SITE INFORMATION AND CORRESPONDENCE

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I. INTRODUCTION The Safe Drinking Water Act (SDWA) of 1974, as amended, requires the U. S. Environmental Protection Agency (U.S. EPA) to establish a program which provides for the safety of the nation's drinking water. The Underground Injection Control (UIC) program was established under the SDWA to prevent contamination of underground sources of drinking water from improper use of disposal wells. Underground sources of drinking water vary in depth and quality from pristine aquifers a few feet beneath the ground surface to aquifers that are thousands of feet deep containing up to 10,000 parts per million of dissolved solids, usually in the form of salts. Over 50% of the U.S. population relies on these aquifers for drinking water, and the percentage is increasing every year. Disposal wells covered by the UIC program include bored, driven or drilled shafts or dug holes whose depth is greater than the largest surface dimension, where the principal function of the shaft or hole is the emplacement of fluids. Under certain conditions, sumps, septic tanks, cesspools and drainfields may also be considered disposal wells. For the purposes of the UIC program, a fluid is any material or substance which flows or moves, whether in a semisolid, liquid, sludge, gas or any other form or state. Contaminants introduced into underground sources of drinking water through the use of disposal wells include bacteria and viruses, minerals and nitrates, heavy metals, organic chemicals and pesticides. Most types of disposal wells are subject to construction, performance and monitoring requirements designed to ensure that no contamination of underground sources of drinking water occurs through their use. Wells that discharge fluids into or above an underground source of drinking water are generally classified as shallow disposal wells and are not always subject to these requirements. The disposal of hazardous fluids into shallow wells (Class IV wells) is prohibited under the SDWA. However, many shallow wells (Class V) accept fluids that are not defined as hazardous, but still have a potential to contaminate underground sources of drinking water. EPA Region 9 is requesting closure of such wells. This guidance is designed to aid in the proper closure of shallow disposal wells. In addition to providing guidelines for the closure of these wells, general information is included concerning sampling equipment, methods and procedures for collecting liquid, sediment and soil samples; required methods of sample analysis; contractor and laboratory requirements; and sample chain of custody requirements. 3