Application of Hydrogeophysical Resources as an Onshore Oil Spill Response at Thange, Kenya

Pipeline oil spills are not uncommon in Kenya, with an average of 3 incidents a year being significant enough to require Tier 2 intervention involving other agencies, including those mandated to protect the environment, water resources, forests and wildlife. Due to the insidious nature of few pipeline spills, it is important to establish whether a spill has taken long enough to develop a plume, its direction of movement and impacts on the environment. Electrical resistivity tomography is a geophysical technique that can be used for mapping plumes and geological characterization of the host media for developing a remediation and monitoring plan. The age of the spill and natural ground conditions must be taken into account when using this technique, as new spills increase ground resistivity, while older spills that have undergone degradation by hydrocarbon-feeding bacteria increase conductivity. This study presents the case of a ruptured pipeline and the ensuing oil spill that occurred at Thange village in Kenya, in a tropical sub-humid area underlain by hard rock geology comprising volcanic and metamorphic rocks. This study demonstrated that the method can be used in plume tracing, site characterization, development of the remediation plan, monitoring plan and evaluation of remediation performance. The study also provides a unique reference for 2D electrical resistivity tomography application building on its application in site assessment post spillage and post-remediation. Moreover, this study demonstrates the correlation of 2D resistivity results with water quality data and better interpretation of the results.