SINTEF has evaluated potential environmental inpact caused by an incidental discharge of cement during drilling of the exploration well PL 470 (Caerus) in the Norwegian sea. The cement is listed as a PLONOR chemical. SINTEF has carried out calculations of spreading and deposition of the particle matter discharged. Concentrations in the water column as well as depositions on the sea floor are calculated with the DREAM model operated by SINTEF. The present report shows the results from the calculations, including concentrations in the water column, depositions on the sea floor and also results from environmental risk calculations.