ABSTRACT
A very large environmental experiment in progress has featured not only factual uncertainties and arguments but also a program of balancing acts among alternative sets of costs and benefits. The experiment, at this writing most focally centered in Western Pennsylvania but proceeding nationwide, involves "hydrofracking," the industry shorthand for the drilling process of high-volume horizontal hydraulic fracturing, used to pull natural gas from sites often more than a mile below the surface of the earth. A very large continuing outdoor experiment, one of the biggest in American history and one of the riskiest to human health, took place at a test site for atomic weapons in Nevada over more than a decade beginning in 1951. The story of fracking, oil-slick- and chemical-ridden as it is, will continue indefinitely, and as it continues, it will illustrate the complexity of large-scale environmental experiments.
