FEASIBILITY STUDY

A hydro-geological survey of the area is performed, entailing onshore and offshore geological cartography, bathymetry and borehole campaigns. A pilot horizontal drain is executed to confirm the working hypothesis and perform gauging and chemical tests.
Once the drain feasibility is confirmed, number of drains is worked out, placing them either like a fan or in parallel, just to achieve the flow required.

PILOT DRILLING

Neodren^® is drilled by means of a directional bit that can drill large layouts within the aquifer stratum from the coastline, not affecting intermediate areas. Electro-magnetic steering systems (MGS) are used to know the situation of the directional bit.

REAMING

Pilot hole diameter has to be broaden till reaching the filtering pipe diameter. In this case, reaming is performed pushing towards the sea in order not to affect productive aquifer stretches.
Drilling mud can be reused several times, thus optimising the reaming process.

INSTALLATION OF FILTERING PIPE

A (full-of-holes or micro-porous) tubular drain is pulled into the tunnel along the productive stretch, depending on the soil characteristics. This drain is taken to high sea by vessel and connected to the train of rods. Once it has been connected, it is pulled into towards the coast.

CLEANING AND SEALING

Cleaning operations consist of suction of drilling fluids and usage of dispersing agents by means of a high-pressure (>50bar) device that is pushed into the drain. Afterwards, the remaining space between soil and pipe is sealed using sulphur-resistant cement, especially at initial and end points just to avoid water collection through this areas. Doing this, the filtering stretch remains isolated from freshwater intrusions as well as seawater intrusions coming from the drain end.

GAUGING