3 Site- wide energy strategy 3 Site- wide energy strategy

A achieve high energy and carbon efficiency as well as security of supply to the proposed development. Part of the benefit is due to the diversity of heating and rela resulting in a more constant heating and DHW demand. This allows the heating and DHW systems to be accurately sized in order to operate at a consistent load and consequently to operate more efficiently. of the masterplan to match the phasing strategy of portion of the masterplan to serve the demand of non -residential units concentrated in this area.

A district heating and cooling network strategy is proposed to achieve high energy and carbon efficiency as well as security of supply to the proposed development. Part of the benefit is due to the diversity of heating and domestic hot water (DHW) loads related to different residential and non-residential units, resulting in a more constant heating and DHW demand. This allows the heating and DHW systems to be accurately sized in order to operate at a consistent load and consequently to operate more efficiently.

There are two energy centres planed located in the centre and eastern edge of the masterplan to match the phasing strategy of the development.

The east energy centre will operate as an ambient loop system and, in addition to heating, will also provide cooling to this portion of the masterplan to serve the demand of non -residential units concentrated in this area.

10.11 WATER USE

Below ground tanks have a higher embodied carbon footprint and their use will be limited to areas where open water storage features are not possible. Designing the stormwater storage features for the long-term effects of climate change on rainfall intensities, fluvial levels and mean sea levels would require very significant stormwater storage volumes, the majority of which would consist of in-ground storage tanks. This would result in a six-fold increase in embodied carbon impacts associated with stormwater storage and would compromise landscape and building design.

To achieve resilience to climate change, balance the green infrastructure, place making aspirations and embodied carbon emissions, the stormwater storage features are designed for current rainfall intensities. Stormwater back-up pumps will be installed to ensure that the design criteria are still achieved in the long term. The stormwater back-up pumps will only come into operation during extreme events and to deal with the effects of climate change. They will be designed to be by-passed most of the time to maximise gravity discharge and minimise carbon emissions associated with pumping. This approach achieves resilience and adaptability to climate change.

Extreme rainfall events will be contained on the site, flooding areas of low sensitivity in a controlled manner. Potential overland flows onto the site from the higher parts of the town have also been considered in the design of the drainage system and containment of extreme events.

The south-east of the UK is subject to serious stress on water resources, which will likely be aggravated by climate change. Water demands will be reduced at source with efficient water fittings, leakage control and metering. Native planting will not require permanent irrigation. Potable water consumption targets for residential units will be set at 90-110 litres per person per day.

As part of the sustainable drainage strategy, it is also proposed to harvest rainwater for irrigation of allotment gardens, the proposed urban farm and also flush toilets within some of the nonresidential buildings.

The use of latest smart rainwater harvesting technology is proposed. This technology is based on real-time management of the stormwater storage capacity and would take a feed from the weather forecast and river level telemetry to control the retention and release of water. Water is retained in dry periods for non-potable water use. It is released in anticipation of a storm to free up the surface water storage capacity. This approach removes the need for a dedicated rainwater harvesting tank with its embodied carbon impacts. This will reduce potable water consumption in nonresidential buildings by up to 30%.

Green roofs

Rooftop allotments

Weather forecast and rainfall monitoring

Water level and flow monitoring in river

Irrigation and nonpotable demand

Real-time management of capacity within stormwater storage system to control retention of water for non-potable water use and manage water levels and water quality to support ecology and amenity.

New flood defence wall +6.20-6.50m

AOD

Stormwater water storage primarily within open water features enhancing ecology and landscape. Smart harvesting preferably from localised buried tanks to minimise treatment requirements.

1:100+37% year flood +5.856.20m AOD

Tidal range +1.31-3.91m AOD

10.12 FLOOD DEFENCES

Some of the flood defences will be embedded within buildings, forming either a parapet wall to a front patio garden or being integral part of the building façade. This is consistent with existing river front buildings downstream of Cliffe Bridge in Lewes.

A lightweight timber Belvedere structure is proposed at the back of part of the flood defence wall, to connect to the proposed Thomas Paine footbridge and allow views over the flood defence wall. The flood defence wall and adjacent Belvedere structure will be structurally integrated to achieve material efficiencies.

The new flood defences will be extended to also protect the Pelham Terrace neighbourhood and sensitive facilities within Pells Pool. Existing flood defences around the site are in very poor condition and at levels that would not provide an adequate level of protection to the new neighbourhood. They were largely over-topped when the site was severely flooded in October 2000.

Flood defences along the river front will be upgraded and new flood defences will be provided along the western boundary of the site, facing onto Pells Pool and the Pells Recreation Grounds. Crest levels will range between 6.20 and 6.50m AOD (above ordnance datum) and have been defined to protect the site from fluvial flooding for the 1 in 100-year event with a 37% increase in fluvial flows and accounting for sea level rise associated with climate change.

As the site is currently defended by existing flood defence walls and given the spatial constraints and proposed development density to create a viable and vibrant neighbourhood, these flood defence walls will be upgraded. Vertical flood defences are consistent with the existing character of the river front on the site and wider town centre. For ease of construction, to minimise deep excavation in proximity to the river and achieve a groundwater cut-off to ensure the site is not flooded through the upper permeable ground layers, the flood defences will be constructed as a sheet pile wall, with a design life of at least 120 years.

Flood defences will generally be retreated from their current position, with the new sheet pile wall installed behind existing river walls. Retaining existing river walls and retreating the flood defences will soften the appearance of the flood defence wall, retain some of the existing character and achieve a net increase in river corridor and fluvial floodplain storage.

The design of the flood defence wall has been coordinated with the river access strategy. The residual risk of flooding associated with flood gates have been mitigated through optimisation of their dimensions, regular maintenance and integration with the wider Environment Agency flood management system

A parapet wall with dam-in-dam demountable flood defences will be provided along Pelham Terrace. This will avoid impacting views onto the Pells. A short low-height section of flood defence wall is also proposed at the southern end of Talbot Terrace adjoining the Network Rail tracks. This will achieve a similar level of protection to the Pelham Terrace neighbourhood.

The alignment of the proposed flood defences would not affect views to the Recreation Grounds or create a dominating wall along the Pells. It also leaves the Pells Recreation Grounds and Pells Pool within the floodplain.

A new flood defences wall will be provided around the Pells Pool plant room, complemented by a flood door to the plantroom to protect sensitive equipment. Access from the rear of the plant room will also be improved for delivery of products and equipment.

A robust access and maintenance strategy has also been developed to ensure the flood defences can be inspected, repair works can be carried out, and flood defence can be potentially upgraded in the future.

The construction of the proposed flood defences will be done as part of the enabling works for the development. A combination of permanent and temporary defences will be in place prior to occupation of the development.

Structurally

1 2m wide single leaf flood gate to allow access to foreshore and slipway.

2 Most flood defence walls on riverside will be installed behind existing river walls, to avoid foundations, retain character and create ecological shelf

3 5m wide twin leaf flood gate to allow access and view to river from the Foundry Yards.

7 Flood defence wall and flood door to pool plantroom. 6.10mAOD (1:50 year +37% 2125 MHWS)

8 6m wide twin leaf flood gate across Brook Street

9 Parapet wall to 5.40mAOD and Dutch damin-dam flood defences to 6.50mAOD

Existing

4 Flood defence crest level raise to 7.35mAOD to meet footbridge deck level. Soffit of bridge 600mm above design flood level

5 2.5m wide single leaf flood gate to allow access to boardwalk and river level gauge.

6 3.0m wide single leaf flood gate to allow access to Pells from North Street

10 Dutch dam-in-dam flood defence across Pelham Terrace to 6.50mAOD.

11 Circa 0.5m tall flood defence parapet wall and demountable panel though opening to allow continued access to rail tracks. Flood defences crest level defined as 1:100+37% fluvial +2125 MHMW event +300mm freeboard. Flood defences designed for minimum 120 year life

10.13 SUSTAINABLE DRAINAGE

A sustainable drainage strategy is proposed, in integration with the green infrastructure and biodiversity enhancement proposals, circular approach to water resources management and with climate resilience at its heart.

The key strategic principles and aspirations of the drainage strategy include:

Adopting the most sustainable disposal route and discharging all surface water drainage flows to the River Ouse. This will contribute to reducing discharge to the combined sewer system, and associated pumping and treatment requirements

Implementing a resilient approach to flooding considering the effects of climate change and making a positive contribution to reducing flood risk on the wider river catchment

Implementing source control measures to reduce surface runoff and intercept diffuse urban pollutants at source, including green roofs, generous soft landscape areas and permeable pavement within courtyards will be maximised

Managing stormwater in efficient multifunction open water bodies integrated with the green infrastructure, enhancing the existing landscape and biodiversity

Controlling diffuse urban pollution to protect the receiving water environment. This includes rain gardens and urban swales along streets will collect and treat road runoff at source and will contribute to achieving pollution control requirements

Harvesting of rainwater in a carbon and land efficient way using latest smart technology to reduce pressure on scarce regional water resources

Ensuring that the performance of the system is maintained over its life through active maintenance

The stormwater drainage system will include five new outfalls into the River Ouse, defining five drainage catchments. The definition of the drainage catchments has been integrated with the site levels strategy, which is the result of an initial exercise to balance cut and fill on the site. The design of the drainage outfalls will carefully consider the control of erosion, ecological impacts and will be sensitively integrated within the foreshore.

Stormwater attenuation and control of peak discharge rate is not required for discharge to the tidal River Ouse. However, storage capacity will need to be provided to hold stormwater flows when high river levels do not permit gravity discharge.

Drainage strategy

Primary adoptable surface water sewer

Private stormwater back-up pumping station to ensure no surface flooding for the 1:30 year + climate change event

Open water SuDS features within courtyards to hold flows when high river level prevent gravity discharge

In-ground attenuation tanks where open water SuDS features not feasible

Rain garden and tree pits along street to collect and treat road runoff

Catchment divides

Back-up

Pumping station designed to be normally by-passed and only come in operation during extreme events to ensure most flows are discharge by gravity.

Excess volumes for 1:100 year + climate change events will be contained in low vulnerability areas without flooding buildings.