Clear-span bridge replaces perched culvert on Tywi tributary at National Botanic Garden of Wales

Natural Resources Wales (NRW) and the National Botanic Garden of Wales have replaced a culvert on Afon Glir in Carmarthenshire with a clear-span bridge, prefabricated off site and installed in five days by contractor Spencer Quantum.

The stream, known locally as Clearbrook Stream, runs through the Garden's Restored Landscapes and on into the River Tywi Special Area of Conservation (SAC). NRW said the work was carried out in partnership between its Four Rivers for LIFE project and the Garden's team.

According to NRW, the old culvert had become perched above the level of the stream bed over time. That broke the continuity of the channel and left the Garden managing the surrounding banks and crossing on an ongoing basis.

Ieu Davies, National Nature Reserve and Farm Manager at the National Botanic Garden of Wales, said: "Replacing the crossing with a clear-span bridge gives the channel more space to function naturally, improving connectivity for aquatic wildlife and providing us with a robust and practical crossing for the future."

The works

NRW said the clear-span structure removes the restriction and lets the channel and bed function more naturally beneath the crossing. It also gives livestock and visitors a stronger and safer route across the stream.

Taking out the culvert reconnects the stream, so small fish and invertebrates can reach habitat further upstream, NRW said. The bridge was engineered for minimal disruption, with the structure fabricated off site before being placed in position.

Chris Thomas from the Four Rivers for LIFE project said: "Replacing the culvert with a clear-span bridge improves the natural function and connectivity of this important tributary of the River Tywi SAC, and should help reduce pressure on the stream banks and movement of sediment downstream."

Spencer Quantum lists river restoration and minor civils works among its land services and says it has been delivering services for more than 30 years. Companies House records Spencer Quantum Limited (02928764) as an active private limited company with its registered office in Helsby, Cheshire.

Earlier culvert removal

The Afon Glir scheme follows similar work on the Afon Lwynor. In October 2025, NRW said, the LIFE project removed a culvert on that river and replaced it with a clear-span bridge. The culvert was a two-metre diameter pipe 12m long, which restricted the river and disrupted fish movement; its removal restored access for all fish species to 4.5km of upstream habitat.

NRW said it has addressed seven barriers to fish migration on the Tywi in recent years, and the project has completed 14km of riverside fencing on the river so far. The Tywi flows 120km from the Cambrian Mountains to Carmarthen Bay.

The Afon Tywi / River Tywi SAC (site code UK0013010) covers 375.83 hectares, according to the Joint Nature Conservation Committee, which cites the river's large spawning population of twaite shad as a primary reason for its designation. NRW says the SAC is currently in unfavourable condition and the project aims to return it towards favourable condition.

The programme

Four Rivers for LIFE is funded by the EU LIFE Programme with support from Welsh Government. NRW said the project received £9m of EU LIFE grant funding, with support from Welsh Government and Dŵr Cymru/Welsh Water, under LIFE reference LIFE20/NAT/UK/000100.

The programme covers four rivers, the Teifi, Cleddau, Tywi and Usk, and aims to improve 776km of river in mid and south Wales over four years. Its targets include improving fish passage at 12 sites by tackling in-river barriers such as weirs and other structures, planting 50,000 native trees supplied by the Woodland Trust along river banks, and engaging 350 farms.

At the Garden end, the bridge sits within parkland the National Botanic Garden of Wales has spent five years restoring, reinstating pathways, bridges and lakes. The parkland, lakes and woodlands are managed as part of its Waun Las National Nature Reserve, which extends to 400 acres.