This article departs from the view in which ignorance is seen as necessarily detrimental and analyses how specified ignorance (here called ‘nonknowledge’) can even serve as a productive resource. By using the example of cleaning up contaminated land in a timely and effective manner, it is argued that nonknowledge is a useful resource; in some instances, on a par with knowledge in its importance. The article discusses some of the strategies used to cope with ongoing situations involving ignorance in the remediation of areas containing multiple contaminant sources and plumes. Analysis of these processes indicates that planning and policymaking may benefit when limits to knowledge are openly acknowledged.