huntingdon hall bat mitigation method statement · pdf fileand associates bat mitigation...

Cameron S Crook and ASSOCIATES Bat Mitigation Method Statement – Huntingdon Hall, Dutton

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Bat Mitigation Method Statement Huntingdon Hall, Dutton

Cameron S Crook & Associates

Bio-Ecological Consultancy 8 Woodstock Close, Lostock Hall,

Preston, Lancashire PR5 5YY Telephone: (01772) 316717

Fax: 08707 626071 e-mail: [email protected]

November 2014

Drafted: CSC 10/11/2014 Checked: CTC 23/11/2014 Updated: CSC 06/02/2015

Report Version: 1.3

© CSCA 2014


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1.0 Introduction

1.1 This mitigation statement has been prepared in respect of proposed building renovation works, including re-roofing, at Huntingdon Hall, Huntingdon Hall Road, Dutton, due to the presence of two active bat roosts located within the roof space of the building. The bat survey and assessment upon which this statement is based was commissioned by Stanton Andrews Architects on the 18th August 2014.

1.2 The location of the building concerned is shown in Figure 1 below. The loft spaces and approximate location of the roosting areas are shown in Figures 2 & 3.

1.3 Proposals relevant to this method statement are for the works necessary to repair and consolidate the existing roof as required to obtain listed building consent. Full details of proposals are provided within the documentation prepared and submitted to the local planning authority by Stanton Andrews Architects.

1.4 Based on current survey results, the proposed works will have no significant impact upon any adjacent vegetation such as trees and shrubs likely to be used for foraging and commuting by bats. However, whilst the existing roost site will remain in situ and ultimately the roost site will remain unaltered, there is potential for temporary disturbance of roosting bats. Appropriate precautions will therefore be necessary to ensure there is no inadvertent impact upon roosting bats or loss of the existing roost site as a result of site the proposed renovation works.

Figure 1 Site location (within red circle)

Ordnance Survey © Crown copyright 2012 All rights reserved. Licence number WL1005705

Legislative Considerations

1.5 All bats and their roosts are fully protected under the Wildlife & Countryside act 1981 and the Habitat Regulations 1994 and it is unlawful to demolish or dismantle any buildings where bats are may roost without first carrying out adequate mitigation.


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Where bats are known to roost and there will be disturbance of bats or loss or medication of a roost site, this must be carried out under licence from Natural England. Where, after a detailed survey, no signs of bats have been found, or, where works can be carried out without either disturbing bats or damaging, modifying or destroying the roost site, a Natural England licence is not required. There is an active bat roost located within the roof space of the eastern section of the building.

1.6 In accordance with Natural England advice, it is the developer that must make the decision upon whether or not a licence is required, based on the advice of a consultant ecologist. Specifically, advisory document WML-G12-EPS Mitigation Licensing – How to Get a Licence (December 2013) states:

“If the consultant ecologist, on the basis of survey information and specialist knowledge of the species concerned, considers that on balance the proposed activity is reasonably unlikely to result in an offence under Regulation 41 or 45 then no licence is required”

“A licence is not always necessary. Natural England advocates the use of good practice and avoidance measures to minimize the impact of a proposed activity on wildlife, and in particular EPS, to avoid committing offences. Licensing should be seen as the last resort where all other alternative ways of avoiding impacts on the species have been discounted”

“Ecological consultants are expected to advise their clients on whether works can proceed in the absence of a licence. It is not Natural England’s role to do this”

Rationale

1.7 Since the building subject to this mitigation statement supports two active bat roosts, whilst there will be no likely loss or destruction of the roost site itself, a precautionary approach must be adopted to ensure that there is no adverse impact upon any bats that may use the site. Consequently, this method statement has been prepared to ensure that all reasonable precautions are taken and that the proposed site works will comply with current legislation. With regard to the need for a Natural England Licence, if works can be undertaken during the relatively safe period of late October to the end of March, and the recommendations below can be implemented in full, no licence should be required, the works thereby taking place under a Reasonable Avoidance Measures regime (see third paragraph in 1.6 above).


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2.0 Survey Methodology

2.1 The survey was carried out in accordance with recommendations in NCC (1987), the Bat Mitigation Guidelines (English Nature, 2004) and the Bat Conservation Trust (BCT) Best Practice Guidelines (Hundt, 2012) comprising a detailed daytime site inspection on the 22nd August 2014 to examine the section of the existing building that will be affected in relation to potential bat roosting, and to assess any potential for foraging and commuting in the parts of the site located beyond the existing building but within the site boundaries.

2.2 A further detailed inspection using a high-powered torch and endoscope were carried out within the building on the 22nd September 2014 to examine any internal roosting space within the roof void. A sample of droppings was also taken from within the void and sent for DNA testing (Warwick University).

2.3 In addition to the daytime inspections two nighttime (dusk) surveys were carried out by three surveyors on the 22nd and 27th August 2014 respectively. The surveys commenced at fifteen minutes before sunset and continued until one hour and fifteen minutes after sunset. Surveyors were stationed strategically, the positions chosen to afford good views of all parts of the building that will be affected by proposals, concentrating on the parts of the site most likely to be used for roosting. A static ultrasonic recorder (Wildlife Acoustics SM2+) with two microphones on extension leads was also used to pick up any echolocation calls that may have been missed otherwise. All bat activity was recorded digitally and analysed using Song Scope version 4.1.3.

2.4 The surveys were aided by the use of a GoPro digital camera modified for full spectrum video recording, the building lit by a Clulite Clubman fitted with an near-Infrared filter, along with a Bushnell Equinox night vision scope, to record and observe bat activity during low or minimal light levels

2.5 During both of the night-time surveys, the minimum temperatures were between 13-16 degrees Centigrade light winds (3-6km/h), Relative Humidity 75-95%, with no rain, weather conditions on each occasion being considered optimal for bat activity.


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3.0 Survey Results & Evaluation

3.1 The building in question comprises a large stone-built gentry house dating from around 1600. The building has a multi-pitched roof arranged in an H-plan with four gables and associated valleys. There is lead flashing at the base of a total of five chimneystacks. The roof is clad entirely with thick slate slabs, many of which were noted to have lifted or be loosely fitted and there is missing mortar at the ridge tiles. Overall, there are numerous potential access points for bats.

3.2 Internally, there are three loft spaces accessible from two access points, two of the loft spaces adjoining. The loft spaces are labelled 1a, 1b and 2 in Figure 2 below.

Figure 2 Loft spaces

3.3 Loft 1 consists of two sections orientated north to south (Loft 1a) and east to west (Loft 1b) respectively. The roofs of both sections of loft have the original old wooden beams, all of which have a number of holes and splits due to their age. There is no interior covering beneath the slates of Loft 1a though Loft 1b is lined with roofing felt.

3.4 At the time of survey, daylight was visible through the roof in Loft 1a. A number of gaps in the roof were found with direct access to the adjacent stone walls where an absence of cobwebs and evidence of disturbed dust/mortar at the potential entrance points was noted. Numerous other roosting opportunities occur within both sections of the loft, including access for bats to Loft 2 via the dividing wall where several missing bricks were also evident.

3.5 Numerous (several thousand) droppings of different ages and consistency were found across the entire loft space but were noted to be concentrated beneath the ridgelines. A single adult brown long-eared bat was found roosting in a hole in one of the beams of Loft 1a. The droppings were later confirmed by DNA analysis to be those of brown long-eared bats, intermixed with those of common pipistrelle, though the latter were found in much lower quantities.


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3.6 Loft 2 is divided into three sections but is structurally more recent than Loft 1. There is no interior roof covering and daylight could be seen through the roof at the time of survey. As with Loft 1, the walls were found to be accessible to bats due to the presence of several gaps and a number of missing bricks or stones.

3.7 Again, several thousand droppings were found, concentrated beneath the ridges, as well as several fresh droppings, which were found at both sides of the internal chimney structure. Another brown long-eared bat was found roosting at the ridge, a third close by beneath the slates.

Figure 3 Approximate bat roosting areas (area shaded red)

3.8 During the night-time surveys, extensive activity was recorded across the whole site on both occasions, particularly to the east where the site is more sheltered. During the first of the two night surveys, six common pipistrelles were recorded emerging from the eaves of the southern elevation and a seventh from the northeast corner of the building. The bats emerged from 10-15 minutes after sunset at approximately 30-90 second intervals. Three brown long-eared bats were later recorded (from 55 minutes after sunset), one from the ridge and two from the southeastern gable. Following emergence, the pipistrelles proceeded to feed around the vegetation to the west, then mostly flying eastwards or northwards towards woodland, trees and other vegetation. The brown long-eared bats were noted to fly due east following the hedgeline.

3.9 During the second survey, a similar pattern of behavior was noted although fewer pipistrelles were recorded (only five noted emerging). In addition, on both occasions, several records of a Myotis species were recorded (most likely Natterer’s bat from an analysis of the echolocation recordings). These did not appear to emerge from the building though their time of arrival (60 minutes after sunset) would suggest that this could not be ruled out. The location of the roost sites and indicative behavior and activity is shown in Figure 4 below.


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Figure 4 Indicative bat activity is shown by dashed lines, the arrows indicating the direction of travel. Red indicates brown long-eared bats; yellow indicates pipistrelle; purple indicates Natterer’s bat.

Significance & Likely Impact

3.10 The presence of droppings of two species and records of bats emerging from the building confirms the presence of two active bat roosts. The number of droppings and bats noted combined with the time of year, type of building, and location, would indicate that both are small maternity roosts. The number of droppings and anecdotal evidence suggest that the roost site is well established and has been active for at least ten years.

3.11 As the critical period for maternity roosting is May to August inclusive, any works carried out or any disturbance during this period are likely to have the greatest impact. Were works to be carried out during the critical period of May-August, in accordance with the Bat Mitigation Guidelines: Guidelines for Proportionate Mitigation (Mitchell-Jones 2004) the brown long-eared bat and common pipistrelle roosts are of High conservation significance; correspondingly the Scale of Impact is also High. Therefore, unless unavoidable, all works affecting the roof void should be confined to the relatively safe period of late October to March inclusive.


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4.0 Method Statement

4.1 Taking the survey results into consideration the following precautions and actions shall be implemented to reduce the likelihood of any impact upon bats. Any works that are likely to affect the roof void or upper sections of the building where bat roosting is likely to occur (see Figure 3 above), should only take place during the relatively ‘safe’ period of late October to the end of March inclusive, under the close supervision of a licenced bat worker.

4.2 Any works to the roof should be to be carried out section by section, commencing at one corner of each respective section of the building then working slowly backwards, removing any roofing slates, cladding, plaster board, woodwork and roofing slats as required. Should any bats or signs of recent bat usage be discovered, all works to cease and the following actions taken.

(i) If the roosting area is still intact, all work should cease, site workers to retreat from the respective part of the site and a previously appointed bat worker should attend site as soon as possible. All bats found (or suspected) should be left in situ unless the appointed bat handler considers them to have been unduly disturbed, in which case, the second action shall be implemented.

(ii) If the roosting area has been damaged or has lost integrity, or if on attendance the appointed bat worker considers that the bats have been unduly disturbed, the bat or bats shall be removed from site and held in captivity by a suitably licenced and experienced bat carer for as long as required until either, the roost has been repaired or secured, or, if this is not possible, until works on the respective section of the building are complete.

(iii) In either case, if any bats or signs of recent bat usage are found, all works on the respective building shall cease immediately, and any further works shall only take place as part of the mitigation scheme prepared for the respective building in respect of a required Natural England licence.

(iv) Any captive bats shall not to be released until the roosting area from whence they came has been repaired or the building works completed.

4.3 Once the super-structure of the building has been removed or dismantled to the level required and no bats have been found, no further roosting areas remain and no bats are reasonably likely to be present (as confirmed by the bat worker) works may continue (as appropriate) without further restriction. However, if at any stage there is evidence to suggest or if there is any suspicion that bats may be present, all work shall cease immediately and further investigation by the appointed bat handler shall be carried out before any site works continue.

4.4 To that end, all site workers should be fully briefed on the possible presence of bats and be made fully aware of this method statement, prior to commencement of site works. Should any bats be found, there should be no attempts made to handle them, except in extreme circumstances to remove them from immediate danger until the appointed bat handler is able to attend to the situation, but only where workers are wearing gloves. No bats should be touched or handled with bare hands.

4.5 No such works should be carried out beyond the perceived safe period of late October to the end of March inclusive and it must be ensured that no potential exit or entry holes are blocked or impeded at any time. All works affecting the roof void or upper sections of the building must take place under the close supervision of a licenced bat worker.

4.6 Should works result in the unavoidable blocking or impedance of any roost entry or exit points (permanent or temporary) a number of replacement access points and


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roosting features shall be incorporated into the building. These shall comprise the following:

• Appropriate gaps of minimum dimension 20 x 100mm to be created or allowed for beneath gables to allow unimpeded access to the roof void.

• Any roofing materials removed or dismantled during site works, including damaged or rotten timbers, to be retained and stored in appropriate locations within the roof void to provide familiar conditions for roosting bats

• Slots of minimum dimension 30 x100mm to be cut in roof felt alongside roof boards at 3m intervals (adjacent to access points) along the ridge of roof above roosting area within the roof void

• To allow bat access to the roosting area, the top slate or tile batten to be placed 20mm from ridge board

• Roofing felt to be supported by slate at the end of the wall adjacent to the roosting void to ensure that roost entrance is not blocked

• Any replacement roofing felt to comprise traditional bituminous or Hessian materials

• Only timber treatment products (where required) approved by Natural England to be used within the roof void

• All the works and new bat roosting features to be checked by the appointed bat worker on completion of works to ensure that adequate access points have been provided. Any required modifications to be made, as appropriate, prior to sign-off

• All the above to be completed by between late October and the end of March of any year with no works taking place that are likely to affect the integrity of the roof beyond that period

4.7 In the event that works are likely to extend into the critical period of May-August inclusive, in addition to the above, provision of an alternative roosting site will be required. To that end, conversion of an existing building within the same site boundaries (as indicated on Figure 5 below) shall be implemented in advance of any works commencing, or, if works have already commenced, no less than six weeks prior to the first week of the May during the same year. Specifications for the proposed new roost site are provided below.

4.8 Should the above (4.7) be applicable, a licence from Natural England will be required.


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5.0 Mitigation Proposals

5.1 In addition to the precautions taken during dismantling and demolition outlined above, alternative roost sites should be provided to compensate for the loss of the bat roosts within the existing building. The alternative roosting sites must be provided on a ‘like for like’ basis within the near vicinity of the existing roost site. For summer roosting purposes, the new roost site shall closely match the existing roosting site by providing suitably-sized voids with open rafters and appropriate roof pitch, to be constructed of suitable materials to create optimal environmental conditions, in particular temperature and humidity, whilst still allowing unimpeded entry and access. For winter roosting purposes, a combination of crevices or cavities suitable for hibernation and suitably designed bat hibernation boxes shall also be provided.

5.2 The replacement roost sites (bat boxes and proposed new bat loft, if required) should be fully established prior to dismantling works commencing on the existing roost sites. It is proposed that the new bat loft be established within the existing building shown in Figure 5 below, the roof space of which is of similar dimensions to that of the existing roost site.

Figure 5 Proposed location of new bat loft

5.3 With respect to detailed design, in order to provide suitable crevices for roosting bats, the bat loft should be modified to allow an appropriately sized roof-voids fitted with internal (artificial) rafters (if required) and wooden battens attached to walls and ceilings using appropriate fixings using the following specifications:

• Roof void dimensions should be equal to or greater than the 5m x 4m x 2m recommended minimum with access points at the gable ends of the building and beneath ridge tiles. All roost entrance orientations have been allowed for

• Roofing felt comprising traditional bituminous or Hessian materials

• To allow bat access, top slate or tile battens placed 20mm from ridge board


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• Slots of a minimum dimension 30mm x 100mm to be cut in roof felt alongside roof boards at two metre intervals along ridge of roof above roosting voids

• Gable ends adjacent to roof voids fitted with overhanging soffits

• Roofing felt to be supported by slates at end of wall to ensure that roost entrance is not blocked

• Wooden tiles to be attached directly to the battens using appropriately sized nails

• All timber used for the battens, rafters and tiles to be untreated

• Gaps of between 15-20mm to be allowed beneath each of the battens and wooden tiles

• Rafters to be affixed directly to the ceiling of the building with or without gaps beneath

• Bat loft not to be used for any other purpose than bat roosting

5.4 Once established, the new bat loft should be “inoculated” with droppings and material such as roofing materials and stained timbers taken from the original roost sites to provide familiar conditions to encourage the return of the bats.

5.5 Supplementary to the above and prior to site works taking place (to ensure there is no gap in roost availability) a sufficient number of bat boxes (at least 12; exact number to be agreed) shall be placed on suitable trees either within or closely adjacent to the existing buildings to allow for differing environmental conditions. The following proprietary bat boxes are proposed:

1 Schwegler 1FS Woodcrete Large Colony box, 44cm x 30cm

1 Scgwegler 1FFH Woodcrete Universal bat box 87.5cm x 24.5cm

3 Schwegler 2FN, Woodcrete, Larger Species box, 36cm x 16cm

3 Schwegler 2F, Woodcrete, General Purpose box, 33cm x 16cm

3 Schwegler 1FF, Woodcrete Rectangular box, 43cm x 27cm

1 Schwegler 1FW Woodcrete Hibernation Box, 50cm x 38cm

5.6 With respect to general site design, either no lighting, or only low-level lighting (type and design to be agreed) shall be used within 20m of the new bat loft and bat box locations. Any lighting that is unavoidable should be directed away from the bat loft roost access points and bat feeding areas (woodland edge and other mature vegetation).

5.7 Existing mature trees and linear vegetation such as hedgerows and the woodland edge shall be maintained as flight lines.

5.8 The new bat loft, all bat boxes, shall be subsequently monitored once per year during June-August for at least five consecutive seasons or at least until establishment of one or more bat roosts has been determined.


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6.0 References

Bat Conservation Trust (2007). Bat Surveys – Good Practice Guidelines. Bat Conservation Trust, London.

British Government (1994). Conservation (Natural Habitats, &c.) Regulations 1994. Statutory Instrument 1994 No 2716 Wildlife, Countryside. HMSO

British Government (1981). Wildlife and Countryside Act 1981 with Amendments. HMSO

Mitchell-Jones, A. J., (2004). Bat Mitigation Guidelines. English Nature.

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