10 Ecology and Nature Conservation

Transcription

1 10 Ecology and Nature Conservation 10.1 Scope of the assessments The assessments in relation to ecology and nature conservation have been focused on sites designated for their ecological / nature conservation value, terrestrial and aquatic habitats and fauna associated with the proposed scheme corridor identified during scoping and as described in Chapter 7. Designated sites Statutorily designated sites considered include Sites of Special Scientific Interest (SSSIs). Non-statutory designations include Local Nature Reserves (LNR) and Wildlife Sites: Croxley Common Moor SSSI and LNR Lairage Land LNR Grand Union Canal - Rousbarn Lane N. to Ironbridge Lock Wildlife Site Ascot Road Scrub Wildlife Site Holywell Farm Allotments Wildlife Site Croxley Green Junction Sidings Wildlife Site Habitats Habitats considered comprise: Semi-natural broadleaved woodland Running water Fauna Fauna considered comprise: Widespread reptiles (slow worm and grass snake) Breeding birds Badger Bats Consideration has also been given to the following matters in accordance with the requirements of the scoping opinion: an outline of management opportunities in respect of existing or future management resources; and proposals for maintaining the existing role and functions of the used and disused railway lines as green corridors following implementation of the scheme Statutory and planning context The following legislation, policies, plans and guidelines have been taken into account. Further explanation of the identified legislation and Ecology and Nature Conservation 10-1

2 documents and their content in relation to designated sites, habitats and fauna is provided in the descriptions of the detailed baseline studies and surveys undertaken to inform the assessment in Appendices 10A to 10G. EU Water Frameworks Directive (Directive 92/43/EEC) The directive includes ecological commitments to protect wildlife within streams. Directive 2009/147/EC on the conservation of wild birds (the Birds Directive) The directive includes commitments relative to the protection of wild birds. The Wildlife and Countryside Act 1981 (as amended) Part I of the Act provides for the protection of birds and other wild animals and specified plants in the UK. It also makes it an offence to plant or cause to grow non-native invasive plant species. Part II affords powers to Natural England to designate SSSIs. Conservation of Habitats and Species Regulations The regulations make it an offence to deliberately capture, kill, injure or disturb a European Protected Species (EPS). It is also an offence to damage or destroy a breeding site or resting place of these species. EPS include all species of bat. The Countryside and Rights of Way Act 2000 (as amended) Schedule 12 of the Act modifies and strengthens the provisions under the 1981 Act relative to disturbance or damage to wild birds and their eggs or nests The Act also affords stricter enforcement provisions for control of invasive species. Actions that might trigger an offence include moving contaminated soil from one place to another, or incorrectly handling and transporting contaminated material and plant cuttings. National Parks and Access to the Countryside Act 1949 (as amended) The 1949 Act affords local authorities powers to designate relevant areas as local nature reserves (LNRs). The Natural Environment and Rural Communities Act Schedule 11 of the Act amends and updates the provisions made in the 1949 Act relative to local authorities and the designation of LNRs. It also commits LU as a public authority to have regard for conserving biodiversity in its activities. The Protection of Badgers Act The Act makes it an offence to wilfully kill, injure or take a badger Meles meles or attempt to do so. It is also an offence to obstruct, destroy, or damage a sett or disturb badgers when in their setts. Ecology and Nature Conservation 10-2

3 Environmental Permitting (England and Wales) Regulations There is a requirement for parties intending to dispose of controlled waste, including invasive plant species, to seek and obtain a permit in accordance with the regulations. The regulations also set out offences in relation to water pollution in terms of discharge to watercourses and groundwater. Environmental Protection Act The Act defines the legal framework for collection, disposal or treatment of controlled waste, including invasive plant species Reference has also been made to the following policy documents: Planning Policy Statement 9: Biodiversity and Geological Conservation (PPS9) UK Biodiversity Action Plan (BAP) Hertfordshire s Local Biodiversity Action Plan (LBAP) Watford District Plan Three Rivers District Plan LUL BAP PPPS 9 contains government policy and guidance to local authorities relating to planning, development and biodiversity. It not only addresses issues of the protection and conservation of biodiversity and ecological resources but advocates the promotion and securing of measures which will serve to enhance such resources The UK Biodiversity Action Plan was published in It details strategies and action plans for priority species and habitats which the Government has identified in response to commitments agreed relative to the conservation and protection of existing biological diversity under the Convention on Biological Diversity (Rio de Janeiro -1992). Local Biodiversity Action Plans (LBAPs) identify local priorities for biodiversity conservation and work to deliver agreed actions and targets for specific habitats and species Policies related to biodiversity and nature conservation within the two District Plans and which are currently saved pending finalisation of local development framework documents are detailed in Volume 3, Appendix 10-B. The focus of the policies is the protection of sites of nature conservation interest and specific habitat types. Reference is made in the relevant baseline and impact assessment sections of the chapter where such policies are of particular relevance to a site, habitat type or species. Ecology and Nature Conservation 10-3

4 10.3 Methods of assessment The assessments have been undertaken in accordance with the Institute of Ecology and Environmental Management (IEEM) Guidelines for Ecological Impact Assessment (2006). They have involved: identification and description of the baseline environment including identification of resources to be assessed and establishment of their value; evaluation of potential impacts; identification of mitigation measures for likely significant adverse impacts; and description of the predicted residual impacts and their likely effects taking into account proposed mitigation. The baseline environment The identification, description and evaluation of the baseline environment have involved a combination of desk-based review of existing data sources, consultation with statutory and non-statutory agencies and organisations and site surveys Sources of existing data referred to include: online databases (magic.gov.uk, nbn.org.uk, natureonthemap.org.uk and ordnancesurvey.co.uk); and Hertfordshire Biological Records Centre The following organisations have been consulted: Natural England Butterfly Conservation - Hertfordshire and Middlesex Branch Hertfordshire Bird Club Hertfordshire & Middlesex Badger Group Hertfordshire & Middlesex Bat Group London, Essex and Hertfordshire Amphibians and Reptiles Trust (LEHART) Information has also been gathered from the LUL environmental database in relation to records in the vicinity of the proposed scheme corridor, the Metropolitan Line and west and south Watford Site surveys for particular habitats and species have been undertaken as indicated in Table Detailed explanation of the surveys, their timing and adopted survey methods is provided in Appendices 10A to 10E. Ecology and Nature Conservation 10-4

5 Table 10-1: Site surveys Surveys Timing Method Appendix Habitats Habitats and Invasive Species July 2009 May 2010 September 2010 Standard Phase 1 habitat survey (JNCC, 2007). Walkover invasive species survey. 10A Protected Species Badgers July 2009 September 2009 May 2011 Search for field signs of badgers and their setts as Harris et al. (1989). 10D (Confidential) Bats March-September 2009 March-September 2011 As Bat Conservation Trust good practice guidelines (BCT 2007) Visual inspection of trees and bridges. Bat activity surveys and automatic static surveys. 10E Breeding Birds April-June 2010 As Bibby et al. (2000) 10C Reptiles August 2009 Artificial refugia surveys as Froglife Advice Sheet 10 (1999) and Gent and Gibson (2003). 10B Biodiversity value Each of the sites, habitat types and species identified has been assigned a biodiversity value based on the IEEM guidelines as indicated below. National - warranting designation as a Site of Special Scientific Interest (SSSI) or of conservation value to England. Regional - of conservation value to the East of England. County - warranting designation as a County Wildlife Site or of conservation value to Hertfordshire. District - of conservation value to the districts of Watford or Three Rivers. Local - of conservation value within approximately 5 km of the proposed scheme. Within zone of influence only - of conservation value solely in the context of the proposed site and its immediate surroundings. Potential and predicted impacts Impacts related to loss, fragmentation or degradation of habitats, death or disturbance of animals and potential changes in species range have been defined and described taking into account: Ecology and Nature Conservation 10-5

6 Magnitude - the size of an impact in quantitative terms where possible. Extent - the area over which an impact may occur. Duration - the time for which an impact is expected to last. Reversibility - a permanent impact is one that is irreversible within a reasonable timescale or for which there is no reasonable chance of action being taken to reverse it. A temporary impact is one from which short-term recovery is possible. Timing and frequency - whether impacts are constant, ongoing, separated but recurrent or single events and whether they occur during critical seasons or lifestages of habitats and fauna. Significance of impacts The IEEM guidance defines an ecologically significant impact, whether negative or positive, as one that affects the integrity of a defined site or ecosystem and / or the conservation status of habitats or species It also advocates an approach whereby the impact, once determined by reference to the criteria in , is described in terms of the geographic scale at which it would be significant. For example, a significant impact at a local scale The geographic rating of the impact does not inevitably correlate with the value assigned to a site, habitat or species in the baseline description. It can be the case that an impact on a habitat of national importance would be significant at a local level depending on the implications relative to the parameters considered during the evaluation of the impact as outlined in Any legal implications are also described along with policy implications. Probability In addition to significance, the probability that the impact will occur has been defined in accordance with IEEM guidelines and as indicated below: Certain / near certain - probability estimated at 95% chance or higher. Probable - probability estimated above 50% but below 95%. Unlikely - probability estimated above 5% but below 50%. Extremely unlikely - probability estimated at less than 5%. Mitigation Where likely significant impacts have been identified, mitigation measures have been included as part of the proposed scheme to ensure legal compliance relative to designated sites and protected species and to reduce or compensate the potential significance of impacts and their effects upon relevant receptors. Ecology and Nature Conservation 10-6

7 10.4 Baseline environment Designated sites Croxley Common Moor SSI and LNR (Site 1 - Figure 10.1) Croxley Common Moor is located approximately 700m south-west and downstream of the disused branch line. It comprises some 40ha of varied habitat including dry acidic grassland, marshy areas, tall fen vegetation, groundwater fed hollows and scattered scrub. There is an extensive area of low-lying grass heath. It is an important site for invertebrates. Four of the habitat types found within the site are UK BAP priority habitats: lowland dry acid grassland, lowland heathland, fen and undetermined grassland The SSSI is of national biodiversity value. Lairage Land LNR (Site 2 - Figure 10.1) The LNR comprises a 4.8ha area of meadow located within the River Colne floodplain immediately east of Holywell. The northern boundary of the LNR directly abuts the disused branch line boundary. Habitats include semi-improved neutral grassland, a small area of secondary woodland and areas of tall herbs and scrub. The river margins are rich in flora and fauna with some associated reed beds The LNR is of local biodiversity value. Wildlife sites There are four wildlife sites in addition to the nationally and locally designated site which are located in close proximity to the proposed scheme or where there is a potential linkage by virtue of features such as a watercourse All four sites are of county biodiversity value. Grand Union Canal - Rousbarn Lane N. to Ironbridge Lock (Site 5 - Figure 10.1) This comprises 2.4ha of land comprising the Grand Union Canal and adjacent land at the southern end of Cassiobury Park. It is an important corridor linking various wildlife sites. Ascot Road Scrub (Site 8 - Figure 10.1) The site comprises some 0.63ha of long-established secondary wet alder / willow woodland and scrub on former alluvial grassland on the eastern bank of the River Gade and the line of the disused branch line. The Beggars Bush Drain, a small north to south slow flowing stream passes through the site. The stream supports a diverse aquatic flora. The vegetation ranges from fen-swamp communities to almost acidic communities on alluvial gravels. The scrub and alder / willow woodland Ecology and Nature Conservation 10-7

8 Ecology and Nature Conservation 10-8 merges with dry secondary scrub woodland on the railway bank. The site supports a diverse bird population. Holywell Farm Allotment (Site 13 - Figure 10.1) An area of allotments located immediately adjacent to the southern boundary of the disused branch line on Vicarage Road. The site supports a good population of slow worms. Croxley Green Junction Sidings (Site 12 - Figure 10.1) Some 50% of this 3.8ha site has been cleared for various businesses / industry-related compounds. Birch woodland and scrub dominated by buddleia and elder Sambucus nigra extend along the northern and western site boundaries, the most extensive of the habitat being along the western boundary with the disused line. Wet willow woodland defines the southern boundary with the River Colne. Three of the willows are mature specimens with bat roosting potential. There are several small open areas of rough species-poor semi-improved grassland within the scrub habitat. Japanese knotweed is well established particularly on the banks of the River Colne. Grassland and rubble areas comprise habitats with the potential to support reptiles. There is also evidence of use by breeding birds in the form of old nests and by foraging badgers in the form of snuffle holes. Habitats Habitat types identified during the Phase 1 Habitat survey are described in Volume 3, Appendix 10A. Those which it was concluded should be subject to detailed assessment are described below. Their distribution within and neighbouring the proposed scheme corridor is shown in Figures Semi-natural broadleaved woodland Areas of semi-natural broadleaved secondary woodland are located: along the margins of the disused branch line between the grounds of St Anthony s Primary School and Vicarage Road (Figure 10.3); along the margins of the disused branch line east of Vicarage Road and extending in a large block north east towards Willow Road and Cardiff Road (Figure 10.4); within the Colne Valley east of the disused line, north of the River Colne and south of the Fisher Industrial Estate (Figure 10.5); and at the north eastern end of the disused branch line where it merges with the existing Euston to Watford line (Figure 10.5) Dominant species include semi-mature and immature ash Fraxinus excelsior and silver birch Betula pendula with an understorey of scattered scrub (predominantly bramble Rubus fruticosus agg.) and tall ruderals

9 Ecology and Nature Conservation 10-9 (such as common nettle Urtica dioica). Other species include: rowan Sorbus aucuparia, Swedish whitebeam Sorbus intermedia agg.,field maple Acer campestre, hazel Corylus avellana, lime sp Tilia sp. and pendunculate oak Quercus robur. The area in the vicinity of Willow Road / Cardiff Road comprises mature woodland Wet woodland associated with the Ascot Road Scrub Wildlife Site (Site 8 - Figure 10.1) is dominated by goat willow Salix caprea, white willow Salix alba, common alder Alnus glutinosa and hawthorn Crataegus monogyna. Drier peripheral areas are composed of horse chestnut Aesculus hippocastanum, wild cherry Prunus avium, ash and crab apple Malus sylvestris The embankments of the Metropolitan Line, at the western end of the proposed scheme corridor are dominated by pedunculate oak, sycamore Acer pseudoplatanus and ash. Dense scrub understorey includes hawthorn, elder, dogwood Cornus sanguinea, blackthorn Prunus spinosa and bramble. Ground flora is limited by the heavy shading All of the areas of semi-natural broadleaved woodland other than the wet woodland at Ascot Road are of biodiversity value within the zone of influence only. The wet woodland is of county biodiversity value. Running water These habitats are represented within the proposed scheme corridor as outlined below: where the River Gade and the Grand Union Canal cross the disused branch line west of Ascot Road (Figure 10.2); where the Beggars Bush Drain is culverted beneath the disused branch line east of the River Gade in the vicinity of the Ascot Road dual carriageway(figure 10.2); where the River Colne flows in a south-westerly direction to the southeast of Cardiff Street and Willow Road Figures 10.4 and 10.5); and where a small stream runs under the disused branch line adjacent to Fisher Industrial Estate at the eastern end of the scheme (Figure 10.6) The River Gade is a chalk river. It is approximately 8m wide. The banks are heavily shaded by overhanging trees and scrub. There is a narrow strip of semi-natural habitat on the western bank between the river and Beggar s Bush Lane. Ascot Road wet woodland is on the eastern side. There was no evidence of submerged vegetation at the time of the survey. Marginal vegetation comprises common reedmace (Typha latifolia), gypsywort (Lycopus europaeus) and yellow iris (Iris pseudacorus) The Grand Union Canal is 10-15m wide. It is well used by river craft and members of the public use the footpath on the western bank. The banks

10 are canalised. There was no evidence of vegetation within the water channel at the time of survey. Vegetation bordering the watercourse comprises amenity grassland on the western bank and amenity grassland and scrub on the eastern bank The Beggars Bush Drain is a small, sluggish stream running north to south through the Ascot Road Scrub Wildlife Site east of the River Gade. The stream is in culvert at either end. As it passes through the wildlife site it is heavily shaded by the surrounding wet woodland. There was a large amount of rubbish in the vicinity of the culvert at the northern end of the open channel at the time of the survey The River Colne is a clay river over which the disused branch line is bridged in two locations to the east of Cardiff Road. It is approximately 8m wide and shaded by overhanging trees including common alder and willow species. There is marginal vegetation on the banks, but no submerged vegetation within the channel in the section associated with the proposed scheme corridor The stream at the western end of Fisher Industrial Estate is about 2m wide and runs beneath the disused branch line. This stream was dry during the surveys in There was water present with a thick scum on the surface of the water in May The banks are covered in dense scrub. Japanese Knotweed is established on the southern side of the channel The River Colne and River Gade and the adjacent stream are of district biodiversity value. The Grand Union Canal and the stream at the Fisher Industrial Estate are of value within the zone of influence only. Invasive species There are a number of established areas of Himalayan balsam and Japanese knotweed and a single instance of Virginia creeper within or immediately adjacent to the proposed scheme corridor. Protected species Widespread reptiles The site surveys established the presence of slow worm (Anguis fragilis) and grass snake (Natrix natrix) along sections of the disused branch line as detailed in Volume 3, Appendix 10B and shown in Figure Good populations of slow worm were recorded in three locations; between the River Colne (East) and River Colne (West), adjacent to Holywell Farm Allotments and adjacent to the Westfield Community Sports Centre. Low populations were identified in a further three areas; adjacent to housing on Cardiff Road, to the east of the River Colne (East) and over the eastern Ecology and Nature Conservation 10-10

11 Ascot Road. A low population of grass snake was recorded in one location, adjacent to Holywell Farm Allotments The areas where presence of both species has been established generally correspond to the sections of the proposed scheme corridor which are adjacent to semi-natural habitats such as the margins of the River Colne, allotment lands and sports grounds Twice as many females compared to males were recorded. Many juveniles were also present indicating that slow worms breed on the site. There was no evidence that grass snakes breed on the site The reptile populations identified are of local biodiversity value. Breeding birds The surveys identified 60 breeding territories and 13 bird species distributed along the proposed scheme corridor between Ascot Road and the junction with the existing Watford to Euston Overground line as detailed in Volume 3, Appendix C and shown in Figures Most of the 13 species are relatively common The highest numbers were recorded in the River Colne floodplain near Riverside Park, west of Wiggenhall Road, and within the cutting near Tolpits Lane. There is a locally extensive covering of dense scrub in the latter two areas It is suggested that sites supporting between 25 and 49 species are valuable at the local level for breeding birds. Consideration does, however, need to be given to the conservation status of the species identified and the context of the particular site / area. In this instance, the presence of 13 relatively common species suggests a biodiversity value within the zone of influence only. However, an urban context where there are relatively few semi-natural sites with low levels of disturbance or large amounts of unmanaged dense scrub available, heightens the importance of the location and numbers of birds. Breeding birds associated with the proposed scheme corridor have accordingly been classified as being of local biodiversity value. Badgers The findings of the badger surveys are detailed in Volume 3, Appendix 10D (note - due to the requirement to maintain as confidential the precise location of badger setts, this appendix is available only to those who have a legitimate need for this information) At the time of the surveys there were two disused outlier setts within the disused branch line corridor and two active main setts located some 30m and 200m outside of the corridor. In the latter case there is evidence of Ecology and Nature Conservation 10-11

12 movement associated with foraging and commuting between the main sett and the disused branch line corridor Whilst the proposed site offers a relatively undisturbed habitat for badgers, its narrow, linear form suggests it is likely to form only a small part of any individual badger clan territory The corridor constitutes relatively undisturbed habitat for badgers to reside, forage and commute. Evidence of foraging activity was found in the vicinity of the two disused setts, within the site identified for the electricity sub-station on Tolpits Lane and at the proposed compound site off Wiggenhall Road. These are locations which are directly connected to semi-natural habitats of semi-improved grassland and broadleaved woodland. These neighbouring habitats are likely to be more attractive foraging territory than the dense scrub and less mature woodland distributed along much of the proposed scheme corridor Badgers associated with the proposed scheme corridor have a biodiversity value within the zone of influence only. Bats The site surveys established the presence of bats along sections of the proposed scheme corridor as detailed in Volume 3, Appendix 10E No evidence of bats roosting or of roosting potential was found within the survey area. Three mature willows in wet woodland along the margins of the River Colne in the Croxley Green Junction Sidings wildlife site have potential as roost sites. The activity surveys recorded predominately common and widespread species such as the common pipistrelle (pipistrellus pipistrellus) and soprano (pipistrelle pipistrellus pygmaeus). A significant number of bats and high levels of bat social activity was noted around Tolpits Lane and the Grand Union Canal. The remaining sections of the survey area were found to support fewer bats The areas surrounding Tolpits Lane and the Grand Union Canal have a local biodiversity value relative to bats. The remaining parts of the corridor have a biodiversity value within the zone of influence only Predicted impacts Designated sites Croxley Common Moor SSSI and LNR (Site 1 - Figure 10.1) The potential for impact on the SSSI solely relates to the River Gade. The river crosses the line of the proposed scheme corridor such that there would be potential for contamination of the watercourse during construction and consequential impact on aquatic and marginal habitats in the SSSI some 700m downstream. The potential for contamination during Ecology and Nature Conservation 10-12

13 construction is described in detail as part of the assessment of impacts on running water below. That assessment has concluded that with the adoption of appropriate measures during construction it is unlikely that there will be a significant impact on the watercourse in the vicinity of the works In relation to the four BAP habitats which form part of the mosaic of habitats within the designated site, there is no potential for direct impact associated with construction of the proposed scheme some 700m to the north or interaction by way of the watercourse as indicated above It has accordingly been concluded that the magnitude of any potential impact will be negligible and that it is extremely unlikely that construction of the proposed scheme will have a significant effect on the designated site. Lairage Lands LNR (Site 2 - Figure 10.1) Proposed works immediately adjacent to the LNR will involve the construction of a short section of gabion walling along the toe of the existing embankment which forms the northern boundary to the designated site. Modification to the two bridges over the River Colne side channel will involve work directly at the watercourse but will not involve construction within the channel or modification to the abutments and hence potential disturbance to the existing channel banks The installation of the gabion toe wall will involve work in very close proximity to the LNR boundary such that there will be likely to be some degradation of habitat on the immediate boundary of the designated site. This will be negligible in the context of the principal habitats that constitute the value of the 4.8ha site There will also be potential for contamination of the River Colne as it flows south and through the LNR as a result of localised sedimentation associated with the works and accidental spillage of construction materials and fuel from construction plant. Mitigation measures focused on such risks are described in relation to the river as part of the running water type of habitat in With the proposed mitigation measures in place it is unlikely that construction will result in significant impacts or effect on the LNR. Grand Union Canal - Rousbarn Lane N. to Ironbridge Lock (Site 5 - Figure 10.1) The wildlife site is located immediately north of the A412 and upstream of the proposed scheme corridor. Construction and future use of the proposed scheme will not result in direct or indirect impacts on the site. Ecology and Nature Conservation 10-13

14 Ascot Road Scrub (Site 8 - Figure 10.1) The removal of the existing embankment west of Ascot Road and installation of the proposed reinforced soil wall as the link between the new Ascot Road Bridge and the viaduct will involve the loss of a strip of land at the southern end of the wildlife site to provide essential working space. Some 15% of the 0.63ha site will be cleared of existing wet woodland. The existing culvert beneath the embankment will be replaced with a culvert through the earth wall It is also likely that there will be some temporary disturbance to the common species of birds which are currently associated with the woodland, though it is likely that a number will return once work is complete. Once construction is complete shrub planting will be introduced on the cleared ground other than for a maintenance strip at the foot of the earth wall. Measures to ensure that birds are not disturbed during the breeding season will be adopted as described under the assessment for breeding birds in paragraphs The impact of the loss of planting in relation to the area of the designated site will be negative, certain, and significant at a county level. Holywell Farm Allotments (Site 13 - Figure 10.1) Proposed works immediately adjacent to the allotments will involve the construction of the southern part of the Watford Hospital Station. The compound and works site required for construction of the station will be located on the recreation ground to the north of the disused branch line Construction of the southern station building will involve the taking of an approximate 20m by 1m strip of land along the northern edge of the allotments. There is the risk that working in such close proximity to a population of slow worm, which is the basis for the designation of the wildlife site, could result in harm to the species in contravention of the Wildlife and Countryside Act 1981 (as amended). Mitigation will be provided in the form of temporary reptile fencing located along the boundary between the working site and the allotments. The fencing will be installed following completion of the removal of vegetation and destructive search described in relation to the wider mitigation strategy for the species in to ensure the proposed scheme corridor has been cleared in advance of construction commencing The wildlife site will remain substantially unaffected as will its capacity to support the current population of slow worm that is the basis for its designation. The new station buildings will also constitute a barrier to movement of the species onto the proposed scheme corridor. Ecology and Nature Conservation 10-14

15 Taking into account the small extent of land loss within the wildlife site it is extremely unlikely that the proposed scheme will have a significant impact or effect on the wildlife site during construction or operation. Croxley Green Junction Sidings (Site 12 - Figure 10.1) The use of part of the existing wildlife site for a work compound will involve the loss of a small area of birch dominated woodland and buddleia and elder scrub along the eastern margin of the disused line to provide for access from the compound onto the construction corridor. Much of the compound and access road from Wiggenhall Road will, however, be located on the existing hardstandings and rubble areas that constitute the central part of the site. The substantial woodland framing the western side of the site will remain as will all of the wet willow woodland and scrub with its associated grassland along the southern boundary with the River Colne. The break in the planting to accommodate access during construction will be re-planted upon completion of the works Pre-construction surveys for badger and reptiles will be undertaken. Subject to the findings, appropriate mitigation measures to exclude both species should they be present will be implemented as described in and Taking into account the retention of the substantial part of the existing habitats and their associated wildlife interest and the proposed mitigation measures, the impact will be significant at the local level during construction. Once the site is reinstated following construction and the proposed planting along the western margin of the area established and matures the medium to longer term impact will not be significant. Habitats Semi-natural broadleaved woodland Impacts on the wet woodland at Ascot Road Scrub Wildlife Site have been described in Lengths of the more extensive linear belts of semi-natural broadleaved woodland along the cutting and embankment slopes of the disused branch line will be removed where reinforced soil embankments, sheet pile toe walls and gabion toe walls are to be introduced Some 40% of the habitat type within the corridor between Ascot Road and Vicarage Road will be lost Proposed planting with species reflecting the composition of the existing planting will be introduced onto the upper sections of the re-graded cutting slopes. The magnitude of loss will therefore be markedly reduced as the new planting establishes and matures. Ecology and Nature Conservation 10-15

16 The loss of the planting as an ecological resource will be of moderate magnitude in the context of the existing planting as a whole. It will be temporary as new planting matures and adds to the diversity of species composition and stages in succession. The short-term impact (< 5 years) will be adverse and significant within the zone of influence of the proposed scheme. With management focused on the retention of diversity and composition as the proposed planting establishes and matures in the medium term (5-10 years), it will become beneficial and certain within the zone of influence of the proposed scheme. The existing value of the disused branch line as an established green corridor will, therefore, be reinstated and enhanced. Running water Construction of the proposed dual-track over the Grand Union Canal, River Gade and River Colne will involve the retention of the existing structures over the watercourses and the spanning of the Canal and River Gade by the proposed viaduct In the case of the canal and River Gade and adjacent stream there will be a pier located between the canal and river with access via Beggars Bush Lane but no requirement for work within either watercourses or modification to their existing form. The construction of the pier and the viaduct decking will involve localised clearance of vegetation on the margins of the watercourses Localised loss of marginal vegetation, scrub and tree planting will not affect the integrity of the water-related habitats which contribute to the River Gade and the nearby stream s district level value. Once constructed the viaduct will increase localised shadow over the watercourses. Highly localised shading in the context of the watercourses will not, however, have a material impact on the habitat type Construction close to both watercourses will present the risk of spillage of building-related materials or sedimentation where excavations and movement of soils is required and works are undertaken on bridges over the watercourses. Detailed method statements for the construction in such locations will provide for the inclusion of measures recommended in the Pollution Prevention Guidelines published by the EA. Measures will include working distances relative to the watercourses, requirements relating to stripping and storage of soils, storage and handling of building materials and fuels. Specific measures will include: the establishment of a minimum 20m buffer for the location of soil stockpiles; limitations on stockpile height and side slope gradients; enclosure and bunding of fuel storage areas; Ecology and Nature Conservation 10-16

17 storage of potentially contaminating construction materials, such as concrete, outside of the buffer zone and in contained storage areas; and sheeting beneath bridge decking during the dismantling of the existing decks and installation of new decks to avoid accidental discharge of materials into the watercourse With such measures in place the risk of localised pollution of the watercourses and consequent impacts on water related habitats or downstream of the working areas will be appropriately managed Once constructed and open to use the risk of impact as a result of passage of trains over the watercourses on the viaduct and existing bridges will relate to accident and spillage (such as oil from trains). These are rare events in the context of the rail network such that it will be extremely unlikely that such impacts will occur and that the proposed scheme will have a significant effect on the habitat as represented in the proposed scheme corridor It has been concluded that the impacts associated with habitat loss will be certain, short term, adverse and significant in the zone of influence of the proposed scheme whilst those related to pollution associated with construction will not be significant with the proposed mitigation measures in place. Invasive species There are areas of Japanese Knotweed, Himalyan Balsam, Virginia Creeper and Cotoneaster horizontalis within or close to areas which will be disturbed during construction. There is a consequent risk that vehicles and machinery accessing, working and leaving the site could spread these invasive species within the working corridor and beyond the site area in contravention of wildlife legislation A programme of eradication will be undertaken prior to any construction works. This will be carried out by an experienced specialist contractor If any invasive species are still present when construction starts the following mitigation will be adopted to prevent its spread: relevant areas will be fenced off and clearly marked; all site contractors will be made aware of its presence on site and where it is located; no tracked vehicles will be allowed to enter areas where invasive species are present, and there will be no movement of soils contaminated by invasive species fragments around or from the site; and a programme of eradication will be continued. Ecology and Nature Conservation 10-17

18 Fauna Widespread reptiles Construction will require the removal of existing vegetation and modification of embankment and cutting slopes in two areas identified as having good populations of slow worm and one as having a low population. The two good areas comprise sections of the line east of Ascot Road and the location of the proposed station at Vicarage Road. The latter area is also one where it has been established that there is a low population of grass snake. The area of low slow worm population is located between Ascot Road and the first of the good areas Low population levels of slow worm have been identified in two other sections of the proposed scheme corridor which will not be subject to changes in profile but where the ballast will need to be extended and the two new lines installed. They are located between the two bridges on the River Colne and north of the river as far as the junction with the Network Rail line between Watford Junction and Euston All of these works will involve clearance of vegetation and disturbance to areas currently used by slow worm. It is therefore probable, increasing to certain in areas of good population, that there will be a reduction in habitat available for foraging, basking and sheltering / hibernating and displacement from areas that currently support both species. There is also a risk that such works could result in harm to both species in contravention of the Wildlife and Countryside Act 1981 (as amended). A destructive search, which involves the stripping of the top layers of soil in a controlled manner and under the supervision of a suitably qualified ecologist, will be carried out in advance of any vegetation clearance works Measures which will be adopted to mitigate the potential impacts and ensure statutory obligations are met will comprise a combination of trapping and relocation and habitat manipulation and exclusion from the working areas during construction. The sections of the proposed scheme corridor that will be subject to each approach are shown in Figure Trapping and relocation is proposed where land adjacent to the corridor does not comprise semi-natural habitats of a type favoured by reptiles. Habitat manipulation and exclusion is proposed where land adjacent to the corridor does comprise semi-natural habitats of a type favoured by reptiles Trapping will involve fencing of the identified areas and the introduction of artificial refugia to attract the species, supported by selective habitat manipulation to enhance the appeal of the refugia. The work will be undertaken by a suitably experienced ecologist in advance of construction Ecology and Nature Conservation 10-18

19 and between April and October. Any reptiles found will be moved to a pre-arranged receptor site. Potential receptor sites identified by the project promoters include Lairage Land LNR owned by Watford Borough Council and Croxley Common Moor Site of Special Scientific Interest (SSSI). The specific locations and extents of areas, and the duration of trapping required, will be subject to detailed agreement with Watford Borough Council and Natural England The loss of available habitat will be certain and negative at a local level, whilst the adoption of the measures proposed will ensure that the species are safeguarded from harm in accordance with the requirements of the Wildlife and Countryside Act 1981 (as amended) Once the railway is operational reptiles will be able to re-colonise the railway verges from adjacent land though the area of the new track ballast will not be suitable and will represent a loss of habitat. This loss of habitat is not considered significant in relation to the wider area and thus the impact upon widespread reptiles will be negligible. Breeding birds The clearance of broadleaved woodland and dense scrub to facilitate the introduction of the two new tracks and modification of embankment and cutting slopes as described in Chapter 6 will reduce the extent of habitat currently available to some 13 relatively common species of bird. Subject to timing, clearance could result in disturbance or harm during the breeding season in contravention of the Wildlife and Countryside Act 1981 (as amended) The loss of habitat will affect three UK BAP Priority species: Dunnock, house sparrow and song thrush. There is, however, readily available woodland and scrub planting in open land in the vicinity of the proposed scheme corridor which offers alternative suitable habitat for the species and numbers identified within the corridor The re-introduction of planting on the upper sections of modified cutting slopes will also serve to re-establish the integrity of the existing linear planting along the corridor and the availability of habitat to the relatively common species currently associated with the corridor and neighbouring areas It has accordingly been concluded that the proposed scheme will not have a significant impact on the conservation status of breeding birds In relation to compliance with the protection afforded to birds under the WCA, the following measures will be adopted to ensure legal compliance: clearance will be undertaken outside of the bird nesting season (typically March to July inclusive); and Ecology and Nature Conservation 10-19

20 surveys will be undertaken by an appropriately experienced ecologist to check for the presence of active nests to establish if clearance can proceed during the breeding season. Where active nests are identified, work in the vicinity of such areas will not be allowed to proceed until the young have fledged. Badgers The surveys have indicated that the construction of the proposed scheme will not involve the loss of any active setts. There is, however, the potential for harm during construction, there being evidence of use of the corridor and proposed working areas for foraging. Typical examples of such harm include badgers falling into open trenches, or seeking shelter under construction materials resulting in death or injury There will be a risk of disturbance to a badger sett outside of the proposed scheme construction and operational areas. This relates to a single active sett located some 30m from the boundary of the proposed scheme. Required work would involve the installation of gabion walling on the boundary of the proposed scheme and installation of sheet piling retention at the foot of existing cuttings adjacent to the ballast base accommodating the proposed tracks. At the distance from the proposed works there will be a low risk of direct disturbance to tunnels associated with the sett. There will, however, be a risk that noise and ground borne vibration associated with the installation of the sheet piling could constitute disturbance as defined in Section 3 of The Badgers Act There will be a risk that badgers could be killed or harmed in as a result of accidental collision once construction is complete and trains become operational It is also likely that some badgers will be deterred from using established commuting routes to foraging areas where this will require them to cross the newly active rail corridor with consequent impacts for the extent of foraging available relative to numbers in a clan. Such potential is likely in the vicinity of the proposed Ascot Road Station and Watford Hospital Station The following measures will be adopted to address the potential impacts: A pre-construction badger survey will be undertaken to confirm the status of previously identified setts, whether further setts have been established, presence along the proposed construction corridor and movement patterns across the corridor. Non-active setts within the working corridor will be removed. Should the currently abandoned setts have been re-occupied or new setts have been established within the working corridor, proposals for provision of an alternative sett, exclusion from the active sett and Ecology and Nature Conservation 10-20

21 Ecology and Nature Conservation destruction of the sett once exclusion has been proved would be prepared and a licence sought from Natural England to authorise the works. Subject to consenting of the TWA application, a licence permitting the construction works in the vicinity of the main sett located relatively close to the proposed scheme will be sought from National England as provided for in Section 10 of The Badgers Act. Temporary badger fencing will be installed along the boundary of sections of the working corridor to prevent access and inadvertent harm where the surveys confirm evidence of continued use of the corridor and cross movement by badgers. Trenches will be covered overnight or an earth ramp will be provided to allow badgers or other mammals to climb out. Works close to badger setts will be restricted at night to reduce disturbance to badgers. If such works are essential they will be completed under ecological supervision. Permanent badger fencing will be provided along both sides of the railway boundary between River Gade and Ascot Road and Vicarage Road and the Fisher Industrial Estate. The extent and location will be reviewed in light of the pre-construction surveys With the incorporation of measures proposed above, it is considered that the construction and operation of the proposed scheme is unlikely to have a significant impact on badgers. Bats The loss of existing planting will fragment existing commuting routes and reduce foraging habitat The most significant severance of an established commuting route will occur where established planting along the eastern margin of the existing Metropolitan Line will be removed to accommodate the diversion onto the new viaduct. The opening of a gap in this well-used corridor could result in collision and bat casualties where trains are introduced in the gap along the commuting route. Planting will be re-introduced to close the gap as far as is practicable and larger planting stock at close planting centres will be used to encourage bats to take a higher flight path over the railway line to avoid potential collision and casualties Initial loss of foraging habitat and fragmentation of commuting routes associated with loss of planting where cutting slopes and embankments are to modified will be certain, adverse and negative at a local level. The impact will, however, be substantially reduced as a result of the proposed planting of the upper slopes of the modified earthworks such that the impact on the species will not be significant. It is also proposed that bat boxes will be introduced along the proposed scheme corridor.