Tipner Lake Coastal Defence Scheme

Transcription

1 Tipner Lake Coastal Defence Scheme Protecting the future of our community /EasternSolentCoastalPartnership /EasternSolentCP

2 Introduction This booklet provides an overview of the Tipner Lake Coastal Defence Scheme. It includes information about what the new defences will look like and how residents may be affected during construction. For further information on the scheme please visit: Contents Policy and Strategy 2 Extent and Risk of Flooding 3 Tipner Lake Scheme 4 Tipner Lake Seawall 5 Lower Wade Way 6 Construction Site 7 Site Operation 8 Landscaping and Replanting 9 Social Spots 10 Social Spots pg 2 11 When will the work happen? 12 The Story So Far 13 Completed Works 14 Environment and Heritage 15 Find out More 16 Page 1

3 Policy and Strategy Shoreline Management Plan A Shoreline Management Plan (SMP) is a high level policy document setting out a framework for future management of the coastline. The SMP aims to balance the management of coastal flooding and erosion risks with natural coastal processes and the effects of climate change. The North Solent SMP covers the coastline from Hurst Spit in the west to Selsey Bill in the east and sets the policy for the whole of the Portsmouth coastline. The SMP makes recommendations on how the coastline should be managed over the next 100 years. A Hold the line policy to maintain or upgrade the level of protection provided by the existing defences was identified for the North Portsea Island coastline by the North Solent SMP. Portsea Island Coastal Strategy Study A strategy looks at how the SMP policy can be implemented at a more local level and identify areas where work may be required. The Portsea Island Coastal Strategy Study (PICSS) was concluded in The strategy supported the recommendations of the North Solent SMP and adopted a Hold the line policy for Portsea Island. The strategy looked at the likely risk of coastal flooding to Portsea Island, the condition of existing defences and the number of properties and assets at risk in the event of flooding over the next 100 years. Seven distinct flood cells were identified, meaning that a flood in one cell will not impact any other, and of those seven cells, two were identified as priority areas Flood Cell 1 (Southsea) and Flood Cell 4 (North Portsea Island). The strategy identified significant risk to properties, businesses and key infrastructure within these two priority areas and proposed that schemes should be developed for these frontages. Shoreline management plan North Solent SMP (2010) Strategy Portsea Island Coastal Strategy Study (2010) North Portsea Scheme Scoping/ data collection Option development Southsea Scheme Working together - protecting our coastline Page 2

4 Extent and Risk of Flooding Present day ,414 residential and 147 commercial properties are currently at risk from a 1 in 200 year tidal flood event. This increases to 4,234 residential and 490 commercial properties over the next 100 years. These Flood Risk maps indicates the extent of flooding from a 1 in 200 year event if the coastline was left undefended. The value of property and infrastructure within North Portsea Island is estimated at 642m. North Portsea Island contains the only rail link and two of the three road links onto Portsea Island. 89 electricity sub-stations are also located within North Portsea Island. All of these assets are at risk from flooding during a 1 in 200 year tidal flood event. Hazard map This map indicates the level of risk from a present day 1 in 200 year flood event if the coastline was left undefended. Definition of undefended flood hazard index as displayed on SFRA map set 1B Classification Description Low Caution Flood zone with shallow flowing water of deep standing water Moderate Dangerous for some people (i.e. children) Danger: Flood zone with deep or fast flowing water High Dangerous for most people Danger: Flood zone with deep fast flowing water Very High Dangerous for all peopl e Extreme danger: Flood zone with deep fast flowing water Working Page 3 together - protecting our coas tline

5 Tipner Lake Scheme The coastline of Tipner Lake represents the third construction phase of new coastal flood defences being delivered as part of the North Portsea Island Coastal Defence Scheme. The Tipner Lake scheme will cover 1.85km of coastline from the Mountbatten Centre to the Ports Bridge roundabout and will take 3 years to complete. The work will cost approximately 11 million and take place between April and October each year in 2017, 2018 and The new defences are designed to significantly reduce the risk of coastal flooding over the next 100 years. On completion, the North Portsea Coastal Defence Scheme will offer protection against a 1 in 500 year coastal flood event, one of the highest standards of flood protection in the UK, outside London. The design of the defences has been developed in collaboration with key stakeholders, including environmental and heritage advisors. It also incorporates many ideas and aspirations received from the public during option selection and consultation events held in The desire to maintain the natural character of the area and to enhance the value of this important open space is at the forefront of the new coastal defence design. Artist impression of seawall replacement Image not to scale The new seawall will provide the primary defence against coastal flooding and erosion. Area of the works Seawall Landscaping works Aerial Photography 2013: Image Courtesy of CCO Artist impression of landscaping works The area behind the wall will be enhanced by the new landscaping and social spots. The shared use coastal path will be retained and a new network of paths will improve access. Working together - protecting our coastline Page 4

6 Tipner Lake Seawall A new seawall is to be built along the entire length of the Tipner frontage, from the Mountbatten Centre to Ports Bridge roundabout. The new seawall will form a continuous defence along the full 1.85km of Tipner Lake and will replace the existing seawall which is in poor condition and too low to provide adequate protection against flooding. LDA Design image of the seawall Waves at Tipner Lake The current seawall was built in phases over the past 80 years and no longer provides adequate protection. In places it is in poor condition and has come to the end of its useful life. Seawall Design LDA Design image of The Snug During the design process, a variety of wall profiles were explored in order to select the wall which best suited the overall design. The chosen design has a tapered profile, reducing the size of the wall and visual impact. LDA Design image of Castle View The top of the new seawall will be no more than 1.2m above the coastal path which will be 4m wide and is designed as a shared use cycle and foot path. The area behind the wall will be enhanced with new paths, landscaping and planting. At various locations, the wall will be embossed with a decorative timber effect finish. Did you know? 3 It is estimated it will take 6450m of concrete to build the new seawall. This is enough to fill the Mountbatten Centre 1 swimming pool 2 times. 2 Page 5

7 Lower Wade Way Removing the lower section of the Wade Way will create important intertidal habitat legally required to build the flood defence. Lower Wade Way is a concrete slipway and causeway that extends from Horsea Lane into Tipner Lake. Slipway: Causeway: As part of the coastal defence works, approximately 250m of the causeway will be removed. Access to the foreshore at this location will be maintained with a new, shorter slipway. A slope leading into water, used for launching and landing boats. A roadway or track on a raised bed, in this case concrete, crossing open water or low ground. Habitat Creation 2 Removing the causeway will create 600m of important intertidal habitat within the environmentally protected Portsmouth Harbour. This new habitat will provide the legally required mitigation for the minor loss of existing habitat due to the construction of the new coastal defences. Image of geese Mike Baird Slipway at Lower Wade Way Lower Wade Way Condition The Lower Wade Way slipway and concrete causeway is currently in poor condition and is not often used along its full length. The works to remove the causeway will take place in the summer of Causeway at Lower Wade Way Working together - protecting our coastline Page 6

8 Construction Site The construction site will be set up to ensure public safety and allow the work to progress in a safe, efficient and controlled environment. Site set up will begin in April 2016, with one of the first tasks being to set up fencing along the site boundary. During the work there will be no access to the areas within the site boundary, however alternative routes will be available throughout construction. Site Compounds During years 1 and 2 the main site compound will be on Alexandra Park and contain the site offices, welfare facilities and storage areas. Smaller compounds will be positioned around the site for additional storage of materials and machinery. Once the 2018 construction is complete, the main compound will be located near to Hilsea Lido and the Alexandra Park site will be reinstated. Temporary Cycle Path Diversion A formal diversion will follow Northern Parade for the three years of works. Local access and diversion routes will be available around working areas where possible. Access Routes During 2017 and 2018 the main site access route will be via Alex Way and a haul route will be specially constructed across the park. Accessibility during the works In year 3, The Lido compound will be accessed from London Road. Limited secondary access will be via Spinnaker Drive and Twyford Avenue. A Traffic Management Plan will be in place and will ensure all traffic is well managed. Silt Curtain A bespoke silt curtain will be installed around the working area to limit sediment from the construction works entering the wider harbour. This helps to protect designated eelgrass beds and other special habitats within the harbour. Silt curtain Fences being installed Haul route example Haul route construction Working together - protecting our coastline Page 7

9 Site Operation Through good site management, every care will be taken to minimise disruption from construction activities. The construction works will be undertaken by a competent contractor with proven experience in the successful delivery of similar schemes. The Portsmouth City Council site supervision team will be onsite during all working hours. Site Access From the outset, the site compounds, haul routes and working areas will be securely fenced off to prevent public access into the site. All entry points will be locked out of hours and measures will be in place during working hours to prevent unauthorised access. Harbour working Haul Routes A number of haul routes will be established within the site to move machinery and plant around the various working areas and to minimise traffic on the public highway. Driving sheet piles Noise, Vibration and Dust Working hours near residential properties will be restricted in order to reduce disturbance to residents caused by noise and vibration from construction works and machinery. Vibration will be actively monitored using specialist equipment throughout the scheme to ensure vibration is kept to a minimum. Site boundary banners Dust suppression will be used to reduce the amount of dust released into the air and regular road sweeping will be carried out during construction. Construction Machinery Large construction machinery will be used during the works. The types of machinery that you are likely to see on site will be excavators, articulated dump trucks, bulldozers, tractors, rollers and concrete wagons. Smaller road vehicles will be used to transport personnel around the working areas. These could include small all-terrain vehicles and 4x4 road vehicles. Working together - protecting our coastline Page 8

10 Landscaping and Replanting On completion all working areas will be reinstated to their former condition. There will also be an extensive landscaping and replanting programme using specially selected plant species. LDA Design image of The Lookout Replanting We have worked with experts to better understand the environmental features of the Tipner Lake area and ensure the most appropriate species are selected. Areas cleared of vegetation will be replanted with a range of specially chosen species. These include a mixture of herbaceous perennials, grasses, trees, shrub and species rich meadow. The new plants will be more visually and ecologically diverse than what was there previously, creating a better habitat for local wildlife. Landscaping work will be progressed throughout the autumn and winter of 2017, 2018 and 2019 to suit planting conditions. Example species The species being planted include: Herbaceous Image Pryma Shrubs Image Luc Viatour Hedges and Grasses Hummelo Moonshine Red Thunder Echinacea Viburnum opulus Sambucus nigra Rosa canina Prunus spinosa Goldtau Image Peter Rosbjerg Image Kristian Peters Whilst the replanting programme is extensive, it will naturally take some months to fully establish. Image Daderot Wildflower Turf Parthenocissus tricuspidata Calamagrostis Image Tom Koerner Page 9

11 Social Spots Social spots have been added to the Tipner Lake frontage to make the area more enjoyable and provide places for people to stop, rest and enjoy the views. When completed, the scheme will create a new linear park that will provide opportunities for socialising, exercise, informal play and contact with nature while maintaining this popular commuter route. Tipner Gateway Includes a raised decked area and seating nestled among decorative planting to allow visitors to sit and enjoy the views across Tipner Lake. The existing mature trees will remain. Portchester Castle View Visitors will be able to stop and rest on the raised timber seating terraces while enjoying the views across the harbour to Portchester Castle. The integrated bird hide allows observation of the rich and varied habitat in the harbour without disturbing the birds. Page 10

12 Social Spots The Social Spots will provide places for people to stop, relax and enjoy the views across Tipner Lake. The scheme will deliver a more diverse setting with extensive landscaping to ensure the new coastal defences tie seamlessly into the environment. The Lookout This split level social spot provides two paths; the lower path takes visitors down into the landscaped parkland and the upper path gives access to the raised lookout. The raised area is at the full height of the wall and allows visitors to enjoy an elevated view of the harbour. Both upper and lower paths lead to seating areas. The Snug Set back from the coastal path, the snug encourages visitors to stop and relax on the bespoke loungers. Set among the trees and planting, this social spot focuses on the parkland aspects of the completed works. Page 11

13 When will the work happen? Programme of works Subject to final approval of all relevant licences and consents, construction work is expected to commence in April 2017 and will be completed by October No construction works will take place over the winter period due to environmental restrictions, however soft landscaping works will be undertaken during this time. The coastal path will be re-opened between October and April during each year of the works. Site Construction The majority of construction work will be undertaken during normal working hours to minimise disturbance to the community. Deliveries of material and equipment will be managed and restricted to avoid busy times. Piling: The new seawall will have steel pile foundations. These will be driven using vibration to reduce disturbance. North Portsea Island Construction Phasing Construction works have been split into distinct phases which will be delivered over a period of seven years. Phase 3 Tipner Lake Construction starting Spring 2017 Demolition: In order to build the new defences some of the existing structures will need to be removed. Phase 1 Anchorage Park COMPLETE September 2016 Due to the tidal working window, it is likely that some construction will need to take place outside of normal working hours, including weekends. To reduce disturbance to residents, the following restrictions will be applied: PORTSMOUTH HILSEA Copnor Rd Evening working - all works will be outside a 100m radius of the nearest house. Noisier works, such as piling, will be kept outside a 200m radius from the nearest house. Night working - all works will be kept outside a 200m radius of the nearest house. Noisier works, such as demolition, will not be permitted during this time. Queen St LANDPORT Portsea Island Milton Common and Great Salterns Quay FRATTON COMPLETE September 2016 St Marys Rd Phase 2 Milton Rd MILTON COMMON Such occurrences will be closely managed by the project team and advanced notification will be given to local residents. Clarence Pier Elm Grove SOUTHSEA Albert Rd Highland Rd Normal working hours: Monday to Friday: 7.00am 7.00pm Evening working hours: Monday to Friday: 7.00pm 11.00pm Night working hours: Monday to Friday: 11.00pm 7.00am Clarence Parade Phase 1: Anchorage Park ( ) Phase 2: Milton Common (2016) Phase 3: Tipner Lake ( ) Phase 4: Eastern Road ( ) Phase 5: Kendall s Wharf (2021) Phase 6: Ports Creek (2022) Map of scheme area Timeline 2017 Spring Summer Autumn Winter Spring Summer Autumn Winter Spring Summer Autumn Winter Construction works Planting & reinstatement Page 12

14 The Story So Far... Tipner lake represents the third phase of construction of new coastal flood defences as part of the North Portsea Island Coastal Defence Scheme. The full scheme extends from the Mountbatten Centre in the west, along Ports Creek in the north to Milton Common in the east and covers 8.4km of coastline. Approved Funding A formal business case for the scheme was submitted to the Environment Agency (EA) to secure grant funding from central government. Members of the project team attended a series of meetings with the EA s Large Project Review Group who scrutinise the business case against economic, technical, environmental and social factors. In total 58m of funding has been approved to deliver the North Portsea Island Coastal Defence Scheme. Licences and Consents Before we can start work onsite we must obtain the necessary licences and consents. These include planning permission; a Marine Licence from the Marine Management Organisation; and consent from Natural England to work within Portsmouth Harbour. Part of our planning application included an Environmental Statement which covers many aspects of the potential impacts of the construction work, including noise, wildlife and visual impact assessments. Vegetation clearance LDA Design image of Tipner Lake Previous ESCP exhibition Site investigations To support the detailed design process we have undertaken a range of site investigations and surveys. You may have seen us and our contractors carrying out structural investigations of the existing defences, undertaking topographical land surveys and drilling boreholes around the North Portsea Island coastline. We have completed specialist habitat surveys to confirm which species could be impacted by the works and produced a mitigation plan that will guide the construction works and minimise impacts. Ecological surveys In order to understand the potential impacts that our work may have on local species of flora and fauna, we have worked with environmental specialists to carry out a series of surveys around the Tipner lake area. These included detailed habitat surveys which recorded important plant and animal species and habitats with the potential to support wildlife. Detailed design The detailed design has been developed by a team of specialist engineers and architects. The design process has drawn upon the findings of site investigations, wave modelling and stakeholder engagement. We have also incorporated feedback received from the public exhibition events held in March Working together - protecting our coastline Page 13

15 Completed Works Anchorage Park Anchorage Park was the first stage of the wider North Portsea Island scheme. The works consisted of earth embankments, rock slopes on the seaward side and a new concrete abutment for the Eastern Road bridge. Eastern Road Bridge As part of the works a new flood wall and revetment was constructed along the Eastern Road bridge. Milton Common and Great Salterns Quay The Milton Common scheme covers 750m of coastline and included two key elements - construction of coastal defences and removal of Great Salterns Quay. Great Salterns Quay Excavation of material from the internal body of Great Salterns Quay was removed along with the retaining steel piles. A new section of the seawall was constructed where the quay joined the coastline. Removing the Quay will provide new habitat legally required to enable construction of the scheme. Earth Embankments 1.4km of new embankments from Kendalls Wharf to the railway bridge along Ports Creek have been constructed using a total of 52,000 tonnes of earth. Surfaces along the creek have been improved with wider path ways and improved views. Shoreline Footpath The existing coastal path was replaced with a new improved path along the top of the rock revetment. The new path has an improved surface and offers a pleasant route to cycle or walk along the coast. Rock Revetment Rock revetments have been constructed along the seaward side of the earth embankments to protect them from erosion. The rock used for the scheme was imported from Larvik in Norway and was brought in by ship to Southampton. It was specially selected due to its strength and weather resistance. The rock is a waste product sourced from a quarry that produces high quality polished worktops and building facades. Bunds Chalk bunds were constructed behind the rock revetment to provide the flood defence, and were constructed from the excavated chalk material from Great Salterns Quay. New paths have been constructed along the top of the new bunds and have been tied in to the existing footpath network on the common. Landscaping Trees, shrubs and hedgerow have been planted in areas across the site to provide natural screening and to replace any plants removed during the construction works. The earth embankments, haul routes and compounds have been re-seeded enhancing their natural character. An orchard of twelve fruit trees have been planted in the meadow area to feed the birds and bees. Landscaping Seed mixes, shrubs and trees were specially selected to enhance the natural biodiversity of the area. Page 14

16 Environment and Heritage Portsmouth Harbour and the surrounding land supports a large variety of wildlife and habitats, the majority of which are protected at an international level. Environmental Designations Internationally important populations of rare wildfowl and wading birds visit Portsmouth Harbour during the winter. The harbour contains areas of saltmarsh, mudflat and eelgrass habitats that support these bird species alongside fish and marine mammals (including common and grey seals). These habitats are internationally protected and the harbour is environmentally designated as a: Wetland of International Importance (Ramsar Convention). Special Protection Area (SPA) Site of Special Scientific Interest (SSSI) Mitigation A Construction Environmental Management Plan will be written in conjunction with the appointed contractor to reduce and manage any environmental impacts during construction. Long term, the local environment is expected to become more interesting and diverse following landscaping works. Ecological Surveys We have completed specialist habitat surveys to confirm which species could be impacted by the works and produced a mitigation plan that will guide the construction works and minimise impacts. Our surveys and reporting include: Phase 1 and Phase 2 Habitat Surveys An Environmental Statement A Habitat Regulations Assessment A Water Framework Directive Assessment Branta Bernicla Ómar Runólfsson These ecological surveys have been undertaken by ecological experts and advice sought from Natural England, the Environmental Agency, the RSPB, Langstone Harbour Board, the Wildlife Trust and Hampshire County Council s ecology team. LDA Design image of Hilsea Lines Heritage Portsea Island has a long military history, and evidence of this can be found at Tipner Lake. Since Tudor times the Hilsea Lines have been part of Portsmouth s defences. They have been remodelled several times and the current structure was completed in the 1870 s. The lines and moat are scheduled monuments and will be protected during the works. An Archaeological Mitigation Strategy and Heritage Statement have been prepared to support the construction work. Working together - protecting our coastline Page 15

17 Find out More Visit our website: Like us on Facebook: www. facebook.com/northportseaisland Follow us on Follow us on Or follow us on LinkedIn: Eastern Solent Coastal Partnership Working together - protecting our coastline Page 16

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