Two Tree Island Coastal Defence, Leigh-on-Sea, Essex

Two Tree Island is now a nature reserve but for several decades large areas of the island were used as a rubbish tip. 
The waste deposits where encapsulated with clay and the coastal frontage was protected with rock and Essex blocks. 
This protection required upgrading and the specified solution was to install a new revetment using concrete block mattresses.  At tender stage Hesselberg Hydro put forward a solution using asphalt.  We developed the solution with the main contractor (Fitzpatrick) and the Engineer (Halcrow) to provide a system to suit the environmental and installation constraints as well as giving the client a significant cost saving.

Details

• 5,000 m2 revetment with 225mm Open Stone Asphalt placed on 150mm Lean Sand Asphalt.
• 2,000 m2 revetment with 150mm Open Stone Asphalt placed on 150mm Lean Sand Asphalt.
• Geotextile placed between asphalt layers, anchored at top to provide support if toe undermined.
• Delivery vehicles to island restricted to 10T gross weight.
• Work completed in 7 weeks.