the communauté d'agglomération saint germain boucles de seine is the "communauté d'agglomération", an intercommunal structure, in the western suburbs of paris. it is located in the yvelines and val-d'oise departments, in the île-de-france region, northern france. it was created in january 2016. its population was 330,097 in 2016. its seat is in le pecq.