Regulation of injected ground water tracers

Ground water tracer tests are routinely performed to estimate aquifer flow and transport properties, including the determination of well capture zones , hydrogeologic parameters, and contaminant travel times. Investigators may be unaware of tracer test reporting requirements and may fail to notify th eir regulatory agency prior to conducting tracer tests. The injection of tr acers falls under the jurisdiction of the federal Underground Injection Con trol (UIC) program, which regulates the introduction of substances into und erground sources of drinking water as part of the Safe Drinking Water Act. The UIC program is administered by the U.S. Environmental Protection Agency (EPA) and by states with EPA-approved programs. The federal UIC program re quires that tracer tests must not endanger underground sources of drinking water, and all tracer tests must be reported prior to injection. We contact ed the UIC program administrator for every state in early 1997, Some states report having more stringent requirements, while some states do not meet m inimum federal requirements. Although the primary responsibility for ground water tracer selection and use rests on the investigator, national guidanc e is required to assure compliance with the UIC program. To assist investig ators, we present acceptable tracers that have been identified by two state s, Nevada and South Carolina, that require no further regulatory review.