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Gold mining may bring to mindimages of grizzled prospectorsprodding stubborn, overloadedburros or standing knee-deep in

cold California steams, panning for nuggets.Modern gold mining, however, is a machine-and chemical-intensive endeavor in whichhundreds of tons of rock are moved andprocessed for every ounce of gold extracted.“It’s common now to talk about a one billionton open-pit mine,” says Glenn Miller, aprofessor of environmental and resource sci-ences at the University of Nevada at Reno.

According to the Worldwatch Institute,all mineral mining in Canada generates 650million tons of waste per year. Miller esti-mates that each year gold mining alone in theUnited States generates about 1 billion tonseach of waste rock and tailings (the finelyground remains of milled ore), numbers thathave actually gone down in recent years, dueto the drop in gold prices and the scarcity ofhigh-grade ore.

The gold nuggets and rich veins of gold ofa hundred years ago are tapped out, andtoday’s miners work deposits containing as lit-tle as 0.015 ounce of gold per ton of rock, inthe process excavating as much as 4 billiontons of rock during the course of a mine’soften short working life, Miller says. Thesemassive operations bring with them newpotentials for environmental damage includ-ing accelerated acidic runoff, accidental wastereleases, and leachate that can infiltrate water-ways and aquifers.

By no means, however, are modern mega-mines the only, or perhaps even primary,source of environmental damage. Long-abandoned North American gold mines andcontemporary small-scale artisanal mines inthe Amazon are an ongoing source of mercu-ry, which is bioaccumulating in food fish.

As the extent of damages from miningbecomes more apparent, scientists, engineers,and regulators are investigating ways to miti-gate the impacts of old mines and prevent

current and future mines from developingsimilar problems. The most environmentallyresponsible gold mining companies arespending millions of dollars restoring the sitesof closed mines and developing technologiesto minimize the impacts of current mines.But many of these techniques are unproven inthe long term or have already been provenineffective, environmentalists warn.

A better solution, they say, is to site goldmines in only the driest and most seismicallystable locations possible and to reduce goldconsumption, because most—as much as90% by some estimates—goes to nonessentialapplications such as jewelry. “There’s no pointin destroying communities, the environment,the water that we drink to mine a mineralthat has no particular use other than to fulfillcertain cultural fantasies,” says CatherineBaldi, information coordinator for ProjectUnderground, an extractive industry–focusedenvironmental group based in Berkeley,California.

A 474 VOLUME 109 | NUMBER 10 | October 2001 • Environmental Health Perspectives

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Acid Mine Drainage: Eating Away atthe Environment In the United States and Canada, gold mines—some more than 100 years old, some recentlyclosed, and some active—are leaking acidicwater, resulting in hundreds of millions of dol-lars in remediation costs. U.S. EnvironmentalProtection Agency (EPA) officials estimate that40% of western U.S. watersheds are affected bymining pollution. There are more than 25mines, some of them active, on the U.S.Superfund list.

Of all the environmental hazards that goldmining presents, the mining industry and envi-ronmentalists agree that acid mine drainage(AMD) is by far the most serious. AMD is aprocess in which acidic water is produced fromthe combination of sulfide minerals (such aspyrite, marcasite, and chalcopyrite), water, air,and highly specialized bacteria.

Naturally occurring acid rock drainage hasbeen around as long as sulfide minerals, air, andwater have, and anthropogenic AMD dates back

to at least the Middle Ages. But new techniquesin mining in the last three decades have pro-duced a virtual flood of acid water throughoutthe American West, Canada, and overseas,resulting in billions of dollars of expenses tomining companies and, more often, taxpayers.

Naturally occurring acid rock drainage canproduce a trickle of acidic water that stains rockfaces red. In fact, “red water” and the stains itleaves were one of the first signposts miners usedto find mineral deposits. But mining can great-ly accelerate the process. “When that rock wasburied in the ground two, three, four, five hun-dred million years ago, whatever oxidation wasgoing to occur in those systems has occurred oris occurring very slowly because it’s all coveredwith water or isolated,” Miller explains. “What[mining has] done is bring up that very reactive,potentially thermodynamically very unstablerock with respect to oxidation and put it nearthe surface.”

According to the December 1994 U.S.Geological Survey (USGS) technical document

Environmental Health Perspectives • VOLUME 109 | NUMBER 10 | October 2001 A 475

Focus • Tarnishing the Earth

Gold Mining’s Dirty Secret

Acid Mine Drainage Prediction, once thosesulfide materials are exposed to a steady sup-ply of water and air, they begin producingsulfuric acid, and that in turn provides amedium in which thrive microbes that fur-ther oxidize the minerals, producing a self-perpetuating chain reaction. The resultingwater can be so acidic that in undergroundmines it has dissolved iron tools, and in pitlakes it has killed migrating waterfowl thatstopped for the night. (The most acid waterin the world is found in underground cavesat the Iron Mountain mines in northernCalifornia, a source for many metals, includ-ing gold. The pH there is -3.6, 10,000 timesmore acidic than battery acid.)

AMD seeps out of fields of tailings, pilesof displaced surface matter (“overburden”),and piles of rock being slowly processed forgold removal. If left unchecked, it can con-taminate groundwater and entire watersheds,contributing not just acidity but heavy met-als—such as arsenic, lead, cadmium, mercury,zinc, iron, copper, aluminum, manganese,and chromium—which it releases from theore it passes through.

At Spirit Mountain, Montana, AMDintroduced lead, arsenic, and cadmium intothe streams and aquifers that supply drinkingwater for about 1,000 people who live nearby.And the open pits themselves often fill withacidic water after mining operations cease.

Many mining pits intrude below thewater table and so must be continuallypumped dry. After the mine closes, thepumps are switched off, and the pit fills tobecome a small lake, in many cases an acidicone. As the level of the toxic water rises, it canbegin to infiltrate into groundwater. Such isthe case at the notorious Berkeley Pit, thelegacy of a Butte, Montana, copper mine thatused some of the same methods as goldmines. Today this pit threatens Butte’s shallowdrinking water wells.

Although a boom industry has emergedthat specializes in AMD prevention and siteremediation, acid drainage is difficult to pre-vent and even harder to stop once started.“There’s not much you can do from a micro-bial standpoint to affect those processes,”Moore says. “Once you get acid minedrainage, it’s extremely difficult to stop it, andbasically all you can do is treat it.”

Typical treatments for already activeAMD include adding lime to acidic waterand intercepting and transporting leachatebefore it can enter ground or surface water.But these methods are expensive and, if AMDisn’t halted, must be maintained indefinitely.

Preventing AMD in the first place is a bet-ter option, and good business too, says KeithFerguson, vice president of sustainability forCanadian operations for the Vancouver-basedPlacer Dome mining company. That’s why

Placer Dome and other companies areresearching ways to operate mines that do notproduce acid. “There is a long-term liabilityand cost to [AMD],” he says. “That’s not theway you want to operate mines.”

Assuming that the rock bears sulfides,that means preventing either air or waterfrom contacting the rock, says DebraStruhsacker, a geologist and environmentaland government relations consultant to themining industry. “If you point to old mines. . . many of them have acid rock drainage oracid mine drainage problems. But that’sbecause those mines were built without thebenefit of any kind of engineering designcontrols or environmental awareness aboutthat problem,” Struhsacker says. “Before youcan get a permit at a mine today, you have toknow whether the rocks you’re exposing havethe potential to be acid-generating. And if

they do, you have to design the mine toaddress that issue.”

In Nevada, where current and potentialAMD mines abound, a wide variety of tech-niques are used to protect sulfide-bearingrock, says David Gaskin, chief of Nevada’sBureau of Mining Regulation and Recla-mation. “It’s a new science. There are a lot oftraditional methods, but there are always newmethods coming out,” he says. Most systemsare quite simple.

In a dry climate such as Nevada’s, wasterock and tailings are covered with a layer ofsoil so thick that it can absorb all of the rainthat is likely to fall in a given year. Sometimesa lower-permeability layer, such as clay, sepa-rates the rocks from the soil layer. On top,indigenous flora are planted. When rain fallsin the wettest season, the soil absorbs thewater before any can reach the sulfide rocks,

and it holds the moisture until the dry season,when it evaporates.

In other situations, such as moderatelywet climates, it is often more practical todeprive the rocks of oxygen by covering themin water, says Ferguson, which usually meansplanning in advance to build an additional pitin which to dump waste or to design a tailingsimpoundment that can contain waste rock aswell. After the mine closes, the pit impound-ment is flooded and then protected with a soilcover that lets rain in and keeps the rock sat-urated with water.

To further deprive the rock of oxygen,Placer Dome is experimenting with introduc-ing biological agents in the wetted rock pile.Says Ferguson, “You then build up an organ-ic layer where you get bacteria, like algae, andin that way you reduce oxygen right at the toplayer of your tailing.” To reduce the availabil-ity of sulfides to both water and air, other newtechniques have been tried, such as autoclav-ing and encapsulating the rock in materialssuch as silica.

None of these techniques, however, aremore than two decades old, and many maynot work adequately or at all, Myers warns.“We have models that are being used thathave never been properly validated. They’venever been tested against a real-life situation.”

Covering rocks and tailings, for example,may not prevent oxygen from reacting to sul-fides in the rocks, he says. Substantial quanti-ties of oxygen can be trapped in waste rockand tailings, and oxygenated water can infil-trate the area from other sources.

“No one will know [how effective thesetechniques are] until we start having some ofthese larger pits fill and see whether they goacidic or not,” says Myers. “The miningindustry and state regulators assume that itwill all be submerged and will shut off theoxidation process. We say maybe, but ifthey’re wrong we have a huge problem.”

What’s Wrong—and Right—withCyanideThe term cyanide encompasses a variety ofcompounds produced by plants, soil bacte-ria, and invertebrate organisms, as well ascommercially, that have a single carbon atomand a single nitrogen atom. According to theMineral Policy Center, a mining environ-mentalist organization based in Washington,D.C., fatal human doses range from about40 to 200 milligrams of pure cyanide orabout a teaspoon of 2% cyanide solution.According to the World Health Organ-ization, about 200 tons of sodium cyanideare produced per year, about 180 tons ofwhich are used in gold mining.

Early methods of separating gold fromunwanted materials relied on either flotationmethods (in which a slurry of powdered ore,



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From gold to red. Wastes from gold mininghave leached acid and heavy metals intoFisher Creek, just outside YellowstoneNational Park, turning its waters red.



water, and chemicals is injected with air bub-bles, which forces gold flakes to the slurry’ssurface) or mercury amalgamation (in whichraw materials are passed over sieves that arecoated with mercury, which bonds to gold).But these methods aren’t efficient enough tomake extremely low gold content ore worthprocessing. Instead, large commercial minesuse a “lixiviant” to dissolve minute particles ofgold, freeing them from the ore to which theyare bound. Cyanide has a virtual corner onthe lixiviant market.

The “vat leach” technique of mixingcyanide and gold in containers has been inuse since the nineteenth century. In vat leach-ing, the highest gold content ore is finelymilled and mixed in vats with a combinationof sodium cyanide and lime. This removes upto about 97% of the gold. Left over is a slur-ry of tailings that is stored in ponds where iteventually solidifies.

More recently, cyanide has been used withthe technique of “heap leach” mining thatsupplements and sometimes replaces the vatleach technique. Proposed in 1969 by theU.S. Bureau of Mines and pioneered startingin 1973 by the Zortman and Landusky minesin the Little Rocky Mountains of Montana,cyanide heap leach processing is named forthe vast heaps of ore it involves, which cancover tens of acres and reach several hundredfeet high.

Ore that has too little gold content tojustify vat processing is piled in heaps overwhich a solution of water and about250–500 ppm sodium cyanide is sprayed. Asthe cyanide drips through the heap, it attach-es to particles of gold and forms a water-soluble gold–cyanide compound from which

the gold is later extracted. The gold-ladencyanide solution is collected at the bottom ofthe heap, which is usually lined with plasticover a barrier such as clay.

Typically, the heaps are built andprocessed in layers, or “lifts,” with new layersadded when lower layers have surrenderedmost of their gold. When the heap grows tootall to manage, typically about 300 feet high,a new heap is started. By the time the goldmine is ready to close, it can have excavated apit as much as a mile across and half a miledeep, leaving behind acres of processed oreheaps and hundreds of millions of tons ofwaste rock, overburden, and tailings.

“[Cyanide is] so impressive, I can see whymetallurgists don’t even want to talk aboutanything else,” Miller says. “It’s so incrediblyeffective at pulling gold. There are no alterna-tives to cyanide that even really come close,except in specialized circumstances.”

It is this very effectiveness, says SteveD’Esposito, president of the Mineral PolicyCenter, that has made mining companiescomplacent about finding a substitute forcyanide. “There are very few in industry whoperceive a need for it,” he says.

The other lixiviants for gold all have atleast one fatal flaw, adds Miller. Thiourea wasfirst mentioned as a lixiviant at least 60 yearsago. But although it is less acutely toxic thancyanide, it is a suspected carcinogen. Likecyanide, it also dissolves heavy metals in addi-tion to gold and so has the potential to causesome of the same damaging environmentaleffects as cyanide. Other possible replace-ments, such as thisulfate and halides (a groupof chemically similar chlorides, bromides, andiodides) have similar disadvantages.

Mercury: The Old-FashionedApproachAlthough not feasible for use with low goldcontent ore, perhaps even more effectivethan cyanide is the oldest chemical methodfor separating minute particles of gold fromsurrounding materials: amalgamation withmercury, which was used in ancient Romeand in the United States during theCalifornia gold rush, and is still used todayat artisanal mines deep in the Amazon jun-gles. Typically, gravel and mud are combinedwith liquid mercury, which binds to goldparticles in the mix.

But mining with mercury invariablyintroduces mercury to the environment.“Mercury is a huge issue these days inSouthern California, environmentally, andthe reason it’s out there is mining, both mer-cury mining and gold mining,” says CharlesAlpers, a research chemist with the USGS. Injust over three decades ending in 1884, goldmines in California’s Sierra Nevada rangeintroduced 3–8 million pounds of mercury tothe environment.

Today hundreds of thousands of poundsof mercury remain at each of the hundreds ofgold mining sites in the area, according tothe USGS report Mercury Bioaccumulationin Fish in a Region Affected by Historic GoldMining: The South Yuba River, Deer Creek,and Bear River Watersheds, California, 1999.This mercury converts into the more danger-ous methylmercury form and bioaccumu-lates in invertebrates, amphibians, and fish,resulting in severe restrictions in the recom-mended safe consumption levels of game fishfrom the area. “We found more than onepart per million in some of the bass in lakesD

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Unhealthy alchemy. People are exposed to serious health hazards in the Amazon through the prac-tices of panning with mercury (left) and torching mercury–gold amalgam to extract the gold (right).

on the Bear River,” Alpers says. “The averageis around point-nine or point-nine-five forbass in those lakes. And some of the troutwere over point-three, which is the new EPAguideline for mercury in [food] fish.”

More than a century after mercury-basedgold mining effectively ended in California,the environmental and financial effects contin-ue to impact hundreds of miles of U.S. riversystems. The Amazon’s 25-year-long gold rushmay cause similar effects for years to come.

In the late 1970s increasing gold pricesand the discovery of alluvial gold depositsalong scattered river systems sent small bandsof miners called garimpos prospecting deepinto the Amazon jungle, says David Cleary,who is the Amazon program manager of theBrazil Division of The Nature Conservancy.Like the California miners of the nineteenthcentury, who often poured hundreds ofpounds of mercury into troughsusing a 76-pound flask, theAmazon miners use mercury-coated sluices to glean gold fromriver deposits. “The rock comesout of the sluice boxes as mercu-ry–gold paste,” Cleary explains,“and the miners at the point ofmining generally just put itunder a blowtorch and boil themercury off it. Then it goes intoa trading chain, and at each stageon the trading chain the traderswill blast it again under a blow-torch to get the residual mercuryout.”

According to Roberta White,a professor of neurology atBoston University MedicalCenter, this mercury has enteredthe food chain and has led tomeasurable mercury poisoningof indigenous populations whoeat fish from these rivers. And because theminers both eat fish and breathe fumes, theyare doubly afflicted. “They often hadstraight-out mercury exposure as well asmethylmercury exposure, and some of themwere quite impaired on neuropsychologicaltests,” White explains. As in California 120years ago, since the late 1970s vast quantitiesof mercury—at least 2,000 metric tons byone estimate—have been added to regionalwaterways in Brazil and neighboring coun-tries, according to an article in the 1 May1998 issue of Environmental Research.

When metal mercury is methylated in theenvironment into methylmercury—typicallyby bacteria—it builds up in the food chain. Atlow levels methylmercury can cause subtlesubclinical nervous system dysfunction suchas that noted by White, and at high levels ithas been linked to tremors, paralysis, anemia,bone deformities, and death. “I think that the

whole area is contaminated, with more effectsthan we realized,” White says.

Research published by White and col-leagues in the July 1999 issue of EHP hasdemonstrated that mercury poisoning trace-able to the Brazilian gold mining boom hasdecreased the performance of indigenous chil-dren on a battery of cognitive tests of visualspatial function and memory. “What this sug-gests to us is that the central nervous systemhas been affected by the methylmercury,”White says.

Tailings Spills Take a Toll“The problem with cyanide is the scale ofmining that it [allows],” says Tom Myers, ahydrologist and director of Great Basin MineWatch, a Nevada environmental group.Cyanide, he says, has allowed heap leaching,and heap leaching lets mines profitably work

deposits that otherwise would stay in theground. That very scale magnifies the poten-tial environmental impacts that have longbeen associated with mining. The 1 billiontons of tailings produced in the United Stateseach year are contaminated with cyanide andheavy metals and must be disposed of or con-tained. And, Miller says, tailings impound-ments often leak or fail completely.

The techniques used to manage tailingsare identical for gold mining and other met-als, such as copper, but the application ofthese techniques to gold mining is relativelynew. As a result, there haven’t been as manyopportunities for toxic pits to develop andtailings dams to fail. But over time, ifunchecked—and checking may not be possi-ble—the outcomes will be the same for goldmines as for other, older mines.

Because these large-scale mining opera-tions are fewer than three decades old, the

technologies for lining tailings impoundmentsare also new—in fact, about half that age—and so unproven, says Dirk van Zyl, a profes-sor of mining engineering and director of theMining Life-Cycle Center at the University ofNevada’s Mackay School of Mines. Unlikeheaps, which must be lined to collect cyanideleaching solution, some tailings impound-ments are unlined, and others are lined withjust a layer of clay (in the United States andCanada, requirements for liners depend onstate and provincial regulations).

But most new tailings impoundments,Van Zyl says, use composite liners, which arealso used for heaps. The composite’s base isusually clay, and above that is a plastic layer,typically polyethylene or polyvinyl chloride.The plastic sheets are rolled and then weldedtogether with heat, the extrusion of moltenpolyethylene, or chemical bonding. But if

during installation the seamsaren’t connected properly or thesheets are somehow perforated,the liner will leak. “You are real-ly very dependent on theintegrity of the synthetic layer,”Van Zyl says. “There is alwaysspeculation about how longthese materials will last.”

According to geology pro-fessor Johnnie N. Moore of theUniversity of Montana atMissoula, the liners won’t lastlong enough. “People say they’renot going to leak,” he argues.“Yes, they’re not going to leakfor twenty years or maybe thir-ty years, but all of the linermaterials that are produced arenot going to last for a hundredyears, and they’re probably notgoing to last for fifty, andthey’re certainly not going to last

for five hundred years.”Cyanide is the most likely substance to

leak from gold mining tailings. In spite ofcyanide’s extreme toxicity, the environmentalimpacts of noncatastrophic releases ofcyanide from impoundments are mitigatedbecause cyanide breaks down quickly in sun-light. But sometimes free cyanide (cyanideions and hydrogen cyanide) breaks downslowly—for example in water that is ice-cov-ered and so protected from direct sun. Moreoften, it can break down into less toxic butlonger-lasting forms, such as cyanate andcyanogen, according to Cyanide Uncertain-ties, a 1998 issue paper written for theMineral Policy Center by geochemical andhydrogeological consultant Robert Moran.Free cyanide will quickly kill aquatic animals,and although the toxicity of individualcyanide complexes and their propensity tobioaccumulate in animals is not well



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View to a kill. An aerial view of the environmental damage wreaked bythe Summitville mine in Colorado.



understood, fish are known to be more sensi-tive to cyanide than mammals.

Cyanide is highly reactive with manyheavy metals, and during either heap leachingor vat leaching can form a variety ofmetal–cyanide complexes. “When you runcyanide through a heap, it leaches not onlygold and silver,” says Myers, “it also leachesarsenic, mercury, selenium, and certain otherheavy metals.” Although cyanide doesn’t reactdirectly with many of these metals, it doesbreak down the sulfides to which they arebound, releasing them. As a result, when tail-ings containments leak, these metals oftenenter ground or surface water. Increases inmercury levels in water systems, Miller says,have been linked to tailings leaks.

Arsenic is often found in runoff fromgold mines, says Kirk Nordstrom, a hydroge-ologist with the USGS. Hydrothermal golddeposits, thought to be formed when hotwater moving through the earth’s crust dis-solves metals and is carried closer to the sur-face, almost always will have significantamounts of arsenic associated with them, hesays. Although the cyanide doesn’t reactstrongly with the arsenic itself, he explains, itdoes attack the metals to which the arsenic isbound—the sulfides and pyrite. As a result,Nordstrom says, “the arsenic that is in there isgoing to mobilize faster.”

Although tailings ponds eventually dryout to become tailings fields, they continueto pose environmental hazards, Miller says.Rain passing through the materials can mixwith metal–cyanide complexes, and leak outof impoundments and into ground or sur-face water. Even if tailings stay dry, he says,they can generate potentially hazardousdust. The milling step of the vat leachingprocess generates fine particles, and the limethat is mixed with cyanide prevents smallparticles from binding together as large par-ticles. The smallest of these particles—smaller than 1–5 micrometers across—canlodge deep in the lungs, says Miller, andeven normally inert substances such as silicaare, at such small sizes, suspected to be bio-logic irritants associated with fibrosis andlung cancer.

Some of the metals found in these dusts,Miller says, include selenium, antimony, andcopper, as well as such known and suspectedcarcinogens as arsenic, cadmium, andchromium. Placer Dome’s strategy for pre-venting these sources of toxic dust, Fergusonsays, is to use earthen covers to control watercontent in the tailings fields and to recreatethe area’s original landscape and replant nativefauna. But an added hazard, says Van Zyl, isthat these released metals will be absorbed byplants that are eaten by either humans or ani-mals, starting a process of bioaccumulation inthe food chain.

The homogenous nature of these tailingsfields, Miller says, assures that they willremain an “unlimited reservoir” of dust foryears to come. If the fields were a mixture offine and coarse materials, he says, the finematerials would soon disperse, and coarsermaterials would then protect the layersbelow them from further erosion. Butbecause the materials are uniformly fine andoften elevated more than 50 meters abovesurrounding terrain, they are an ongoingsource of dust in Nevada. “The good news isthat if you get lost out there within thirtymiles, you can find out where you are just byseeing the white cloud of dust coming offthe tailings facility,” Miller says.

In sparsely populated Nevada, relativelyfew people are likely to come in contact withthese dusts, Miller says, but in other areasaround the world the risks are far greater. “In

South Africa, for every ounce of gold pro-duced they have ten times more workers thanin the United States,” he says. These workerstypically live with their families in denselypacked communities surrounding the minefields, exposing adults and children alike topollutants from these facilities.

When impoundment dams fail, spectacu-lar disasters can follow. In the last decade,accidental tailings releases in several countriesaround the world have contaminated hun-dreds of miles of rivers, killing thousands oftons of fish and resulting in hundreds of mil-lions of dollars of cleanup costs.

Tailings spills—from gold mines andother types of mines that use the sameimpoundment methods—are not unusual,either. For example, according to the 1997EPA report Risks Posed by Bevill Wastes,cyanide solution leaking from theSummitville, Colorado, gold mine—a

Superfund site—contaminated the AlamosaRiver and penetrated as deep as 10 feet intothe soil. The EPA estimates cleanup of the sitewould cost about $150 million. In 1998between 6 and 7 tons of cyanide-tainted tail-ings leaked from a South Dakota gold mineinto the Black Hills’ Whitewood Creek, dam-aging the stream for years to come, saysMoran. The 1990s saw equally damagingreleases in Montana, Nevada, and SouthCarolina.

But although leaks can have significantenvironmental impacts, more damaging arethe massive spills that result when a tailingsimpoundment collapses. Unlike in theUnited States—which, according to Van Zyl,requires cyanide-containing tailings im-poundments to be lined and built of coarsematerials such as waste rock—tailingsimpoundments overseas are made by bull-dozing the first batch of tailings into a dam.After the dam dries, it is used to containmore wet tailings. As the facility grows, thedam is continuously layered with additionaltailings, using a variety of techniquesdepending on local climate, seismic stability,and regional regulations.

But no matter which method is used,Moore says, a wet tailings dam can collapse asquickly as a sand castle. “As long as it’s dryand you’ve got enough of it, it’s a pretty gooddam,” he says. “But if you don’t keep it thatway, they’re very prone to failure.” That’s why,Miller says, the first requirement for openinga mine that is ultimately going to have a high-er probability of closing without environmen-tal problems is to find a place that has lessthan 10 inches of precipitation per year and ahot climate.

According to Moore, tailings dams breakregularly. “When they break,” he says, “it’sdisastrous because the tailings spread over awide area.” In June 2001, for example, a tail-ings dam in Brazil fractured, killing at leastfive people and dumping mine waste into theGreen River. A 1995 dam break in Guyanasent more than 2.5 billion liters of cyanide-tainted water into the Essequibo River, thecountry’s primary waterway. In March of1996, a badly sealed tunnel in a tailingsimpoundment gave way in the Philippines,completely filling a 26-kilometer-long riverwith 4 million tons of tailings containingcopper, lead, mercury, cadmium, and otherheavy metals. And in Spain on 25 April 1998,a tailings dam failed at a lead–zinc mine nearSeville, releasing 6.8 cubic meters of acidicand heavy metal–laden tailings into the AgrioRiver, a tributary of the Guadiamar River.The slurry also flooded thousands of hectaresof farmland.

More widely reported was a tailings damfailure at a Romanian gold mine on 30January 2000. The tailings dam at Baia MareM

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Split earth. At the Omai Mine in Guyana, 3.4 million cubic meters of cyanide-rich efflu-ent was released when a tailings dam failed.

ruptured, releasing an estimated 100,000cubic meters of cyanide-tainted liquid intothe watershed that feeds the Danube River.The material deposited heavy metals includ-ing copper, lead, and zinc, and killed virtuallyall aquatic life (while threatening fish-eatinganimals such as otters and eagles) for the 250miles of the river system that passes throughHungary and Yugoslavia before emptying intothe Black Sea. According to Hungary’sMinistry of Environment, drinking water for2 million people was affected, and long-termproblems may exist because of metals releasedin the sediments.

When Waste Meets WaterIn especially wet climates, companies some-times forgo tailings storage entirely. Instead,they dispose of their tailings directly in riversand oceans. Although the original method oftailings disposal in North America was topour the waste directly into rivers, by theturn of the nineteenth century that practicewas severely restricted in the United Statesand is now outlawed in the United Statesand Canada. Some North American compa-nies, however, do continue to employ “sub-marine tailings disposal,” or STD (dumpinginto oceans), and “riverine tailings disposal”(dumping into rivers) in Third World coun-tries such as Papua New Guinea, Indonesia,and the Philippines.

In the lush hills and mountains of PapuaNew Guinea, several mining companiesdump mining wastes directly into rivers andoceans. Placer Dome operates gold mines thatuse both techniques. “It’s an area of extreme-

ly high rainfall. I think it’s approximately fourmeters a year,” says Ferguson. “It’s extremelyrugged terrain with landforms that tend to berather unstable. And it’s also in a high seismicarea with very high earthquake potential. Soyou put all those together, and certainly a[tailings] dam poses its own risk.”

It is because of these physical characteris-tics, Ferguson says, that it is environmentallysafer to use rivers and oceans to continuouslyremove tailings and waste rock from certainmining operations than it is to take thechance of a catastrophic containment failure.At Placer Dome’s Misima mine in Papua NewGuinea, the company sends tailings through apipe that leads to the edge of the ocean shelf.From there, Ferguson says, the tailings travelin a cohesive stream, like toothpaste squirtedfrom a tube, into a deep ocean trench 1,000meters below the surface. To ensure that STDdoesn’t harm sensitive biota, the companymonitors areas such as nearby coral reefs;according to Ferguson, the waste rock andtailings travel well below the coral withoutaffecting it.

Environmentalists warn, however, thatSTD is fraught with potential environmen-tal impacts even when the system works per-fectly, which they say is rare at best.Sometimes mechanical devices fail. In Julyof 1997, for example, the Misima mine’spipe ruptured at 55 meters below the sea,shallow enough, says Catherine Coumans,research coordinator for the environmentaladvocacy group MiningWatch Canada, tostill threaten sensitive ecosystems.

“I haven’t been able to find a single [STD

system] where the pipe hasn’t broken, eitheron land or in the sea,” she says. “That’s a realweak point with submarine disposal. Thesepipes are constantly corroding and breaking.”Such spills have been linked to sea life killsand bioaccumulation of toxicants in food fishharvested by local people, adds Baldi.

Almost as troubling, Coumans says, arethe impacts of submarine disposal even whenthe systems work as intended. At Misima, thelevel of cyanide in the tailings is so high, evenafter a 7:1 dilution with seawater in a shore-line mixing tank, that there needs to be a1,200 × 530 meter mixing zone in the sea toallow water to meet Papua New Guineanstandards for cyanide in seawater. After thecyanide-laden tailings leave the underwaterpipe at the Misima mine, she says, rather thantravel as a coherent mass, “some of the fineparticles actually shear off from the main cur-



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A poisoned river runs through it. Tailings from the Porgera gold mine in Papua NewGuinea meet the waters from a clean tributary about 30 kilometers downriver from themine (left). Nearby, children play in the tailings, which were found to contain unhealthy lev-els of lead, arsenic, cadmium, and other toxic metals (right).

More mine waste. Cyanide-tainted effluentfrom the Baia Mare gold mine in Romaniapoisoned fish in the Danube River.

rent at various depths,” something she sayscommonly occurs in STD systems. Once sep-arated, the toxic particles can become trappedbetween layers of water of contrasting tem-peratures and densities, and these turbidityplumes have been known to be carried hun-dreds of kilometers away from their intendedresting place.

Even those tailings that do settle at theirtarget depth may not stay put. “If there’s anupwelling or an earthquake, those tailingsare going to get remobilized, they’re goingto go wherever they go, and no one will beable to do anything about it,” Coumanssays. And even if the hundreds of millionsof tons of waste material doesn’t stray, shesays it will at the least blanket tens to hun-dreds of square kilometers of ocean floor,smothering all life below it and providing acontinuous source of metal contaminationup the food chain.

Disposing of mining wastes directly intorivers presents, if anything, more serious haz-ards than STD, environmentalists say. “Bydumping toxic tailings that contain heavymetals into fisheries, it ends up killing offfisheries and effectively making communitiesaround it sick, because people eat the fish thatdo survive, and the fish will collect and con-centrate heavy metals,” Baldi says. “We havefreshwater rivers where tailings are beingdumped, and communities are drinkingwater out of it so they’re getting directlyexposed to the [toxicants] in the tailings.”

According to Ferguson, riverine disposal,when executed correctly, is environmentallybenign. The trick, he says, is to employ large,

turbulent rivers that are capable of transport-ing significant quantities of solids. It’s alsoimportant that the mine be far enoughupstream from inhabited areas to allow timefor the waste materials to disperse.

Such is the case, he says, with PlacerDome’s Porgera gold mine near the FlyRiver system in the Papua New Guineahighlands. Placer Dome and the Papua NewGuinean government—which owns a shareof the Porgera and Misima mines—considerthe first 160 kilometers of the river to be amixing zone in which mining wastesbecome diluted to safe concentrations. Thecompany conducts an extensive environ-mental monitoring program of the region inwhich the mine operates, Ferguson says,including sampling stations 40 and 160kilometers downstream from the mine. Bythe 160-kilometer point, the water meetsPapua New Guinean regulatory require-ments for heavy metal content.

Environmentalists, however, contend thatriverine disposal is never harmless. Coumanscites the Fly River as proof that no river is bigenough, sufficiently fast flowing year-round,or far enough from people and sensitivebiosystems to safely transport and dispersemillions of tons of tainted wastes. A stretch of160 kilometers, she says, is far too long astretch of water, accessed by far too manypeople and animals, to be allowed to exceedheavy metal level standards.

The result, Coumans says, is depositionof tailings sediments and heavy metals in theriver bed and on its banks hundreds of kilo-meters downstream (where the river slows

down), contamination of food fish supplies,as well as disturbing anecdotal reports such aslivestock dying after drinking river water andhuman health problems such as a mysterioushemorrhagic disease of unknown origin.

She adds that the point at which the tail-ings enter the river system presents its ownserious human health hazards. When the dis-posal pipe breaks, as it frequently does, localpeople pan for gold in the tailings as they spillout of the crack. “That location is absolutelyswarming with children and with adults whoare actually panning the tailings, panning thewaste rock, for gold,” Coumans says. “Theirbodies are just powdered with these tailings.”

Gold FuturesAs long as people demand gold, miningcompanies are going to mine gold, saysBaldi. The sad irony, she says, is that virtual-ly all of the gold mined is used for frivolousapplications. “People need to figure out thatthere is no point in mining [gold] anymore,that whatever we have in reserve can be usedto fulfill industrial production,” she says.

According to David Chambers, a geo-physicist and executive director of theBozeman, Montana–based Center forScience in Public Participation, all of thegold required by industry could be suppliedby the 10% of total annual production thatrecycling generates (for example, gold fromindustrial applications and old jewelry). “Ifyou look at the production figures—howmuch gold is produced in the world everyyear—and then you look at how much goesto jewelry, there is almost a one-to-one cor-relation,” he explains.

A mantra of the mining industry is that ifyou want gold, you have to mine where thegold is, which may not be the best place toopen a mine. As the demand for gold increas-es, so will the likelihood of mining companiesopening facilities that are either in increasing-ly remote, pristine locations or that processdecreasingly rich ore. “If gold goes to fourhundred [per troy ounce], all hell’s going tobreak loose around here,” says Myers. “Thereare an awful lot of deposits around here thatare profitable at four hundred dollar gold.”

And that, says Moore, is bad news forboth the environment and taxpayers. “I don’tknow of any mine anywhere that doesn’t havewater quality problems,” he says. “And I don’tknow of any closed mines anywhere, evennew ones, that don’t have tremendous long-term problems that are going to saddle thetaxpayers with cleanup and monitoring andremediation methods for perpetuity. That’snot a very good industry, in my view—onethat you have to pay for the product forever.”

Scott Fields



Mining and DiseaseAnother impact of gold mining on the indigenous peoples in the Amazon is theintroduction of diseases such as new strains of malaria, says StephanSchwartzman, director of international programs for Environmental Defense.“The great effects and the tragedy of uncontrolled contact with outsiders—astypically occurs in gold rush situations—is that [indigenous peoples] get dis-eases to which they have no resistance,” he says, because they were previous-ly isolated. Thousands of Yanomami Indians died in the Brazilian gold rush.Some tribes lost 80% of their populations to diseases within five years of theirfirst contact with gold miners in 1968.

The disease that has had the most lasting impact, says Cleary, is malaria. Thegold rush produced a three-pronged attack. It introduced methylmercury tothe local diets, which, according to a presentation given by Ellen Silbergeld ofthe University of Maryland School of Medicine at the 1998 annual meeting ofthe Society of Toxicology, may lower immunity to malaria.

It also pummeled rivers with water cannons, dredges, and other miningequipment, creating still pools of water that serve as breeding grounds formalaria-carrying mosquitoes. “What [mining] does to the rivers is disastrous. Itlooks like a moonscape. You have pits of standing stagnant dirty water on allsides,” Schwartzman says. “The natural flow of the river is completely disrupt-ed, as are all the streams that feed into it.”

Finally, miners from other areas imported new strains of the disease. “Themines open up, the miners go in,” says David Cleary, the Amazon programmanager of the Brazil Division of The Nature Conservancy, “and then you havedevastating malaria epidemics.” –Scott Fields

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