Background
We are living at a time of existential crisis for wildlife, people and the environment, resulting from human-made and absolute climate breakdown. The impact of our behaviour on the environment has never been more obvious or more prominent as it is today. The legacy of our industrial past and its impacts on air, land and water act as physical barriers to progress towards a greener and more sustainable future for current and future generations. The water environment has been hit especially hard with 86% of England’s rivers failing to meet acceptable ecological status. A staggering 99% of UK rivers are constrained by man-made barriers such as weirs, sluices, culverts, dams or other structures, preventing all fish species from accessing valuable spawning and feeding habitats and impacting biodiversity and ecological connectivity.
The SUNRISE Project is an ERDF (European Regional Development Fund) funded partnership project which aims to improve biodiversity and ecological connectivity across Stoke-on-Trent and Newcastle-under-Lyme, Staffordshire. The project partnership includes Staffordshire Wildlife Trust, Stoke-on-Trent City Council, Environment Agency, Newcastle-under-Lyme Borough Council, Groundwork West Midlands and The Wild Trout Trust. In addition to local authority owned sites, Staffordshire University were delighted to welcome the restoration and realignment of the River Trent through their Leek Road Campus in Stoke-on-Trent.
The River Trent in Stoke-on-Trent
The Trent and its tributaries are key features in the planning of the Sunrise Project, forming a hugely important but largely hidden ‘green blue corridors’ which connects many people and places. Within the University campus the Trent has been historically straightened and its banks armoured, limiting opportunity for hydrological, geomorphological or biological diversity and dynamism. The site is prone to high flow events and flooding resulting in the river appearing like an open sewer, with the bankside vegetation serving to capture litter and sanitary products emerging from combined sewer outfalls which sadly reach the river during high flow events.
The Project has worked closely with the University to agree an ambitious river realignment / restoration design spanning 400m of the existing channel to significantly improve this stretch of the river for people, wildlife and the environment. The design sees a series of new meanders, the widening of the flood plain, resulting storage areas, the creation of offline ponds and scrapes as well as the placement of a series of riffle pool sequences and gravel bars to help naturalise this new section of the River Trent.
Environment & Ecology
The River Trent is designated as a main river, forming part of the ‘Trent from Fowlea Brook to Tittensor’ waterbody and has an overall 2016 classification of moderate. Ecological (both biological and physicochemical quality) elements are currently failing; invertebrates and phosphate driving the failures. Reasons for not achieving good status are diffuse and point source sewage discharge together with physical modification. Despite the current classification, and due to the sites intrinsic value within the wider Trent catchment, this waterbody and its adjacent waterbodies, provide valuable habitat for a range of ecological receptors. Historic electric fishing data from the Environment Agency (EA) supports this, with Brown / Sea trout (Salmo trutta) and a range of coarse fish species recorded. A salmonid, main river designation dictated that in channel works will not be permitted into fish spawning seasons as directed by the Environment Agency. In parallel with Sanctus’ mobilisation activities our experienced fisheries ecologists liaised with the client and the Environment Agency to conduct a full walkover survey of the project reach and the existing channel was completed before works within the existing channel begun. An FR2 application (licence to use instruments other than rod and line) was submitted that outlines the equipment and personnel required to carry out the operation safely. Given the width and depth of the channel a twin anode electric fishing (three personnel team) setup was required and delivered in partnership between Sanctus and Severn Rivers Ecology. This demonstrates both Sanctus’ commitment to ecological standards whilst also supporting Wildlife and Rivers Trusts who do so much good for people and the environment. Ahead of excavation works a programme of vegetation clearance was completed. This involved an initial search conducted by a Sanctus ecologist and included an inspection of potential bat roost sites to ensure suitable features were not impacted / removed. Surveys for nesting birds were also completed with no birds found within or neighbouring the work area. To minimise the risk of harm to any hibernating reptiles, vegetation was cut to 100mm above ground level with all arisings kept in-situ and retained as habitat. Local species records identified that Great crested newt (Triturus cristatus) and Water Vole (Arvicola terrestris) as being recorded (historic and recent) within surrounding areas of the River Trent, but during initial site surveys and searches no evidence or individuals were found. Sanctus’ ecological works were supported by Staffordshire Wildlife Trust performing final checks confirming the absence of protected species or resting areas, in the vicinity of the works site or access routes prior to the commencement of works.
Site Presence & Working Arrangements
Sanctus appreciated throughout that we were working within a relatively discrete footprint and that both the amenity and ecological value of the site had to be retained. As a result, Sanctus operated in the smallest practical space and in a location preferable to our clients and in this case, landowners. Sanctus located our compound on an area of hard standing neighbouring the river to avoid damaging green landscaping and minimise any disruption to the campus or students. In consultation with the University, it was agreed that fencing would also be kept to a minimum and only deployed to ensure safe segregation of people and plant during earth works activities. This low impact approach to contracting also meant that the site team could react quickly to rising flow levels or sustained inclement weather and remove any equipment / obstacles from the flood plain where necessary. Sanctus’ commitment to working safely, sensitively and sustainably was especially important during a delivery phase that overlapped with heightened Covid-19 restrictions. Sanctus implement a Covid-19 compliant Safe System of Work (SSoW) developed (and regularly updated) referring to advice from the Construction Leadership Council (CLC). This included making provision for extra parking, staggered break times and social distancing. During the works, all personnel arrived individually (avoiding car sharing). Each plant operator was assigned a machine and operators did not change between machines, unless thoroughly cleaned. The Sanctus site manager also ensured that all plant and equipment was cleaned at the start and end of each shift, as part of the daily plant and equipment checks. To minimise disturbance to the campus and surrounding environment, Sanctus only utilised plant and equipment that had been recently serviced (less than 1 month) to ensure that it was mechanically sound and well maintained, preventing the chance of avoidable noise while operating. The working windows were limited to 08:00 – 17:00 to help ease disturbance on the University with no works undertaken at weekends. All efforts were also made to phase and schedule deliveries at a time which was convenient for the University.
Biosecurity
Sanctus operate to strict biosecurity controls on all its sites and appreciate the ecological harm that the introduction and / or spread of Invasive Non-Native Species (INNS) can cause. The presence of Himalayan balsam (Impatiens glandulifera) was noted throughout the catchment and an INNS site plan generated. Working areas were designed and designated such that these areas were not disturbed or impacted by our works. Similarly, whilst the presence of North American Signal crayfish (Pacifastacus leniusculus) was recognised and briefed to the project team, however none were encountered during works. In line with our biosecurity protocols, all equipment was disinfected with an appropriate treatment (in this case shoe picks, hard brushes and Virkon S Aquatic). Sanctus personnel followed best practices with the Check, Clean, Dry prevention method throughout works in line with our inhouse biosecurity training. All plant and machinery that was delivered and used on site was inspected for foreign objects within the tracks e.g. invasive, non-native plant species by staff trained in their identification. In addition, machinery tracks and attachments e.g. excavator buckets were disinfected with Virkon-S Aquatic to eliminate the risk of introducing signal crayfish plague spores to the site as per strict Sanctus biosecurity protocols. The same procedure was followed when plant and machinery left the site.
Tree Protection, Removal and Reuse
A group of bat boxes had recently been installed in a small cluster of trees west of the upstream footbridge as a mitigation measure for demolition work elsewhere on the University Estate. These trees were designated for protection and therefore not encroached towards during work activities. These and all other protected trees, as designated by the technical specification of the works, were marked and protection measures, in accordance with BS 5837, put in place. Where trees needed to be removed two approaches were taken. The first as whole tree removal for reinstatement along the new river corridor. Where this wasn’t possible trees were retained on site to provide habitat improvement and woody debris within the new channel.
Levelling, Surveying and Design
The ambitious new design for the river was provided by the fantastic team at AquaUoS. Each new feature was accurately planned and positioned to help ensure improved hydrological and ecological performance of the new channel. As such the client understandably requested high precision GPS tracked excavation to ensure the design was accurately delivered. Unfortunately, the baseline information supplied to the design team was based on publicly available lidar data, such that it contained errors of up to 0.5m in levelling information. This presented a huge challenge for the delivery team to achieve a precision design without the baseline information required to achieve it. Building on Sanctus’ extensive earthworks experience we were able to combine rapidly generated 3D earth works models with traditional land surveying and earth works techniques to mitigate a potentially project threatening additional cost to the client or fatal delays to the delivery programme.
When all compound, welfare and ecological arrangements were in place, a Sanctus engineer began the process of setting out the modelled realignment, working in parallel with the client and the designers. The realignment, and all design features, were marked and re-validated in agreement with the client and design team before physical excavation took place.
Contracting Delivery
Our commitment to working sensitively and sustainably extends to our selection of plant and machinery. To reduce the impact of heavy plant and machinery on the site(s), rubber tracked, low ground bearing pressure equipment was used throughout. All machinery was powered using biodegradable fuels and hydraulic oils to further protect the river and natural environment. All excavated material, surplus to the required channel reinstatement volumes, was transported along temporary haul roads, supported by a banksman. This material was shaped and sealed at the end of each working shift to prevent the material becoming waterlogged and un-manageable with each area being seeded in the spring. Sanctus’ delivery plan saw the design split into three phases, working upstream with the natural process of the River Trent.
Phase 1
The first phase saw new sections of the channel cut offline to ensure these could be formed, shaped and prepared ahead of individual sections coming online. Material was handled once and immediately moved to designated storage areas outside of the flood plain.
Phase 2
Phase 2 saw the addition of new meanders and modification of the existing middle section of the channel to introduce a braided arrangement with gravel bar and riffle pool sequences placed throughout.
Phase 3
Phase 3 saw the excavation of a new meander to the right side of the channel and widening of the flood plain area in this part of the channel. On departure from the working area, a series of ponds and scrapes were created neighbouring the middle reaches of the channel, which vastly increased the storage area throughout the reach to help improve flood risk and also create valuable new habitat.
Gradual Release of the New Channel
The excavation of the new channel sections was prioritised in dry conditions at the beginning of the delivery programme. A minimum of 5m of ‘untouched’ channel was retained before breaking through and bringing the new section of river online. A catch all silt curtain (encompassing the full channel width) was securely staked at the downstream extent of the working area, in addition to specific mitigation deployed throughout each phase. All sediment control measures were monitored throughout the project programme to ensure they remained effective. Sanctus’ approach to temporary works and sediment management received hugely positive feedback as the quality of water improved throughout works and was described as having transformed the channel by the lead designer.
Challenging Weather Conditions
The nature of earth works in autumn is always challenging and as such can often results in difficulties in sensitively and safely completing works and moving material across site. At the University, we experienced one of the wettest Octobers on record with the majority of rain focused in an intense two-week period. As a result of delays in remodelling, the earth works contracting were pushed back into this challenging period. Building on our extensive experience we knew accuracy of machine movement and reducing traffic across the working area was fundamentally important working with what the environment and climate will allow. On that basis we prioritised activity in specific parts of the site and benefited from our commitment of single handling material ensuring its structural integrity. We also adjusted our schedule of working to ensure that we immediately placed gravel on open excavations once cut to ensure these were protected from any future rainfall again ensuring the engineered structure of the channel.
Conclusions
Delivery of this project realises a decade long ambition to re-naturalise a historically straightened section of the River Trent through Stoke. A once abused and discarded river corridor has now been replaced with a more sinuous and hydraulically diverse channel that will benefit both people and wildlife. Fragmented habitats have been connected and are now truly ecologically viable. We hope this project will serve as a best practice example for river restoration practitioners and partnerships throughout the country.
Client Feedback
The Sanctus site team worked closely with the client appointed designer throughout the construction phase to overcome a number of challenge obstacles. Under hugely difficult circumstances, design changes were made quickly and flexible by Sanctus against a fixed delivery programme as mandated by the conditions of an environmental permit and the restrictions of the natural environment and ecology. The huge success of this project and quality of delivery was captured in feedback received: “Sanctus have done an excellent job in the face of very difficult conditions to create a diverse and extensive new river and connected floodplain” – Design Director.
