To cope with saltwater intrusion, coastal cities have drilled new wells farther inland. They have pumped those harder and relied less on their eastern wells, usually tapping them only in wet periods. Some towns put their endangered wells on standby. But coastal towns are reluctant to abandon coastal wells altogether. The water that bleeds into them has moved much farther through geological filters, including fine-grained sand, and is clearer than water in western wells, he said.
Western water is darker, more tea-colored, from soaking through Everglades muck and organic matter.
It costs more to clean because there is more color to strip out. Wells closer to the coast are more productive, too, because their aquifer rock can absorb and transmit more water with less pumping. But Lake Worth had to cut back on coastal water by 75 percent because of rising salt levels in monitoring wells to the east, he said. One of those, a 170-foot deep sentinel between Federal Highway and the Intracoastal Waterway, saw chlorides leap from 275 parts per million in January to 800 ppm in April, Thew said. The drinking water standard is 250.