Proposal for Northern Extension of Northolt Tunnel sift report
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- Bu səhifədəki naviqasiya:
- Location: Colne Valley OPTIONS CONSIDERED: Option A The Proposed Scheme as submitted in the hybrid Bill
- Above ground section between Northolt and Chiltern tunnels placed underground in bored tunnels with provision for connection spurs to Heathrow
- QUALITATIVE IMPACT DESCRIPTION and/or QUANTITIVE ASSESSMENT RATI NG
- Level of SIFT
- Appendix A Options Drawings A.1 C222-ATK-CV-DPP-020-000001
- C222-ATK-TN-DSK-020-000340
- C222-ATK-RT-DSK-020-011303
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Accepted Uncontrolled when printed INTERNAL INFORMATION Northern Extension of Northolt Tunnel SIFT Report
C222-ATK-DS-REP-020-000034 Revision – P06
Page 55
INTERNAL INFORMATION
Key Sustainability Issue Topic STAGE: Constructio n or Operation EDA Considered (incl. Topic and Ref no.) Comment QUALITATIVE IMPACT DESCRIPTION and/or QUANTITIVE ASSESSMENT RATI NG QUALITATIVE IMPACT DESCRIPTION and/or QUANTITIVE ASSESSMENT RATI NG QUALITATIVE IMPACT DESCRIPTION and/or QUANTITIVE ASSESSMENT RATI NG B. All excavated material would be removed from site via the M25 generating significant additional traffic movements with consequential temporary impacts on the road traffic network and possibly local air quality.. No detailed assessment of traffic and air quality impacts has been undertaken to confirm the severity of the potential impacts from off-site material disposal. material to be removed off-site reduced.
1. The appraisal has been based on the information provided by Atkins Engineering Design Team at the time of appraisal (please note: no digital information has been provided and appraisals have been undertaken from drawings only). 2. The comparison of options has been undertaken as instructed using the Proposed Scheme as a base case. 3. All impacts reported here are potential predicted impacts and will be subject to surveys, assessment and professional interpretation and judgement as part of the EIA process. 4. Advice has been obtained from topic specialists in agriculture, community, socio-economics, cultural heritage, landscape, noise, traffic and transport, ecology and water. 5. Potential impacts have been identified on the basis of a mitigated base case (the Proposed Scheme) 6. Construction noise impacts are based on qualitative judgement taking account of information provided by Atkins Engineering Design Team on potential construction methods. Where applicable, this information is also set out in section 6 and table 7.1 of the associated engineering sift report. 7. Property demolitions, loss, or direct impacts to designated features and resources are addressed as construction phase impacts. 8. Construction impacts for cultural heritage has assumed that all construction activity within the land required, temporarily or permanently, for the Proposed Scheme, will result in the removal of archaeological assets. Operational impacts for cultural heritage considers the impacts on the setting of heritage assets. 9. The assessments have been scored based on the HS2 Ltd guidance i.e. Proposed Scheme is scored as neutral and all other options are scored either better than or worse than the base case . Where there is no base case (e.g. for site compounds, road realignments etc, the scoring is reflective of the options on their own merit and will use the scoring matrix as below:
Major worsening on the Comparator Scheme
Minor worsening on Comparator Scheme o Neutral / no change to Comparator Scheme + Minor improvement on Comparator Scheme + + + Major improvement on Comparator Scheme N/A Not applicable `Code 1 -
Accepted Uncontrolled when printed INTERNAL INFORMATION
Northern Extension of Northolt Tunnel SIFT Report
Northern Extension of Northolt Tunnel SIFT Report C222-ATK-DS-REP-020-000034 Revision – P06
Page 56
Uncontrolled when printed INTERNAL INFORMATION
1. This matrix has been prepared for the comparison of alternative engineering options at particular locations. 2. The entries should be abbreviated as much as possible and should report the key issues only. (This matrix should be a summary document for the comparison of alternative options, and it should be supported by more detailed assessments, where appropriate.) 3. The matrix has been prepared using the framework of key sustainability issues as set out in the Appraisal of Sustainability (AoS). Each sustainability issue is then subdivided into a number of topic headings, which broadly correspond with the section headings of the Environmental Statement, as set out in the EIA Scoping and Methodology Report (SMR). 4. It is intended that that the methodology set out in the SMR will be applied for the assessment of the magnitude of impacts. 5. The first column should include a brief written assessment of the likely impacts, drawing out the key issues and including any quantitative assessment made, such as the number of properties affected by a particular issue. 6. The second column, headed “Rating”, should be a colour coded assessment of the likely impact of the option, as follows:
Major worsening on the Comparator Scheme
Minor worsening on Comparator Scheme o Neutral / no change to Comparator Scheme + Minor improvement on Comparator Scheme + + + Major improvement on Comparator Scheme N/A Not applicable
7. Separate lines are provided for the construction and operational stages. For some topics, an assessment will be required at only one of these stages, but for others, assessments will be required at both the construction and operational stages. Any stage that is not relevant should be marked as N/A (Not Applicable). Reference should be made to the SMR for further guidance.
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Accepted Uncontrolled when printed INTERNAL INFORMATION
Northern Extension of Northolt Tunnel SIFT Report Northern Extension of Northolt Tunnel SIFT Report C222-ATK-DS-REP-020-000034 Revision – P06
Page 57 Uncontrolled when printed
INTERNAL INFORMATION Level of SIFT 10.1
This report applies to Sift Level 2.
11.1 An engineering review of a tunnel under Colne Valley has been carried out in this report, which would link the Proposed Scheme Northolt tunnel with the Chiltern tunnel. Options B and C have been assessed and compared in engineering terms with the current Proposed Scheme (Option A). Option B is a subsurface alignment to include a 700m long ‘gap’ which provides compliance with the European Technical Specification of Interoperability (TSI) 2014, including passive provision for the future Heathrow spurs. Option C is similar to Option B, without the provision for Heathrow spurs. 11.2 An intervention gap would be located to the south of the M25 to meet the TSI recommendations for tunnel length and associated fire and safety requirements, and to also provide a location from where the Chiltern tunnel southern portal and tunnel drives could be situated. The intervention gap would need to be a minimum of 700m long, with a maximum width of 70m to include for the provision of Heathrow spur turnouts, and at this location of around 20m deep. 11.3
To provide passive provision for the Heathrow spurs, an underground cavern would be required on the south side of the Colne Valley. Provision for turnouts from the north would be accommodated within the intervention gap. 11.4
In terms of construction logistics a significant area is required to be available to support the launch and operation of the TBMs. Given concerns over the availability of additional train paths for extra spoil disposal from the Ruislip railhead, it is envisaged that the Colne Valley tunnel would need to be driven from the intervention gap by the M25. Four TBMs would be launched from the intervention gap, two driving north to construct the Chiltern tunnel and two driving south to construct the tunnel under Colne Valley. Northolt tunnel construction would commence from the location of ventilation shaft F southwards. 11.5 The extension of the Northolt Tunnel under the Colne Valley would create around 4.3million m3 of earthwork in total. This material wold principally comprise Chiltern tunnel spoil (no longer required for mitigation earthworks in this area) and the excavation material from the intervention gap as well as the new tunnel under the Colne Valley. Approximately 4.2million m3 of this would require disposal by road via the M25 from the construction compound adjacent to the Chiltern Tunnel south portal. 11.6
Key Rail systems issues and risks that the longer tunnel would introduce would include:- The need for an intermediate firefighting point, suitably equipped and potentially requiring special purpose rescue vehicles It is likely that some form of tunnel cooling will be required A specialised air supply system may be required for the rolling stock. Such a special measure might only be achievable on the captive rolling stock. `Code 1 -
Accepted Uncontrolled when printed INTERNAL INFORMATION
Northern Extension of Northolt Tunnel SIFT Report Northern Extension of Northolt Tunnel SIFT Report C222-ATK-DS-REP-020-000034 Revision – P06
Page 58 Uncontrolled when printed
INTERNAL INFORMATION Additional ventilation measures are likely to be required at the proposed turnout cavern, which could result in changes to the proposed configuration of stub tunnels. The necessary additional equipment may be challenging to maintain. A journey time increase is likely to result, due entirely to tunnel resistance increases and a significant increase in air mass movement. This impacts on the robustness of the operational timetable. There may be a potential requirement for a speed limit due to pressure waves generated when trains pass through the Heathrow spur cavern with likely impact to the signalling headway. Cable shaft(s) would need to be provided between Ickenham ATFS (Auto Transformer Feeder Station) at surface and the tunnels or the shaft size increased to allow for additional traction power cables. The loss of a maintenance siding will add risk to the maintenance strategy in undertaking the required work within the maintenance period. 11.7 The current estimated construction of Option B is £215.0 million more than the Proposed Scheme, and for Option C £185.1 million more than for the Proposed Scheme. 11.8
All construction cost estimates include associated civil engineering and rail systems works.
11.9 Options B and C both incur a potential increase of some 5 months in the construction programme due to longer construction and rail systems fit-out requirements. 11.10
It is recommended that the Proposed Scheme (Option A in this report) be retained, on grounds of cost, construction safety and programme implications and for avoidance of major traffic movements for the removal of tunnel excavated material.
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Accepted Uncontrolled when printed INTERNAL INFORMATION
Northern Extension of Northolt Tunnel SIFT Report Northern Extension of Northolt Tunnel SIFT Report C222-ATK-DS-REP-020-000034 Revision – P06
Page 59 Uncontrolled when printed
INTERNAL INFORMATION Appendix A Options Drawings A.1 C222-ATK-CV-DPP-020-000001 Main Line Sheet 20 of 49 Chainage 25+600 to 32+000 (Plan & Profile presenting Option A ‘The Proposed Scheme’)
Community Forum Request Northolt Tunnel Extension Options B Key Option Requirements
Community Forum Request Northolt Tunnel Extension Option B Plan & Profile Sheet 1 of 2
Community Forum Request Northolt Tunnel Extension Option B Plan & Profile Sheet 2 of 2
Colne Valley Tunnel Eastern Heathrow Spurs Track Alignment Plan & Profile
Colne Valley Tunnel Western Heathrow Spurs Track Alignment Plan & Profile
Colne Valley Tunnel Eastern Heathrow Spurs Cross Sections
Colne Valley Tunnel Eastern Heathrow Spurs Cross Sections
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Accepted Document Outline
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