This section sets out a description of the alternatives to the project proposals studied by the Anglian Water.

Site selection

The site of the proposed WWTP was selected through a systematic four stage process. The first three stages of this process were consulted on during our first consultation. Full copies of the site selection reports are available in the document library on the CWWTPR website. The study stages were used to assess location options in increasing levels of detail, each building on the findings of the previous stages. Less suitable options were eliminated resulting in the identification of the best performing site to progress through the consultation and environmental impact assessment processes required for a DCO application. The site selection approach is summarised in the figure below.

Short-listed site areas

The Stage 4 assessment used the information collated during the first stages of the site selection process combined with the results of further technical feasibility assessments, initial environment walkover surveys and phase one non-statutory public consultation to assess each of the site area options against one another.

The three short-listed site areas are shown on the map below. Click on each to view further information.

Balancing all the risks and opportunities it was considered that site area 3 represented the best performing site area. It was considered that site area 3 presented the greatest opportunity to deliver a development that includes wider benefits, rather than seeking to solely mitigate negative impacts, contributes to Anglian Water Services Limited’s corporate objectives and addresses the concerns posed by the local community and stakeholders. Site 3 was therefore selected for the Proposed Development.

Having selected site 3, the design and layout of the site was refined further.

Confirmation of project footprint

An indicative project footprint of 22ha was selected for the site selection process as being suitable for the development of a relocated waste water treatment plant. A range of treatment processes were considered in reaching this optimal size, balancing potential land take against cost, carbon, deliverability, and other operational considerations. This footprint size was subsequently tested through further study with several technologies being rejected as they would either give rise to a significantly larger footprint than the 22ha used to inform site selection, adversely impact carbon targets or place additional risk on achieving water quality targets.

Selection of treatment processes

The treatment processes and technologies outlined in the project description have been selected through a series of “Risk, Opportunity and Value” (ROV) studies and workshops. This technical analysis considered a wide variety of technologies, concluding that Membrane Aerated Biofilm reactor technology (MaBR) for secondary treatment represented a well-balanced outcome, considering a wide number of factors including capital cost, operational cost, carbon, reliability, odour profile and operational complexity. However, the final choice of technology will be kept under review and enhanced activated sludge processes (ASP) remain under consideration.

Development of Preliminary Concept Design

We followed the National Infrastructure Commission’s Design Principles for National Infrastructure to develop a set of project level design principles, as follows:

  • to create a state of the art, low carbon water recycling centre of the future.
  • to reduce the footprint of the modern plant to 22 hectares, which is about half the size of the existing plant.
  • to create a strong identity for the site while screening the facility and reducing visual impacts on the surrounding community and landscape.
  • to re-use excavated material on site which can be used to screen the facility and also reduce the carbon and traffic impact from construction.
  • to minimise odour by incorporating solutions to address it at source and using best operational practices.
  • to reduce harmful carbon emissions through sustainable design, helping address climate change.
  • to increase biodiversity by creating new wildlife habitats.
  • to improve access to the countryside with new paths and accessible open spaces; and
  • to connect the site into the wider landscape and establish new wildlife corridors.

Subsequently, guided by advice from architects, landscape architects, ecologists and other design professionals, further environmental objectives for the project design were developed, as shown in the figure below, together with a design narrative, which is set out in the Outline Landscape, Ecology and Recreation Masterplan (LERMP), which forms part of this PEIR.

Building on the design narrative and environmental objectives, and supported by the Design Council, three design concepts were developed for Anglian Water by its architectural and landscape architectural advisors, as follows:

Following advice from the Design Council, including formal design panel review from independent built environmental experts of the three design concepts, the “rotunda” concept design was selected for further consideration.

Preliminary consultation took place with stakeholders in our technical working groups, which include Natural England, National Trust, RSPB, Wildlife Trust, Cam Valley Forum, Quy Fen Trustees, the Environment Agency and Cambridge Past, Present and Future (CPPF). Discussions included the three design concepts and more detailed elements of the “rotunda” design, including landscaping. Further refinement of the landscape design was carried out to mitigate adverse visual impacts and increase opportunities for ecological and recreational benefits.

Location of the project within selected site

Having developed an outline design, including landscape and ecological mitigation, the proposed location of the project was refined within the site boundaries derived from the site selection exercise described above. The position selected, as shown in this PEIR, took into account issues including proximity to ecological receptors, including the county wildlife site, odour modelling and the three potential access arrangements described below.

Vehicular access

In parallel with the design processes outlined above, a range of potential permanent vehicle access options to the site were explored, including through engagement with National Highways (formerly Highways England) and Cambridgeshire County Council as the relevant highway authorities. Issues considered as part of this work included the safety of road users, compatibility with relevant policy and standards, the management of potential disruption to local communities and the existing road network and project economics (the relative costs of different options). As a result of this work, three potential permanent access options were taken forward to Phase Two Consultation (June to August 2021). These were:

  • Option 1: Access off Junction 34 of the A14 (Fen Ditton) which consisted of two sub options (1A and 1B);
  • Option 2: Access off Junction 35 (Quy); and
  • Option 3: A new junction on the north side of the A14.

Following the close of Phase 2 consultation we took careful consideration of all consultation responses from the local community, local authorities and other stakeholders, including the relevant highways authorities​. We incorporated these responses into the process for selecting our preferred access option. This process drew on technical studies and expert judgement to inform an appraisal of relevant social, economic, environmental, technical, operational and policy aspects.

Option 1b (as shown on the figure to the right) was found to be the best performing access option across a range of other, non-highways, criteria including land use, green belt, air quality, carbon, operational management, and cost.

This option minimises the amount of construction and operational traffic which will use Horningsea Road, allowing direct access to the site from junction 34 of the A14, by crossing Horningsea Road under signal control, rather than having to travel along Horningsea Road before accessing the site.

Option 1b

Further design refinements

The other main alternatives considered in the evolution of the project design are:

  • Consideration of architectural finishes – this issue was consulted on and it was concluded that bold or striking finishes would not be incorporated in the project design.
  • Digester height and visibility – following stakeholder feedback the digester heights have been reduced from 26m to 20m. We have considered the potential for these structures to be sunk in the ground but concluded that such an approach would increase the risk of environmental impacts to groundwater; decrease the operational efficiency of the digesters, would present health and safety challenges (particularly during maintenance); and would only be possible at significant additional cost.
  • Screening of structures – the decision was reached to adopt a planted screen on the landscaping bund, rather than an engineered structure.
  • Use of biogas – in order to maximise the carbon performance of the plant it was decided to promote a “gas to grid” solution, exporting biogas to the domestic gas network, although burning the gas on-site through combined heat and power (CHP) units has been retained as an option for this phase of consultation.