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TO "LIMITATIONS OF ROI TESTING FOR VENTING DESIGN: DESCRIPTION OF AN ALTERNATIVE APPROACH BASED ON ATTAINMENT OF A CRITICAL PORE-GAS VELOCITY IN CONTAMINATED MEDIA
Citation:
DiGiulio*, D C., R. Varadhan, AND M. L. Brusseau. TO "LIMITATIONS OF ROI TESTING FOR VENTING DESIGN: DESCRIPTION OF AN ALTERNATIVE APPROACH BASED ON ATTAINMENT OF A CRITICAL PORE-GAS VELOCITY IN CONTAMINATED MEDIA. GROUNDWATER MONITORING AND REMEDIATION Winter 2001:97-114, (2001).
Description:
In this paper, we describe the limitations of radius of influence (ROI) evaluation for venting design in more detail than has been done previously and propose an alternative method based on specification and attainment of critical pore-gas velocities in contaminated subsurface media. We utilize data from a Superfund site in which ROI testing was conducted for venting design to assess whether ROI testing results in higher estimates of radial gas permeability compared to axi-symmetric cylindrical solutions which allow leakance (permeability of a semi-confining layer divided by its thickness). We also assess whether ROI testing exacerbates nonuniqueness in estimation of kr/kz ratios and leakance. We utilize information from published studies on rate-limited vapor transport to provide the basis for selection of a minimum or critical pore-gas velocity for use at this site. Using single-well gas flow simulations, we assess whether this pore-gas velocity can be achieved at measured ROIs for six wells. We then conduct a series of multiple-well gas flow simulations to assess how variation in anisotropy and leakance values affect three-dimensional vacuum and pore-gas velocity profiles and determination of an ROI. Finally, we evaluate when attempting to achieve a critical design pore-gas velocity, whether it is more efficient to install additional wells or pump existing wells at a higher flow rate.