On September 26, 1908, a chlorination plant designed by the sanitary chemist John L. Leal began operating at the Boonton Reservoir, twenty-three miles from Jersey City, New Jersey, releasing a diluted solution of chloride of lime into the pipe carrying water to more than two hundred thousand people. Nobody had disinfected an American public water supply this way before, continuously, at this scale. A New Jersey court had already ruled that the water sometimes failed the one promise the company had made in writing, and had given the company ninety days to propose a fix, though proving it actually worked would take the court nearly two more years.
That promise was two sentences in an 1899 contract: the water delivered must be pure and wholesome for drinking and domestic purposes, free from pollution deleterious to health. Jersey City sued, and on May 1, 1908, Vice Chancellor Frederick Stevens agreed, narrowly. Two or three times a year, during floods, bacterial counts at the delivery point ran high enough to call the water's quality doubtful. Stevens's opinion dismissed one fix, a filtration plant, as too expensive and never part of the contract, and suggested instead, from evidence the city itself had offered, that sewers be built across the watershed. Leal, the company's sanitary adviser, believed the contamination came mostly from farm runoff, not sewage, and that sewers would not fix it. The court's June decree gave the company ninety days only to propose that remedy, not to prove it worked.
Leal's fix cost fourteen cents per million gallons, a dose of 0.2 parts of chlorine per million parts of water, raised to 0.35 only during floods, too faint to taste or smell. That faintness is why the case turned on laboratory counts rather than anyone's word. Raw water reaching the reservoir carried from two hundred to twenty thousand bacteria per cubic centimeter, with the intestinal organism B. coli often detectable in samples as small as a tenth of that volume. After the plant started, water reaching Jersey City averaged twenty to thirty bacteria per cubic centimeter, and B. coli turned up in a ten-cubic-centimeter sample only three times in the next seven months, as Leal reported that June.
A second trial, meant to test the effectiveness of the new process, opened three days after the plant did. Nineteen months later, on May 9, 1910, special master William Magie ruled that it worked. Economists later studying thirteen major American cities that adopted chlorination and filtration found their combined typhoid mortality fell more than ninety percent within five years of adoption. Jersey City itself never built the filtration plant the lawsuit once threatened to require; chlorine alone remained its proof of purity for the next seventy years.
None of that required trusting the water company, the city, or Leal himself. It required a test nobody could out-argue: a measured volume of water, a nutrient plate, and a count of what grew on it overnight. The contract had promised wholesome water for nine years before anyone could say what the word actually meant. A bacteria count said it first.