Environmental Statement volume 4 - Chiltern Evergreen3

3 Application of the Sequential Test andException Test to Development Locations3.1 IntroductionThe railway is an Essential Infrastructure project, and the location of the tracks, andover and under-bridges (where the railway crosses roads and watercourses) and stationsare determined by the current infrastructure. Consequently, the Sequential Testprocedures, as laid out in PPS25, are not applicable for these elements of the scheme.For all other elements of the scheme, for example, new over-bridges, the SequentialTest is to be applied.Application of the PPS25 Exception Test is required for Essential Infrastructuredevelopments that lie within Flood Zones 3a and 3b. As previously introduced, the levelof assessment conducted and reported within this FRA is appropriate to the level ofdesign detail available at TWA level. In order to pass aspects of the Exception Test atthis stage, a reasonable worst case has been applied to ensure that flood water flowsand storage can be balanced and mitigated. Level 3 FRA assessments are, however,required to be conducted for aspects of the Scheme at detailed design level. The reporttherefore specifies the Level 3 FRA commitments for sites where the application of theException Test requires a Level 3 FRA assessment of detailed engineering designs. Incases where Level 3 FRA requirements can be met at this stage without detailed designcommitments, these are made. In line with the reasonable worst case approachadopted, adequate provision of land within the LOD and LLAU has been incorporatedwithin the TWA Order in order to compensate for any loss or change in storage. Suchprovisions will be refined during detailed design as informed by the Level 3 FRA process.3.2 The Requirements of the Sequential TestThe Sequential Test is a risk-based approach to be applied at all stages of the planningprocess, and aims to steer new development to areas at the lowest possible risk offlooding. Flood Zones are the starting point for this approach, and it is thereforeimperative that the most accurate measure of Flood Zone is used within the SequentialTest; where specific SFRA output is not available then the Flood Zones from the EA FloodMap are to be used.Development is to be steered towards Flood Zone 1. PPS25 states that where there areno reasonably-available sites in Flood Zone 1, reasonably-available sites in Flood Zone 2are to be considered, taking into account spatial plans. Where necessary, the ExceptionTest should be applied (see below). Only when there are no reasonably available sites inFlood Zones 1 or 2 should decision-makers consider the suitability of sites in Flood Zone3; this should take into account the vulnerability of land uses and again apply theException Test if required.This section outlines the Sequential Test process for each development site within thescheme in turn. This involves stating whether it is required to be proven that it passesthe Sequential Test, and if the answer is ‘yes’, reporting the results.26