SUNRISE Project - River Reinvention by Sanctus
Shortlisted for Brownfield Awards Category 13 - Best Biodiversity Enhancement
Staffordshire University, Stoke-on-Trent
Background – SUNRISE Project
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, or dams, 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 Staffordshire. The project partnership includes Staffordshire Wildlife Trust, Stoke- on-Trent City Council, Environment Agency (EA), 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
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 capturing litter and sanitary products emerging from combined sewer outfalls.
The SUNRISE 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 (GB104028053271) and has an overall 2016 classification of moderate. Ecological (both biological and physico- chemical 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 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.
In parallel with Sanctus’ mobilisation activities our experienced fisheries ecologists liaised with the client and the EA to conduct a full walkover survey.
A fish survey and translocation was completed before works within the existing channel began. 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. 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.
Site Presence & Working Arrangements
Sanctus appreciated the need to protect the amenity and ecological value of the site throughout works. 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.
Sanctus’ commitment to working safely, sensitively and sustainably was especially important during a delivery phase that overlaps heightened Covid-19 restrictions. Sanctus implement a 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. The Sanctus site manager also ensured that all plant and equipment is cleaned at the start and end of each shift, as part of the daily plant and equipment checks.
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 in- house biosecurity training.
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 BS5837, put in place.
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 requested precision GPS guided excavation.
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 deliver this truly unique design.
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 banksperson. 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 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.
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
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 was 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.
