The A465 Heads of the Valleys Dualling Abergavenny to Hirwaun (Section 2) is part of the overall dualling of the key east-west A465 route in Wales. Construction started in January 2015.
The road passes through the Usk Bat Sites Special Area of Conservation (SAC), designated, in part for lesser horseshoe bat and caves not open to the public. There are numerous caves along the route and four lesser horseshoe bat maternity roosts in close proximity, one of which is in a viaduct directly under the road. Extensive baseline bat survey was undertaken from 1995 to 2014 to inform design and ecological assessment. A Technical Advice Group (TAG) was also set up, consisting of bat and highway ‘experts’, to provide opinion on the validity of the Assessment of Implications on European Sites (AIES) conclusions, assisting the Welsh Government in advising the Minister on the robustness of the conclusion, i.e, that it was ‘beyond reasonable scientific doubt’ (following the Waddenzee decision Case C-127/02). The TAG also provided an opportunity to seek the views of the experts on the likely effectiveness of the proposed mitigation/compensatory measures in progressing the design of the scheme.
Lesser horseshoe bat mitigation has included:
- maintaining flight lines, including retaining existing under-road culverts and maximising their cross-sectional area, whilst providing temporary screening until connecting vegetation matures;
- providing replacement bat foraging woodland habitat in the early stages in areas likely to provide the most benefit;
- sensitive working practices, in particular over caves and the viaduct maternity roost, and during destruction of bat roosts in buildings and trees;
- provision of replacement bat roosts, including a bespoke bat house, already being used by lesser horseshoe bats, and ‘stepping-stone’ night roosts, required as compensatory measures at stage 4 (IROPI) of the AIES process; and
- closure of a mine-adit use by bats, using smoke to exclude them.
- pre-parturition and juvenile counts at maternity roosts;
- hibernation survey of caves;
- use of replacement roost structures; and
- monitoring of bat flight lines through culverts.
During the bat flight line monitoring it became evident that mitigation provided for Section 1 on an under-road crossing, including grilled entrances over a bat underpass, was not effectively getting bats safely under the road. The grilles have been replaced by security fencing in February 2017, with a larger gap over the top of the fence, and monitoring survey results have shown a marked improvement.
Lesser horseshoe bat numbers in both maternity roosts and caves do not appear to have been affected by the Scheme, with numbers increasing during the construction period.