Building an Extension in Caerphilly – Bat Mitigation Installed

Planning permission was granted for the erection of a two-storey side extension with a front gable, rear balcony and a revised car park for a community centre in Caerphilly. Previous bat surveys were conducted in 2012 and 2013 which indicated that the building was used by a small number of roosting soprano pipistrelle bats (Pipistrellus pygmaeus). However, as these surveys were out of date, further surveys were required before work could commence, which were completed by Acer Ecology.

Surveying for Bats

Two bat activity surveys were carried out by Acer Ecology: one dusk emergence and one dawn re-entry survey. We were able to confirm the presence of roosting soprano pipistrelle bats, likely to be males or non-breeding females. This assessment was based upon the small numbers of individual bats noted returning during the dawn survey and a lack of bat dropping accumulations. Additionally, up to eight Daubenton’s bats (Myotis daubentonii) were recorded foraging along the river adjacent to the survey, and two noctule passes were recorded. Mitigation was designed according to individual species’ requirements and implemented accordingly. An EPS Licence was applied for in order to undertake the development works.

Mitigation for Bats

Whilst work was carried out on the extension, a temporary bat box was erected on a nearby tree in order to provide an alternative bat roost before work commenced. The extension was then built and adapted in order to provide a modified roost for the soprano pipistrelles. This included the provision of new exterior fascias, soffits and bargeboards which sit on spacers to provide crawling space. Furthermore, the new fascias, soffits and bargeboards were made of tanalised timber and pre-treated with non-toxic, water-based, ‘bat-friendly’ formulations.

Bat Mitigation
Top: Open Soffit Box. Bottom: Closed Soffit Box with bat access gaps along the wall.

Lighting was also an important consideration when designing mitigation. The lighting design for the site was of a ‘bat friendly’ specification, whilst accommodating for both security and health and safety needs. By considering these aspects, the design ensured that, where lighting was necessary, it was directed away from roost access points and confined to areas where there are security or health and safety issues. Finally, lighting is angled downwards to highlight walking areas only and at a height no higher than 2m above ground level. This demonstrates the attention to detail that Acer Ecology pays when designing bat mitigation. Not only are Acer Ecology able to design mitigation that preserves and protects bat populations, but they are also able to meet the needs of the client in a way that allows them to achieve their project aims.

At each stage of the development, Acer Ecology ensured that there was always a bat specialist available on-call to deal with any bat incidents, to provide advice, and to carry out post-development checks. The post-development monitoring will be carried out by Acer Ecology over one year consisting of an internal and external inspection and one activity survey. Acer Ecology is committed to ensuring the success of each individual project and achieves this with the help of its team of dedicated professionals.

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Author: Rebecca English