Criteria for identifying areas of vulnerable hydrogeology under the Resource Conservation and Recovery Act: statutory interpretive guidance. Guidance manual for hazardous waste land treatment, storage, and disposal facilities. Interim report (Final)

Description/Abstract

In response to one of the requirements of Section 3004(o)(7) of RCRA, as amended by HSWA of 1984, the guidance presents guidance criteria for identifying areas of vulnerable hydrogeology. The guidance document specifies a method for determining ground-water vulnerability at hazardous waste facilities that requires the calculation of the time of travel (TOT) of ground water along a 100-foot flow line originating at the base of a hazardous-waste unit. Locations where the ground water moves fairly rapidly (those with short (TOTs) are considered more vulnerable than those with high TOTs). In general, EPA uses 100 years as the criterion for determining vulnerability; sites used for the disposal of hazardous waste are vulnerable if the ground water takes less than 100 years to travel 100 feet. The TOT concept integrates various aspects of hydrogeology into a single measure that reflects the potential for pollutant migration and exposure at a site. EPA developed the methodology for use with well-prepared, complete permit application data. The methodology depends heavily on the determination of effective porosity, hydraulic gradient, and hydraulic conductivity.