From Open Risk Manual
BAT-AEPL. Best Available Technique-Associated Environmental Performance Level.
For each individual BAT, a BAT-AEPL can be indicated. A BAT-AEPL is an environmental performance levels associated with the best available techniques’. It means the range of emission levels obtained under normal operating conditions using a best available technique or a combination of best available techniques, as described in BAT conclusions, expressed as an average over a given period of time, under specified reference conditions.