CELTIC won most sustainable remediation project in the BB Remediation Innovation Awards for its work at a West Midlands gasworks.
This project, for National Grid and with principal contractor Edmund Nuttall, concerned one of the UK's largest town gasworks. Significant contamination, including two underground tanks containing coal tar and liquor, was present and posed a threat to a major aquifer.
Sustainable objectives
The objective of remediation works was to remove the contents of the tanks. During initial design development, sustainable objectives were set. CELTIC prepared a remediation design in consideration of these objectives:
Environmental - Risk-based remedial targets were derived and agreed. Recovery of neat contaminated liquids was proposed, avoiding bulking the liquids and increasing waste volumes, and maximising recyclable materials.
Social - The tanks were situated in the car park of an operational National Grid site. To minimise impact on site users and neighbours, it was proposed to empty the tanks before removing their lids (carried out by subcontractor Acumen Waste Services). A temporary car park was prepared. A locally based principle contractor and sub contractors were employed, minimising travel to and from site.
Economic - Works were strictly limited to what was necessary to remove the most significant contamination sources. Sampling and analysis mechanisms were designed to ensure only soils failing the reuse criteria were disposed of.
Natural resources - Fossil fuel consumption was minimised by the proposed recovery of neat liquids, minimisation of waste volumes landfilled and maximisation of soil reuse, for which a target of 80% was set. Project team mileage was recorded, as well as fuel (32,221 litres) and water usage (39m3).
This enabled the team to track consumption and enabled National Grid to build up a databank to help inform the reduction of the carbon footprint of its remediation projects. This project used on average 2.8 litres of fuel per m3 of soil excavated and managed, compared to an average of 5 litres of fuel per m3 on the 2007/8 National Grid remediation programme.
Remediation works
Works were carried out by Edmund Nuttall, and the car park reinstated. During the works, 2250m3 of water was treated and disposed to foul sewer, 1000m3 of liquor/water was treated by Biffa with the water effectively reused, and 625m3 of tar was incinerated, with 185m3 contributing to cement manufacture.
On completion of the liquid removal works only 9.6t of waste remained that could not be put with one of these three streams. Soil disposed of amounted to 950m3, and was sent to Biffa/Biogenie's Risley facility to be treated and reused as restoration material.
A total of 8250m3 (94%) of the backfill material was won from the wider site during the works and 500m3 of clay, subbase and tarmac imported. It is estimated that the use of site-won material saved 600 lorry movements, 3,600 litres of fuel and 9.5t of CO2 emissions.
Overall, it is estimated that the project 2,800m3 of material from landfill, as well as 31,600 litres of fuel and 83t of CO2 emissions.
"A genuine attempt to quantify all impacts and reduce them." Stephan Jefferis
