The purpose of this report was to investigate whether operators, in the municipality of Örnsköldsvik, comply to current regulations and guidelines regarding oil separator. In addition to this, the report also identify which standards the regulatory authority can demand of identified deficiencies, as well as an examination in how the status of oil separator are in other municipalities in Sweden. First a delimitation was made to only investigate environmentally hazardous activities such as haulage contractors. Inventories were made of a total of 12 haulage contractors, with questions from a previously made checklist. The results of the inventory indicated deficiencies in operators existing knowledge, regular self-inspection of oil separators, control frequency, record-keeping and documentation, lack of 5-year inspection and lack of oil- and sludge level alarm. This report also shows that regulatory authority can require the operators to rectify these deficiencies, in accordance with standards and established guidelines. The report also showed similar results when compared with similar surveys of operators' self-inspection of oil separator, in other municipalities in Sweden. The study suggests that regulatory authority should priority to oversight these environmentally hazardous activities with oil separators.