Drainage, monitoring and stabilisation works continue on coal tips

The latest works to keep hundreds of coal tips safe over the course of a year have been revealed.

There are 371 tips in Rhondda Cynon Taf (RCT), 106 of which are wholly owned or partially owned by the council.

A report going before the council’s overview and scrutiny committee in January says that with coal tip safety grant funding, the authority has been able to put in place a programme of work on tips including minor and major maintenance, studies and investigations.

In progress is the remediation of two deteriorated drainage channels on RH002 Tylorstown tip and repair of the eroded invert of a cascade on RH003 Wattstown National tip.

The 2024/25 works to the mid-berm drainage channel at RH003 Wattstown National continues to work as intended, the report said.

Data from soil moisture monitoring instruments shows that the soil moisture levels have reduced significantly since the works were completed.

At RH077 Graig Ddu Dinas the existing monitoring system continues to demonstrate that the temporary drainage system is working to reduce the risk of movement in the tip.

Procurement for major works at this site to stabilise the tip is ongoing and funding is being sought for construction in 2026/27.

The Afon Cynon riverbank immediately downstream of the new blockstone retaining wall on tip CV128 Penrhiwceiber suffered further erosion during Storm Bert in 2024.

A site meeting with consultants and a contractor has taken place to review a trial for a proposed stabilisation solution.

The access track works on tip CV129 Cefnpennar completed in early 2025 are working as intended, the report said.

Repairs on drainage channels and upgrade works on further access tracks were completed by RCT’s streetcare department over the summer months.

Additional blockstones and stiles were installed at the site entrances to prevent unauthorised vehicle access.

Further access track upgrades and vegetation management are expected in quarter four of the 2025/26 financial year.

Desk study works were completed during 2024/25 with survey works on the culvert being carried out over this summer.

The installation of new drainage infrastructure on tip TE003 in Cilfynydd was completed on quarter 4 of 2024/25 and continues to work as intended.

Landslip 

Major work at the site of the Tylorstown landslip is said to be progressing.

Since the landslip from Upper Llanwonno Tip in February 2020, the council has implemented a four-phase remediation plan for the site.

Phase one included emergency clearance work in the weeks that followed.

Phases two and three involved the removal of the slipped material from the valley floor and reinstatement of the river channel and were completed in June 2021, followed by additional work in autumn 2021 to stabilise the slope.

Alongside phase four, permanent works to the phase two and three receptor sites are said to be practically completed.

A pump track has been built and is now a community leisure asset off Station Road, Ferndale.

The phase four works are progressing and works to the receptor site are “practically complete” with features installed and biodiversity improvements being seen as it regenerates.

Progress to install significant drainage infrastructure on the donor site continues but progress is hampered due to weather, ground conditions and design iterations, the report said.

Long-term management 

A working group of council officers has been created to consider and implement the long-term management of the hillside, including tip safety, ecology, land management and access.

Discussions with the fire service have taken place around the measures that can be incorporated into the management plan to mitigate fire risk on the hillside with a trial fire break having been created by the fire service.

Tip RH058 PenyrEnglyn, a joint NRW and RCT Council owned tip in Treherbert, is being considered for remediation by NRW.

The majority of the tip area is within the Treherbert ward but a small section is in the Treorchy ward.

NRW carried out a pre-application  consultation for their proposed work in September 2025 and the tip safety team gave feedback on the proposals.

Effective and efficient 

The RCT tip safety and estates teams are working with NRW to try and rationalise land ownership to make the future maintenance and responsibility of the proposals as effective and efficient as possible, the committee report said.

For minor maintenance works identified from inspection reports, the council has worked with highways streetcare and once completed the maintenance works are inspected on site and signed off by a member of the tip safety team.

Due to the size and nature of many of the tips and the amount of ageing drainage infrastructure on many it is impossible and impractical to undertake all maintenance work immediately, the report said.

As a result, there is a prioritised system in place to address the work that, if left unmitigated, could contribute towards increased risks.

Typical maintenance can include vegetation clearance, clearing out and repairing drainage channels, repairing pipes and culverts, reinstating drains, scour infill and repair.