Background
Drakelow Tunnels are a former top-secret underground military complex beneath Kingsford Country Park in Worcestershire, UK. The tunnels were built between 1941 and 1942 as a shadow factory for the Rover car company. Parts for aircraft engines were built in the over-5-km of tunnels throughout World War II. Post-war, the tunnels produced parts for tank engines until 1958, when the tunnels were handed over to the Ministry of Supply and later the Ministry of Works.
In 1961, the government converted half of the tunnels into a top-secret facility, along with 12 other facilities scattered across the UK. They formed a national network of highly classified nuclear bunkers to be used by the government in the event of a nuclear war.
In 1980, Drakelow was re-designated as Regional Government Headquarters. The tunnels were upgraded to bring the complex up to full nuclear bunker status. Throughout the 1980’s, Drakelow operated under secrecy until the end of the Cold War in 1990. In 1993, the Ministry of Defence deemed the facility surplus to requirements and the complex was decommissioned and sold.
Application proposal
In May 2019, London City Bond submitted plans to develop the tunnels into a warehouse and distribution centre for 10,000 tonnes of wine, creating 40 full-time jobs, with part of the tunnels renovated to museum standard. Planning permission for the redevelopment was granted in January 2021.
SES’s involvement
Southern Ecological Solutions (SES) designed, planned and implemented a series of ecological surveys to assess the site’s biodiversity value and inform the planning proposals. Our work included significant bat survey effort, including non-standard techniques, to overcome specific site constraints.
Our bat surveys ranged from preliminary appraisals (in 2019) to targeted bat surveys to understand how bats used the tunnels and associated substations throughout the year. Surveys included detailed internal inspections of the tunnel system and substations by licensed bat ecologists, hibernation surveys during the winter and roost characterisation surveys in the summer. The surveys recorded bats roosting throughout the tunnel system and substations in summer and winter. Species included lesser horseshoe and greater horseshoe bats, Natterer’s bats, brown long-eared bats and common pipistrelle bats. Other bat species such as soprano pipistrelle and other Myotis species are believed to forage but not roost in the tunnels.
To enable the work, Natural England obtained a European protected species mitigation licence. SES developed the equired mitigation design with Natural England’s approval. Owing to the complexity of the proposals (converting a warehouse to store wine), the roosts in the tunnels and substations were retained. However, there was a risk of disturbance through the addition of lighting, adjustments to humidity levels and wine racks, as well as creating a museum (which would result in small sections of the tunnel being sealed off). Therefore, mitigation and compensation measures were needed to maintain the favourable conservation status of the bats.
A 40-m tunnel section of substation 1 was retained for the bats. Within the bat tunnel, crevice roosting opportunities were created for horseshoe bats to hang freely and an access point was created at the bricked entrance of tunnel 2 so that bats could access the tunnel from the outside. Another access point permitted bats to fly freely between the bat tunnel and the remaining tunnels. Substation 1 was modified to secure access for humans with the addition of a grille over the second half of the doorway, with new access points created to lead into the back room of the substation. Partition walls, wooden boards, a cool tower and hot boxes were installed to enhance the substation for bats.
A sensitive lighting strategy inside and outside the tunnel ensured a dark corridor was maintained in the surrounding woodland and entrance to tunnel 2. Inside the tunnels, the lighting system was designed to minimise impacts to bats using motion-sensor settings and positioning below ceiling height to enable bats to fly above the lighting.
During the construction phase, SES bat-licensed ecologists supervised and guided the contractors to ensure minimal impacts to bats. This included toolbox talks and routine inspections during the work.
Ongoing monitoring is required as part of the EPSM licence and will continue until 2026. To date, bats (including horseshoe bats) have been recorded using the bat tunnel and substation in summer and winter.