High Resolution Data Collection for Stratigraphic Analysis and Improved Conceptual Site Models

High-Resolution Data Collection for Stratigraphic Analysis and
Improved Conceptual Site Models

 Bradley D. Cross, R.G., P.G.; LFR Inc.

 Abstract

 Of critical importance to any remedial investigation and groundwater remediation program is the development of a conceptual site model (CSM). The CSM must incorporate details of the fundamental hydrostratigraphic framework that will control the physical distribution and migration mechanisms of contaminants of concern. By contrast, groundwater flow and contaminant transport models represent a simplification of those details necessary to solve complex mathematical algorithms that attempt to simulate the CSM. Detailed site characterizations are often constrained by the practical and economic limitations of data collection.  As such, our industry has often focused on the collection of highly precise and accurate chemical data collected under low resolution sampling programs (i.e., interval soil sampling and long well screen intervals) resulting in CSMs that often misguide remediation strategies.

 Aquifer heterogeneity is a primary factor controlling the duration of groundwater remediation programs. Fluid migration pathways are best defined at the facies level and can’t be adequately characterized without high resolution sampling methods. Today there are numerous high-resolution sampling technologies, including the membrane interface probe (MIP) and other direct-push geophysical tools, which can be used to provide a detailed understanding of the hydrostratigraphic framework. This presentation will provide several examples of faltering remediation strategies based on ill-defined CSMs that have been turned around by the collection of high-resolution hydrostratigraphic and chemical data, resulting in a more complete understanding of mass distribution, flux, and transport in the subsurface.