Sandia National Laboratories Chemical Waste Landfill: Innovative strategies towards characterization and remediation

The Chemical Waste Landfill (CWL) was used by Sandia National Laboratories (SNL), Albuquerque for disposal of hazardous chemicals from the years 1962 to 1985. During routine sampling in the spring of 1990, low levels of trichloroethylene (TCE) were detected in groundwater samples from a water table aquifer approximately 146 meters below ground surface. Therefore, a RCRA Site Investigation (RSI) has been initiated and remediation of organic contaminants will be performed at the CWL prior to closure of this landfill. The RSI is focused on optimal characterization of the volatile organic contamination (VOC) and dense non-aqueous phase liquid (DNAPL) contamination at this site. This will be possible through application of innovative strategies for characterization and promising new technologies which are discussed in this paper. The first part of this paper provides a discussion of conceptual models of VOC and DNAPL transport at the CWL and an overview of our investigative strategy. Each stage of the RSI has been developed to gather information which will reduce the uncertainty in the design of each subsequent phase of the investigation. Three stages are described; a source characterization stage, unsaturated zone characterization stage, and a saturated zone characterization stage. An important focus of the unsaturated zone characterization phase is to provide all data necessary to make decisions concerning the necessity of additional saturated zone characterization. The second part of this paper presents a brief discussion of some innovative approaches to characterization and remediation that are being applied at the CWL. Through the. SNL Environmental Restoration Program's desire to find new and improved methods for site characterization and remediation, several innovative technologies have been identified. These technologies include: the surface towed arrays developed by the Naval Research Laboratory for use in locating buried ordinance, core drilling using sonic energy, and soil gas measured from monitor wells to aid in characterization of the soil gas plume. Additionally, as the CWL is part of Department of Energy's (DOE) Integrated Demonstration Program, an on-site demonstration of the thermal-enhanced vapor extraction system (TEVES) will be completed and a discussion of this demonstration at the CWL is provided. (author)