Characterization of Flow Parameters Controlling Soil Vapor Extraction

Abstract

Soil parameters controlling vapor flow in the subsurface are necessary to design soil vapor extraction (SVE) cleanup systems. Previous work assumes a confined flow model, with concrete and asphalt surface covers providing the confining layer and preventing air leakage into the zone of vapor transmission. SVE field tests conducted as part of this investigation, however, exhibited responses that are inconsistent with a confined flow model; it appears that the real world leaks. This paper develops a transient soil vapor extraction (SVE) testing method that considers the effects of vertical leakage. Analytic methodologies are developed that allow use of commonly available ground‐water flow type curves to evaluate SVE test data. The key implications of leaky compared to confined flow are (1) smaller values of derived vapor permeability, and (2) decreased radial cleanup efficacy, both with time and distance.

High Purge Volume Sampling—A New Paradigm for Subslab Soil Gas Monitoring

“…A conceptual sketch of the model assumptions is shown in Figure 1. The leaky aquifer model has been used in similar situations for analysis of transient vacuum response during soil vapor extraction (SVE) and landfill gas extraction pilot tests (e.g., Beckett and Huntley 1994;Thrupp et al 1996Thrupp et al , 1998. If the native soil has a high permeability, the analysis may overestimate the leakage through the slab, which is considered conservative in the context of assessing the potential for subsurface vapor intrusion.…”

“…If the native soil has a high permeability, the analysis may overestimate the leakage through the slab, which is considered conservative in the context of assessing the potential for subsurface vapor intrusion. The leaky aquifer model has been used in similar situations for analysis of transient vacuum response during soil vapor extraction (SVE) and landfill gas extraction pilot tests (e.g., Beckett and Huntley 1994;Thrupp et al 1996Thrupp et al , 1998. Transmissivity (T) and leakage (B, or sometimes l) values are adjusted to obtain the best fit between the leaky model type curves and the transient vacuum response (drawdown and recovery) data.…”

From aperture characterization to hydraulic properties of fractures

“…Air was injected under constant pressure (0.5, 1.0, 1.3 bar) and the transient gas pressure buildup and flow rate were measured in the monitoring wells. The transient and steady-state datasets were fitted with the Hantush-Jacob analytical solution (Beckett and Huntley, 1994), and numerical code T2VOC (Falta et al, 1995) to estimate the horizontal and vertical permeability (Table 2).…”

Combining steam injection with hydraulic fracturing for the in situ remediation of the unsaturated zone of a fractured soil polluted by jet fuel

“…Air was injected under constant pressure (0.5, 1.0, 1.3 bar) and the transient gas pressure build-up and flow rate were measured in the monitoring wells. The transient and steady-state datasets were fitted with the Hantush-Jacob analytical solution (Beckett and Huntley, 1994),and numerical code T2VOC (Falta et al, 1995) to estimate the horizontal and vertical permeability (Table 2).…”