Environmentalists working on the Olympic site describe the remediation challenges they faced
The ODA’s first challenge was to prepare the highly contaminated brownfield site in the Lower Lea Valley. With a budget greater than any of the high-profile venues, the enabling and remediation works involved clearing and cleaning the derelict site to prepare it for the “big build” and ultimately the creation of an urban park with meadow flowers, trees and waterways.
When work started in October 2006, the 245-hectare site had suffered more than 200 years of industrial pollution, which had left a legacy of contamination. At site handover there were still warehouses, car breakers, chemical works, food processing facilities, concrete plants, railway sidings and bus garages using the land.
For the enabling works, which were project-managed by Atkins, the park was divided into north (run by Morrison Construction) and south (run by BAM Nuttall). The main aims of the remediation strategy were to protect against risks to the human health of the legacy users and prevent future contamination to watercourses and aquifers. To identify and target the contamination – which included oil, petrol, tar, cyanide, arsenic and lead – the project completed more than 3,500 boreholes, trial pits and window samples.
Although the site’s long industrial history was well known, the extent of the contamination, particularly on part of the site formerly occupied by a chemical storage facility, was unexpected. “To find arsenic down into the alluvium, the layer that is supposed to prevent downward migration of contaminants into the chalk and lower aquifer, was quite a surprise,” says Kene Onwubuya, an Atkins supervisor for the remediation works.
With its sustainability targets in mind, the ODA opted for on-site treatment of contaminated material from the bulk earthworks. This not only helped it reuse more than 80% of the excavated soil, but also reduced the need to bring in virgin aggregates and to transport large amounts of material on and off the site. The decision to clean the material in situ saved approximately £68 million compared with the costs associated with off-site disposal.
An on-site laboratory first sampled and tested all the excavated materials to decide whether they were appropriate for reuse, disposal or treatment. “Any material that was too contaminated was disposed off-site, but most material was washed and reused as backfill to build up areas,” explains Onwubuya. “Not much of it went off-site, except materials like highly contaminated alluvium, which doesn’t lend itself to washing.”
Two “soil hospitals” with five soil-washing plants using physicochemical technology to remove a range of contaminants – including organics, such as petrol, and inorganics, like heavy metals – were used at the park.
The soil treatment centres had bioremediation areas, using biopiles (a form of soil treatment where bulking agents, nutrients and water are added) and windrows (long triangular piles of soil formed out of the excavated material). They also contained two soil-stabilisation plants, which used specially prepared chemicals to bind contaminants so they became immobile.
Before treated material was supplied back to the individual projects – for use in everything from reinforced embankments (gabion baskets) to road capping – it was geotechnically and chemically tested to ensure that it met the applicable criteria for each construction zone.
The project also treated more than 20 million gallons of contaminated groundwater using a hydraulic capture system and innovative techniques, such as injecting compounds into the ground and generating oxygen to break down harmful chemicals.
In a UK first, a new bioremediation technique was used to remove ammonia from water beneath the site of the Olympic stadium. This involved introducing archaea – naturally occurring microorganisms – into pumped groundwater, where they “eat” the ammonia, completely degrading it prior to its reinjection into the aquifer.
To protect human health from any remaining ground contamination, the park’s “human health separation layer” of clean surface material, which is based on Building Research Establishment guidance, was established at a minimum thickness of 0.6m, setting a benchmark for future large land development works.
Down with the old
During the site clearance, a total of 215 buildings were demolished, as well as a number of walls, bridges and roads. The target of 90% (by weight) reuse or recycling of demolition material was exceeded, reaching 98.5%. This equates to more than 425,000 tonnes of waste diverted from landfill.
Although reuse of materials is more desirable than recycling, the general target of 90% did not include a specific reuse target. In practice, there were high levels of recycling and negligible levels of reclamation for reuse (an estimated 0.5%).
“A high level of reuse was difficult to achieve due to the tight timescales and complex scope of the project,” says Noah Bold, sustainability manager for CLM, the ODA’s delivery partner. (CLM is a joint venture between CH2M Hill, Laing O’Rourke and Mace). “One of the issues was that there was no permanent store area put aside or dedicated person focused on reuse.”
Among the achievements, however, was the deconstruction and reuse of 18 steel-frame buildings, reclamation and reuse on the park of 660 tonnes of various brick types, 176 tonnes of paving material and 5,400m of kerbs.
In future, the ODA suggests clients set a specific reuse target, rather than just a combined figure. Other recommendations include appointing specialist reuse/salvage contractors during the pre-demolition and demolition stages, carrying out detailed reclamation surveys and establishing a storage area on-site or nearby.
One of the early successes in managing the excavation and demolition waste was a 2007 memorandum of understanding (MoU) for waste management licensing between the ODA, CLM, the tier-one enabling works contractors, and the Environment Agency.
The MoU, which provided the platform for obtaining waste recovery licences (now environmental permits under the Environmental Permitting Regulations) from the EA, helped avoid unnecessary regulatory delays and inconsistencies by using standardised regulatory measures and documentation.
To make sure the venue, infrastructure and landscaping contractors involved in the build phase understood the ongoing requirements of maintaining and protecting the brownfield remediation, the ODA set up an innovative “permit to proceed” (PTP) protocol.
The PTP set out the requirements to be followed by all contractors when carrying out any excavations relating to the construction of any infrastructure and venue works on the Olympic park.
“We really needed to protect the remediation works when the venue contractors started work,” says Onwubuya, who was part of the PTP team. “We supported and advised the contractors, making sure they were aware of the on-site remediation systems and auditing their activities once their works started.”
The process, which involved issuing more than 1,200 permits across 50 projects, helped integrate remediation measures across the park and supported site validation and the subsequent discharge of planning conditions.
Programme manager, environment and sustainability; design manager and sustainability champion, the athletes’ village
An architect by training, Gary Gordon has spent much of his career managing the design and execution of complex projects and the teams that deliver them. He has worked on the Olympic park since September 2007.
His first role, to June 2009, was programme manager, environment and sustainability (E&S), which meant he was the main point of contact between the ODA and its contractors, and project manager for the E&S team. He was also responsible for all external reports.
“My role as programme manager was to ensure individual members of the E&S team could concentrate on their own specialism,” he says. “I ensured they all understood their day-to-day objectives, and had the tools and resources to deliver success.”
Gordon explains that his previous role as a project director, first for Kent County Council and later at South Kent College, meant he had the skills to manage multiple projects and a team of talented professionals, while his architectural background gave him knowledge of and a keen interest in sustainability issues.
In June 2009, Gordon became CLM design manager at the athletes’ village, working with the main contractor, Lend Lease. This role involved having oversight of the process and sustainability aspects of the project. The village is the first large-scale, high-density, high-rise scheme to be developed to level four of the code for sustainable homes.
Two years later, Gordon was appointed handover manager for the village, which involved the creation and implementation of a handover strategy and the processes employed to manage the progressive inspection and acceptance of nearly 3,000 townhouses and flats between the ODA and LOCOG (the games’ organising body). The village was transferred to LOCOG at the end of January 2012. During the games, the village will house about 23,500 athletes and officials, before being converted into 2,818 homes after the games.
Gordon says that one of the best things about his involvement with London 2012 was working with his colleagues in the E&S team. “Being surrounded by a team of excellent and committed people was a highlight for me,” he says. “I think we all realised that we had a unique opportunity to make a real difference.”
Gordon is also a project manager at CH2M Hill.
Environment scientist, Atkins
Environment scientist Kene Onwubuya has six years’ experience of site characterisation and brownfield regeneration, and has worked at the Olympic park on and off since September 2007, as part of Atkins’ enabling works team.
Up until February 2008, he coordinated data management of the soil and water laboratory scheduling for the investigation works across the 245-hectare site. This off-site role involved managing and assessing the data that formed the basis for the site-specific remediation strategy documentation for the remediation works.
Between March 2008 and May 2009, Onwubuya worked as assistant supervisor in the enabling works team, which managed the remediation of the east London site. His responsibilities included: supervising the contractors in implementing the remediation design; reviewing method statements prior to implementation; supervising remediation techniques on-site, such as bioremediation, soil washing and soil stabilisation; and monitoring all earthworks and material treatment processes.
In October 2009, Onwubuya joined the permit-to-proceed assurance team, which was responsible for ensuring that more than 50 contracting companies complied with the project’s environmental plans, maintained the integrity of the completed remediation works and monitored contractors’ duty of care. This role, which mainly entailed communicating with contractors on the integration of site remediation and designs for civil works, ended in May 2011.
Since then, Onwubuya has been part of the RemTech (remediation technical) and validation support teams, providing technical guidance to on-site projects to ensure compliance with established environmental protocols as well as the remediation and validation planning requirements.
Onwubuya considers the enabling works – preparing the site – to be the big success story of the Olympic park. “This is a brownfield site and the contractors did a great job cleaning it up, so that all the wonderful venues could be built,” he says.
In terms of major challenges, Onwubuya singles out communicating with contractors on remediation standards as demanding. “We had remediation planning conditions that needed to be discharged and, at times, it was difficult to get across that information,” he explains. “We had to keep reinforcing the message.”
Onwubuya is an AIEMA and a Fellow of the Geological Society.