Godre’ graig School Landslide Risk, Lower Swansea Valley

Details:

We have been working to provide assess landslides within the terrain above Godre’ graig and hazards and risks to the school for the Local Authority and Welsh Government.

Godre’ graig has a long history of ground movements, however the school lies outside the large post-glacial landslide that is well documented.

 

Our input to date has comprised:

• A geological and historical desk study;
• Aerial photograph interpretation, including stereographical analysis;
• Initial morphological assessment;
• Generation of a preliminary morphological map with the assistance of low-level LiDAR information;
• Liaison with the Coal Authority to undertake an inspection of historical mining related features in the area;
• A preliminary site investigation in easily accessible areas and groundwater monitoring;
• Generation of a conceptual engineering geological model; and
• Development of a preliminary qualitative assessment of the hazards/risks and definition of next steps.

Our assessment has shown that there are four types of landslide hazard that have the potential to impact the school.  Of these, two are natural process and two are man-made landslide/instability hazards:

 

 

 

 

 

 

 

 

 

 

 

 

 

• Hazard type 1. Rock fall – possible structural damage, impact on people;
• Hazard Type 2. Debris avalanche initiating from quarry spoil – impact loading on structures, impact/burial of people outside building, burial of people inside buildings (ground floor) if sufficient volume;
• Hazard Type 3. Debris avalanches initiating from over steep slope – impact loading on structures, impact/burial of people outside building, burial of people inside buildings (ground floor) if sufficient volume; and
• Hazard Type 4. Shallow earth slides – slow ground displacement leading to vertical or lateral displacement, or undermining of structures and infrastructure.

 

 

Testimonial from the Head of Engineering & Transport (NPTCBC)

“The Earth Science Partnership have provided professional and technical advice for Neath Port Talbot County Borough Council on a number of projects of different sizes and complexity since early 2015. Whilst working for the Council, they have provided a number of different ground investigation solutions and advice.” 

They have also been appointed to advise on the high profile Pantteg and Godre’r Graig Landslide since 2015 and have provided a number of factual reports that are helping Neath Port Talbot to formulate a Management Strategy for the area.

Part of ESP’s work involved the production of a Ground Instability Risk Map of Pantteg and then a Residential Property Risk Map.  They have also attended televised public meetings to discuss their findings following the publication of the work and have given Expert Witness evidence on behalf of Neath Port Talbot at Residential Property Tribunals.

As part of their works they have employed a number of techniques some of which are listed below:-

• Boreholes and log to a depth of 40m using traditional, tracked and slope climbing drilling rigs.
• Installation of piezometers and inclinometers.
• LiDAR surveys to establish and monitor land movements.
• Geophysical surveys to obtain Seismic Resonance Images of the sub stratas.
• Rain Gauges.

In closing, I can advise that we have had a positive experience in working with ESP and their employees who have always acted professionally and supplied information and reports within agreed timescales.”