage

anhydride lay

r belonged to

which is being

hich was runn

ver aquifer. T

eology and S

tions 69-87) (T

the

tion.

e can

eady

g the

vities

fully

h the

ound

The

the

after

hese

as a

ving

large

the

uting

The

m the

gher

e of

yers.

o the

g fed

ning

This

aqu

imp

of o

of

perf

the

diff

pum

con

the

exp

6. (Ge

G

As

this

loca

bec

this

flow

eve

diss

exp

cm/

at a

fron

cou

Safety Concer

The black spots

uifer was also

pounding. Fig

one spring wh

the tunnel

forming muc

Wadi Der M

ficulties it had

mp storage

ntributed to th

right bank

plained later o

Grouting eneral)

Grouting such

such groutin

s will result in

ally in adjace

comes chemic

s zone of satur

w continuous

entually pass

solution rate

perience it is

/sec in a 2 cm

a rate of few c

nt. If the velo

uld dissolve at

rns

show location

o fed directly

g. 16 is a pho

hich had erup

and could

ch grouting w

alih aquifer i

d caused duri

scheme, but

he formation

downstream

on.

of Gyps

h formations

ng begins to

n an increase

ent parts. Wa

cally saturated

ration no furt

s, the zone

ses from th

es accelerate

known that s

m wide gypsu

centimeters pe

ocities were a

t a rate of 9 m

ns of some of th

y from the re

otograph of th

pted during th

only be st

works. The Im

is not only du

ing the constr

t it is also

of a series of

m of the m

siferous F

is very trick

seal some se

e of the hydra

ater passing o

d within a flow

ther dissolutio

moves dow

he exit. At

e again sha

seepage velo

um vein, it sho

er year from

about 10-2 cm

meter per year

he major grout

eservoir after

he water flow

he excavation

topped after

mportance of

ue to the great

ruction of the

believed it

f sinkholes at

main dam as

Formations

ky operation.

eepage paths,

aulic gradient

over gypsum

w path and in

on occurs. As

wnstream and

this stage,

arply. From

ocities of 10-4

ould dissolve

an advancing

m/sec gypsum

r. Dissolution

t

r

w

n

r

f

t

e

t

t

s

s

.

,

t

m

n

s

d

,

m 4

e

g

m

n

Fig. 15 Sche

Fig. 16 The from Wadi D

ematic diagram

flow (360/sec)er Malih aquif

Mo

m showing the

) from undergrfer [9].

osul Dam: Ge

formation of a

round aquifer

eology and S

a breccias laye

into the intake

Safety Concer

er.

e/tailrace tunn

rns

nel of the pump

p storage schem

163

me originating

3

g

Mosul Dam: Geology and Safety Concerns

164

occurs until seepage water reaches a calcium sulfate

saturation of 2,000 ppm. Hence the dissolution zone

moves downstream as greater quantities of unsaturated

water attack a gypsum vein [10, 11].

From this it seems that it is most difficult to seal a

cracked or fissured gypsum formation permanently,

especially in the presence of other formations

which are also jointed, cracked and highly conductive

to flow as in the case of Mosul dam foundations

especially in view of the very high heads created by the

reservoir.

Nevertheless, the designers of the dam considered

that grouting should be used as the anti-seepage

element for the deep cutoff under the dam, while

construction of positive cutoff in the form of concrete

diaphragm could have been used instead. A better

choice of anti-seepage measure should have been the

construction of concrete diaphragm especially that

hydro-fraise machines which could go to a depth of 140

m for the construction of such diaphragm were

available and the work could have been done from river

bed level.

7. The Grouting Works Program

An extensive grouting works program was

anticipated by the designers in view of the soluble

nature of the foundation and its configuration. One

report in 1991 estimated that dissolution intensity at

Mosul dam foundations ranged from 42 to 80 tons per

day. This process coupled with the presence of karstic

limestone and calcareous marls as well as anhydrite

presented a very problematic and difficult foundation,

which was anticipated by everybody since the

beginning, and the consultants and the IBOE

(International Board of Expert) which had been

appointed to follow the design and construction of the

dam agreed the design outlines of the grouting works

and their acceptance criteria only after extensive

discussions and lengthy meetings.

The first element of grouting works is the contact

blanket grouting covering the contact area of the clay

core with the foundation surface to close all

preferential seepage paths by filling all fissures and

joints and protect from concentrated seepage flows

directly under the core. The second is the deep three

rows curtain which extends down to the karst line.

A concrete grouting gallery was constructed at the

bottom of the cutoff trench so as to continue the grout

curtain works without interfering with the embankment

construction. It was also meant to be used for

continuous observation of the curtain performance

during operation. Pairs of open pipe piezometers were

installed upstream and downstream of the curtain, one

pair at each section of the gallery in order to be able to

measure the efficiency of the curtain. The gallery

proved to be of immense usefulness to carry out

maintenance grouting of the curtain in what was to be

defined as massive grouting, a process which has

continued from the first filling of the reservoir up to

now. The required efficiency of the grout works was to

reduce the seepage flow to safe limits to allow the

water upstream the curtain to be saturated with calcium

sulfate and therefore stopping any further dissolution

of gypsum or t hydration of anhydrites. In the

limestone beds grouting was to plug and seal all

anticipated cracks and joints and hinder the free flow of

seepage. The criteria were expressed in terms of

Lugeon units of rock mass permeability values which

were defined specifically for each of the blanket

grouting, and the various depth and parts of the grout

curtain. During the progress of the work it was evident

that while cracks and cavities in limestone could be

reasonably filled, the criteria could not be achieved

over many locations in the GB beds in the deep curtain

at depth which remained open to seepage and were

described at the time as windows. These windows

remained open in many locations under the central part

of the dam even after the full scale impounding of the

reservoir had started in the spring of 1985 when the

grouting problem was not yet settled; a thing which

could not be stopped due to the early closure of the

river in October 1984.

The beds

were the bre

difficult to g

again to the

within the lo

accelerated d

during the li

In spite o

tried to solv

mix designs

persisted an

different sol

8. Problemof the Res

The first

requiring m

resulted in r

following:

8.1 Seepage

As water

springs bega

once were

spillway buc

further left.

measuremen

of seepage w

Fig. 17 Cheperiod Febru

where this p

eccias aforem

grout, and if te

flow after th

oose matrix.

dissolution an

ifetime of the

of the many g

ve this probl

and using di

nd even the u

lutions was eq

ms Encountervoir (198

filling uncov

much serious

remedial wor

Springs in L

r level in th

an to develop

close to the

cket structure

. The seepa

nt and chemic

was 830 l /se

emical test resuary-August 19

Mo

roblem had s

mentioned wh

emporarily se

he dispersion

This situatio

nd formation

e dam.

grouting tech

em including

ifferent pressu

use of chemic

qually unsucc

tered durin85-1988)

vered many s

s attention a

rks. All is su

eft Bank

he reservoir

in this bank.

e right and l

e and chute an

age water w

cal testing. T

econd (on 22

ults of water s986 [12].

osul Dam: Ge

severely occu

hich proved v

ealed they ope

of the grout

on led later o

n of large cav

hniques that w

g changing g

ures, the prob

cal grouting w

cessful [8].

ng First Fill

serious probl

and studies

ummarized in

increased m

The more ser

left sides of

nd others wer

was collected

The total quan

2nd March 19

seepage from t

eology and S

urred

very

ened

mix

on to

vities

were

grout

blem

with

ling

lems

and

n the

many

rious

f the

re at

for

ntity

986)

whi

Thi

seco

Che

indi

Thi

met

seep

wat

Aug

F

mor

disc

the

add

Arr

pipe

wer

also

chu

and

to t

perf

outf

curt

A

of s

not

the most impo

Safety Concer

ich correspon

is could yield

ond at full

emical tests

icating leachi

is is equival

ters. Fig. 17 s

page from th

ter level was

gust 1986 [12

Further hydro

re open pipe

cover seepage

depth of the

ding another

rangements w

es to dischar

re covered by

o constructed

ute to stop se

d across it from

the left bank

formed also

flanked by

tain.

Although thes

seepage and t

eliminate the

ortant five spri

rns

nded with a re

d, if extrapola

reservoir e

showed an

ing of gypsum

ent to void

shows the obt

he most impo

s raised duri

2].

geological in

e piezometer

e paths show

e grout curtai

line of gr

were made to

rge away the

y filter materia

d along the le

eepages flow

m the upstrea

k grout curta

to protect th

water seepin

se additional w

the dissolutio

em.

ings vs. water

eservoir level

ated to 2 cub

elevation of

increase in

m at a rate of

volume of

tained test res

ortant five sp

ing the perio

nvestigations

rs and use o

wed the need f

in at certain

routing hole

o catch som

e water safel

al. Anew deep

eft side of th

wing undernea

am direction. A

ain along da

the left bank

ng around t

works reduce

on of gypsum

level was rais

165

l of 304 masl.

ic meters per

f 330 masl.

salts content

f 30 tons/day.

10-15 cubic

sults of water

prings as the

od February-

by installing

of tracers to

for extending

sections and

s in others.

e springs by

y and others

p curtain was

he spillway’s

ath the chute

An extension

am axis was

k from being

the executed

ed the amount

m, they could

sed during the

5

.

r

.

t

.

c

r

e

-

g

o

g

d

.

y

s

s

s

e

n

s

g

d

t

d

e

166

8.2 Deterio

Dam

Similar m

quality from

which was

coffer dam

alarming d

transmissibi

indicated in

The incre

by reduction

sections in th

the increased

to increased

various par

difference in

and downst

pairs in the

and still are

the formatio

indicate the

procedure.

As water

formation of

to the stab

introduction

called (Mas

Fig. 18 Incrfor the increawas due to th

ration of the

measurements

m under the da

collected fro

no 6 used du

dissolution o

lity during

Fig. 18.

ease in seepag

n of the grou

the river chan

d size of the

d dissolution.

rts were m

n the hydraul

tream piezom

grouting gal

up till today

on of cavitie

need for filli

level was re

f large cavitie

bility of th

n of introducin

ssive Groutin

reased transmiased head showe washing awa

Mo

e Grout Cur

of seepage w

am at the river

om the pond

uring river di

of gypsum

the same

ge quantity w

ut curtain effi

nnel and coul

aforemention

Grout curta

measured by

ic head betw

meters that w

lery. These p

as the only m

es in the fo

ing grouting a

eaching high

es was posing

he dam. Th

ng a new tech

ng) to inject

issibility vs. timwn in Fig. 17. ay of gypsum p

osul Dam: Ge

tain under M

water quantity

r channel sect

d created by

iversion, sho

and increa

period [12],

was accompa

ciencies in m

d be attribute

ned windows

in efficiencie

observing

een the upstr

were installed

piezometers w

means to disco

oundation and

as a maintena

er elevations

g a constant th

his required

hnique which

thick grout

me (February-A(Dissolution ha

particles filling

eology and S

Main

y and

tion,

y the

owed

ased

, as

anied

many

ed to

due

es at

the

ream

d in

were

over

d to

ance

s the

hreat

the

was

(by

add

ben

carb

requ

con

bor

from

and

ope

from

form

this

wor

inje

was

tons

wer

8.3

I

the

bee

reac

insp

sink

met

righ

was

August 1986), ad leveled off

gs in the cracks

Safety Concer

ding 3 weigh

ntonite that n

bonate using

uired the fas

nditions by tru

eholes lined w

m the crest of

d injected in

eration know

m 1986 up to

ms of conven

s procedure is

rld. Grouting

ected grouting

s 25,000 tons

s are of mass

re pumped in

Developmen

n September

reservoir wa

en drawn dow

ched during

pection revea

kholes at the

ters from t

ht abutment.

s located also

and continuouafter the initia

s and joints of

rns

ht sand to 1

needed to be

g 1:1 water

st transport o

uck mixers to

with steel pip

f dam to the ga

the require

wn as “Massi

o the present

ntional grouti

s probably a

g records sho

g from 1986

of injected s

ive grouting

the following

t of Sinkholes

1986 an insp

s carried out

wn to EL.316.4

the previo

aled the dev

right bank at

he contact

One sinkho

at about 1 kil

us dissolution oal increase in tthe rock forma

1 weight cem

e activated u

r/cement rat

of the grout

o the location

pes that penetr

allery, where

ed treatment

ive Grouting

days in addi

ing as needed

unique case

ows that the

up to and inc

solids out of w

and even larg

g years [8].

s

pection of the

when the wa

4m from El.3

ous flood s

velopment of

many points

of the dam

ole of major

lometer or so

of gypsum in ththe first three ation) [12].

ment, 4% of

using sodium

tio). It also

t mix in dry

of three deep

rated the core

it was mixed

zones. This

g” continued

ition to other

d. The use of

in the whole

e quantity of

cluding 1988

which 12,200

ger quantities

e right rim of

ater level had

09m which it

season. This

f a series of

at about 150

m with the

r proportions

o away. These

he same periodmonths which

f

m

o

y

p

e

d

s

d

r

f

e

f

8

0

s

f

d

t

s

f

0

e

s

e

d h

sinkholes sh

layers which

the operatio

1991 to 199

the downstr

followed a st

the dam and

were indicati

Careful obse

the ground

settled gra

underground

fluctuation

operation of

south of the

to Der Male

the dam area

the reservoir

the right rim

in Fig. 19, an

in Fig. 20 sh

Fig. 19 Loca

howed dram

h were expos

on years of th

8 new series

ream area o

traight line al

at about 400

ion of an acti

ervations and

surfaces at

adually and

d cavities wh

of the wate

f the reregula

main dam an

eh undergrou

a and being c

r through the

m. The locatio

nd the photog

how the initia

ation of downs

Mo

atic solution

sed on the sh

he dam and s

of sinkholes

f the dam.

lignment para

meters away

ive process of

d measuremen

the sinkhole

d collapsed

ich were form

er level res

ating dam 8 k

nd partly due

und aquifer w

charged from

gypsum laye

on of these sin

graphs of sink

al phase of its

stream sinkhol

osul Dam: Ge

n of the gyp

hore line. Du

specifically f

began to form

These sinkh

allel to the ax

y. These sinkh

f rock dissolut

nts indicated

es locations

d in enlar

med partly by

ulting from

kilometers to

to the connec

which runs un

m the right rim

ers day lightin

nkholes is sh

khole (SD2) g

s formation in

les which had d

eology and S

psum

uring

from

m in

holes

xis of

holes

ution.

that

had

rged

y the

the

o the

ction

nder

m of

ng at

hown

given

n the

con

shap

T

sink

aqu

stor

sink

alig

afte

ope

sink

com

B

by g

sett

sink

dam

Feb

situ

dow

I

developed duri

Safety Concer

ntractor’s con

pe after full d

The chemica

khole gave th

uifer encounte

rage scheme

kholes locatio

gnment at the

er the erosion

eration. This

khole pheno

mposition of D

By contrast to

ground surfac

tlement until t

khole at the l

m of dam sho

bruary 2002

uated close

wnstream of t

n Fig. 23, thi

ing the period

rns

ncrete paved

development.

al compositio

e same result

ered during th

tailrace tunn

on. Further fr

river bank o

n of the alluvi

spring seem

omena and

Der Maleh aq

o the right ban

ce cracking fo

the occurrenc

eft bank very

own in Fig.

without pre

to housing

he left flank

is sinkhole se

[9].

work area a

.

on of the w

ts as those fro

he excavation

nel not very

rom this area

one spring wa

ium cover du

ms to follow

its water

quifer (Fig. 2

nk sinkholes

ollowed by gr

ce of the full

y close down

22 occurred

revious warn

ng colony

eems to be lo

167

and the final

water in the

m Der Maleh

n of the pump

far from the

a on the same

as discovered

ue to spillway

w the same

has same

1).

which began

round surface

collapse, one

stream of the

suddenly in

ning. It was

150 meters

ocated on the

7

l

e

h

p

e

e

d

y

e

e

n

e

e

e

n

s

s

e

168

Fig. 20 Two

Fig. 21 Spri

o views of sinkh

ing downstream

Mo

hole SD2 at the

m of dam [9].

osul Dam: Ge

e initial stage a

eology and S

and final stage

Safety Concer

s of developme

rns

ent [9].

Fig. 22 Phot

Fig. 23 Aeri

same line of

suggestion t

the possible

9. Mosul Question o

In early 19

possible dam

Mosul Dam

released in

contract with

such study. T

ready in 198

tographs of the

ial view of the

f the other sin

to the sudden

infiltration o

Dam Flooof Badush D

984, the Mini

mage that cou

m failure and

the Tigris R

h the same co

The study be

85 showed th

Mo

e right bank si

Dam area show

nkholes on the

n collapse of

of

od Wave SDam

istry felt the n

uld be incurre

d the subsequ

River valley.

onsultant of M

ing done, and

e colossal da

osul Dam: Ge

nkhole showin

wing alignmen

e right bank .

this sinkhole

Study and

need to assess

ed as result f

uent flood w

. So it signe

Mosul dam to

d the report b

amages that co

eology and S

ng developmen

nt of downstrea

.One

es is

the

s the

from

wave

ed a

o do

being

ould

resu

prop

bey

sho

prob

for

fail

in T

be

tim

and

[13

T

Safety Concer

nt stages and sk

am sinkholes [

ult in such an

perties and in

yond Baghdad

owed that: (1)

bable cause w

the various sc

ure, the initia

Table 2, with

expected (Sc

es to various

d flooded are

].

These alarmi

rns

ketch indicatin

9].

event to both

nfrastructures

d. The main

) if failure wo

would be the

cenarios of th

al wave hydro

peak discharg

cenario A);

cities on the r

as are shown

ng results pr

ng mapped dim

h human lives

s with its imp

conclusions

ould occur at

e foundation

he reservoir w

ograph would

rge of 551,000

(3) the calc

river, max he

n in Table 2

rompted the

169

mensions [9].

s and material

pact reaching

of the study

all, the most

geology; (2)

water levels at

d be as shown

0 cumecs can

ulated travel

eight of wave,

and Fig. 24

Ministry of

9

l

g

y

t

)

t

n

n

l

,

4

f

170

Table 2 Floo

Hours/Case

0

1

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

6.0

8.0

10.0

12.0

18.0

24.0

Table 3 Floo

od wave hydro

od wave discha

Mo

ograph at vario

A

1

13

80

215

372

474

535

551

538

507

405

271

186

123

37

18

arge, time of a

osul Dam: Ge

ous initial cond

arrival and floo

eology and S

ditions of failu

B

1

13

80

210

356

452

499

510

469

469

382

266

192

136

47

2

oded areas at v

Safety Concer

re.

C

1

13

80

215

335

422

480

509

497

497

435

186

195

130

39

19

various locatio

rns

ns in the Tigri

D

1

13

80

212

325

404

453

475

460

460

405

278

198

142

49

22

is River Valleyy.

Fig. 24 Wav

Irrigation, w

grave hazar

construction

from Mosul

Dam flood w

called Badus

this size

Unfortunate

completing 3

UN econom

invasion of K

10. Safety

10.1 Evalua

From the b

the completi

by the Intern

Owner; the M

water resour

reaching saf

dam. The Bo

final selecti

previously b

diaphragm

grouting, as

works were

ve height at va

when it was c

rd on the po

n of a protect

Dam to cont

wave in case

sh Dam whic

in the hist

ly the works

30-40% of th

mic sanctions

Kuwait.

Evaluation

tion of the Da

beginning of

ion of Mosul

national Boar

Ministry of Ir

rces. This B

fe and sound d

oard however

ion of the

by others, nor

for anti-see

the last deta

not ready w

Mo

rious distances

clear that the

pulation, to

tive dam 40

tain the full v

of its failure

ch is probably

tory of dam

were suspen

he works, whi

s imposed o

n of the Da

am Safety Co

the detailed d

Dam, it was

rd of Experts

rrigation; late

oard helped

design and co

r did not have

dam site w

r of selecting

epage meas

ailed geologi

when the Con

osul Dam: Ge

s downstream

dam present

design and

km downstr

volume of M

. This is the

y a unique cas

m construct

ded in 1991 a

ch was due to

on Iraq after

m

onditions in 1

design phase u

followed clo

appointed by

er the Ministr

tremendousl

onstruction of

any saying in

which was d

positive conc

sure instead

ical investiga

nsultant had t

eology and S

of dam and tim

ted a

start

ream

Mosul

dam

se of

tion.

after

o the

r its

988

until

osely

y the

ry of

ly in

f the

n the

done

crete

d of

ation

their

prel

But

fou

adv

how

seal

for

acc

was

exc

198

com

trea

con

was

con

Con

in t

cav

of s

10.2

N

unti

revi

repo

Safety Concer

me of travel tim

liminary plan

t the Board re

ndation and g

vice to refine

wever, from r

l the brecciae

all, these bre

ept any form

s considered

cept for its fo

88 by both

mpletion and

atment works

ntinue for the

s supported by

ntractor at t

nsultant to ful

treating many

vities, of whic

solid grouting

2 Evaluation

No general rev

il 1995. A g

iew of all th

orts and me

rns

me of arrival.

nning report

cognized the

gave early w

the grouting

reaching the d

ed gypsum in

eccias beds a

m of grouting

by the dam a

oundation. Th

the Board

operation of t

s, massive a

whole life of

y training an

he urging o

lfill this task.

y grave cases

ch the case of

g materials is

of the Dam S

view of the d

general inspe

he accumulate

easurements

approved by

problem of g

warnings and

g criteria; it st

design criteri

n the foundati

are recognize

g. The dam a

as safe from

he conclusio

and Consu

the dam was

and conventi

f the dam. Th

Iraqi grouting

of both the

This team w

s of very larg

f one that too

well docume

Safety Condit

dam safety wa

ection of the

ted data and

were conduc

171

y the Owner.

gypsum in the

all necessary

topped, short

ia required to

ons once and

d now not to

as completed

in all aspects

n reached in

ultant at the

that grouting

ional, should

is conclusion

g team by the

e board and

was successful

ge dissolution

ok 5,000 tons

ented.

tions in 1995

as carried out

e dam and a

all available

cted by two

1

.

e

y

t

o

d

o

d

s

n

e

g

d

n

e

d

l

n

s

t

a

e

o

Mosul Dam: Geology and Safety Concerns

172

Bulgarian Specialists. They judged that the dam

condition was generally acceptable, but they

recommended taking the actions which are

summarized in Table 3.

10.3 Evaluation of the Dam Safety Conditions in

2004-2005

After the 2003 war, and the occupation of Iraq by the

United State and Britain, the US army corps of

engineers performed a quick survey and a safety of Iraq

dams and concluded that Mosul Dam was in a

precarious state and formed severe threats on the

occupation forces stationed in the Tigris River Valley.

A complete safety assessment study was then initiated

in which Washington group International & Black and

Veatch (JV) were contracted in 2004 to do. Their report

was submitted in August 2005 and included the results

of thorough investigation of the dam conditions; it even

included the assessment the dam safety conditions that

was carried out by a PoE (panel of experts) which was

formed especially to carry out this task. The panel

assessment was based on potential FMA (failure mode

analysis) and recognizing the usefulness of Badush

Dam.

The PoE summary of the findings included the

following main points:

(1) Construction of Badush Dam between Mosul

Dam and the City of Mosul would address downstream

loss-of-life risks for all possible positional failure

modes.

(2) Construction of a diaphragm wall from the crest

of the dam using current technology is an unproven

alternative that could not, therefore, be relied upon to

reduce loss-of-life risk sufficiently, considering the

very large downstream population-at-risk. In addition,

this alternative would be more costly than building

Badush Dam.

(3) Construction of an upstream diaphragm cutoff

wall and upstream impermeable face might reduce

loss-of-life risk sufficiently, however, it would require

an extended reservoir lowering and it would be more

costly than building Badush Dam.

(4) Foundation grouting does not provide acceptable

long term loss-of-life risk reduction, considering the

very large downstream population at risk.

(5) Continued and improved foundation grouting

and careful monitoring and visual inspection would be

reasonable risk reduction measures to extend the

economic benefits of the Mosul Dam (power

generation and irrigation) as long as practical

From the above it is clear that the PoE recommends

the necessity for continuing the maintenance grouting

works, the usefulness of Badush dam, but it rules out

the use of diaphragm wall as a replacement of the grout

curtain. It is worth mentioning that the diaphragm

alternative was proposed in 1987 by two consultants

during construction and that it was rejected by the

International Board of Experts of the Dam.

Table 3 Summary of recommended actions.

Item examined Recommended action

1 State of gypsum dissolution Continue the grouting programs as before as maintenance work for the whole life of the dam and never atop

2 Deep grout curtain Breadth of curtain is not sufficient according to Soviet and Bulgarian standards. Add two more grouting rows, one at each of the U/s and D/S of existing curtain

3 Instrumentation Readings were judged acceptable, no action is required except routine maintenance

4 Seepage and dissolved salts quantities

The quantities of these seem to increase with rising water level of reservoir, so it is recommended not to accumulate water above Maximum Operation Water Level (EL. 330 masl). If such event occurs in the event of very high floods, then the reservoir is to be drawn down immediately below this level. WL should not be kept for appreciable length of time at this level in any event

5 Ground water measurement at downstream

Many more open pipe piezometers should be installed at the near vicinity of the dam at the downstream. I is most important to observe ground water movement there and relate this to reservoir water level fluctuation

Mosul Dam: Geology and Safety Concerns

173

10.4 Evaluation of the Dam Safety Conditions in

2006-2007

A new PoE was formed by the Ministry of Water

Resources in 2006 to follow up the dam safety question.

This PoE was formed mainly from Engineers from

Harza Engineering (USA) and one member from Italy;

but it shall be referred to as the (Harza PoE). The PoE

had a series of meeting extending over 2006 and 2007.

The main worries of this PoE were about the seepage

under the dam and the possibility of the formation of

new sinkholes; this was highlighted by the formation of

the sinkhole on the left bank very close to the dam in

2002 (Fig. 22). During these meetings the following

conclusions and recommendations were forwarded:

(1) The dam safety was questionable even with the

continuation of the maintenance grouting program.

(2) There was g a very high possibility of the

occurrence of sinkholes on the left bank close to the

dam body.

(3) The need for intensive new geophysical

investigation to be carried out using Geo-Radar in

addition to the other conventional investigation that

was ongoing at the time.

(4) Install many more open pipe piezometers at this

bank to observe ground water movement and give early

warning of the formation of new sinkholes and take

action by emptying the reservoir.

(5) Limit the maximum operation level of the

reservoir to (319 masl) instead of the maximum

designed operation water level of 330 masl.

(6) Construct a positive cut-off in the form of

concrete diaphragm as a permanent solution as the

protracted grouting had not been sufficient to stabilize

the situation. Admitting that such a cut-off would have

unprecedented depth, therefore its implementation

should be studied by uniquely specialized contractors

and equipment manufacturers.

(7) The PoE went further to cast doubts on the

usefulness of Badush Dam stating that the current

design of the clay core may not be sufficient to sustain

the Mosul Dam flood wave and that the bottom outlets

may get clogged by debris leading to overtopping of

the dam.

While the limitation of the reservoir water level was

enforced during the subsequent years the question of

the diaphragm was not settled and maintenance

grouting work was continuous by the site crew as

previously done until June 2014 when the Mosul City

fell to ISIS terrorists. Even the dam site was captured

by them but only for 20 days before they were repelled

back by government and coalition forces. However the

grouting works activities as the crew left and did not go

back to site again.

10.5 Evaluation of the Dam Safety Conditions in

2015-2016

The repercussions of the halting of the grouting

maintenance work was visualized and sensed sharply

by USACE who were very much aware of the fragile

situation of the dam foundation and their reaction to

this was prompt. An interagency team from many

United States agencies was formed in the beginning of

2015 which was lead by the USACE to carry out

measurements, surveys and observations to follow

developments that might lead to the dam failure. The

following was done: (1) An early warning system

consisting of remote sensing instruments was installed

to check for movement and settlement in important

locations on the embankment and structures; (2)

Installing observation cameras on the dam crest and

downstream berms for the same purpose; (3) A

bathymetric survey upstream and downstream of the

dam was conducted by socialized divers.

The findings of the US interagency team were

alarming and may be summarized in the following:

(1) There were signs of increased formation of

caverns and sinkholes under the dam. The

discontinuation of grouting works from August 2014

until beginning of 2016 has resulted in an increased

loss of gypsum and formation of new cavities of about

174

10,000 cubi

have happe

shown in Fig

(2) Increa

water was m

gypsum.

(3) Signs

grouting gal

measured. I

results of se

foundations.

grouting ga

extended to

settlement in

situation in t

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[1]

[2]

[3]

[4]

Safety Concer

Recent word

aluation of th

the question

uld happen in

phragm or c

sued. One th

lacement of p

weaker grout

nditions than

l it contribut

mations. The

q even with c

pondered by

nning regard

commissioned

manent solu

sued.

ferences

Adamo, N., a

Story: Engin

and Geotechn

Adamo, N. 20

in the World.

in Lålue Tech

Adamo, N., A

Knutsson, S

Dangerous D

during and

of Earth Sci

47-58.

Swiss Consu

rns

from the s

e conditions

n that remain

n the future

construction o

hing remains

parent rock i

ting material

the first day

te to lower p

dam will co

continuous gr

the Iraqi pol

ding the dam

d sometime

ution other

and Al-Ansari, N

eering Problem

nical Engineeri

014. “Mosul Da

” Lecture deliv

hnical Universit

Al-Ansari, N.,

S. 2015. “My

Dam in the W

after Impound

ence and Geot

ultants. 1979. M

site gives a

at the site at

ns without an

, and wheth

of Badush D

s for sure; t

in Mosul dam

ls will not re

ys of dam op

possibilities

ontinue to pos

routing [17] a

licy makers i

m. The dam

in the f

than groutin

N. 2016. “Mosu

ms.” Journal of

ing 6 (3): 213-4

am: The Most D

vered to PhD stu

ity on 10th Nov

Issa, E. I., Siss

ystery of Mo

World: Problem

ding the Reser

technical Engi

Mosul Dam Pr

an optimistic

t the present,

nswer is what

her driving a

Dam will be

the continual

m foundation

sult in better

peration, nor

of sinkholes

se a threat to

and this must

in any future

m should be

future or a

ng must be

ul Dam the Full

f Earth Science

44.

Dangerous Dam

udents audience

vember 2014.

sakian, V., and

osul Dam the

ms Encountered

rvoir.” Journal

neering 5 (3):

roject Planning

c

,

t

a

e

l

n

r

r

s

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t

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e

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Mosul Dam: Geology and Safety Concerns

177

Report. The State Organization for Dams and Reservoirs, the Ministry of Irrigation, Iraq.

[5] Sissakian, V., Al-Ansari, N., Issa, E. I., Adamo, N., and Knutsson, S. 2015. “Mystery of Mosul Dam the Dangerous Dam in the World: General Geology.” Journal of Earth Science and Geotechnical Engineering 5 (3): 1-13.

[6] Sissakian, K, Adamo, N, Al-Ansari, N, Knutsson, S, and Laue, J. 2018. “Badush Dam, NW Iraq; A Geological Study.” Journal of Earth Science and Geotechnical Engineering 8 (2): 1-15.

[7] Issa, E. I., Al-Ansari, N., and Knutsson, S. 2013. “Changes in Bed Morphology of Mosul Dam Reservoir.” J. Advanced Science and Engineering Research 3 (2): 86-95.

[8] Adamo, N., and Al-Ansari, N. 2016. “Mosul Dam the Full Story: Engineering Problems.” Journal of Earth Sciences and Geotechnical Engineering 6 (3): 213-44.

[9] Washington Group International, Black and Veatch J. V. 2005. Mosul Dam Study. Final Report, Task Order No. 8. Republic of Iraq Project Contracting Office, Provisional Coalition Authority.

[10] James, A. N., and Kirkpatrick, I. M. 1980. “Design of Foundations of Dams Containing Soluble Rock and Solis.” Quarterly Journal of Engineering Geology and Hydrogeology 13: 189-98.

[11] Morrison-Knudson Inc. 1989. Solution Equilibrium and Kinetic Rate Studies. Unpublished report.

[12] Guzina, B., Sarić, J., and Petrovic, N. 1991. “Seepage and Dissolution at Foundation of a Dam during the First Impounding of Reservoir.” Paper presented on ICOLD Meeting, Vienna, Austria.

[13] Swiss Consultants. 1984. Mosul Dam Flood Wave Study Report (Vols. 1-3). Security measures II, Addendum 3, Task 2. Confidential report submitted to the Ministry of Irrigation, Republic of Iraq.

[14] Adamo, N., and Al-Ansari, N. 2016. “Mosul Dam the Full Story: Safety Evaluations of Mosul Dam.” Journal of Earth Science and Geotechnical Engineering 6 (3): 185-212.

[15] The Japan Times, News. 2016. “Most Dangerous Dam Facing Collapse, Threatens Half in Mosul: Us Army.” February 10th, https://www.japantimes.co.jp/news/2016/ 02/10/world/dangerous-dam-facing-collapse-threatens-half-million-mosul-u-s-army/#.XII8ECJKjZ4.

[16] Annunziato, A., Andredakis, I., and Probst, P. 2016. Impact of Flood by a Possible Failure of the Mosul Dam, Version 2. JRC technical reports. EU Commission. http://publications.jrc.ec.europa.eu/repository/bitstream/JRC101555/lbna27923enn.pdf.

[17] Kelley, J. R., Wakeley, L. D., Broadfoot, S.W., Pearson, M. L., McGrath, C. J., McGill, T. E., Jorgeson, J. D., and Talbot, C. A. 2007. “Geologic Setting of Mosul Dam and Its Engineering Implications.” USACE, Engineering Research and Development Center. https://apps.dtic.mil/dtic/tr/fulltext/u2/a472047.pdf.