I am delighted to open this symposium on underground waste management. It would be difficult at this juncture to count the number of projects undertaken cooperatively by the AAPG and the USGS, for they have been numerous, indeed, and have taken place over several decades. Whatever the number, both organizations can take pride in the way in which they have joined their efforts to advance geologic knowledge in the service of the nation. Speaking for the Geological Survey, I am eager to see this cooperation continue and expand, and I intend to offer some suggestions for additional cooperative projects. Now, however, I want both to commend and thank those in both organizations who were responsible for arranging this fine symposium on such a timely and important topic.
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This publication consists of papers based on oral presentations at a symposium of the same name co-sponsored by the United States Geological Survey and the American Association of Petroleum Geologists. A wide range of technical issues are covered, as well as regulatory and liability concerns. Documentation of two areas in Colorado where earthquakes had resulted from subsurface fluid injection set the stage for modern debates regarding possible similar results elsewhere. A wide range of fluid compositions are subject to subsurface waste disposal. The largest volumes are brines separated during the production of oil and gas wells, but acid-water and industrial wastes of all types can be disposed in significant quantities in local areas. Large hydraulic fracture treatments never recover all of the injected fluids, and the chemical additives in the fluid that remains underground can be a concern. The subsurface injection of radioactive waste is a topic for three of the papers. The possible need for sequestration of carbon dioxide was not a significant concern at the time and was not covered, but many of the papers provide insight into the issues related to modern proposals. When fluids are injected under pressure into subsurface aquifers, they interact in numerous ways. The fluids can potentially migrate for long distances and potentially interfere with other uses for the native aquifer fluids. If the aquifer cannot transport all of the fluids away, the buildup in pressure can cause fracturing of the rock. Differences in composition between the injected and native fluids can cause chemical reactions to occur; in some cases these can be desirable in that they can immobilize certain solutes in mineral form. The long-term environmental consequences are a common theme in many of the papers because of the recognition that the disposed fluids would become a permanent fixture in subsurface aquifers and could have long-term consequences for their future utilization.