Lamellae sedimentation is an efficient and compact solution for handling high stormwater influx at wastewater treatment plants during rainy periods. This paper presents and comments on the results obtained at several different sites using specially adapted lamellae settlers. Surface hydraulic loads above 100 m3/m2.h have been reached using optimized doses of chemical reagents. One key advantage of the reactor is that start-up is practically instantaneous; this means that efficient treatment is obtained right from the start of the high flow period.