Word: gravel
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South of Los Angeles and inland from Manhattan Beach is a flat suburban area that was once semidesert. It had no surface water, but under its tight clay subsoil lay water-saturated gravel. When real-estate boomers discovered this treasure, they drilled well after well, and the well water, used recklessly, made the land salable for home sites and industries. Now the "west basin," as the geologists call it, has oil refineries and factories, as well as 500,000 people. But its underground water is almost gone. The water table is some 50 to 60 ft. below sea level...
Local boosters and realty boards were not anxious to shout about this creeping threat to their real-estate values, but Water Engineer Oswald A. Gierlich of Manhattan Beach refused to keep mum. He knew that the west basin's gravel recharges very slowly, that fresh water comes a long distance from inland mountains and filters through gaps in an impermeable barrier called the Inglewood-Newport Fault (see diagram). The invading sea water moves much faster. Gierlich figured that, if nothing were done, sea water would fill the whole basin in about ten years and permanently spoil the vital wells...
After years of study, the Los Angeles County Flood Control District finally decided to try an experiment. Last year its engineers pumped 100 million gallons of fresh water into the salted gravel under Manhattan Beach. Observation wells drilled alongside showed that the fresh water did not mix much with the salt, but forced it away, forming a mound of freshwater gravel. The sea water still seeped inland around the mound, like a stream flowing around a rock, but at that one point it was stopped...
...Flood Control District is drilling a line of twelve-inch "injection wells" 1,000 ft. apart and parallel to the beach. When fresh water is forced into the wells, it will form a dike of saturated gravel that will keep the sea water from entering the pumped-out basin. Gierlich hopes that the basin will eventually be filled to above sea level by the natural seepage of mountain water. Then the sea will no longer try to invade it. The industries and the people who depend on west basin water will never be able...
...damming half a dozen mountain lakes, creating a waterfall 15 times as high as Niagara, to power the world's biggest aluminum plant. In Northwestern Ontario, engineers are draining a 150-ft.-deep lake; when it is dry, they will dredge away 70 million tons of clay and gravel from the bottom to get at an iron-ore deposit that lies underneath...