Coast defence work at Coronation Parade
Coronation Parade was built in the late 1930s as a series of concrete arches and a promenade with retaining wall to the rear. The structure stops the cliff from eroding and protects a significant number of homes and businesses.
The frontage lies within the South Foreland to Beachy Head Shoreline Management Plan. The policy for this unit is 'Hold the Line' (i.e. to maintain the current level of protection to ensure that the cliff does not erode) for the next 100 years.
At its western end is the Southern Water Pumping Station and at its eastern end is the internationally important National Grid Transco interconnector station that, through eight undersea power cables, allows electricity to be shared between the UK and Europe.
The land at the top of the cliff is subject to erosion as a result of regular shallow land slips. The most recent slips occurred during winter of 2015/16 where freezing conditions followed by a prolonged period of wet weather caused a slip. The eroded soil falls to the toe of the cliff, where it is washed away under tidal action.
Why is repair work needed?
There is visual evidence of deterioration to Coronation Parade. There are cracks throughout the structure. The concrete cover to the reinforcing steel has been eroded throughout the eastern half of the arches. The reinforcing steel has corroded to a varying degree, even where it remains embedded within the concrete. Consequently the arches in the worst condition would continue to deteriorate and eventually collapse.
Repairing the concrete arches
This involves repairing the damage and the installation of a protection system to stop any further corrosion of the reinforcing steel (cathodic protection). To protect the promenade/access way and waterproof the structure, an asphalt course will be laid. Timber fenders will be attached to the front for protection against mechanical abrasive action from the beach.
The work involves clearing vegetation on the upper slope on a width of 26m and 75m enabling the installation of vertical drains on a 5m grid, minimum 2m into sandstone. Soil nails, 32mm hollow bar, will be installed in boreholes. The soil will then be retained by mesh and erosion control matting.
Rock revetment work
The revetment protection work off the eastern end of the promenade is proposed as a replacement for the existing protective concrete apron. This was originally constructed using concrete poured onto the rocks from the end of the promenade as a temporary means of protecting the cliff from erosion and so protecting the Interconnector.