This paper addresses the investigation and remediation work carried out at a contaminated site in the Sultanate of Oman. Groundwater and soil are contaminated by diesel. Tasks conducted in this work include, drilling/core-sampling of boreholes, permeability and pumping tests, collection and analysis of water and soil samples for hydrocarbon contamination, groundwater level monitoring, air-sparging (AS), soil vapor extraction (SVE), free product recovery and pump and treat (P&T). After six months of SVE, benzene in the soil gas was reduced from a range of 15-60 ppm to a range of 0-1 ppm. No benzene has been detected during the last 12 months. Also during the past 12 months, AS with P&T treatment has reduced the total petroleum hydrocarbons (TPH) in the groundwater from as high as 25-50 ppm to less than 0.5 ppm. Treatment processes are being shutdown in stages and groundwater and soil gas quality are being observed for any rebound in contamination.