Environmental Statement volume 4 - Chiltern Evergreen3

ParkwaysidingsAP15Gosford and Water EatonFootbridge No. 10Replacement of pedestrian LC withnew footbridgeAP16Wolvercot Tunnel and FirstTurn OverbridgeLowering track and track sideretaining structuresAP17 Aristotle Lane Footbridge Addition of ramp to accessallotment gardens due to closure ofpedestrian level crossingAP18 Sheepwash bridge Replacing bridge spans and widenbridge (re-decking)AP19 Oxford Station Refurbish parcel platforms forpassenger useTable 1Preliminary geotechnical studies have identified certain sections of the existingembankments between the A41 overbridge and the Cherwell and Millstream Viaductsthat may need to be reinforced for the installation of double track. The options forreinforcement include stabilisation of the existing embankment, widening with retainingstructures at the toe of the embankment or, as a last resort, widening to include theembankment toe. The TWA Order includes land take for the worst case. The detaileddesign for these will not be progressed until after the Order has been granted and it isappropriate to agree a procedure for assessing any flood impacts at detailed design.2.2 AP1 – Bicester ChordAP1 is a line extension enabling trains from Oxford to transfer to the London-bound trackrunning from Birmingham. Figure 2 shows the footprint of the proposed land take forthe embankment, along with the EA Flood Risk Zones 2 (red) and 3 (green). A newdouble chord line track is to be built upon a significant embankment, up to 8 m high, inorder for the track to gain the required height to join the Birmingham to London line.The development crosses Flood Zone 3, the floodplain of the Langford Brook. It shouldbe noted that there appears to be an error in the floodplain mapping that does not takeinto account the existing embankment, and what appears to be a degree ofchannelisation of the brook through this existing embankment.A new pedestrian overbridge is to be built across the new chord line to maintain accessthrough the public right of way (running essentially parallel with the Bletchley to Oxfordline, as shown in Figure 2). As the footpath crosses agricultural land, access will be viasteps rather and will not be DDA compliant.Furthermore, the Langdon Brook crossing (already in place as a masonry arch culvert) isto be extended by 7.5 m to accommodate the widened embankment footprint using precastreinforced concrete box culvert sections.The Langford Brook is a Main River hence the work will require a Flood Defence Consentunder the terms of the proposed Protective Provisions in the TWA Order. The conditionsof the consent will be included within the Construction Method Statement developed forthe works. This is discussed further within Section 3.6.6