Analysis of DNAPL Source-Depletion Costs at 36 Field Sites
A recent U.S. Environmental Protection Agency (US EPA) expert panel on dense nonaqueous phase liquid (DNAPL) remediation concluded that uncertainty in the costs and benefit of applying source-depletion technologies (i.e., active remediation in source zones) is one key factor that discourages widespread use of these technologies at DNAPL sites (Kavanaugh et al., 2003). To reduce this uncertainty, a detailed evaluation of remediation costs for four active source-depletion technologies was conducted. The source-depletion technologies evaluated were enhanced bioremediation, chemical oxidation, surfactant/cosolvent flushing, and thermal treatments. An extensive review of peer-reviewed literature, conference proceedings, state and federal government agency reports, Internet databases, and technical surveys yielded cost and performance data at 36 full-scale and pilot-scale source-depletion sites. The data indicated that enhanced bioremediation has the lowest median cost per treatment volume of $29/yd3 (n = 11), followed by thermal, chemical oxidation, and surfactant/cosolvent at $88/yd3 (n = 13), $125/yd3 (n = 6), and $385/yd3 (n = 6), respectively. Only a slight correlation was observed between treatment size and total treatment cost; however, longer treatment durations correlated to lower treatment costs per volume. Treatment performance appeared to be independent of unit treatment costs. The resulting cost statistics and unit costs can be used to compare the cost of source-depletion projects against the life-cycle cost of long-term plume management techniques such as monitored natural attenuation or plume containment.