Sustainable Remediation

Introduction / principles
The Sustainable Remediation Forum UK (SuRF-UK) is an initiative set up to progress the UK’s  understanding of sustainable remediation.  SuRF-UK defines the process of identifying sustainable remediation as: 
“the practice of demonstrating, in terms of environmental, economic and social indicators, that the benefit of undertaking remediation is greater than its impact and that the optimum remediation solution is selected through the use of a balanced decision-making process.”

The benefits of undertaking a Sustainability Assessment for Remediation works
When designing soil and groundwater remediation the main design focus is to remedy contamination levels to reduce risks to human health and/or the environment.  By undertaking a sustainability assessment in accordance with the SuRF-UK framework, an assessment of environmental, economic and social impacts is undertaken.  This allows the designer to consider the wider implications of the remediation project and ensure that the remediation works themselves do not cause a greater impact to the wider environment.  

How and when to adopt a Sustainability Assessment 
A sustainability Assessment can be undertaken at any stage of a project, however to maximise the sustainability of remediation schemes one of the key times an assessment can be undertaken is prior to applying for planning permission.  At this stage it is possible to consider any potential contamination issues, prior to designing the site layout.  For example, if a development comprises both commercial and residential development, it may be more sustainable to build the residential properties on the least contaminated part of the site, rather than undertaking extensive remediation works to protect the more sensitive receptors.  It may also influence to the choice of remediation technique such as solidification/stabilisation, soil washing or bioremediation.  

Another key stage of the process at which a sustainability assessment can be undertaken is during the remediation options appraisal; this is demonstrated by the example below:     

Example
VertaseFLI was employed by Dorchester Group to design a practicable and cost effective de-commissioning strategy for the base’s fuel storage and distribution infrastructure with due consideration to its listed status. The site is also located over a particularly sensitive aquifer and contains large areas of protected grasslands which in turn are home to various protected species of flora and fauna.  The fuel storage and fuel distribution system consisted of 99 tanks ranging in size from 50,000 litres up to 4,800,000 litres and a buried fuel distribution pipeline over 23km in length. The tanks and pipeline contained significant quantities of aviation fuel and oily water, and posed an on-going risk to this sensitive environment.  Following an extensive options appraisal process, VertaseFLI designed an innovative and particularly sustainable approach whilst ensuring the site’s heritage was protected. 

Water Treatment 
The remediation options appraisal and sustainability assessment concluded that the two best options for the removal and treatment of the water were either off site disposal in tankers or on site treatment.  The main limiting factor for onsite treatment was the capacity of the foul sewer on site. Therefore, following discussions with the Environment Agency, tank water was treated and discharge to the surface of the site.  These discussions allowed the most sustainable remediation option to be adopted for the site and the assessment helped the Regulator with their decision making.    

Key Sustainability Achievements:  
 - Oils and sludges were recovered for offsite recycling normally as a secondary fuel.

 - Contaminated tank water was treated on site in mobile WWTP units, saving 638 tanker movements and  significant disposal costs.

 - On site treatment of water saved 84 tonnes of CO2 emissions, primarily through the reduced number of traffic miles.  It should be noted that the carbon impact of the offsite disposal of the tank water does not include the carbon impact of treatment which is included in the onsite treatment calculations.  

 - Treated tank water was used in the manufacture of grout, saving the use of 2,500,000 litres of mains water.
  
 - Treated tank water was discharged to land providing 6,400,000 litres of recharge to the local aquifer, which is currently depressed due to drought conditions in the area. 

Tank Decommissioning  
A SuRF:UK assessment was undertaken for the various remedial options that were considered technically relevant to aid decision making.  The remediation options appraisal and sustainability assessment concluded that the two best options for the decommissioning of the tanks were to fill them with either foamed concrete or a PFA grout.  The assessment then looked at optimising the sustainability of the chosen technique helping to optimise the chosen technique by considering all factors of the sustainability including, carbon footprints, social factors like lorry movements and also costs.  

 - Undertaking bench scale trials to determine the mix design of the PFA grout reduced the cement content significantly resulting in a total carbon saving of 655 tonnes of CO2 compared to foamed concrete.   

 - Grout manufacture on site reduced the number of vehicle movements by 430 trips.     

 - Grout was manufactured using PFA under the WRAP Quality Protocol which allowed us to design a mix using far less OPC and diverted thousands of tonnes of PFA from landfill.  The PFA was sourced from a nearby power station which reduced the carbon emissions generated through haulage.  

 - The OPC / PFA grout is suitable for recycling in the future if and when tanks are demolished.

In summary the most sustainable remediation solution was adopted for the site and the SuRF assessment was essential in aiding and informing these decisions and in communicating them to other stakeholders including the regulators.  The assessment process also informed a commercial appraisal and it is no surprise that the increased sustainability has also had commercial benefit.  By adopting the most sustainable remediation solution, CO2 emissions were reduced by 771 tonnes, there were 1,498 less vehicle movements to and from site and 173,342 km were not travelled on the roads. Further, if the tanks are demolished in the future, the method of de-commissioning will not incur exceptional financial or environmental impact.