Penyrenglyn Coal Tip Risk Management and Forest Operation

Closes 29 Nov 2025

Opened 29 Nov 2023


This is an update on works currently underway and planned by Natural Resources Wales in the Penyrenglyn area.

Coal tip risk management

Penyrenglyn has a coal tip on the hillside and is located within the area of our tree felling operation. This coal tip is one of our top priority sites to undertake remedial drainage intervention work to reduce the risk of landslip.

Many disused coal tips have drainage systems to reduce water content. No such system is in place at Penyrenglyn, which is classified as a Category D Tip. When rainwater penetrates the top layer of soils and gets into the tip material below, it can increase the risk of landslides.

Our plans aren’t fully developed yet, but we anticipate a design which includes a network of surface drains across the coal tip to reduce water infiltration to the tip soils. Some of the drainage could look similar to cascades installed within the local area, Figure 1.

Figure 1 - Block stone cascades in the local area - Example of what could be installed at Penyrenglyn

Figure 1 - Block stone cascades in the local area - Example of what could be installed at Penyrenglyn

As our plans become more defined, we will share drawings and information and ask for feedback. The design works are expected to last around 12 months. We hope to start this next phase very soon with a plan to gain planning permission and start construction by Spring 2025.

For more information on mine and coal tip safety visit The Welsh Government website.

Tree removal

As you will have no doubt noticed, we have been working with our contractors to remove trees on the hillside above Penyrenglyn. Figure 2 shows areas where trees have already been felled, purple, and those yet to be felled, red.

Figure 2 - Areas felled (purple) and remaining (red) – October 2023

Figure 2 - Areas felled (purple) and remaining (red) – October 2023

These works were required to remove trees that are infected with a regulated disease called Phytophthora ramorum. This disease particularly affects larch trees, which made up most of the trees felled, and a Statutory Plant Health Notice had been served on the site in order to reduce the spread of the disease.

The disease had killed over half of the trees and were a risk to people accessing the forest. The dead and decaying trees were frequently blown over. The infected trees also posed a risk to other species of trees and shrubs.

More information about Statutory Plant Health Notices can be found on our website. Further information on rationale for this approach can be found in the Welsh Government’s Phytophthora Ramorum Strategy for Wales.

The removal of the trees provides an opportunity to increase species diversity, improve the biodiversity and create a more resilient woodland for the future. The tree felling works should be completed early 2024. Felled areas that are outside of the coal tip boundary are expected to be restocked as soon as possible.

Flooding concerns

On receipt of a heavy rainfall alert, the Coal Authority, who are part of the Coal Tip Safety Task Force (the Task Force), will inspect the coal tip area at Penyrenglyn and advise NRW of any concerns or actions that need to be undertaken to reduce the risk of landslip.

NRW, which is also part of the Task Force, will regularly monitor and inspect the culverts on and below the site to ensure the drainage infrastructure remains open and free flowing during the winter months.

This monitoring is planned to be undertaken every week. However, additional inspections will be carried out when heavy rain is forecast.

The proposed drainage scheme on the coal tip will be designed to ensure no increase in flow into the drainage systems below.

Contact us

If you have any queriers or concerns in relation to the works, please contact:

Lester Fulcher, Operations Manager (Land and Assets)

November 2023


  • Treherbert



  • Forest Management