«LONDONWEST MIDLANDS ENVIRONMENTAL STATEMENT Volume 2 | Community Forum Area report CFA7 | Colne Valley November 2013 ES 220.127.116.11 VOL LondonWest Midlands ...»
7.1.2 The principal ecological issues in this area are the loss of habitat used by and disturbance of breeding birds in the Mid Colne Valley Site of Special Scientific Interest (SSSI), the Mid Colne Valley Site of Metropolitan Importance (SMI) and the loss of woodland, of which some is ancient woodland and some supports coralroot, a notable plant species.
7.1.3 Volume 5 of the ES contains supporting information to the ecological assessment
reported in this section, including:
ecological baseline data (Appendix EC-001-002, EC-002-002, EC-003-002, and EC-004-002);
register of local/parish level effects, which are not reported individually in Volume 2 (Appendix EC-005-002); and data obtained from bat trapping/radio tagging study (Appendix EC-007-002).
7.1.4 As well as survey data, the assessment draws on existing information gathered from national organisations and from regional and local sources including the Environment Agency; Hertfordshire and Middlesex Wildlife Trust; Berkshire, Buckinghamshire and Oxfordshire Wildlife Trust; Buckinghamshire and Milton Keynes Environmental Records Centre; Hertfordshire Biological Records Centre; Greenspace Information for Greater London; Hertfordshire Bird Club; London, Essex and Hertfordshire Amphibian and Reptile Trust and Hillingdon Natural History Society.
Scope, assumptions and limitations 7.2 7.2.1 The scope and methodology of the ecological assessment are introduced in the SMR (Volume 5: Appendix CT-001-000/1) and SMR Addendum (Volume 5: Appendix CT-001-000/2). Further detail, including the study area for individual surveys, is provided within the SMR Addendum (Volume 5: Appendix CT-001-000/2). The assessment methodology is summarised in Section 8.5 of Volume 1, along with routewide assumptions and limitations. Limitations associated with particular surveys are reported, Volume 5: Appendices EC-001-002, EC-002-002, EC-003-002 and EC-004-002.
7.2.2 A Water Framework Directive assessment has been undertaken in conjunction with
the environmental assessment. Details of this assessment are presented, Volume 5:
7.2.3 A Habitats Regulations Appraisal (HRA) screening exercise was undertaken in consultation with Natural England during 2011 and 2012. The HRA concluded that the
CFA Report – Colne Valley/No7 | Ecology
South West London Waterbodies Special Protection Area (SPA), some 12km south of the Mid Colne Valley SSSI, will not be significantly affected by the Proposed Scheme.
This conclusion has been agreed by Natural England. The HRA is presented, Volume 5:
7.2.4 As well as the standard range of bat surveys described in the SMR, additional bat trapping and radio-tracking surveys of noctule bats were undertaken to provide information on the likelihood of collision risks with moving trains and the Colne Valley viaduct. A lake habitat survey was also undertaken to provide information on plant, fish and invertebrate assemblages in the Mid Colne Valley SSSI.
7.2.5 Access was not obtained to all of the land area where general habitat survey (Phase 1 habitat survey) was proposed. Locations with the potential to support key ecological receptors where access could not be gained for survey include Dew’s Farm and the Newyears Green Bourne; Savay Lake; Harefield No.2 Lake and surrounding habitats (although some survey data were collected from public rights of way for these lakes);
Uxbridge Golf Course; Buckinghamshire Golf Course; farmland between the A412 Denham Way/North Orbital Road and M25; farmland east of South Harefield and lakes and woodland south of the Chiltern Main Line. Further details are provided, Volume 5: Appendices EC-001-002, EC-002-002, EC-003-002 and EC-004-002.
7.2.6 Where data are limited, a precautionary baseline has been built up according to the guidance provided, Volume 5: Appendix CT-001-000/2. This constitutes a ‘reasonable worst case’ basis for the subsequent assessment.
7.2.7 The precautionary approach to the assessment has been adopted to identify the likely significant ecological effects of the Proposed Scheme.
Environmental baseline 7.3 Existing baseline 7.3.1 This section describes the ecological baseline relevant to the assessment at the designated sites, habitats and species recorded in this area. Further details are provided in the reports and maps presented, Volume 5 (Appendices EC-001-002, EC-002-002, EC-003-002 and EC-004-002 and Map Series EC-01 to EC-12, Volume 5, CFA7 Ecology Map Book). Statutory and non-statutory designated sites are shown on Map EC-01 (Volume 5, Ecology Map Book).
7.3.2 Land required for the construction of the Proposed Scheme and that adjacent to it includes the valley of the River Colne where past mineral extraction has created a series of large lakes. These lakes support important populations of breeding birds and waterfowl as well as wetland and wet woodland habitats. Many of the lakes are used for angling and Tilehouse Lake South, Harefield No. 2 Lake and the northern part of Broadwater Lake are all used for water sports. Lafarge Aggregates operates on the eastern side of Broadwater Lake and Harefield Moor Lake is a gravel washing lagoon.
Large areas of arable farmland are present to the west of the A412 Denham Way/North Orbital Road and farmland is present between Harefield No. 2 Lake and Harvil Road; both areas are crossed by hedgerows. There are several ancient woodlands in the surrounding area.
The Mid Colne Valley SSSI includes the following lakes: Broadwater Lake, Harefield Moor Lake, Korda Lake, Tilehouse Lake South and Long Pond.
Coppermill Down is over 900m away from the land required for construction of the Proposed Scheme.
Non-statutory nature conservation sites in London are designated at four levels: SMI contain features, which are notable across Greater London scale; SBI.I (grade 1) and SBI.II (grade 2) contain features, which are notable at the London Borough scale (grade 1 sites are more important than grade 2 sites).
Parts of the Colne Valley area are situated in Buckinghamshire, Greater London and Hertfordshire and thus there are five types of non-statutory nature conservation site: Local Wildlife Sites (LWS) and Biological Notification Sites (BNS) in Buckinghamshire, Sites of Metropolitan Importance (SMIs) and Sites of Borough Importance (SBI) in Greater London and LWS in Hertfordshire.
The SMI overlaps the smaller Mid Colne Valley SSSI north of Moorhall Road. Korda Lake, Harefield Moor Lake, Broadwater Lake, Tilehouse Lake South and surrounding woodland and wetland habitats are both in the SSSI and the SMI. Broadleaved woodland at Ranston Covert and Battlesford Wood is in the SSSI but it is not in the SMI.
The Mid Colne Valley SMI includes all of the lakes in the Mid Colne Valley SSSI and Harefield No. 2 Lake, Savay Lake, Denham Quarry Lake and other lakes (un-named) south of the Chiltern Mainline.
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scrubby, birch dominated woodland. Alder woodland in the north-west of Northmoor Hill Wood is managed by rotational coppicing;
Great Halings Wood LWS (9.5ha) – designated for ancient woodland that is relatively species-rich and dominated by mature beech and hazel coppice. It is adjacent to an area of land required for construction of the Proposed Scheme that will be used for ecological compensation;
Colne Valley Gravel Pits Hertfordshire LWS (114ha) – is designated for wintering birds and wetland habitats. It includes several lakes north of the Mid Colne Valley SSSI. A small area of this site is in the land required for construction of the Proposed Scheme at the western edge of Pynesfield Lake;
Tilehouse Gravel Pits BNS (26ha) – is within the Mid Colne Valley SSSI and is centred on Tilehouse Lake South. It is designated for standing water, wetland vegetation and water-birds, including breeding pochard. Woodland at the south-west corner of the site is within land required for the construction of the Proposed Scheme;
Juniper Wood BNS (15.4ha) – designated for ancient woodland. It is adjacent to the land required for the construction of the Proposed Scheme (part of which will be used for ecological mitigation) between Tilehouse Lane and the M25 motorway;
The River Colne east of Denham BNS (4.6ha) – designated for river habitat including aquatic plants and fauna. This site lies partly in land required for construction of the Proposed Scheme, south of the Chiltern Main Line where National Grid overhead power lines will be realigned;
Dew’s Dell SBI.I (8.9ha) – is designated for broadleaved woodland with small areas of species-rich grassland. It lies partly within land required for construction of the Proposed Scheme west of Harvil Road;
Harefield Hall and The Lodge SBI.II (11.2ha) – is designated for broadleaved woodland and lies partly within land required for the realignment of the National Grid overhead power lines; and Breakspear House Woods SBI.II (5.5ha) – is designated for broadleaved woodland with several species of ancient woodland indicator plant (although it is not listed on the ancient woodland inventory). It is adjacent to the Proposed Scheme, east of South Harefield.
7.3.6 The statutory and non-statutory designation, part of the Mid Colne Valley SSSI (Korda Lake, Long Pond, Harefield Moor Lake and the western part of Broadwater Lake) is managed as a nature reserve by the Hertfordshire and Middlesex Wildlife Trust.
7.3.7 In addition to the ancient woodland within the designated sites, Pinnocks Wood, a broadleaved ancient semi-natural woodland is partly in land required for the construction of the Proposed Scheme (where electricity cables will be bored underground). This ancient woodland represents an irreplaceable resource.
Habitat of principal importance includes 56 habitats that form priorities for conservation in the UK as identified in Section 41 of the Natural Environment and Rural Communities (NERC) Act 2006.
JNCC (2011) UK BAP Rivers – Qualifying Reaches. Available online at: http://jncc.defra.gov.uk/page-4863 (accessed September, 2013).
A RCS and RHS survey of the River Colne was undertaken from Moorhall Road north to Tilehouse Lake South.
The Ecology section considers all woodland types, including immature re-growth. Therefore, there may be differences between the figures quoted in the Agriculture assessment (which are taken from the Forestry Commission’s national woodland inventory).
The National Vegetation Classification (NVC) a common standard developed with the purpose of producing a comprehensive classification and description of the plant communities of Britain.
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excelsior-Acer campestre-Mercurialis perennis woodland. Two NVC subcommunities are present: W8d Hedera helix sub-community (ivy subcommunity) and W8e Geranium robertianum sub-community (herb robert subcommunity). The woodland is moderately species-rich and includes two populations of coralroot. It qualifies as lowland mixed deciduous woodland, a habitat of principal importance. It is of county/metropolitan value;
the western bank of the River Colne consists of a mixture of alder woodland W6 Alnus glutinosa – Urtica dioica woodland with some hawthorn scrub W21 Crataegus monogyna-Hedera helix scrub. The ground flora includes abundant common nettle and frequent dog’s mercury. Wet woodland is uncommon nationally and the example here qualifies as a habitat of principal importance.
It is of county/metropolitan value;
Great Halings Wood and Juniper Wood are both semi-natural broadleaved woodlands that are also ancient woodland. They are adjacent to the land required for ecological mitigation. They are likely to be fairly species-rich and to qualify as lowland mixed deciduous woodland and a habitat of principal importance. These woodlands are each of county/metropolitan value;
Harefield Hall and The Lodge contains semi-natural broadleaved woodland that is partly in land required for construction of the Proposed Scheme. Parts are ancient woodland and it is likely to be a habitat of principal importance. It is of county/metropolitan value;
Pinnocks Wood is a broadleaved ancient semi-natural woodland that lies partly within the land required for the construction of the Proposed Scheme, where electricity cables will be tunnelled underground. It is of county/metropolitan value;
woodland around many of the lakes in the Mid Colne Valley SSSI is dominated by willow and alder with frequent sycamore and oak. The shrub layer has occasional elder, hawthorn and dogwood and the ground flora is dominated by common nettle and bramble. The majority of this woodland qualifies as wet woodland that is a habitat of principal importance. However, it is less speciesrich than some of the wet woodland in the wider landscape and it includes a high cover of ruderal species. This type of woodland is also frequent in the River Colne valley and is of district/borough value;
the woodland around Harefield No. 2 Lake and Savay Lake and the woodlands south of the Chilterns Main Line at Widows Cruise Covert and Flagmoor Covert are on similar soils to woodland found around the lakes in the Mid Colne Valley SSSI. Therefore, they are likely to be wet woodland dominated by alder and willows. These woodlands are all in the Mid Colne Valley SMI and may qualify as wet woodland, a habitat of principal importance. Individually, they are of up to district/borough value;
woodland at Dew’s Dell contains semi-natural broadleaved woodland that is in land required for construction of the Proposed Scheme. It is not on the ancient The Hedgerows Regulations 1997 (1997 No. 1160). London. Her Majesty’s Stationery Office. The Hedgerows Regulations 1997 comprise two criteria for determining whether a hedgerow is important or unimportant: Wildlife and Landscape, and Archaeology and History. The Ecology Chapter and the Technical Appendix for hedgerows refer to the Wildlife and Landscape criteria. Therefore it is likely that there will be differences between the total number of important hedgerows in the Ecology and the Cultural Heritage chapters of the ES.
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Road, one adjacent to the east side of Korda Lake and the other adjacent to the north east part of Savay Lake. All of these areas are partly within the land required for the construction of the Proposed Scheme. This type of grassland does not qualify as a habitat of principal importance, nor does it support any notable species. It is common in the surrounding landscape and each area is of local/parish value.
19 In the Mid Colne Valley SSSI, the majority of the lake shores have steep banks and are shaded by trees. However, small areas of swamp vegetation are present around Broadwater Lake, Korda Lake, Harefield Moor Lake, Tilehouse Lake South and Long Pond (no more than 3ha in total). This vegetation is dominated by either common reed or reedmace or a mixture of wetland plants such as greater willowherb, purple loosestrife, gypsywort and yellow iris. This habitat type is included on the SSSI citation but is not a primary reason for designation. It is species-poor and each area is of local/parish value.
7.3.20 Along the River Colne there are occasional stands of swamp dominated by reed sweetgrass, reed canary grass or lesser pond sedge. Shading from adjacent trees restricts the extent of swamp to no more than 0.5ha in total. This habitat type is species-poor and of local/parish value.
Water bodies 7.3.21 There are eight lakes (water bodies over 2ha in size) relevant to this assessment:
Harefield No. 2 Lake, Savay Lake, Korda Lake, Harefield Moor Lake, Long Pond and Denham Quarry Lake south of the Chiltern Main Line are all within the land required for construction of the Proposed Scheme;
a small area of Broadwater Lake is also within the land required for construction of the Proposed Scheme (for part of an ecological mitigation area); and Tilehouse Lake South is adjacent to the land required for construction of the Proposed Scheme.