Berthin Brook Bridge

Bridge Repair Project at Coleg Gwent – Bat Mitigation Successfully Implemented

Acer Ecology Ltd. became involved with Coleg Gwent’s Berthin Brook Bridge Repair Project at its licensing stage. The bridge needed to be repaired due to the supporting pillar between Arches 2 and 3 crumbling and the outer layer of bricks under Arch 3 being in danger of falling.

The initial inspection and dusk emergence/dawn re-entry surveys were undertaken in 2016 by another ecological consultancy. They found that a total of eight bats emerged from the bridge representing three different species: five soprano pipistrelle bats (Pipistrellus pygmaeus), one common pipistrelle (Pipistrellus pipistrellus) and two Daubenton bats (Myotis daubentonii).

The bridge had numerous crevices and opportunities for bats to roost inside and there was a danger of bats being entombed in the bridge during the repair work. Some of the bricks had to be removed, crevices re-pointed and netting was attached to the underside of the bridge and sprayed with cement afterwards.

It was decided that the gaps would be inspected with an endoscope and exclusion devices attached onto them before works began, so that the bats had a chance to leave the bridge but were not able to re-enter it. Before the exclusion devices were attached, a dawn re-entry survey was undertaken at the end of April in order to record the bat activity in connection with the bridge. The crevices were inspected with an endoscope on the same day and no bats, or their droppings, were found. Exclusion devices were installed on the same day and left in place for the following three weeks. The exclusion devices were taken off after the tree week period and the gaps re-checked with an endoscope to ensure that there was no evidence of bats being present, before the crevices were sealed on the same day.

Because bat roosting crevices were lost as a result of the repair works, four specially designed bat bricks were installed onto the underside of Arches 2 and 3 of the bridge. The bricks were made by Liz Greenwood from Greenwood’s Ecohabitats from EcostyrocreteTM material, which is shredded polystyrene mixed with cement. The shredded polystyrene is sourced from recycled plastic. More about the material can be read here.

The four bat bricks were uniquely designed to fit the bridge. The bricks were 44cm in length, 22cm in width and 14cm in depth. Crevices were created, which did not extend all the way to the back and therefore expand into a narrow cavity. The bats can move horizontally along the back of the brick. These bricks were screwed onto the ceiling of the bridge with four stainless steel screws and nylon plugs.

Bat boxes attached underneath bridge

Bat BrickBat Brick

More information on wildlife related products from Greenwood’s Ecohabitats can be found here.

Further monitoring will be required in order to confirm whether the bricks are successfully used by bats.


Our guide to bat mitigation can be found here. For more articles on the mitigation that we have conducted, please see the following links: Bat mitigation Forest of Dean and Bat mitigation St Tewdrics.

For more information about bat surveys, please see the following links:

Bat Survey Information   I Need a Bat Survey