«LONDONWEST MIDLANDS ENVIRONMENTAL STATEMENT Volume 2 | Community Forum Area report CFA7 | Colne Valley November 2013 ES 220.127.116.11 VOL LondonWest Midlands ...»
2.6.38 However, locating the porous portal at the base of the cutting for the Proposed Scheme, as with the January 2012 announced route, results in a reduced visual impact, thereby addressing the primary concern of the Community Forum.
2.6.39 For these reasons Option A was adopted for the Proposed Scheme.
The National Grid overhead power line diversion over the Colne Valley 2.6.40 The Proposed Scheme includes a diversion to the National Grid overhead power line that currently crosses the lake used by HOAC for sailing activities. The scheme in January 2012 did not identify the need for diversion and this has been identified as part of the subsequent development of the scheme design.
2.6.41 The purpose of the diversion is so that the existing overhead power line does not conflict with the Colne Valley viaduct as it crosses the lake. Two options
Option A: the Proposed Scheme, which is an above ground diversion of the National Grid overhead power line. The diversion will be from the south of the Chiltern Main Line and run eastwards across the Denham Quarry Lake, the Uxbridge Golf Course and Harvil Road. The diversion will then turn north, across the Proposed Scheme at Newyears Green Covert and then returning west across the Harvil Road. It will then rejoin the existing overhead alignment north-east of HOAC and next to the proposed National Grid feeder station; and CFA Report – Colne Valley/No 7 | Overview of the area and description of the Proposed Scheme Option B: a part buried and part overhead option that begins above ground south of the Chiltern Main Line. This option crosses Denham Quarry Lake to the aggregate storage site at the western end of Skip Lane. From here the buried cable diversion route would run northwards under the Chiltern Main Line, along the eastern side of the HOAC lake and under Dew’s Lane before re-emerging north-east of HOAC, next to the National Grid feeder station where it ties into the existing overhead power line.
2.6.42 Both options would require a temporary overhead diversion approximately 80m west of the existing alignment during the construction phase of the Colne Valley viaduct.
2.6.43 Option A, being an above ground diversion, has a greater landscape and visual impact over Option B although the existing landform, the Chiltern Main Line and intervening linear vegetation along the Grand Union Canal and other water bodies goes someway to screening this within the local environment. In landscape and visual terms both options benefit from the removal of the overhead power lines that cross the HOAC lake.
2.6.44 Option A also passes close to and would affect the setting of a number of cultural heritage assets. In addition an area of land would have to be cleared for this Option resulting in ecological impacts.
2.6.45 Option B would be shorter and has a reduced impact in terms of landscape, visual, cultural heritage and ecological impacts but it has a significantly greater cost and long term maintenance issues in relation to the buried element of this Option.
2.6.46 Depending on the exact construction method for Option B, it could result in more intrusive construction impacts arising from burying the cables and the space separation required for this type of power line.
2.6.47 In addition Option B would be closer to other works required under the Proposed Scheme including a number of road crossings. This would result in work being undertaken close to the new power line (which would have to be in place in advance of these works). This would result in greater safety and construction issues when compared to Option A.
2.6.48 Due to the significant costs and construction issues associated with Option B and the relative screening provided by existing vegetation and the Chiltern Main Line it was decided to include Option A within the Proposed Scheme.
The Northolt tunnel boring machine (TBM) power supply 2.6.49 A power supply connection is required for the TBM used to construct the Northolt tunnel, the portal of which is located in the adjacent CFA6 area. The power supply, either as an overhead power line or as a buried cable route will be required from south of the A40 at Fray’s Farm, on the boundary between the CFA Report – Colne Valley/No 7 | Overview of the area and description of the Proposed Scheme Colne Valley area and CFA6. The alignments of Options A to F listed below are located wholly or partially in this area.
2.6.50 The power supply will require two separate route options to ensure resilience of supply during construction and operation.
2.6.51 The following options were considered:
Option A: a buried cable route running within the tow path on the eastern side of the Grand Union Canal between the A40 and the Chiltern Main Line and then diverting east to the West Ruislip tunnel portal. This option will go through Fray’s Valley Local Nature Reserve (in CFA7);
Option B: an overhead power line route following the alignment of the disused railway between the A40 and the aggregate storage site at the western end of Skip Lane and then diverting east to the West Ruislip tunnel portal. This option will go through Fray’s Farm Meadow SSSI and Fray’s Valley Local Nature Reserve (both in CFA7);
Option C: an overhead power line route from the A40, across Fray’s Farm Meadow SSSI and Fray’s Valley Local Nature Reserve and Uxbridge Golf Course to the aggregate storage site at the western end of Skip Lane and then diverting east to the West Ruislip tunnel portal;
Option D: the Proposed Scheme (along with Option F), a variation on Option C that avoids Fray’s Farm Meadow SSSI and is buried through the Uxbridge Golf Course and under the ancient woodland at Pinnocks Wood. It passes around the edge of the Uxbridge Golf Course to the aggregate storage site at the western end of Skip Lane before diverting east to the West Ruislip tunnel portal;
Option E: a buried cable option passing along the A40, the B467 Swakeleys Road and Harvil Road to the Chiltern Main Line then diverting east to the West Ruislip tunnel portal; and Option F: the Proposed Scheme (along with Option D), a buried cable option passing along the A40, the B467 Swakeleys Road and Breakspear Road South to the Chiltern Main Line then diverting east to the Northolt tunnel portal.
2.6.52 Option A was not included within the Proposed Scheme as it would have had an impact during construction on the tow path for the Grand Union Canal and associated recreational activities. It would have also passed through Fray’s Valley Local Nature Reserve resulting in a direct impact upon it.
2.6.53 Option B and C would also have passed through the Fray’s Valley Local Nature Reserve and in addition would pass through Fray’s Farm Meadow SSSI. For this reason they were not included within the Proposed Scheme. Option D would CFA Report – Colne Valley/No 7 | Overview of the area and description of the Proposed Scheme avoid these impacts although it would result in a temporary impact on Uxbridge Golf Course.
2.6.54 Option D was included as one of the two power supply routes as it will avoid the SSSI and Local Nature Reserve impacted in Option C but in avoiding the SSSI the buried cable section of this alignment is needed to remove direct impacts on the ancient woodland of Pinnocks Wood. Therefore, this option was preferred compared with options A, B and C.
2.6.55 Option E was discounted due to the impacts this buried cable option would have during construction on traffic using Harvil Road, including the construction vehicles. In addition this option was longer than others and would be more costly.
2.6.56 Option F was included as one of the two power supply routes as it will avoid impacts to traffic on Harvil Road, avoid impacts to designated environmental sites, avoid use of Network Rail land and is a more direct alignment than Option E.
2.6.57 To ensure power supply and provide resilience, two supplies are required during construction and operation. Option D and Option F have been included within the Proposed Scheme to achieve this. It is intended that Option F will be delivered through existing powers outside of the hybrid Bill process.
M25 temporary slip roads 2.6.58 The Proposed Scheme includes the provision of a pair of temporary slip roads onto the M25 north of Chalfont Lane between the existing junctions 16 and 17, for the sole use of construction traffic during the construction phase of the Proposed Scheme.
2.6.59 The alternative option for site access to the main construction compounds for the Colne Valley viaduct and Chiltern tunnel, would have been be off Chalfont Lane, onto the A412 Denham Way/North Orbital Road. Under this option delivery vehicles would either exit the M25 at Junction 17 and travel south on the A412 through Maple Cross, or vehicles would travel north on the A412 through Denham. This would have a significant impact on traffic volumes through these communities. To avoid this impact the option of a new temporary junction on the M25 was included within the Proposed Scheme.
CFA Report – Colne Valley/No 7 | Overview of the area and description of the Proposed Scheme
3 Agriculture, forestry and soils
Introduction3.1 3.1.1 This section provides a description of the current baseline for agriculture, forestry and soils and an assessment of the likely impacts and significant effects as a result of the construction and operation of the Proposed Scheme.
Consideration is given to the extent and quality of the soil and land resources underpinning the primary land use activities of farming and forestry and the physical and operational characteristics of enterprises engaged in these activities. Consideration is also given to diversification associated with the primary land uses and to related land-based enterprises, notably equestrian activities.
3.1.2 The quality of agricultural land in England and Wales is assessed according to the Agricultural Land Classification (ALC) system which classifies agricultural land into five grades from excellent quality Grade 1 land to very poor quality Grade 5 land. Grade 3 is subdivided into Subgrades 3a and 3b. The main issue in the assessment of the impacts on agricultural land is the extent to which land of best and most versatile (BMV) agricultural quality (Grades 1, 2 and 3a) is affected by the Proposed Scheme.
3.1.3 Forestry is considered as a land use feature and the impacts have been calculated quantitatively. The qualitative effects on forestry land and woodland are addressed principally in the ecology and landscape and visual assessments (see Sections 7 and 9).
3.1.4 Soil attributes, other than for food and biomass production, are identified in this section but the resulting function or service provided is assessed in other sections, notably cultural heritage, ecology and landscape and visual assessment (see Sections 6, 7 and 9).
3.1.5 The main issue for farm holdings is the disruption by the Proposed Scheme of the physical structure of agricultural holdings and the operations taking place upon them, during both its construction and operational phases. Key engagement has been undertaken with farmers and landowners affected by the Proposed Scheme to obtain factual information on the scale and nature of the farm and forestry operations and related farm-based uses.
3.1.6 Details of published and publically available information used in the assessment, and the results of surveys undertaken within this area are contained, Volume 5: Appendix AG-001-007.
Scope, assumptions and limitations 3.2 3.2.1 The assessment scope, key assumptions and limitations for the agriculture,
forestry and soils assessment are set out in Volume 1, the SMR (see Volume 5:
CFA Report – Colne Valley/No 7 | Agriculture, forestry and soils Appendix CT-001-000/1) and the SMR Addendum (see Volume 5: Appendix CT-001-000/2). This report follows the standard assessment methodology.
3.2.2 The study area for the agriculture, forestry and soils assessment covers all of the land that will be required for the construction and operation of the Proposed Scheme. The resources and receptors that are assessed within this area are agricultural land, forestry land and soils; together with farm and rural holdings.
The assessments of the impacts on agricultural land quality and forestry land are made with reference to the prevalence of BMV land and forestry in the general locality, taken as a wider 4km corridor centred on the Proposed Scheme.
3.2.3 Common assumptions that have been applied to the Proposed Scheme, such as the restoration of agricultural land to pre-existing quality, the handing back of land used temporarily to the original landowner and the non-replacement of capital items demolished, are set out in Volume 1. There are no assumptions or limitations that are specific to the assessment in this area.
Environmental baseline 3.3 Existing baseline 3.3.1 This section sets out the main baseline features that influence the agricultural and forestry use of land within this area. These include the underlying soil resources which are used for food and biomass production, as well as providing other services and functions for society and the associated pattern of agricultural and other rural land uses.
Soils and land resources Topography and drainage 3.3.2 The main topographical features within the study area are described in the landscape and visual assessment (Section 9).
3.3.3 The arterial drainage in this area is provided by the River Colne which, together with the Grand Union Canal and the Colne Valley lakes, defines the central character of the area. This mosaic of water features runs in a north-south direction. Many of the lakes are the remnants of gravel abstraction and are divided by spurs of land that have become heavily wooded. These water bodies mark the lowest altitudes of the section at around 40m above Ordnance Datum (AOD). Above these water bodies, the valley sides rise to higher ground reaching around 80m AOD at the Chiltern tunnel south portal just east of the M25. The Chiltern Hills rise further to the west.
Geology and soil parent materials 3.3.4 The main geological features within the study area are described in the land quality assessment (Section 8). The principal underlying geology mapped by the
British Geological Survey (2013) http://bgs.ac.uk/geologyofbritain/home/html; Accessed 14/08/13.
Soil Survey of England and Wales, (1984), Soils and their Use in South East England.
Cranfield University (2001) The National Soil Map of England and Wales 1:250,000 scale.
The Wetness Class of a soil is classified according to the depth and duration of waterlogging in the soil profile and has six bands.
FCD is a meteorological parameter which estimates the duration of the period when the soil moisture deficit is zero. Soils usually return to field capacity (zero deficit) during the autumn or early winter and the field capacity period, measured in days, ends in the spring when evapotranspiration exceeds rainfall and a moisture deficit begins to accumulate and opportunities for mechanised fieldwork are then possible.
Defra (2005) Likelihood of Best and Most Versatile Agricultural Land.
Defra (2009) Soil Strategy for England.
Defra (2011) The Natural Choice: securing the value of nature.
properties, have a low sensitivity. The holding/reference name provides a unique identifier and relates to Map Series AG-01-011 to AG-01-013a (Volume 5, Agriculture, Forestry and Soils Map Book) and Appendix AG-001-007, Volume 5.
Table 5: Summary characteristics of holdings
An extant planning consent has commenced which will reduce the size of the holding temporarily to 85ha.
CFA Report – Colne Valley/No 7 | Agriculture, forestry and soils replacement field access incorporated into the Harvil Road realignment;
and agricultural access incorporated into the access overbridge at Tilehouse Lane.