580 m HDD in extremely difficult ground

TIGF is the major gas network owner in South West France and is facing on some of its networks the demand to perform system improvements. In compliance with these improvements, a gas line, DN 350, located between the communities of Allier and Momères near the offshoots of the northern Pyrenees, needed replacing. LMR Drilling GmbH installed a 580 m gas pipeline DN 350 in a nature reserve under the River Adour in Bernac-Debat (southern France) for the major gas network owner, TIGF (Figure 1). The soil consisted of layers of sand and mudstone, marl and gravel with boulders, superimposed by 20-30 m gravel with stones and boulders.