Esso Norge AS’ (ENAS) Valløy site is one of the oldest industrial sites in Norway. Refinery activities have been performed there for nearly 100 years, from 1900 to 1993, and parts of the refinery were also bombed during World War II and rebuilt in the early 1950s. All oil-related activities at the site were discontinued by 2001.
Following the closure of the refinery, cleaning and demolition works took place, after which the site was thoroughly investigated and widespread soil contamination was discovered which needed to be remediated.
Various fuels and petroleum-related products were produced during the refinery operations, including transformer and lube oils. The production process resulted in waste materials such as acid tar and Fuller’s Earth. Remediation is required to comply with the ‘Miljødirektoratet’ criteria, whereby the land has to be suitable for commercial and residential use.
The soil remediation activities involve the removal of the most heavily impacted soil materials and any free-phase oil products encountered. Activities proposed for the two site areas, Area A and B, will effectively remove the most important contaminants that could impact the groundwater and then in the long-term, groundwater quality will further improve through natural attenuation. The groundwater will be monitored during and after remediation to verify that natural attenuation is taking place.
All waste above Site Specific Acceptance Criteria (SSAC) will be removed layer by layer using 25 x 25 m grids. Non-hazardous waste (Class 2 to 5), if feasible, will be sorted and segregated, and the different waste fractions (soil, bricks, concrete, metal) will be delivered to ExxonMobil-approved landfills, if it is not possible to reuse them on site. In Area B, the hazardous acid tar will be conditioned in a mixing plant by using lime and wood fibre. The neutralised and stabilised material will be stored on site until it is accepted at an approved hazardous waste (co)incineration plant. Material will be transported off site by truck and boat.
Boulders, with a surface contamination requiring treatment, will be cleaned mechanically using a scrubbing process (impact crushing), which results in a reduction of the size of the boulders. The contaminated fines fraction removed from the coarse fraction by segregation will be subjected to chemical analysis to determine the appropriate treatment/disposal method. After verification of its quality, the coarse fraction will be reused on site.
Project preparation and site installation got underway in late 2015 and the site is expected to be fully reinstated with demobilisation taking place between July 2017 and August 2018.