Sustainable risk-based analysis towards remediation of an aquifer impacted by crude oil spills

Abstract

Uncontrolled release of hydrocarbons from pipelines results in soil and groundwater contamination. However, due to the geo-environmental properties of the contaminated area, the remediation strategies might vary by light non-aqueous phase liquid (LNAPL) behaviors. In this study, a contaminated area with spilled oil from a pipeline was monitored. In the initial investigation in the 1980s, the contamination was reported in some citizen wells (CIZs), which resulted in drilling of 15 boreholes (BHs) across the Site from February 2001 to February 2007. Additionally, an area of around 0.24 km² encompassing the LNAPL was inferred. The extension of plume in 2016-7 was monitored in this study, in which new farms were impacted by the contamination. Further, a conceptual model based on the previous information and current measured data was developed to better understand the behavior of the plume. The model showed that the Site is very complex, dipping towards the south, and the groundwater contains light hydrocarbons. Pumping tests, as a part of LNAPL remedial technology, were conducted by using three pumping wells (PWs), each accompanied by a monitoring well. Accordingly, a risk-based corrective action was implemented to eliminate and control unacceptable risks in a safe and timely manner. From the remediation approach, a monitoring plan in BHs and CIZs was suggested. In the case of receptors (humans and farms), clean-up of wells, tanks, and water channels as well as replacement of contaminated soils were highly regarded. Although the recent investigation and clean up monitoring wells showed that the LNAPL was very minimal, further steps in the receptor side should be taken prior to irrigation applications.

Keywords: Contamination; Light non-aqueous phase liquids (LNAPL); Pumping test; Remediation; Sustainable risk-based analysis.