Effects on, and recovery of, macroinvertebrates after a discharge of polluted quench water in the Auli river system after the fire at Revac AS in July 2014 – a follow up in November 2014

Summary

A fire in an outdoor storage of plastics mixed with electronic components at the recycling plant company of Revac AS in Vestfold on July 24th 2014 led to discharge of polluted quench water into the Auli river system – with a following episode of fish death. After the accident NIVA got the assignment to assess the consequences of the discharge on the aquatic environment. The results from this first round of sampling are presented in Fjeld et al. (2014). The samples of macroinvertebrates were then taken on August 13th, which is considerable earlier than recommended by the national guidance document (Overvåkingsveilederen 02:2009; Direktoratsgruppen, 2010). The results showed that the invertebrate communities downstream the discharge were strongly affected and much reduced. To follow up on the development of the macroinvertebrate communities after the discharge, and to get more representative samples, more samples were taken in a second sampling round on November 26th 2014. The results from these November samples show that the macroinvertebrate communities have begun to recover after the discharge. But, when compared to the reference stations, the ecological status still appear to be worse than expected. Especially station F, in the lower parts of the water course Merkedamsvassdraget, does not seem to be more negatively affected than stations C and D closer to the discharge in the stream Bjunebekken. However, the lower section of the water course is affected by other sources of pollution that, among other things, contribute a high load of organic material. This could contribute to a low ecological status at station F.