The presence of LNAPL and the characterization of LNAPL in the subsurface is often determined primarily by the measurement and observation of LNAPL in monitoring wells. It is noted, however, that the relative measure of apparent thickness of LNAPL in a well, while indicative of LNAPL presence, has been shown to be a poor … Continue reading
Abs: This section is to provide introduction on technical tools used for LNAPL site characterization The delineation of contamination is contingent on a number of factors. It is important for investigators to understand the extent of LNAPL in a timely manner. Conducting this activity should include upfront planning for, and obtaining access to, locations to … Continue reading
The LNAPL Conceptual Site Model (LCSM) is the body of information describing aspects of the LNAPL and site setting necessary to satisfy the LNAPL remedial objectives. The LCSM is similar to a conceptual site model, which includes the source, pathway, and receptors, but the emphasis in the LCSM is on the source component (i.e., … Continue reading
To begin proper management of an LNAPL site, one must first determine the problems or concerns that the LNAPL poses at the site. A complete site characterization and LCSM will help to identify these concerns. Once the concerns are identified, appropriate “LNAPL remedial objectives” are set to eliminate the LNAPL concerns at … Continue reading
Once the remedial action is implemented, monitoring is required to assess the protectiveness and effectiveness of the chosen interim remedial measures (IRM). The type and frequency of monitoring should be based on the CSM developed for the site which identifies the LNAPL type, source and distribution, site specific receptor issues, hydrogeologic influences on LNAPL behavior … Continue reading
Sites contaminated by chlorinated solvents present a remediation challenge. Chlorinated solvents are among the most difficult groundwater contaminants to remediate, especially at sites with dense, non-aqueous-phase liquid (DNAPL) still present in the source zone. Restoring sites contaminated by chlorinated solvents to regulatory criteria (low parts-per-billion concentrations) within a generation (~20 years) is difficult. Site managers … Continue reading
Type of DNAPL and DNAPL Properties Common DNAPL compounds include materials that have been or are still widely used in industrial and commercial processes, such as the following: chlorinated solvents coal tar creosote heavy petroleum—for example, No. 6 fuel oil products polychlorinated biphenyls (PCBs) pesticides DNAPLs are denser than water, with limited and varying solubility … Continue reading
Integrated site characterization (ISC) is a process for improving the efficiency and effectiveness of characterization efforts at DNAPL sites. It encourages characterization at a sufficient resolution to capture the effects of the heterogeneities that direct contaminant distribution, fate, and transport, and remediation effectiveness, so that an integrated three-dimensional conceptual site map (CSM) can be developed … Continue reading
The Tool Selection Worksheet offers a rapid method of identifying the appropriate tools and information for collecting geologic, hydrologic, and chemical data. Specific tools and techniques are listed in the following categories within the left column of the Tool Selection Worksheet: Geophysics surface geophysics downhole testing Hydraulic testing single well tests cross borehole testing Vapor … Continue reading
Tool List Description Geophysics Surface geophysics 1. Ground penetrating radar locate geologic materials based on reflection of electromagnetic pulse between layer of dielectric properties 2. High resolution seismic reflection seismic reflection for profiling stratigraphic layers to large depths 3. Seismic refraction seismic refraction for 2D interpretation of lithological layer 4. Electrial resistivity tomography indicate broad … Continue reading
