ELEVEN properties in Port St Mary were evacuated after a landslide in the Happy Valley area of the village in January.
Around 50 tonnes of earth was washed away resulting in a 16 metre section of the Happy Valley embankment immediately below Bay View Road slipping onto the footpath above Chapel Bay beach.
The carriageway, retaining wall and some of the foundations to the colonnade support columns were undermined by the landslip and the seating area and fountain at the base of the slope were buried by the material washed out.
A full emergency response was mobilised following the landslip and comprised representatives from the Police, Fire Service, Civil Defence, Department of Transport, Manx Gas, Water Authority and Manx Electricity Authority.
The adjacent properties in Bay View Road were evacuated overnight due to concerns over the integrity of the gas main. Members of the community rallied around to help those who had been evacuated and residents were re-homed for the night with friends and neighbours.
Alec Merchant, chairman of Port St Mary Commissioners said: "There were several bits of good luck. Nobody was harmed or injured, the gas pipe was not fractured, and there was no explosion. Given this was going to happen this could have been worse."
Investigations undertaken the following morning confirmed the undermining of the retaining wall and discovery of a large void behind the retaining wall.
The Department of Transport prepared a repair solution and began work to carry out the cause of the landslide.
The loose material from the slip was removed from the embankment and approximately 600 tonnes of five inch clean stone were imported to stabilise the bank and create a safe and level working platform beneath the colonnade.
Once the embankment was stabilised the foundations, colonnade and retaining wall were underpinned with mass concrete.
The grass slope was re-engineered using a further 1400 tonnes of five inch clean stone finished with an erosion protection mat beneath a layer of hydro-seeded topsoil to replicate the grass finish of the original embankment.
The carriageway was reconstructed between the Baptist Church to Victoria Road due to the works required to repair the landslip and the department took the opportunity to improve the carriageway between Victoria Road and the Promenade at the same time.
Update: After extensive investigations the Department of Transport concluded that there was not a single reason for the landslip. Instead a number of contributory factors were responsible.
These included:
• Water ingress from the surface water trench from Gellings Avenue.
• Surface freezing of the embankment following periods of heavy rain trapping subsurface water.
• Possible small leaks from other services that contributed to the landslip.
• Flow from the "box drains" was causing saturation of the ground behind the sea wall.
• Water build up behind the retaining wall from telecom ducts.
• Saturation of the embankment by dam effect of the sea wall.
