ESP were instructed to by Andrew Scott, acting on behalf of the Local Authority, to provide a Coal Mining Risk Assessment for proposed repairs and betterment to the Gnoll House Ruins in Gnoll Park, Neath.
Neath Port Talbot County Borough Council were looking to sympathetically open up the ruins to enable visitors to explore the former grand house and provide a safer environment for site users. The proposals include a viewing platform and a paved stage to allow open-air performances.
The redevelopment at Gnoll House is within the Coal Authority’s Coal Field Consultation area and any works within this area that requires a Planning Permission, normally triggers a Planning Condition by the Coal Authority. The Coal Authority ask that the impact of former Coal Mining and legacy risk be considered as part of the site investigation, design and development.
The phase 1 desk study revealed a wealth of knowledge of the former house and history. The estate was the property of the Mackworth family during the 18th and 19th centuries. There are few traces remaining of the house, once considered “one of the finest residences in the principality”.
The first recorded individual owner was Evan ap David during the 16th century. The last of Evan’s descendants to own it was Sir Herbert Evans, who died in the late 17th century. Sir Herbert’s daughter and sole surviving heir, Mary, married Humphrey Mackworth (later Sir Humphrey) in 1686 and on her death ten years later, Mackworth became owner of the estate.
Mackworth extended the house (sometimes known as “Gnoll Castle”), and developed various coal mining interests locally, as well as branching out into other industries. His eldest son, Herbert Mackworth, continued his industrial interests, and developed the Gnoll copper works. Sir Herbert Mackworth, 1st Baronet, Herbert’s son, increased the amount of coal mining carried out on the estate.
Through the widow of Sir Herbert’s brother Robert Mackworth (died 1795), the estate passed to Capel Hanbury Leigh, Lord Lieutenant of Monmouthshire, and it was later bought by Henry Grant of Pembrokeshire and Wormley, Hertfordshire. Shortly before his son Henry John Grant’s death in 1861, there was a plan in 1857 to use the castle as a university college and some staff including the gamekeeper moved to Wormley, but instead it was purchased by a cousin Charles Evan-Thomas of Llwynmadoc, who demolished the east wing and added other architectural features. He was the father of Admiral Hugh Evan-Thomas, who was born at the Gnoll. A year after Sir Hugh’s death, the Gnoll was bought by Neath corporation as a site for a war memorial. The castle was demolished in 1957: https://coflein.gov.uk/en/site/18814/
The historical and Coal Authority data showed that the Swansea 5ft Coal Seam outcropped near Gnoll House, mapped to the east in the grounds of Gnoll House. The reported geological dip in the area was shown to the east and this indicated that subsidence from workings in the Swansea 5ft seam was theoretically not likely to impact the former house and much of the redevelopment.
However the precise location of the seam needs to be confirmed to fully discount this risk. The Swansea 5ft Seam was well known in the Neath and surrounding area and heavily worked.
The assessment also considered the risk from other coal seams, those under the Swansea 5ft coal seam. The nearest local seams below the 5ft in the succession are the Little and Hard (also known as Tir Edmond), the Graigola seam (possible named locally as the Swansea 6ft Seam), the Swansea Two Feet seam (Shenkin or Upper Maesmelin Seam) and the Westernmoor Seam (Lower Maesmelin).
Review of information was able to suggest that these seams would be at such a depth that they would unlikely to pose a subsidence risk to Gnoll House.
Speak to Us Today
Get in touch with our team via our email, enquiries@earthsciencepartnership.com or phone number, 02920 813385 and we’ll be very happy to help with and discuss any geotechnical engineering project requirements you may have.
For a full list of all ESP capabilities, please click here.
