Environmental Problems, Their Causes, and Sustainability 1

Figure 22-9 Natural capital degradation: principalsources of groundwater contamination in the UnitedStates. Another source is saltwater intrusion from excessivegroundwater withdrawal (Figure 15-17,p. 320).Polluted airPesticidesand fertilizersHazardous wasteinjection wellCoal stripmine runoffDeicingroad saltBuried gasolineand solvent tanksPumpingwellWaste lagoonLandfillGasoline stationWaterpumping wellSewerCesspool,septic tankAccidentalspillsLeakagefrom faultycasingUnconfined freshwater aquiferConfined freshwater aquiferConfinedaquiferGroundwaterflowDischargeThus it can take hundredsto thousands of yearsfor contaminated groundwaterto cleanse itself of degradable wastes. On a human timescale, nondegradable wastes (such as toxic lead, arsenic,and fluoride) are there permanently.What Is the Extent of GroundwaterPollution? Uncertain Overall but Seriousin Some AreasLeaks from chemical storage ponds, undergroundstorage tanks and well piping, and seepage ofagricultural fertilizers can contaminate groundwater.On a global scale we do not know much about groundwaterpollution because few countries go to the greatexpense of locating, tracking, and testing aquifers. Butscientific studies in scattered parts of the world provideus with some bad news.According to the EPA and the U.S. Geological Survey,one or more organic chemicals contaminate about45% of municipal groundwater supplies in the UnitedStates. An EPA survey of 26,000 industrial waste pondsand lagoons in the United States found that one-thirdof them had no liners to prevent toxic liquid wastesfrom seeping into aquifers. One-third of these sites arewithin 1.6 kilometers (1 mile) of a drinking water well.The U.S. General Accounting Office estimated in2002 that at least 76,000 underground tanks storinggasoline, diesel fuel, home heating oil, and toxic solventswere leaking their contents into groundwaterin the United States (Figure 22-9). In California’sSilicon Valley, where electronics industries use undergroundtanks to store a variety of organic solvents,local authorities found leaks in 85% of the tanks theyinspected.During this century, scientists expect many of themillions of underground tanks installed around theworld in recent decades to corrode, leak, contaminategroundwater, and become a major global health problem.Determining the extent of a leak from a single undergroundtank can cost $25,000–250,000, and cleanupcosts range from $10,000 to more than $250,000. If thechemical reaches an aquifer, effective cleanup is oftennot possible or is too costly. Bottom line: wastes wethink we have thrown away or stored safely can escapeand come back to haunt us.According to the WHO, an estimated 70 millionpeople in northern China and 30 million in northwest-502 CHAPTER 22 Water Pollution