The following operations are carried out: a) digging an exploration hole (8), b) using a branch connection (10) which includes a main plate (12) and a fixing plate (22) which are held together, c) using a device (1) which has: a support (36) retaining elements, (38) which are connected to the support (36), a foot (40) which is articulated so as to rotate relative to the support (36), actuation elements (44) for displacing the foot (40) between an introduction position and a pressing position, d) placing the foot (40) in an introduction position, e) retaining the main plate (12) on the device (1), f) positioning the support surface (14) of the main plate (12) against the pipeline (2), g) bringing the foot (40) into a pressing position, h) fixing the main plate (12) and the fixing plate (22) together around the pipeline (2).