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Straight survey holes with W80 at Mitholz, Switzerland

Division Morissette of Boart Longyear uses Wassara W80 Drilling System to drill 250 meter long survey holes during the construction of the 38 km long Mitholz tunnel. Due to the risk of hitting sections with high pressure water in the formation air hammers was not an option. The survey is done by analyzing the return cuttings and then using radar and digital filming in the hole. A much more cost effective and faster way to survey compared to traditional diamond core drilling. Furthermore, the stabilized hammer casing and drill pipes of the Wassara Drilling System guarantees hole straightness which is a requirement in this project.


The average penetration rate is 2-3 times faster compared to core drilling.



Wassara W80


Wassara 95 mm


2 Cat pumps, 184 litre/minute at 200 bar

Drilling fluid

Clean water

Drill pipe

Wassara 93 mm, stabilized


Longyear LM 150


Hard limestone, quartz, schist