Horizontal dewatering is typically used in projects with shallow linear configurations (railway lines, motorways etc.) or long, narrow excavations.
Horizontal dewatering is normally carried out utilising drainage lines from 80 to 100 mm in diameter which are installed around the site at depths to 6 meters dependant on local circumstances. The trenches for the drainage lines are excavated using trenching machines with mounted rotary cutting chains which create a trench approx. 30 cm wide to the desired depth. The drainage lines are installed at the base of the trench as the trench is excavated.
The trench is then backfilled. If the aquifer at the site has low permeability, filter gravel can be backfilled instead of soil at certain depths to increase drainage capacity.
The installed drainage lines are then connected to a vacuum piston pump which creates the negative pressure gradient required for water transfer. The partial vacuum achieved can range up to 0.9 bar (13 psi).
The collected groundwater is conveyed through the vacuum piston pump and from there to an outlet line leading suitable discharge point.