Investigation and remediation of a 1,2-dichloroethane spill. Part 1: Short and long-term remediation strategies
Release of an estimated 150,000 gallons of 1,2-dichloroethane (EDC) from a buried pipeline into a ditch and surrounding soil resulted in shallow subsurface contamination of a Gulf Coast site. Short-term remediation included removal of EDC DNAPL (dense nonaqueous phase liquid) by dredging and vacuuming the ditch, and by dredging the river where the ditch discharged. EDC saturation in shallow impacted sediments located beneath the ditch was at or below residual saturation and these sediments were therefore left in place. The ditch was lined, backfilled, and capped. Long-term remediation includes EDC DNAPL recovery and hydraulic containment from the shallow zone with long-term monitoring of the shallow, intermediate, and deep aquifers. Ground water, DNAPL, and dissolved phase models were used to guide field investigations and the selection of an effective remedial action strategy. The DNAPL modeling was conducted for a two-dimensional vertical cross section of the site, and included the three aquifers separated by two aquitards with microfractures. These aquitards were modeled using a dual porosity approach. Matrix and fracture properties of the aquitards used for DNAPL modeling were determined from small-scale laboratory properties. These properties were consistent with effective hydraulic conductivity determined from ground water flow modeling. A sensitivity analysis demonstrated that the vertical migration of EDC was attenuated by dissolution of EDC into the matrix of the upper aquitard. When the organic/water entry pressure of the aquitard matrix, or the solubility of EDC were decreased to unrealistically low values, EDC DNAPL accumulated in the aquifer below the upper aquitard. EDC DNAPL did not reach the regional (deepest) aquifer in any of the cases modeled. The limited extent of vertical EDC migration predicted is supported by ground water monitoring conducted over the four years since the spill.
- OSTI ID:
- 20012709
- Journal Information:
- Ground Water Monitoring and Remediation, Vol. 19, Issue 3; Other Information: PBD: Sum 1999; ISSN 1069-3629
- Country of Publication:
- United States
- Language:
- English
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