ENV-07-129 Practical Experience with the New LNAPL Management Paradigm

Description:

The typical approach to evaluating LNAPL impacts, using conventional assessment methods is limited by the location and spacing of the monitoring points and the position of the potentiometric surface during sampling. It often results in an oversimplified understanding of the LNAPL. Unfortunately, this can result in over designed and underperforming recovery systems. Recently, guidance has been developed (e.g. NAPL Alliance, API, ASTM) that presents a more robust approach to LNAPL characterization. This new LNAPL paradigm includes evaluating how the capillary properties of the soil affect the distribution of LNAPL and how LNAPL mobility is affected by subtle changes in soil heterogeneity and fluid properties. Trihydro employs investigative methods (ROST, CPT) that characterize LNAPL impacts on a very fine scale to identify subtle variabilities in the subsurface. Ultimately LNAPL mobility and recovery are controlled by relative permeability and pore throat displacement pressures. These concepts can be applied to optimization of existing remedial systems and can be used to develop remedial endpoints that make sense. Trihydro has implemented the new LNAPL paradigm approach at several sites. In this poster we present practical tips and lessons learned from our experience in the realm of LNAPL assessment. We use these datasets to construct a robust SCM that is applied to remediation system design/optimization, and allows implementation of a consensus-based remedy decision process. Overall, the new LNAPL framework establishes a practicable vision that is consistent with regulatory requirements and establishes goals that can be attained within a realistic timeframe and a reasonable budget, using a phased, stepwise process.