Ilam Hall: Bat Licence Implementation & Mitigation Strategy

Background

BSG Ecology has provided bat consultancy services to the Youth Hostel Association and National Trust on three important projects at Ilam in Derbyshire’s Peak District.  These have  involved the conservation and refurbishment of  Ilam Hall (2008-2010), St Bertram’s Bridge (2008) and Ilam Bunk House (2010-ongoing).

Ilam Hall is a Grade II* listed Victorian Gothic manor house near Ashbourne, leased and run by the YHA. Together with its grounds and Ilam village, it forms part of National Trust’s White Peak Estate. It is surrounded by historic parkland and ancient woodland, enclosed by a meander of the River Manifold. The former stable block now houses a visitor centre, which includes Ilam Bunk House. Formal gardens lead down to the 18th century St Bertram’s Bridge, across the River Manifold.

BSG Ecology’s role in the projects

We were commissioned to undertake bat survey work to inform an assessment of ecological constraints and potential impacts on bats as a result of the proposed  works on the three projects. Our assessment enabled works to St Bertram’s Bridge to proceed without the requirement for a European Protected Species (EPS) Licence. However, survey of Ilam Hall and Bunk House found a number of bat roosts that were likely to be affected by the proposed works.

Seventeen separate bat roost locations were identified in roof voids, walls and chimneys within Ilam Hall. A further six roosts were found in the former stable block. Comprehensive daytime bat surveys and dusk and dawn bat activity surveys identified roosts of four species (common pipistrelle, soprano pipistrelle, brown long-eared and whiskered/Brandt’s bats) and a probable fifth species (serotine) in the buildings. At least seven species (including daubenton’s and noctule bats) forage in the grounds.

Working closely with our two clients and with the Building Surveyors and Architects on the project teams, BSG Ecology successfully applied to Natural England for two European Protected Species (EPS) licences. Due to the number of roosts and the extent and variety of proposed works, the impact assessment and mitigation strategy for Ilam Hall was unusually complex. Thorough and robust assessments, reasoned statements and mitigation strategies all had to be worked up to enable the EPS Licences to be secured successfully at the first application, allowing works to proceed according to schedule.

EPS licence implementation & responding to new findings

We worked with the project teams throughout the works to oversee and advise on the implementation of the EPS Licences. Works to Ilam Hall were extensive and included repairs to stonework, roofs and chimney stacks, all of which required the retention of existing bat roost access points. Once scaffolding was in place, a large chimney stack on a west facing gable end was found to be unstable and in danger of collapse. Survey work had shown the chimney stack contained a common pipistrelle maternity roost. The original proposal was chimney pot replacement but the stack was subsequently found to require complete re-construction. Our liaison with Natural England secured an emergency amendment to the EPS Licence on safety grounds. As the licensed mitigation strategy included timing works to avoid the seasonal presence of bats in this roost, it was possible to undertake this work immediately, without directly disturbing bats, or affecting the client’s timetable.

The construction of the chimney stack was unique. BSG Ecologists worked closely with stonemasons to take the stack down so that roost entry points and the complexities of bats use of the masonry, flues and pots could be studied and re-created. Channels were re-formed in mortar joints and rubble infill in one of the pots was re-established. New timber roosting crevices were created in a flue that was no longer in use and wire mesh was installed to prevent juvenile bats falling down the flues into rooms below (a regular occurrence in the past).

Works to Ilam Bunk House were largely internal, including re-modelling of ceilings on the first floor, where loft voids and roof structures contained bat roosts. Stripping out was supervised by BSG Ecologists and bat droppings were even found in internal partition walls. Again, mitigation included timing works to avoid the seasonal presence of bats. Enhancements included the installation of bat boxes in roof voids and on trees in nearby woodland, to provide additional roosting opportunities.

Outcome

Monitoring surveys in summer 2012 confirmed that the common pipistrelle maternity colony had returned to use the re-constructed chimney on Ilam Hall and Ilam Bunk House. Results from this survey, and monitoring over the last five years has allowed us to build up our knowledge of the bat activity and movements between the roosts, suggesting that the colony moves between the re-constructed chimney and two or three locations in the roof and walls of Ilam Bunk House, throughout the maternity period. At the time of the 2012 survey, the colony was split and 87 bats were seen to emerge. These included juveniles (confirming successful breeding). Data for this roost go back to 1998 and this is the highest colony count recorded. Measures to prevent bats falling down the chimney also appear to have been successful. Monitoring also identified a new common pipistrelle roost in the former stable block, with a count of 129 bats emerging.

The Ilam Hall project demonstrates the importance of working closely with clients to develop a good baseline dataset and knowledge of a project’s requirements.  In this case, we were able to demonstrate that complex historic building restoration can be entirely compatible with the requirements of wildlife legislation.  By integrating ecology advice into the project team from an early stage and throughout the project, The National Trust and YHA have a flagship conservation project in the Peak District.

Ilam Hall: Bat Licence Implementation and Mitigation Strategy – Project Profile

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