Ebbsfleet Garden City

Ebbsfleet Garden City

Engineering and Physical Sciences Research Council (EPSRC)

Project Background

This EPSRC Impact Acceleration Account (IAA) project mainly focused on co-developing a ‘sustainable integrated urban water management’ in the Ebbsfleet Garden City, Kent, by closely working with policymakers and practitioners. Ebbsfleet is the first government-sponsored 21st century ‘Garden City’ situated between the Dartford and Gravesend districts where 15,000 homes are being built over 20 years (2015 - 2035) period. In the Garden City, water supply comes from both Thames Water (67%) and Southern Water (33%) and the wastewater management is largely dealt with by the Southern Water. A growing population, water scarcity, prevailing complex landscape features, ageing infrastructure and involvement of multi-stakeholders in decision making highlight a need for a joined-up planning approach for sustainable integrated urban water management in Ebbsfleet. To meet this need, project had two research themes:

Theme 1: A sustainable water management framework
As part of the project, we developed an urban water ‘metabolism model’ that quantifies important aspects of the performance of an integrated urban water system in Ebbsfleet. The model systematically captures the interdependency and interaction between three of the urban water sub-systems; water supply, wastewater and stormwater. Given the scale of known and potential future water scarcity in South East England, this study explored a range of potential centralised and decentralised sustainable water management strategies developed collaboratively with policymakers (Kent County Council, EDC) and service providers (Thames Water and Southern Water).

Theme 2: Planning a resilient urban water system
The reliable provision of safe drinking water and effective drainage and sewerage services is essential to society. Ebbsfleet water supply comes from the Greater London (Thames Water) and the Medway (Southern Water) water distribution systems; the wastewater system is served by the Northfleet (Southern Water) sewage treatment works. Ebbsfleet Garden City development adds considerable pressure to the existing water supply, wastewater treatment and drainage infrastructure. To enhance water supply network resilience, Thames Water is currently upgrading the water supply network and reservoirs in Ebbsfleet with the guidance of the EDC. In addition, the EDC is actively working with Southern Water to explore the options to increase capacity of the existing centralised Northfleet sewage treatment works, which is currently operating at its capacity, either through an in situ expansion or through development of a new facility elsewhere. In this regard, the integrated urban water metabolism model assesses the impact of population growth, urbanisation and climate change on the urban water system and strategically evaluates the performance of various water supply and wastewater system configurations through social, environmental, economic and asset key performance indicators over the planning horizon.

What was done to help?

A sustainable integrated water management framework:
The integrated urban water system modelling that has been jointly explored with Ebbsfleet Development Corporation, Thames Water Utilities Ltd, Southern Water Services, Kent County Council and Camland developers enabled informed recommendations to be made on urban water management policy and practice in Ebbsfleet Garden City. Specifically, the modelling framework was used to explore a number of local (site-specific) and development scale water management strategies such as household and communal based rainwater harvesting, reuse of pump water from Castle Hill Lake, adoption of water-efficient domestic appliances, stormwater harvesting, and communal based greywater recycling in the Ebbsfleet development. The framework assisted decision making and allowed the benefits of intervention measures to be quantified.

Planning a resilient urban water system:
The developed urban water metabolism model enabled the assessment of operational resilience of the existing and proposed water supply and wastewater systems under future social, economic, technological, climate and environmental changes.

This study resulted a number of recommendations:

• Governance of water reuse strategies to be set out at a site, or development scale. Individual reuse systems such as household rainwater harvesting or greywater recycling should only be implemented where long-term maintenance practices are addressed.
• Water reuse systems designed for Ebbsfleet should not solely be measured by their ability reduce annual water consumption; their ability to reduce peak daytime potable water demand should also be evaluated. The latter is essential for the sizing of the water supply network.
• Centralised greywater recycling satisfies more service water demand across the site than centralised rainwater harvesting.
• Black water recycling has the highest potential to provide service water to the development site and thus reduce potable water demand by up to 40%. At present, Northfleet wastewater treatment which serves Ebbsfleet development operates at its full capacity. Implementation and detailed design of new wastewater treatment plant should incorporate black water treatment facilities.

As a stand-alone solution, site-scale utilisation of excess water from Castle Hill Lake provides a significant opportunity to provide potable water to the development site.

Outcomes ‌

A sustainable integrated water management framework:
A number of local and development scale urban water management strategies were systematically evaluated using the urban water metabolism model. The outcomes of the evaluation were shared with the EDC and fed into the ‘Ebbsfleet sustainable water reuse feasibility’ study. As the Ebbsfleet Garden City is currently being developed, there is a potential for adoption of sustainable water management intervention in the development which will be captured through the details in the planning permission submitted by developers to EDC.

Planning a resilient urban water system:
Ebbsfleet water supply comes from the Greater London (Thames Water) and the Medway (Southern Water) water distribution systems; the wastewater system is part of the Northfleet (Southern Water) sewage treatment works. In this study, we evaluated the impact of Ebbsfleet Garden City development on existing water supply, wastewater treatment and drainage infrastructure. In particular, we explored the options to increase capacity of the existing centralised Northfleet sewage treatment works, which is currently operating at its capacity. In this evaluation, we liaised closely with Southern Water to explore the options to increase wastewater treatment capacity either through an in situ expansion or through development of a new facility elsewhere. We also explored the potential impact of various water management strategies on the resilience of the urban water systems over the planning horizon.

Noteable Successes

The urban water metabolism modelling has provided a platform to explore sustainable integrated urban water management and planning of a resilient urban water system in Ebbsfleet Garden City. The outcome of the evaluation is useful in formulating a ‘water resources management plan’ in Ebbsfleet for EDC. Ebbsfleet Garden City is the first of its kind in the 21st century. The UK government pledged (25th March 2019) of £3.7 million to fund five new Garden Towns to deliver 64,000 homes.as part of a housing revolution. The lessons and recommendations from this evaluation should be transferable to other garden towns and cities across the UK, to encourage their own sustainable integrated urban water management strategies.

The project strengthened links between the University of Exeter and Ebbsfleet Development Corporation. The working relationship between EDC and the University of Exeter has showcased the benefits of translating academic research into deliverables suitable for use in practice.