@Lrj@)

ENVI RONMENTALCASE STUDIES

souTH PACTFTC REGTONAT ENVTRONMENT PROGRAMME (SPREP)

sourH PACrFrc coMMlssloN (sFc), NoUMEA NEW CAITDON|Aproduced with financhl assistance fiorn the

UNITED NAT|oNS ENVTRONMENT PROGRAMME (UNEP)

South

3t".$,.5

THE EFFECTS OF MINING ONTHE ENVIRONMENT OF HIGH'ISLANDS: A CASE STUDY OFGOLD MINING ON MISIMA IS-LAND, PAPUA Nf,W GUINEA

BACKGROUND

Papua New Guinea is currently un-dergoing a minerals explorationboom, especially for gold, and morethan l0 potentially economicdeposits have already been located.The geological and environmentalsettings in which these gold depositshave been found are very like thosein other Pacific countrieso especiallythe Solomon Islands, Vanuatu andFiji, and it is certain that thesecountries will eventually face dif-ficult planning and decision-makingsituations similar to those currentlybeing experienced in Papua NewGuinea.

Like all other mineral developmentprojects, those in Papua New Guineahave associated problems. There hasbeen considerable publicity for in-stance surrounding environmentalmanagement problems such as thoseof the Ok Tedi and Bougainvillemining projects (Chambers 1985),and more recently over a proposedgold mine at Porgera. The even moresevere impact of nickel mining onthe environment of New Caledoniahas been described by Dupon (1986)in the first of the SPREP Environ-mental Case Studies series. As thepace of mineral development in-creases so will the degroe and extentof environmental impact. The bruntof such impact will continue to befelt most keenly by the local corn-munities whose land witl bealienated and whose traditionalresources will be destroyed ordegraded while the benefits arespread more widely throughout thecountry.

MirimE. The rite of the open mine pit.The dirturbance har been caured by drilling to

determins the cxtent of the ore body.

Papua New Guinea is unique in theFacific region in that its Constitutionhas specifically recognised thenationrs responsibility to ensure thatits environment is protected and itsnatural resources are wisely used.This responsibility is given legisla-tive effect through the EnvironmentPlanning Act, 1978 which requires

that the proponent of a newdevelopment project liaises with theDepartment of Environment andPlanning and if necessary prepares

an Environment Plan. The Plan,along with the economic and techni-cal feasibility studies, provides thebasis on which g,overnment approvalfor the project is judged.

In this case study the environmentalplanning and management strategyproposed in the Environmental Planfor the Misima Island gold miningproject (Natural Systems ResearchPty. Ltd. INSRI 1987) is describedand analysed. A major feature ofthis strategy is that it will be thefirst in Papua New Guinea to utilisemarine disposal of soft rock wasteand of tailing (residue) produced bythe treatment of the ore. This formof disposal has already beenproposed for two other high islandgold mines in Papua New Guinea,on Lihir and Fergusson Islands, andis likely to be widely implementedon high islands throughout thePacific region.

The eite of the open mine pit viewed from the west. The ore body liea beneath the prominenthill which hae been dieturbed by exploration activitiee. When mining haa been completed after l0 years

the hill will have been completely removed and replaced by a deep pit.

THE MISIMA GOLD MININGPROJECT

Government approval for Placer(PNG) Pty. Ltd. to proceed with thisproject was granted in late | 987,construction work began almost im-mediately afterwards and it is ex-pected that the first gold will be ex-tracted in early 1989.

The objective of the project is todevelop and operate an open cutmine and process facilities to recovergold and silver, supported by thenecessary infrastructure (NSR 1987).The total ore to be extracted is 56million tonnes (Mt) at a stripPingratio of 1.3 tonnes of waste to eachtonne of ore. This would allow themine to operate for a little morethan l0 years at the planned produc-tion rate of 5.475 Mt/annum. Miningwill be by conventional open pittechniques and three categories ofmaterial will be removed from thepit: ore (56 Mt), hard rock waste (35Mt) and soft waste (35 Mt).

The ore will be delivered by trucksto the processing plant located onthe coast. The hard rock waste willbe delivered to dumps close to theopen pit. The soft waste comprisesincompetent oxidised rock whichwill not store safely in stable dumps;instead it will be hauled to the southcoast and dumped directly into theocean adjacent to the plant site.

The ore treatment plant will be aconventional gold cyanidation plantwith gold recovery by the carbon-in-pulp process. The ore will be

AA

Kilomelres

I

c)

./ -.

HARD ROCKWASTE DUMPS

/ o*r'(/srocKPrLE 1o.r

\"to(;)*

CONSTRUCTION\ CAMP

\w Norl on

Bwogooio Airporl

--*"""{Ilftt"PLANTSITE

s'yflf\gi"'ISLAND -''

Nor r on

----- E r o u s a/- gs

* o q o o, o-\*J

OPENPIT.,MINE

SOFT WASTE

TAILING PIPELINE ACCOMMODATION CENTRE

ground in a ball mill to a diameterof 125-235 micromillimetres. Thetailing left after the gold and silverhave been extracted will consist of amixture of water, mud and chemi-cals such as cyanide used in the ex-traction process. This tailing willflow to a mixing tank where it willbe diluted with sea water to reducethe residual cyanide concentration toa level acceptable for deep oceandischarge down a pipeline.

The mining, processing and wastedisposal strategy summarised abovewas decided on after more thaneight years of environmental,economic and technical feasibilitystudies, The grade of the Misimadeposit is extremely low at about 1.3grams of gold per tonne of ore. Thisis because in the course of past min-ing activities most of the high gradeore was extracted by undergroundmining methods. In adopting thisstrategy the developer ensured theeconomic viability of an otherwisemarginal project while at the sametime reducing to a minimum thearea of otherwise productive agricul-tural land required. On the negativeside, the dumping of soft waste willadversely affect the nearshore en-vironment, and the resources avail-able from it, for a distance of up to9 km along the coast.

The mine is expected to produceabout 77.2 md 1,175 tonnes of goldand silver respectively. The totalproduction would amount to exportearnings of about US$ 935 million atgold and silver prices of US$ 385and US$ 6 an ounce respectively.

ENVIRONMENTAL AND SOCIALSETTING

The Misima gold deposit lies at the

eastern end of Misima Island whichis 40 km long and l0 km wide at itsbroadest point. The western end isrugged and rises to a maximum al-titude of 1,035 metres above sealevel. The eastern end is less ruggedand at its highest point, in thevicinity of the mine site, rises to 413metres. Most of the eastern half ofthe island consists of low grademetamorphic rocks with porphyriticintrusions. The relatively flat-lyingcoastal strip is largely formed onraised coral limestone terraces.

The hilly interior at the eastern endis covered in lowland hill rainforestwhich shows evidence of havingbeen disturbed within the last 50years by cyclonic activity, timber-getting for mining and by gardening.The coastal strip and foothills havebeen cleared in the course of shift-ing cultivation and the original rain-forest has been replaced by wood-land, characterised by theprominent, fast growing treeKleinhovia hospita.

soon from December to March. Al-though the annual rainfall is over3,000 mm and is relatively regularthroughout the year, droughts areknown to occur, especially duringthe south-east trades season, and thiscan cause food shortages or evenfamines.

The island currently has adequateland to support its population ofabout 9,000 people which is con-centrated along the coastal strip. Itretains ample areas of forest whichare rich in a range of raw materialsand bush foods, and the surroundingsea is rich in marine resources.Commercial and small-holder copraand cocoa production utilises almostall of the flat coastal land, and sub-sistence production from shiftingcultivation is largely confined to thefoothills and mountainous interior.

Misima islanders practise a form ofshifting cultivation characterised bymixed gardens usually dominated bya single staple, in this case yams(Dioscorea spp.).

Alluvial gold was discovered onMisima Island in 1888 and about100,000 ounces was produced fromalluvial workings before the sourceof the gold was traced to the head-waters of Cooktown Creek in 1904.Mining of the underground lode(vein) gold began in l9l5 and con-tinued at the rate of around 100 tonsa day until early 1942 when the ap-proaching Japanese forces caused theevacuation of the island. Attemptsafter the war to re-commence min-ing were unsuccessful, largely be-cause of extensive collapse in theunderground workings.

The total output from alluvial and

Two seasons occur on Misima: thesouth-east trades from April toNovember and the north-west mon- THE HIsroRY oF I\IINING

[o*o"o ,n[+oz" o".rnr"J-lI In open prt

]

h*-

Newly prepared yam gardeng in forest clearing.

OPEN PIT MINE

HARD ROCK WASTE55 Mf

SOFT ROCK WASTE35 Mr

6O o/o stored rnsf oble dumps

,th"*"]

Rapid recovery of the coral reef isexpected once mining stops, as wasthe case along the coast adjacent toCooktown Creek after mining ceasedin 1942. Recovery, or restoration, ofreefs is brought about naturally byrecolonisation and regeneration.

Tailine disoosal

The location of the treatment planton the coast, the avaibility of deepwater a short distance from theshore and the absence of any deepwater subsistence or commercialfisheries resources use, provided anopportunity for the disposal of tail-ing deep in the ocean. The proposedsubmarine tailing disposal systemconsists of a pipeline transportingtailing from the plant, a mixingtank, an outfall discharge PiPe, a

seawater intake pipe and f lowregulating devices (NSR 1987: 27 -30). The tailing will be mixed withseawater in the mixing tank and theresulting slurry will be dischargedthrough the outfall pipe to the oceanat a depth of between 75 and 100

metres. The slurry will be denserthan the surrounding ocean water atthe discharge point and it will flowdown the steep submarine sloPe as a

density current and will not mixwith, or pollute, the surfaceseawater.

The tailings will accumulate on thedeep sea floor and smother marinehabitats there, either forcing away orkilling those animals which cannotadjust to the new conditions. TheMisima people do not fish at suchgreat depths and there is littlepotential for commercial deep waterfishing.

ENVIRONMENTAL MONITORINGAND MANAGEMENT

These assessments of the likely im-pacts of the project on the environ-ment are predictions, not establishedfacts. It is therefore important thatthe actual impacts are carefully andregularly monitored by the govern-ment, the company and the Misimacommunity to ensure that they donot exceed the levels Predicted inthe Environmental Plan, and thatthose impacts which do occur are

managed appropriately so as to mini-mise their adverse effects.

A detailed environmental manage-ment and monitoring Programme was

proposed in the Environmental Plan

(NSR 1987, section l0) and this hasbeen agreed to, with modifications,by the Department of Environmentand Conservation and Placer (PNG)Pty. Ltd.REFERENCES:

Chambers, M.R. (1985) Environmen-tal management problems in PapuaNew Guinea. The EnvironmentalProfessional 7: I 78-85.

Dupon, J.F. (1986). The effects ofmining on the environment of highislands: a case study of nickel miningin New Caledonia. EnvironmentalCase Studies: South Pacific Study I.South Pacific Regional EnvironmentProgramme, Noumea, NewCaledonia.Hughes, P.J. & Sullivan, M. (1987)

Goldmining or gardening? Potentialland use conflict on Misima Island,Papua New Guinea. In A. Conacher(ed) Readings in Australian Geog-raphy. Institute of Australian Geog-raphers (WA Branch) & DePartmentof Geography, University of WesternAustralia, Perth.

Hughes, P.J. & Sullivan, M.E. (t98S)Population, Iand use and mining inPapua New Guinea, Yagl-AmDz. TheUniversity of Papua New GuineaJournal of Social Sciences & theHumanities | 5(D:a0 -62.

Natural Systems Research Pty. Ltd.(f 987) Misima Project EnvironmentalPlan. Placer (PNG) Pty. Ltd., PortMoresby (3 volumes).

Placer Pacific Ltd. (1988) AnnualReport 1987. Placer Pacific Ltd.,Sydney.

This document's contents, conclu-sions and recommendations do notnecessarily ref lect the views ofUNEP or SPC. The designationsemployed and the presentation of thematerial do not imply the expressionof any opinion whatsoever on thepart of UNEP or SPC concerning thelegal status of any state, territory,city or area or of its authorities, orconcerning the delimitation of itsfrontiers or boundaries.

Derelict etamp battety ured to crurh the gold-bearing ore

during the underground phase of mining.

i"lir*

*'*.:i,

*i,

OCopyright South Pacific Commission'l 989.The South Pacific Commissionauthorises the reproduction of thismaterial, whole or in Part, in anY

form. provided appropriate acknow-ledgement is given.Original lext: English.

South Pacific CommissionCataloguing- in-publication dala

Hughes, Philip J.

The effects of mining on the en-vironment of hiSh islands : a case

study of gold mining on Misimalsland, Papua New Guinea.(Environmental case studies :

South Pacific study : 5)

| . Cold mines and mining- -

Environmental aspecls-Misima ls-land (Papua New Guinea) L Titlell. Series

1i3.850995rsEN 9E:-?03-050-9

Leaflets available in this series are:

Leaflet | - -fhe ellacts ol mintng onthe environmcnl ol high rs'lands: ,4 case study ol nickelnining iil New Caledonn

Leaffet 2 - llallis and Futwra: Msuagaiilsl the loresl

L.eaflet -l - Atolls and lhe cl'clotrcha:srd; A case sludl' ol theTuamotu Islands

Leaffet 4 - Paciltc phosphote islandtnrtronmeilIs vcrsus the miil'ing industrt: Atr wtequalslruggl?

Leaflel 5 - fhe ellects ol mining ottthe envinnmtn! ol high is-lands; A case study- ol goldntining on Misima lsland.Popua New Curnea

Copies of leaflels in this series canbe obtained from:SOUTH PACIFIC RECIONALENVTRONMENT PROGR At\IITIESOUTH PACIFIC COMMISSIONB.P. D5. Noumee CedexNew Caledonir

Preoared bv Philip J. HushesUnivirsity "tlltnt: New Guinea

South Pacific Resional Environment ProgrammeSouih Pacifrc eomfirission, Noumeq, Nevy Caledonia,

with financial assistance from theUnited Nations Environment Programme

AACR: Printed bv Stredder Print Limited,Aucklafid, New Zealand, 1989

underground workings since 1888 isestimated to have been aP-proximately 250,000 ounces. Theearly mining activity supported itsown infrastructure and a con-siderable number of expatriates andlocal people were employed by themining companies.

The environment legacy of intermit-tent gold mining over the past 100years is evident today in the form ofold tunnels, roadworks, derelictbuildings and equipment and thedegraded vegetation surrounding theold workings. In Cooktown Creekand its tributaries there was a con-siderable build-up of waste rock andmercury amalgamation and cyanidetailing which were dumped into thestream system without any pre-treatment. Most of this has sincebeen transported out to sea but someof it has accumulated in the lowerCooktown Creek valley.

This long-term but relatively small-scale phase of mining must have hada considerable impact on the ter-restrial, riverine and nearshoremarine environments. The hills sur-rounding the mine site are wellvegetated but the original forestcover has only partially returnedmore than 40 years after miningceased. The Cooktown Creek systemhas fully recovered and sago standshave long since been re-established

in its lower reaches. The coral reefsnear the mouth of Cooktown Creekmust have suffered considerabledamage from the continuous dis-charge of mine wastes from Cook-town Creek but they have now fullYrecovered.

THE PREDICTED ENVIRONMEN-TAL IMPACTS OF THE OPENCUT MINE

The major issues raised in the En-vironmental Plan by the developmentof this open cut gold mine and itsinfrastructure were as follows (NSR| 987:48):

(a) the capacity of the island tophysically accommodate theproject and continue to providesufficient gardening land for a

growing population;

(b) the capacity of the streams andsurrounding ocean to assimilatewastes from the project;

(c) the effects of the project's landrequirements and discharges onnatural ecological values, andthe subsistence and commercialresources utilised by localpeople.

Land and Resource Use Impacls

Land alienation and the associateddepletion of traditional resources was

one major issue. Most of the popula-tion of about 9,000 people livesalong the coast of the eastern end ofthe island, and although there is cur-rently no shortage of gardening landthe population is increasing rapidlyand there was concern that alienationof land for the mining project mightlead to land shortages.

Population-land use studiesdemonstrated that even if the minedid not proceed, by about the year2010 land shortages would begin toseriously affect the local people.Thus it was realised from an earlystage in project planning that it was

highly desirable that wherever pos-sible, project infrastructure shouldbe placed on land of low produc-tivity for use as gardening land andfor exploitation of bushlandresources. The mine site and hardrock waste dumps will be in hillyterrain on largely non-productiveland away from populated and gar-dened land. The processing plant andaccommodation facilities will be lo-cated on freehold land presentlyused as coconut plantations. Only thehaul road and the low grade orestockpile will be situated on produc-tive village-owned land. Moneyreaching the local community frommining will allow increased pur-chases of food from stores and thismay offset some of the effects ofpressure on subsistence land.

Stream Impacts

During the construction phase,which will last about l5 months,about 200,000 cubic metres of sedi-ment (mostly soil) will find its wayinto Cooktown Creek. A further170,000 cubic metres will reach theCreek during the l0 year life of themine. Much smaller amounts willreach other streams surrounding theproject area but the impact on thesestreams will be negligible comparedwith that on Cooktown Creek. Al-though most of this sediment willeventually be washed out to sea,

there will be localised accumulationsof sediment in the valleys which, inthe case of Cooktown Creek, will af-fect a locally important sago swamp.ln addition the stream waters will becontinuously muddy because of theirhigh sediment load.

The loss of sago resources is ex-pected to be small and compensationwill be paid for these losses. Thecompany has already installed pipedwater supply systems for all villagesadjacent to the project area. None ofthese water sources will be affectedby project construction or operation.

Waste Disposal

Waste disposal was the other mainissue. Two alternative tailing disposaltechniques were considered; landdisposal and ocean disposal (NSR1987: 26-30). Land disposal wouldhave required the construction of a

dam capable of permanently storingthe tailing and soft waste rock andwithstanding extreme rainfall andrun-off during cyclones. As all theflat coastal land is currently inproductive use, the tailing dam

would need to be sited in the moun-tainous interior of the island.Preliminary investigations indicatedthat several dams would be neededand that there was a definite riskthat dams in such terrain might faildue to seismic or climatic events.

Hard rock waste disposal

About 60% of the 35 Mt of hardrock waste will be stored in stabledumps in the hilly interior on landwhich is largely unproductive. Theremaining 40% of hard rock wastewill be used to back-fill one end ofthe open pit. Because the rocks arenon-acid producing the leachatefrom these dumps is not expected tobe acidic or to contain high con-centrations of dissolved metals orother contaminants (NSR l9E7:31).

Soft waste rock disoosal

Three alternatives for disposing ofthe 35 Mt of soft waste were con-sidered: containment by a dam lo-cated about I km upstream from theCooktown Creek mouth; milling thesoft waste and disposing it, alongwith the tailing, down the submarine

Sediment washing out from Cooktown Creek as a result of mining exploration activities.The dumping ofsoft wastea into the sea will create a permanent, and even larger,

plume of turbid (dirty) water than thie.

pipeline; and hauling the soft wasteto the ocean for surface discharge(NSR 1987: 32-33). The ocean sur-face disposal method was chosen be-cause it was considerably cheaperthan the other options. A soft wastedump site will be constructed alongthe shoreline below the plant site.When soft waste is dumped from t09tonne rear-dump trucks over thedump face the material will cascadedown the steep slope as a densitycurrent like that produced by thesubmarine tailings disposal system.The submarine slope would becomecovered by a veneer of soft wastesediment and a localised increase inturbidity would occur at and sur-rounding the dump site. Soft wasteproduction will peak at 7.3 Mt ayear, and this corresponds to about20,000 tonnes a day or 183 truckIoads a day.

It was this aspect of the overallwaste disposal strategy that causedthe greatest concern and considerableeffort was given to predicting itsphysical and biological effects (NSR1987: 107-126). In a zone 0.5 kmeither side of the dump site the ef-fects were predicted to be severewith sedimentation damage to thefringing coral reef and with thewater in the nearshore zone beingfrequently turbid. This would lead toa marked reduction in coral faunadiversity and reduced numbers anddiversity of fish. There would be asignificant reduction in the numbersof fish that could be caught by localvillagers.

The effects would be progressivelyless severe either side of this centralzone and would cease about 3 km tothe west and 6 km to the east of thedump site. Compensation will bepaid by the company to the villagersfor losses of marine resources andamenity as a direct result of dis-colouration of nearshore waters fromsoft waste disposal.

Seowoler -loilrng mrxing lonk