INSPECTION OF WATER RETAINING STRUCTURES · An inspection of Ranger water retaining structures was carried out on 22 October 1984 by Messrs Brown, Bastias and Whitehead. NO. 1 RETENTION

Technical Report WRD84042

Viewed at 14:07:14 on 29/07/2010 Page 1 of 40.

I I I I I I I I I I I I I I I I I I I I

INSPECTION OF WATER RETAINING STRUCTURES

ALLIGATOR RIVERS REGION

OCTOBER 1984

G D BROw~, J G BASTIAS AND B WHITEHEAD

JB:MB:108 1.7 B(l)

DEPARTMENT OF MINES AND ENERGY




1

Inspection of dams in terms of the Mines Safety Control

Regulations Section 392 paragraph 3 should be carried

out by the Company. Consequently it must be noted that

these inspections in no way relieve the management of

Ranger and Nabar1ek from their responsibilities to

ensure the dams are safe.

JB:MB:108 1.7 B(2)




cm,TENTS

A. RANGER PROJECT

CERTIFICATE OF INSPECTION

WATER MANAGEMENT STRUCTURES PLAN

NO 1 RETENTION POND

NO 2 RETENTION POND

NO 3 RETENTION POND

NO 4 RETENTION POND

TAILINGS DAI1

TAILINGS PIPELINE CORRIDOR

PLANT RUN-OFF POND

STOCKPILE AREA

RECOMMENDATIONS

LIST OF PHOTOGRAPHS

PHOTOGRAPHS

B. Nl'.BARLEK PROJECT

CERTIFICATE OF INSPECTION

WATER MANAGEMENT STRUCTURES PLAN

NO 1 EVAPORATION POND

NO 2 EVAPORATION POND

STOCKPILE RUN-OFF POND

PLANT Ru~-OFF POND

AIRPORT RUN-OFF DRAINS


WASTE ROCK RUN-OFF POND

RECO¥1MENDATIONS

LIST OF PHOTOGRAPHS

PHOTOGRAPHS

APPENDIX "A" TERMS OF REFERENCE

JB:HB:I07 1. 7 B(3)

4

5

6

8

10

10

10

11

12

12

12

14

15-20

22

23

24

25

26

26

27

27

27

28

29

30-34

35



I 3

I I I I I I I I I

A. RANGER RETENTION PONDS

I I I I I I I I I I JB:MB:I07

1.7B(4)




4

We certify that the nominated dams in the Ranger mine

site were inspected in accordance with the check list

contained in the Appendix of this report. Within the

limits of our visual inspection no major structural

defects occur and in our opinion the ·dams were safe as

at 22 October 1984.

G D BROWN ACSM, C Eng, MlMM, AM Aust IMM

District Inspector of Mines - Jabiru

J G BAST lAS Min Eng M App Sc Env Po:lution Control

MAlME AM AUS lMM

Senior Environmental Engineer - Darwin

B WHITEHEAD (Geol)

Geologist, Environmental Section NTGS - Darwin

JB:MB:107 1.7 B(5)




5

SSOlOOON ~- \

"

JABIRU i,

• 750 looom ! r= __ ~~i:i~8~-.~~iClJ

SOLE IN M£TR.e:S

EAST

SPILLWAY j~

!NDUSrrRIAL A~e'A

Djolkmora BillaoQng

j RPI

a5geOOON-+--~--------------+-~~~----------~t-----~-----"--~--~~~-; ____ ==r"-=~,,~----------~-.~~\----No 3

OREW~ \

8S97000N~-------------------I~~~~-----f~S~E~E~pj~~G~E~C~O~L~LE~C;T~O~R~---:~~~~~~r-~;;~i=~~~~ I S!;MP SEE~G£ COJLECTOR C::J

. SUMP TURKEY NES" PONO

I TAIl.INGS DAM EMBANKMENT

,

MAIN SECURITY GATE i

I

! I -+-------~i-~-t_t_--~-t_------1l~~~~~~ .. ~~rJ9u.~-----------~~--8596QOON i

! ,TA1LlNr DAM

I I i I i I

TAIL1NGS PIPELINE CORRIDOR

i '8595000N~------------------~------------------+-------------------~-----------------t-------------------+------

@SEEPAGE COLLECTOR SUMP

'" o o o

" ~ N

w w w 0 0 w 0

" 0 0 0

0 0 0 0 0 ~ ~ N ~ ~ ;: ,. N N N N

22~ge~ Project hrea

~ __________ G __ =~ __ =r __ a __ l __ Ma __ D ________ ~

w 0

" 0 '.0 ~ N

E:S4/002E




6

INSPECTION OF DAMS AT RANGER MINE

An inspection of Ranger water retaining structures was

carried out on 22 October 1984 by Messrs Brown, Bastias

and Whitehead.

NO. 1 RETENTION PO~~

Inspection of this pond was made by walking on the

crest, downstream and upstream embankments, all of

which were in sound condition. No structural defects

were noted.

The downstream wall was covered by heavy, almost dry

vegetation but no sign of important erosion was evi

dent. Only small channels of no immediate consequence

were noted.

Some fine material had been dislodged due to wave

action on the upstream face. This does not require any

remedial action.

Three 300 rom pipes have been installed over the spill-

way to discharge water by siphoning this from the pond

to the culvert and Coonjimba Creek. This operation is

necessary, before the onset of the wet season, to

increase the capacity of the pond for the reception of

the first storms run off which generally contain a

large proportion of suspended solids.

JB:MB:107 1.7B(7)

Some settling




7

essential before overflow occurs.

Gabions and concrete wings of the spillway were re-

paired prior to the onset of the last wet season and

are in good shape. However, some cracks in the wings

are appearing again.

Sagging of gabions in the spillway reported in 1983 is

still evident and getting worse. The company intends

to repair these within the next few weeks.

The seepage collector sump was in a satisfactory

condition.

The irrigation system has been installed and appears in

satisfactory condition.

The company carried out test lining on the east side of

the pond to protect the edge of the pond against

erosion by wave action and rain. Pieces of lining

material has been used in the test. The results appear

to be satisfactory.

The two piezometers installed on the downstream side,

east and west of the culvert have been used for moni-

toring piezometric pressures to assess the conditions

and stability of the embankment. This investigation is

now complete and a report prepared by P J Burgess and

Associates, Consultant.

JB:MB:107 1.7 B(8)

This report has not yet been




8

submitted. At the time of inspection piezometer RPl/l

read 0.01 m and piezometer RPl/2 was reading below the

datum level.

NO. 2 RETENTION POND

A visual inspection was carried out by walking along

the crest, upstream and downstream faces of the embank-

ment. Also the toe of the north wall and adjacent area

was inspected.

Some erosion reported in April 1984 is still evident

near the north west corner of the upstream face. No

rubbish inside the pond was noticed this time.

Minor erosion was evident near the pumping station.

Erosion by the switchboard and by the seepage discharge

pipe has been repaired. The seepage discharge pipe has

been replaced.

Rip Rap continues to be in good condition throughout.

The downstream wall appears to be in good condition

except for some minor erosion.

The irrigation system is no·... complete and in good

working condition.

JB: ME: 107 1.7 B(9)




9

Trees more than five feet in height exist along the

downstream embankment as reported before, but these

will be cut within the next few weeks.

Seepage collector and pump appeared in good working

condition.

The company ..has successfully completed the grouting

operation. This ensured the stability of the embank-

ment and significantly reduced the seepage from the

pond. Water still evident in the area downstream of

the embankment and in Djalkmara Creek apparently has

come from sources other than RP2. These sources may be

the orebody No 3 hill and other higher areas.

Readings from the piezometers were as follows:-

RP2/l Nil

RP2/4 0.15

RP2/5 0.47

RP2/6 Nil

RP2/7 Nil

RP2/8 Nil

RP2/9 Nil

Spillage of grout material is still evident in two

places on the downstream embankment and at the toe.

The removal of this material is not considered

necessary.

JB:MB:I07 1.7B(lO)




10

The east side is in good order.

The south side showed minor erosion of no importance.

The wall around RP3 and the western wall were in good

condition.

Oil discharge is still evident on the inner walls of

this pond.

NO 3 RETENTION POND

Crest and wall of embankment were inspected and found

in good order. Spillway aprons were in good condition.

The road along the crest was found in good condition.

Generally, this pond is always in good condition. Only

upgrading of the crest is required from time to time.

NO 4 RETENTION POND (Waste Dump Settling Pond)

Some erosion is evident in the south end of the

dividing wall between RP2 and RP4, but generally both

sides were in good condition. The size of this pond

continues to be reduced significantly by dumping of

waste material.

TAILINGS DAM

The crest, upstream and downstream faces of all four

walls were visually inspected.

spots were observed.

JB:MB:I07 1.7 B(ll)

No seepage or damp




11

Permanent power is now available to pumps at each

seepage collector. New permanent pipe lines have been

installed. All four seepage collector pumps and

pipelines are working satisfactorily.

New drilling investigation is being carried out near

the north wall of the dam for stage 3 construction.

Two diamond drill holes have been completed, one at

chainage 372 m and the other at 730 m and at about 50 m

north of the centre line of the Stage II embankment.


The corridor was inspected and found in good condition.

The bund on the west side of the sump removed to allow

traffic of heavy machinery has been replaced.

The company will upgrade the bunds in the whole

extension of the corridor within the next few weeks.

The concrete lining of the collector sump has collapsed

and further work is necessary. Also the discharging

channels need repair. Several trees of more than five

feet are evident around the sump.

The company will remove these trees within the next few

weeks.

JB:MB: 107 1.7 B(12)




12

PLANT RUNOFF POND

The situation in the pond is still the same as reported

in October 1983 and April 1984, but the works requested

will be carried out within the next few weeks.

STOCKPILE 'AREA

Retaining bunds are in good condition.

RECOMMENDATIONS

To repair the gabion wall at the spillway of RPl

(reported in October 1983).

To repair and regrass areas damaged by grouting

works on the downstream walls of RP2.

Repair any

action to

premises.

damage

pond

made by runoff or any

embankments throughout

other

the

To cut trees more than five feet tall growing in

the embankment faces of all water retaining

structures.

To avoid the discharging of oil into RP2 or any

other water retaining structure within the

premises.

JB:MB:107 1.7B(13)




13

To clean up the bottom of the plant run off pond

and construct a retaining wall on the south side

to protect the access road to the pipeline

corridor. (First reported and requested in

October 1983) .

To repair concrete surfaces at the collector sump

of the tailings pipeline corridor. The use of

wire mesh is recommended to protect the new

concreted surfaces.

JB:MB:107 1.7 B(14)




No

1.

2.

3.

4.

5.

6.

7.

8.

9.

14

RANGER WATER RETAINING STRUCTURES INSPECTION

22 OCTOBER 1984

LIST OF PHOTOGRAPHS

Description

Downstream side of the spillway of RPl showing vegetation covering the embankment.

Pipes used for siphoning water from RPl to Coonjimba Creek.

Gabion on east culvert showing repaired.

side of the spillway near the heavy sagging which needs to be

Lining material used in the test to prevent erosion by wave action and rain at the east side of RP1.

RP2 pump station showing repair works carried out during the last dry season.

RP2 west of embankment and sealed_ road where the grouting operation was carried out. Also showing the new irrigation system.

General view looking down towards RP2 downstream embankment showing spillage of grouting material.

General view looking north east from the top of RP2, showing some surface water in the Dj alkmara Creek bed.

Encased returning seepage pipeline from north central seepage collector to tailings dam.

10. Diamond drill investigation for Stage 3 of the tailings dam construction.

11. Tailings corridor sump showing need for repairs to concrete lining.

12. Discharging channel from the tailings pipeline corridor into the sump showing need of repair.

JB:MB:107 1.7B(l5)



1. Downstream vegetation

side of covering

15

the spillway of the ernbankmen t.

=""'- ~ ~~ - ~ .. -

~ -:~;i7ii;;{i:l;:,~_-;'::i;.~-.

2. Pipes used for Coonjirnba Creek.

siphoning water

"B'MB-107 ,...... • * .. -

1.7B(16)

RPl showing

~_~~!FA~~-' t.;.:.-':':..I~·II&>·"~~

from RPI to



16

3. Gabion on east side of spillway near the culvert showing heavy sagging which needs to be repaired.

4. Lining material used in ~he test to prevent erosion from wave action and rain in the east side of RP1.

JB:MB:I07 l.7B(l7)



17

~ ~.,

' .... , "e

-~ ".. , .' ~,

5. RP2 p~~ station showing repair works carried out during the last dry season.

6.

- ~ ,

,,,,,"-" " :-.-,:--"" ';':-"", ,~.';'-.;--:;;~ -'.-:,' = ~ -.};:~ ::~--<:.

"',.;::-- .,~ ~ . ,," _. -

RP2 crest of embankment and sealed grouting operation was carried ou~. the new irrigation system.

JB:MB:I07 1. 7 B (18)

road where the Also, showing



18

7. Ga~eral view looking down RP2 ~~ankrnent showing spillage of grout;ng

do",-nstream material.

8 • General showing bed.

JB:MB:I07 1. 7 B(19)

view looking north some surface water

east =rom top o£ RP2, in the Djalkrnara Creek



9.

10.

19

--~. :-: ....... --" .~ <, .. ~

--Encased Central

;":.'. -','-~-

<.-- ... ~.:-~. ,,~.,

returning seepaae seepage collector to

Diamond drill investigation tailings dam construction.

JB:MB:I07 1.7 B(20)

pipeline +---il;n ..... s ""'c:._--~-':::l

from datu.

for stage 3

North

of the



20

11. Tailing corridor surr~ showing need for repairs to concrete lin;ng.

.-"0- , .• -:,,...~._.

t ~... ""' ~ic~:':':':':i<~';': .. _-.L' .. ~ ~ .~'''''.

12 .. Discharging chap_~el from the corridor into the sump showing

JB:MB: 107 1.7 B(21)

tailings pipeline need of repair.




21

B. NABARLEK RETENTION PONDS

JB:MB:I07 1. 7 B(22)




22

We certify that the nominated dams on the Nabarlek mine

site were inspected in accordance with the check list

contained in the Appendix of this report. Within the

limits of our visual inspection no major defects occur

and in our opinion the dams were safe as at 23 October

1984.

G D BROWN ACSM, C Eng, MIMM, AM Aust IMM

District Inspector of Mines - Jabiru

~1: J G BASTIAS Min Eng M App Sc Env Pollution Control

MAIME AM AUS IMM

senior Environmental Engineer - Darwin

B WHITEHEAD Geol

Geologist, Environmental Section NTGS - Darwin

JB:MB:107 1. 7 B (23)



I 23

I I I I I I I I I I I I I I I I I I I

~----------------------------I

/

I \ \ \

"

EVAPORATION POND (2.)

/

---1--------

-----

00

>OOs

-+---+-----:------'~~~tf_-IOOOS

QLD MINES LTD

Nabarlek Project

General Map

E83/009E




24

INSPECTION OF DAMS AT QML, NABARLEK

An inspection was carried out on 23 October 1984 by

Messrs Brown, Bastias and Whitehead and included the

following dams.

No. 1 Evaporation Pond (EPl)

No. 2 Evaporation Pond (EP2)

Stockpile Run Off Pond (SPROP)

Plant Run Off Pond (PROP)

Airport Run Off Drains

A visual inspection for the first three ponds, which

are adjacent to each other, was along the crest of .the

out embankment. Upstream and downstream walls were

inspected from the top of the embankment. The dividing

structures were inspected in the same way.

NO. 1 EVAPORATION POND

This pond has no function within the water management

system at present. Only rain water has been collected

in the pond during the 1983/84 wet season. At the time

of the inspection the lower level of the pond was

covered by water. In October 1983 the pond was dry.

Water from this pond is being used as partial

irrigation water in the land application test being

carried out by the company.

JB:MB:I07 1.7 B(25)




25

This pond could be used for storage of treated water if

treatment of waste water is included in the final

decommissioning and rehabilitation proposal for this

mine.

All physical components of this pond ie: walls, crest,

spillway, measuring gauge and rip rap covering are in

good order.

The top of the embankments of this and all other ponds

are in very good condition.

NO. 2 EVAPORATION POND

All walls are in good order. No significant erosion on

the embankments were observed.

Rip Rap in all walls is in sound condition.

The fail safe spillway and the measuring gauge

associated with it are in good order.

No surface water was observed to the north side of this

pond.

No rain water in the silt trap at the north of the pond

was observed. The silt trap is in good working

condition.

JB:MB:I07 1.7 B(26)




26

STOCKPILE RUN-OFF POND

No damp spots were observed in the outer wall. There

was no erosion on either the outer walls or inner walls

of any significance.

The embankment was generally in good order.

The irrigation system to enhance. evaporation installed

on the top of the ore stockpile is working satis

factory. Water used in the system is pumped from this

pond.

PLANT RUN-OFF POND

The embankment was inspected and found in good

condition.

No damp spots were seen in the outer wall. The crest

and inner walls were sound. Bunds to guide plant run-

off water into the"pond were in good order.

Flygt pumps were in position at the pumping station.

They were in good condition. The power supply was also

in good order.

Some cleaning of the bottom of this pond is desirable

but not essential.

JB:MB:I07 1.7 B(27)



=


27

AIRPORT RUN OFF DRAINS

This drain system is in satisfactory condition.

Cleaning of silt traps and some repairs have been

carried out.


Bunds and concrete walls of the corridor are in

satisfactory condition.

WASTE ROCK RUN OFF POND

This pond was decommissioned in 1983.

Rehabilitation works are now been carried out in

accordance with the approved program. Revegetation of

this area is expected to be carried out during the

1984/85 wet season.

A new silt trap has been built at the south of the

former waste rock run off pond.

Some works on the top of the embankments, such as the

installation of pipelines, pumps, water treatment

plant, etc, have been carried out in relation to the

JB:MB:I07 1.7 B(28)



=


28

decommissioning and rehabilitation proposals. These

works have not affected the structures of the dams or

the water management system.

RECOMMENDATIONS

There are no special recommendations. The maintenance

of~ the water retaining structures has been carried out

satisfactorily.

JB:MB:I07 1.7 B(29)




29

NABARLEK WATER RETAINING STRUCTURES INSPECTION

23 OCTOBER 1984

LIST OF PHOTOGRAPHS

No Description

1-

.2.

EPI showing lower level covered by water.

General view showing the crest of wall dividing EP1 and the SPROP.

3. EP2. embankment and north area accumulated during the wet season. now totally dry.

4. Silt trap at north west of EP2.

5. Plant run off pond and pump station.

6. Airport run off drain system.

where water The area is

7. Rehabilitation of the ex waste rock run off pond area.

8. New silt trap located south of the ex WRROP.

9. Pipelines and valves located on the embankment between EPI and EP2 for land application purposes.

IO. Reverse osmosis test treatment plant located on the north east wall of the stockpile run off pond in relation to decommissioning works.

JB:MB: 107 1.7B(30)

I



30

1. EPl showing lower level covered by water.

2. General EPl and

JB:MB:I07 1.7 B(31)

-~-!:~,'~; .. ~:" '7 ,,,

- -7"'''--':''.'"~ ,-'''"/

-~---:'-';:;7;;: --- _.-.-;-

view showing the crest of wall ~ . '1 -& S~OCKP~ e r~nor~ pond.

dividing



31

EP2 embankment and accumulated during the now totally dry.

north area wet season.

4. Silt trap at north west of EP2.

JB:MB:I07 1.7B(32)

where The

water area is



32

5. Plant r~~ off pond and pump stat'on.

6. Airpol. L run off drain system.

JB:MB:107 1. 7 B (33)



7.

8.

Rehabilitation area.

New silt trap

JB:MB: 107 1.7 B(34)

of

33

...... . :~;: -, .....

~G~~;ii;1£_L"'·'·:·:'~ . ~-'

,:",,,,_.-,

the ex' waste rock run off pond

':--'~'<

:::.- ;. .~. ~"

located at south of the ex w~OP.



34

9. Pipelines and valves located on the embankment between EPl and EP2 for land application pULposes.

10. Reverse osmosis test. treatment plant located on the north east wall of the stockpile run off pond in relation to decommissioning works.

JB d.ffi: 107 1.7B(35)




35

APPENDIX A

TERMS OF REFERENCE FOR PERIODIC SURVEILLANCE

INSPECTIONS OF WATER RETAINING STRUCTURES IN THE

ALLIGATOR RIVERS REGION

1. The ultimate responsibility for the operation,

maintenance, monitoring surveillance and safety of

the water management system and structures rests

with the mining company holding a Special Mineral

Lease under the Mining Act or an Authority under

Section 41 of the Atomic Energy Act.

2. During the operational, decommissioning and

rehabilitation phases of the mining operation,

periodic surveillance inspections will be carried

out on mine site water management structures by

the Department of Mines and Energy assisted by the

other Supervising Authorities.

3. As far as practicable, the safety and surveillance

team shall include at least one Engineer

experienced in modern dam technology and a

hydrogeologist.

4. Where necessary, the services of an experienced

geologist, soils engineer or other specialist may

be utilised

inspections.

JB:MB: 107 1. 7 B(36)

to assist with surveillance




36

5. The mine operators shall compile a record of data

obtained in the operation of the water management

system which shall include:

•

•

•

•

•

•

•

JB:MB:I07 1.7 B(37)

observations on conditions of water

management structures~

any repairs carried out on water management

structures~

rainfall, pan evaporation and meteorological

data~

use of water from various structures~

water levels in all storages,

water quality in all storages,

water levels in observation bore holes,

quality of water from bore holes~

quality and quantity of water from leakages~

accurate pumping rates for each unit,

total dry weight of tailings placed and total

volume of tailings held~




6.

37

dry densities of tailings at various tailings

depth,

findings of resistivi ty surveys if carried

out;

established availability and quality of earth

and rock materials for new construction

and/ or repair and maintenance for existing

works.

A technical representative of

shall accompany the team

the mine operator

during all site

inspections and provide additional information as

required.

7. Periodic surveillance inspections shall include

assessments on the following aspects of each water

retaining structure:

•

JB:MB:I07 1. 7 B (38)

Upstream Faces of all embankments

stability

erosion

face protection;

Downstream Face of all embankments

structural integrity - face

leakage, seepage and damp spots

erosion

-::: -"




•

•

•

JB:MB:I07 1.7 B(39)

38

condition of protecting material

structural integrity - downstream toe

seepage

toe erosion or undercutting

vegetative cover,

Crest of 'all embankments

general condition

roadway condition

drainage

if no roads - vegetative cover;

Spillways

general condition

apron condition

wingwall condition

weep drains,

Culverts and other structures

general condition

inlet and outlet condition

seepage,

Drainage

silt accumulation

vegetative growth

general condition,




39

• Assessment

condition and effectiveness. of previous

repairs and maintenance

redesign proposals or modifications.

8. After each inspection, the Department of Mines and

Energy will report to the Periodic Surveillance

committee on its assessment of each water

retaining structure including:

• the overall safety of the structures

• the remedial action proposed to remedy any

faults or deficiencies

• recommendations for any action which may be

necessary to ensure the continued safety of

the structures

recommendations for any changes in the

surveillance procedure

• other relevant comments and conclusions.

9. Surveillance inspections shall be carried out each

April and October and reports presented to the

Periodic Surveillance Committee within two weeks

or such further period as becomes necessary.

10. Where an unusual event occurs at a mine site in

relation to the water retaining structures the

Periodic Surveillance Committee may request the

Department of Mines and Energy to inspect the site

and evaluate and report on that event.

JB:MB:107 1.7 B(40)

Documents

INSPECTION OF WATER RETAINING STRUCTURES · An inspection of Ranger water retaining structures was carried out on 22 October 1984 by Messrs Brown, Bastias and Whitehead. NO. 1 RETENTION