Holt Fish Pass

Holt Fish Pass – Facts & Figures

Holt is the third fish pass that twaite shad and other migratory fish pass through on their way upriver. It is located in the village of Holt, in Worcestershire.

The fish pass at Holt was the most challenging to construct, as the steep river valley sides meant that all equipment had to be transported to site by boat!

Work on the fish pass began in in May 2020, and the team started by setting up the compound 1.2km upstream of the weir, from which equipment would be transported to site via the river.

Due to the challenging nature of the build, it was the final fish pass to be completed out of the four built along the River Severn. In January 2022, Holt fish pass was opened to the river. Landscaping works were complete in April 2022, and by May the team had finished work at the compound upstream.

A challenging build

Located next to a very steep-sided river cutting, Holt fish pass was a tricky fish pass to construct! The fish pass presented many more challenges compared to the other three sites, meaning that our engineering teams had to think outside the box.

The biggest challenge was a lack of road access to the site, so all the materials, plant and equipment had to be delivered to site by boat! This included all the diggers and a huge 100 tonne crane which was brought down the river on a massive floating pontoon. Another challenge to overcome was the transport of concrete used to create the inner structures of the fish pass. All the concrete was transported by barge in small skips, ready to be poured immediately when it reached the site.

Since it was only accessible by water, the site was very sensitive to weather and flow conditions compared to the other sites with land-based access. If the river flows were too strong, this prevented the teams from accessing the site with any boats and equipment.

Exposed to the elements

The weather was certainly not on Unlocking the Severn’s side while Holt was in construction. Heavy rainfall and persistent flooding halted works on a number of occasions.

Unfortunately Holt construction coincided with 3rd October 2020, the wettest day in the history of the UK. Heavy rain filled the River Severn and flooded the site completely. This was was followed by further rainfall events, resulting in the 5th wettest October in over 150 years!

After a very wet autumn and winter, works were able to continue in spring 2021.

A different design choice

You may notice that Holt fish pass looks a little different to Diglis and Lincomb. Can you spot the main difference? The outer walls of the fish pass are made out of a completely different material. At Holt, the design team opted to construct the exterior walls using legato (lego style) interlocking blocks. Whereas at Diglis and Lincomb, the exterior of the pass is created using sheet piling.

The lego-style blocks were chosen for two reasons: the lack of access from the river bank meant that it would be incredibly difficult to use a piling rig at this location, and shallow bedrock at the site would have made the driving of the piles very difficult.

Holt Fish Pass – Facts & Figures

A challenging build

Exposed to the elements

A different design choice

How this pass was designed

Volunteering