Advanced project planning and an innovative remediation strategy are allowing for significant sustainability benefits and time savings on the Selly Oak RSD project in Birmingham.
The former Battery Park site at Selly Oak in Greater Birmingham is set to play a key role in the regeneration and economic growth of the region. The project to develop the industrial and residential area - being delivered by the Harvest Partnership (a joint venture between Sainsbury’s and Land Securities) and Birmingham City Council - will also play a key role in boosting medical and scientific innovation.
Upon completion, the 12ha brownfield site will feature a state-of-the-art Life Sciences campus, student accommodation and high-quality retail facilities, including a new Sainsbury’s store. It will also benefit from improved highways infrastructure and environmental improvements. Ultimately, it will offer a wide range of employment opportunities, with 2,700 jobs created.
Principal contractor PJ Carey (Contractors), part of the Carey Group, was called upon to mitigate health, safety and environmental risks for the critical earthworks phase of the project. Beginning this phase in June 2014, it approached the project from the perspective of achieving an optimum balance between social, economic and environmental sustainability, and productivity.
Indeed, the scheme has attracted significant interest and involvement from local community groups.
Key deliverables include reprofiling the former heavy industry site into three distinct levels, and remediation of vast quantities of variable grades of waste up to depths of 14m in places. This includes over 155,000m3 of ash material and 90,000m3 of commercial and industrial material; in total, 800,000m3 is being moved and more than 400,000m3 remediated. The initial phase of the project will culminate in the construction of a 7m high dividing wall to separate the three distinct plateaus.
This was because the area’s topography dictated that the final buildings would have to be on different levels. At pre-construction stage, the team firstly devised an earth reinforced structure for the dividing wall rather than the previously envisaged CFA piled wall method.
Careys project manager Clive Medden says: “This value engineering was particularly advantageous as, following the excavation phase, the wall could then be constructed from the foundations up, rather than boring down from an elevated platform. Additionally, this alleviated the issue of headroom restrictions due to the existing overhead HV cables, aiding our ability to place the engineered fill material.”
Extensive site-wide trial pits have been carried out, and a desktop design was used to confirm the historic borehole data and actual ground encountered; this gave the team greater visibility of the task ahead.
“From receipt of documents at tender stage, we invested significant time and effort to obtain as much data as possible to evaluate ground conditions and develop a detailed 3D model,” says Careys operations director Tommy Carey. “This enabled us to mitigate risks and develop an effective earthworks remediation strategy that was designed to provide the highest reuse rate of existing materials and divert all waste from landfill.
“This was facilitated through the use of a materials screener and applying techniques from our waste and resource recovery company, Seneca.”
The establishment of an onsite laboratory to test hydrocarbons and heavy metals is enabling the team to gain a real-time understanding of the excavated materials composition and geotechnical characteristics. The results dictate the treatments required for each waste stream in the onsite soil hospital treatment centre. This has helped to expedite the programme by accelerating contamination assessments and allowing a flexible approach to the remediation process. This has resulted in big time savings of up to one week per sample.
Careys materials manager John Heaps says this was key to the remediation strategy. “During the planning stage of the works, several different remediation methods were considered.
“It was decided that the set-up of a bespoke laboratory and soil hospital was the best option. Furthermore, any water ‘run-off’ was captured and cleaned through a granular activated carbon unit before being discharged back into the sewer under licence.”
Sustainability benefits realised include the elimination of waste generation, as the project has, to date, reused over 90% of excavated material and converted all untreatable waste material into refuse derived fuel via its in-house resource recovery facility. The remediation strategy was said to have received positive feedback from operatives on site, who found the onsite laboratory to be widely favourable compared with traditional offsite sampling methods. The careful selection of the construction method saw a robust system implemented to ensure a seamless operation throughout.
As the project progressed, Careys gained a thorough understanding of ground conditions and reports, and benefited from early involvement with statutory services and the Environment Agency, to grasp timescales.
The team has trialled different types of screeners that divide the materials into three streams. “Central to our remediation strategy was a unique system that we created, dividing the entire area of earthworks into 25m2 grids to allow accurate sampling, classification, material movement and verification of materials in known areas,” says Heaps.
The laboratory takes samples from each 25m2 area to ensure it complies with agreed specification levels and is suitable for backfill. This gives the team a systematic means of knowing where material was dug, what it was and where it was to be placed.
Three main utility diversions are required as part of the works and bring their own unique challenges. These include rerouting 600m of 450mm intermediate pressure gas mains, removal of a 350m section of 132KVa overhead cables and pylon tower, 220m diversion of 1.2m diameter storm water drainage and realignment of an 11Kva underground HV cable. With these complexities in mind, the team renewed their focus on maximising productivity, while maintaining health and safety performance.
Structural elements to the project include the construction of two walls, the 200m long dividing wall, which was successfully changed from CFA piled to the “Tensar” eart h reinforced as constructed.
This improved both the aesthetics of the wall, enabled programme efficiencies, and used the site-won demolition material.
Due to the adjacent Network Rail lines, a CFA piled embankment wall was necessary alongside the 200m long dividing wall to enable removal of the tip-waste material down to the required levels.
Advanced project planning resulted in the development of value engineering methods and a determination to create industry-leading practices. It is an approach that is supporting the team in completing ongoing works, accident-free, with considerable programme time savings.
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