Sparging effectiveness for groundwater restoration

Sparging is becoming a widely applied groundwater remediation technology, even though there are few published case studies with post-sparging groundwater monitoring data to document cleanup. The best way to monitor the effectiveness of sparging systems and predict achievable postsparging contaminant concentrations is still uncertain. Most monitoring data from sparging systems are indirect measurements of system performance [dissolved oxygen, groundwater levels, soil vapor pressures, soil vapor oxygen/volatile organic compound (VOC) concentrations] rather than direct analysis of dissolved-phase contaminants. Furthermore, few distinctions have been made regarding achievable cleanup levels and required treatment durations in (1) dissolved-phase plumes and (2) source areas with residual nonaqueous-phase liquid (NAPL). This paper discusses changes in dissolved-phase chlorinated volatile organic compound (CVOC) concentrations at two sites where sparging was undertaken. Both sites are favorable for sparging, having relatively uniform, clean, fine- to medium-grained sandy soil. One site had a known presence of NAPL, while the other was a dissolved-phase plume without NAPL.