25m³ Geotextile Bags and Geotextile Tubes used to protect a 42” pipeline against scouring, 30m deep on the sea bed, Coveñas, Colombia, S.A

Eng. Nicolas Ruiz

TenCate Geosynthetics

Regional Engineer LATAM

Eng. Mauricio Rendon

Geomembranas SAS

General Manager

Abstract

The buoy that is part of the offshore terminal for tanker ships loading oil off the Colombian coastline is anchored to a submerged pipeline 42” in diameter that sits 30m over the sea bed.  Underwater currents have caused localized scouring along the pipeline, creating additional stresses on it.  To provide a definitive solution, it is key to understand that loading of the ships is the number one priority of the facility, therefore very specific windows of operation are open to install or build any solution.

With this restriction in mind, the project opted to fill in land, large Geotextile bags, 25m³ in capacity each, that would be loaded onto a barge, once filled, using a lifting harness made of polyester geogrid and a PVC coating.  The geotextile bags would be lowered into position using a large crawler crane and set into position with the help of deep-sea divers.  With the bags in place, seating on each side of the pipeline, a geotextile tube was placed in between the bags and under the pipeline and filled from the surface with a sand and water slurry.

The geotextile bags are 5.0m long x 3.5m wide x 2.0m high and each has a filled capacity of 25m³ and weighs in approximately 60 to 63 tons.  Once the Geotextile bag and Geotextile tube are in position, a final Geotextile tube type of mattress will be placed overlapping the bags and the geotextile tube and would be filled with a sand slurry to provide just the support required to keep the submerged pipeline stable and in place.  The geosynthetic system will provide a long-lasting solution for this scouring problem for good.