Many decisions related to the protection and remediation of groundwater in the 1970s and 1980s were not informed by a rigorous or systematic evaluation of costs and benefi ts. This circumstance existed because of the concern about widespread contamination of groundwater that had occurred and public outcry for a response. Governments wanted to get the sites and the resource cleaned up as quickly as they could, often without a careful study of the options and because of political pressure. Cost-benefi t methodology had been applied to surface water supply projects for decades. For groundwater, political and public pressure was largely driving funds to be spent without a disciplined approach to the costs and benefi ts. Importantly, cost-benefi t analysis (CBA) should be viewed as a “process meant to yield information rather to make decisions…” (Lave, 1996, p. 128) One of the fi rst reasonably complete treatments of groundwater with a cost-benefi t approach appeared in 1993 (USEPA, 1993). The groundwater supply industry, as a partly regulated sector, makes its investments based on understanding the costs and benefi ts (returns) of options for supplying water. Clearly, the chemical products industry that has large volumes of liquid waste to dispose of has concluded that underground injection of those wastes, even with permit processing requirements, is often more cost effective than other means of disposal in the existing regulatory environment. These relationships suggest that a cost-benefi t framework has application to groundwater resource decision making.