PROJECT:  Branksome Chine Outfall
LOCATION: Branksome Chine, Dorset
CLIENT: Dean & Dyball for Wessex Water
VALUE: £850,000
PROJECT OVERVIEW: CMP were contracted to install a 350m length, 800mm dia HDPE outfall pipeline from Branksome Chine beach out to sea.

WORKS DESCRIPTION:

Inshore Works

• Sheet piled cofferdam installed stretching 100m out to sea from promenade wall
• 40m of cofferdam installed in tidal conditions
• Up to 5m depth of sand excavated from cofferdam using long reach excavator
• End of pipe pulled into cofferdam and attached to promenade wall connection
• Pipe installed into cofferdam trench
• Concrete mattresses installed over pipeline
• Trench backfilled and cofferdam bund removed

Offshore Works

• Buoyant pipe pulled out to jack-up barge using marine craft
• Pipe sunk to seabed using controlled submersion techniques
• Specially designed and developed system which communicates between the pipeline and the long-reach exactor used to dig trench of accurate depth from the jack-up barge
• Once pipeline was to desired depth and position, divers used to place concrete mattresses over pipeline
• Trench backfilled
• Full bathymetric survey undertaken