earlier.52 Each tiny shift Trudy caused at that one sensor, in one place, in one network, at one point in time, made sense on its own. At a privately owned water treatment plant in West Virginia, a conductivity measure reported back that it was detecting higher levels of selenium, which was often caused by runoff from nearby coal mines.53 The system automatically responded, as it was supposed to do, by adding in a pulse of ferric oxide to balance the chemistry.54 At a county-owned plant in Northern Virginia, slight differences in pipe pressures were reported, while at a small town-run plant in
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