CEEQUAL Excellent (87.1%) – Interim Client and Outline Design Award
Version 4, Mar 2013 | Redditch, England
Assessor: Lucie Anderton (Network Rail) and Colin Cartwright (Atkins)
Verifier: Gemma Fenn (Fenn Environmental)
The Redditch Branch Line Enhancement project is a rail scheme, designed to provide capacity improvements to the rail service between Birmingham New Street and Redditch, one of the busiest rail routes into Birmingham.
The existing Redditch branchline is a single-track line, which prevents trains from passing each other along the line, thereby limiting the Cross Country rail service that can be provided. The Redditch Branch Enhancements project comprises the construction of a 3.2km loop running south from just north of Alvechurch towards Redditch. Construction of the loop will allow trains to pass each other on the branch line, allowing an increase in capacity from the current two trains per hour to three trains per hour in each direction. The target date for the installation of the rail infrastructure is summer 2014.
In addition to the new track, the project will provide a new second platform and fully accessible footbridge at Alvechurch Station, which also replaces an existing pedestrian footpath level crossing.
The project team has been committed to a high quality project with minimal impacts to the environment from the outset. This has been demonstrated by a project specific environmental management plan in place from the start and regular discussion across the project team to ensure that environmental issues are identified and managed appropriately. Examples of some of these are described below.
Strategies to minimise land take
The Options Selection Report undertaken towards the start of the project reviewed eight different options to achieve the capacity improvements identified. The option selected was identified as the best solution from an environmental perspective as it crossed the fewest watercourses and had the least direct impact on local residents.
Following the selection of the preferred route option, further measures were taken to minimise permanent land take. The proposed loop will be constructed as far as possible within the footprint of the existing Redditch Branch, and within Network Rail’s land ownership. The existing line will be realigned, and existing embankments and cuttings will be re-graded to enable the minimal land take strategy to be achieved.
Environmental considerations have been a key driver in determining the options for re-alignment. The use of soft-engineering options (re-grading) has been preferred as these minimise the requirement for imported materials, and presents a less impact visually. Where this has not been possible, as a result of the presence of significant trees, areas of wildlife importance (such as badger setts), and properties, then hard-engineering options have been used to prevent impacting on the environmental feature(s).
Ecological assessments (and arboricultural surveys) have been undertaken at design stage, with the findings discussed with Natural England. The project has been aligned so as to avoid direct impacts on two non-statutory designated sites (Special Wildlife Sites) to the west of the project. Surveys for protected species (bats, badgers, amphibians, otters, dormice, reptiles, water voles and white tailed crayfish) identified the presence of great crested newts in a pond within the site corridor. Impacts to this population were mitigated through the construction of two replacement ponds, and the translocation of the newts.
The strategy to minimise the ecological impact of the project has been applied to both the completed project and construction phase. Following the ecological surveys, the construction site compound has been relocated from an area of semi-improved grassland to an arable field of lower ecological value. In relocating a haul road around (rather than through) an existing pond, a risk of isolating the pond from the surrounding habitat was identified, thereby limiting the ability of amphibians reaching the pond. The potential for installing pipes under the haul road (as amphibian tunnels) is being considered to mitigate this.
Energy use during construction
An overarching Active Material Management Strategy has been adopted by the project, with the objective of maximising the re-use of materials available within the site, and minimising the need to import materials. The suitability of excavated materials for re-use has been undertaken at design stage, with the results fed into the cut and fill balance for the project. Approximately 9,400m3 of material on-site has been assessed as suitable for re-use. Maximising the re-use of materials will also reduce traffic and off-site nuisance impacts during construction by reducing the need to transport materials from off-site.
Specific measures have been reviewed at design stage with the objective of reducing energy consumption during construction. These relate to the reduction of the quantity of works required and the selection of particular construction methods that require less time or less machinery. Both strategies will provide savings in energy consumed. The particular examples are:
Reducing the quantity of works –- retaining wall options. The length of the works has been divided into 19 sections, with retaining wall options reviewed separately in each section. Measures have been taken where possible to reduce the required for hard-engineering options within each section, and the use of re-grading instead.
Selection of particular construction techniques – where re-grading is not possible, then kingpost retaining walls, or gabion walls will be used. Kingpost retaining walls have been selected in preference to sheet piling as they offer less machinery requirement for installation, and consequently less energy consumption and nuisance impact.
Fill requirements – the use of lightweight granular fill, instead of conventional fill has been agreed as a strategy to reduce energy demand during construction, and for ease of construction. The lightweight fill is installed by being pumped through a hose, rather than deposited by excavator. As this material is lighter it places less pressure on the retaining walls, thereby reducing the material requirements of those walls.
Prefabricated structures – maximising use of prefabricated structures during construction – for the retaining walls, footbridge, and culverts for example. The use of precast concrete structures has reduced the need for temporary shuttering, and in the case of the drainage culverts will avoid the need to for concrete to be poured near watercourses.
Consultation with the local community and stakeholders has been led by Network Rail, and undertaken since the initial design stage of the project. The project has maintained a communications team to respond to comments received from stakeholders, with these being fed through to the design team. Changes to the visual aspects of sections of embankments, and the new footbridge at Alvechurch have been driven by the consultation process.