An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

Review of Stimulation Fluid Retention Mechanisms and Likelihood of Fluid Communication with Shallow Aquifers: What's New and Different Since the 2004 EPA Study?