URS won Best project closure/verification process in the BB Remediation Innovation Awards for its autonomous field verification of large-scale remedial excavation in Newton Aycliffe
The 2.9ha site, located on an industrial estate in the North of England, was heavily contaminated with BTEX compounds threatening a nearby surface water course and underlying major aquifer. Both LNAPL and DNAPL were also present in the shallow made ground, as well as alluvial material and residual dissolved phase concentrations of brominated aliphatic VOCs.
The site was under consideration as a special site under Part 2A but the proactive and transparent approach adopted by URS and the client meant that remedial works were completed on a voluntary basis.
Commercial constraints - including an overriding requirement for a rapid solution - determined that disposal to landfill was the most practicable option for this site and 27,843 tonnes of non-hazardous and 1,871 tonnes of hazardous waste were disposed of in this way.
However, the judicious application of on-site verification techniques not only maximised the sustainability of this approach, but also resulted in significant cost savings.
Real-time field verification
A DQRA identified three source areas within the made ground/shallow alluvium. These were further defined by the use of MIP drilling methodology to calculate individual remedial volumes. A Verification Plan was subsequently presented to the regulator, incorporating the results of a Demonstration of Method Applicability (DMA) or field trial, which piloted a series of real-time field verification techniques.
This led to the selection of portable gas chromatograph (GC) as the most appropriate field screening methodology. This, in combination with a statistical data analysis methodology (DUMAT) developed by Cybersense Biosystems Ltd, enabled real-time decisions and a reduced reliance on the timing and receipt of sub-contracted lab data.
The resulting speed of analysis significantly increased validation sample density allowing real-time refinement of the CSM and thereby enabling the minimisation of soil export and associated costs. The Environment Agency has since requested that the DMA methodologies undertaken in this project be included as a case study in upcoming EA guidance on the use of real-time field measurement techniques.
Lab analysis
A total of 599 field validation samples were analysed by the GC, of which 488 duplicate samples were sent for lab analysis. The on-site GC, combined with the statistical analysis methodology successfully predicted the MCERTS-accredited lab results in all but nine of the duplicate samples - a 98.6% success rate.
Stakeholder acceptance
Supported by the portable GC and MCERTS-accredited analytical results, URS' Remediation Validation Report demonstrated that all pollutant linkages were effectively broken, and this was formally accepted by the EA and local authority.
A secondary goal of the remediation works was to facilitate the transfer of the lease for the site to the adjacent landowners, with whom regular communication was maintained throughout and to whom the lease was successfully transferred in April 2008.
"Very comprehensive verification based upon lab and in-situ techniques." Matthew Whitehead
