Proposal for Northern Extension of Northolt Tunnel sift report
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- 8 Evaluation against Assessment Criteria Table 8.1 Northern Extension of Northolt Tunnel Engineering Appraisal SIFT Assessment Table Location
`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
41 Uncontrolled when printed
7.5.7 Tunnelling has previously been undertaken in a SPZ1 area (National Grid Croydon Cable Tunnel, London), where contamination was carefully avoided through an extensive pre- construction groundwater monitoring, sampling and testing programme which was developed through consultation with the Environment Agency. 7.5.8
The relocation of the HOAC (Hillingdon Outdoor Activity Centre) site would not be required under Options B and C.
`Code 1 -
Accepted Uncontrolled when printed INTERNAL INFORMATION Northern Extension of Northolt Tunnel SIFT Report
C222-ATK-DS-REP-020-000034 Revision – P06
Page 42
INTERNAL INFORMATION
Strategic Fit Capture whether an option meets the Project Specification The solution is in accordance with the project specification and technical requirements. 0 The solution is in accordance with the project specification and technical requirements. 0
The solution is in accordance with the project specification and technical requirements. 0
Feasibility Assess the relative complexity of construction Assess the relative construction programme Viaduct construction is standard, aligns with rest of adjacent sections of viaduct construction and allows repeated use of formwork and temporary works.
There is a localised diversion of the River Colne to ensure that none of the viaduct piers are located within the river. This may require temporary works in order to construct the piers adjacent to the river bank.
0 The 8.8m internal diameter main tunnels will be constructed by TBM as previously proposed for the Northolt and Chiltern tunnels. The passive provision for the Heathrow spur requires that significant sized caverns are constructed of spans in excess of 20m.
A tapered gap structure with maximum width of 70m, depth of 20m and 700m long box structure will be required with connecting access tracks which will allow passenger evacuation.
Three additional intervention and ventilation shafts will be required at nominally 3000m intervals.
Requires relocation of ATFS compared to Option A. Construction period for the Northolt tunnel extension associated with Options B and C is 19 months assuming 2 No. TBMs which would run in parallel with Chiltern and Northolt tunnel constructions.
Extension of construction time for Chiltern tunnel (1 month), Northolt tunnel (2 months) or Rail Systems (3 Months) may affect overall programme time. - The 8.8m internal diameter main tunnels will be constructed by TBM as previously proposed for the Northolt and Chiltern tunnels.
A tapered gap structure with maximum width of 70m, depth of 20m and 700m long box structure will be required with connecting access tracks which will allow passenger evacuation.
Three additional intervention and ventilation shafts will be required at nominally 3000m intervals.
Requires relocation of ATFS compared to Option A. Construction period for the Northolt tunnel extension associated with Options B and C is 19 months assuming 2 No. TBMs which would run in parallel with Chiltern and Northolt tunnel constructions.
Extension of construction time for Chiltern tunnel (1 month), Northolt tunnel (2 months) or Rail Systems (3 Months) may affect overall programme time. - Assess the relative disruption to existing infrastructure, e.g. rail, highways etc. N/A
0 Additional burden on public roads for servicing tunnel construction.
Removal of excavated material from the construction compound by the M25 would significantly increase the lorry movements within the M25 and local roads.
Diversion of Harvil Road. - - Additional burden on public roads for servicing tunnel construction.
Removal of excavated material from the construction compound by the M25 would significantly increase the lorry movements within the M25 and local roads.
Diversion of Harvil Road. - - HS2 Operation Feasibility – Trains (HS2 and Network Rail) Assess the relative flexibility and reliability of the track layout Assess the relative train maintenance and servicing arrangements Maintenance required on viaduct. 0 Maintenance required through tunnel. 0 Maintenance required through tunnel 0 HS2 Operation Feasibility –Operations (Stations, Depots etc.) Assess the effectiveness of Location and space for station control Location and space for accommodating staff, catering, transport police and other “back of house” activities N/A
0 Required to assess the fire life safety strategy for the cases where caverns present, especially at turnout T2. 0 Required to assess the fire life safety strategy for the cases where caverns present. 0
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