Hydrocarbon contamination was identified on a site in a historically industrial area of north-west England when heavy, high-viscosity bunker oil was found in the site’s drainage system. The heavy oil was entering the drainage system through a broken below-ground drainage pipe that was intercepted by contaminated groundwater. The oil in the drainage system and mobile oil in the subsurface posed potential risks to a nearby brook. RemedX was commissioned to undertake a remediation pilot study to assess the feasibility of steam-enhanced, dual-phase extraction for removing the high-viscosity oil from the soil and groundwater. The trial’s success led to the use of this technique at full scale.
RemedX engineers installed 31 remediation, 18 steam injection and 4 temperature monitoring wells, before subsequently installing a steam-enhanced, dual-phase extraction system. The system included a soil vapour extraction unit, a chiller, a total fluids extraction unit, a buffer tank, two oil–water separators, a dissolved air flotation unit, a sand filter, aqueous-phase carbon vessels and a 2-m3 vapour-phase carbon vessel.
Our remediation strategy involved dividing the plume area into five treatment areas. Each treatment area was targeted individually to maximise the abstraction of high-viscosity oil. During initiation of the targeted strategy, our scientists successfully trialled a new method for gauging high-viscosity oils to provide accurate measurements of the oil thicknesses in the wells. Accurate measurement of the oil thickness was previously complicated by the high viscosity of the heavy oil. Successful gauging enabled better conceptualisation of the site and the oil behaviour during treatment to enhance performance in each targeted extraction phase. Following the remediation operation on-site and the targeted strategy implementation, the oil recovery was declared asymptotic with the oil mass and mobility was reduced to acceptable levels. This information was subsequently validated and agreed with the regulatory authorities. In total, the system extracted 129,845 L of high-viscosity oil from the subsurface and treated 10,575 m3 of groundwater.
This project was a Brownfield Briefing Awards 2018 winner for Best Use of a Single Remediation Treatment Technique.