Rafael Munoz-Carpena Adam Foster Kati W. Migliaccio Yuncong Li Kati Migliaccio Qingren Wang 2010 <p>Groundwater is protected in most areas as it is a primary source of drinking water. In the United States, 50% of the population relies on groundwater supplies (Reilly et al., 2008). Groundwater sampling in the United States became commonplace in the 20th century as contaminated water resources became apparent and a growing public concern emerged to protect water resources. In response to this concern, the U.S. government mandated a study in which scientists identified six categories of groundwater contaminant sources (OTA, 1984):&nbsp;Category 1-sources designed to discharge substances (e.g., injection well) Category 2-sources designed to store, treat, and/or dispose of substances;&nbsp;discharge through unplanned release (e.g., landfills) Category 3-sources designed to retain substances during transport or trans-mission (e.g., pipelines) Category 4-sources discharging as consequence of other planned activities&nbsp;(e.g., pesticide application) Category 5-sources providing conduit or inducing discharge through altered&nbsp;flow patterns (e.g., construction excavation) Category 6-naturally occurring sources whose discharge is created and/or&nbsp;exacerbated by human activity (e.g., salt water intrusion).</p> application/pdf en CRC Press Groundwater sampling chapter