Research, development and remediation
CL:AIRE (Contaminated Land: Applications in Real Environments) is promoting the development of sites of national significance to enhance collaborative research on big issues in the remediation of contaminated land. Two such sites are CoSTaR and SIReN.CoSTaR (Coal Mine Sites for Targeted Remediation Research) which was formerly known as the National Mine Site Research Facility was described in the January issue of IEM.
CoSTaR comprises a group of six mine water remediation sites selected to illustrate the principal types of passive systems currently used to treat polluted mine waters at sites in North America and Europe. All six sites are located within 30 miles of Newcastle at the heart of the old Durham and Northumberland coalfield.
The establishment of CoSTaR by the University of Newcastle, the Coal Authority, Durham and Northumberland County Councils and CL:AIRE addresses two of the key points of CL:AIRE's Research Strategy. These are to identify primary research areas on which to demonstrate remediation research and technologies and to publicise the results of CL:AIRE supported projects on these sites. Another national facility, helped by additional funding from Biffaward, that will have a major impact on contaminated land and remediation research over the next few years is SIReN - the Site for Innovative Research into monitored Natural attenuation.SIReN
SIReN is a joint initiative between Shell Global Solutions UK, the Environment Agency, AEA Technology and CL:AIRE to promote field based research into monitored natural attenuation (MNA). The overall aim is to demonstrate that MNA can be a technically defensible option for contaminated site remediation here in the UK, while also providing a well characterised site for large and small long term research and development projects.
Formed in 1999 following discussions between members of the NNAGS (Network on Natural Attenuation in Groundwater and Soil) management team, SIReN set out to identify a contaminated site that could be used for research into MNA. During phase one of the project over 200 sites were considered and eventually one was chosen that met the site selection criteria.
These included environmental, legal and geological concerns. It was important that the site be situated on an aquifer characteristic of UK conditions and be available for a period of three to five years for research purposes. The site chosen was an operational petrochemicals manufacturing plant occupying 180 Ha.
The site has been in operation for 50 years producing a variety of products from refined hydrocarbon petroleum feedstocks. These included alcohol, glycols, amines, detergents and polystyrene. The land and groundwater was impacted by both petroleum hydrocarbons (BTEX compounds; benzene, toluene, ethylbenzene and xylenes) and petrochemicals, including traces of chlorinated hydrocarbon solvents.
The geology of the site consists of superficial deposits of made ground, sands and gravels and boulder clay overlying consolidated sandstone bedrock. Groundwater occurs at shallow depth in the sands and gravels and in the deeper sandstone. Small co-mingled LNAPL and DNAPL (light non aqueous phase liquids and dense non aqueous phase liquids) contamination plumes are present in the superficial deposits and initial investigations indicate the existence at one location of a small benzene plume at depth in groundwater in the sandstone aquifer.
Initial chemical and microbiological results show that BTEX degradation is occurring in the superficial deposits and groundwater along with the natural attenuation of chlorinated hydrocarbons. The most recent site characterisation has focused on the lateral and vertical extent of pollutants at the site to help understand the behaviour of contaminant plumes in the groundwater.I
n particular, the extent of benzene contamination was investigated through the installation of a multi-level sampling system into one of the boreholes that extends into the deeper sandstone aquifer. Combined with additional deep boreholes within a 50m proximity, this has helped locate a small benzene plume. This plume is of particular interest because the application of MNA to manage benzene contamination in consolidated aquifers has not been studied extensively elsewhere in the world.
Manufactured multi level sampling systems for monitoring wells can include simple continuous multichannel tubing and more complex engineered multilevel sampling systems. For more information on multilevel sampling systems or technical reports on SIReN projects, contact firstname.lastname@example.org or see www.claire.co.uk.Funding
SIReN has been funded by the Environment Agency and Shell Global Solutions together with contributions from CL:AIRE and AEA Technology. The project has received landfill tax funding from Biffaward which is managed by CL:AIRE as an environmental body registered with Entrust. The Biffaward funding allows CL:AIRE and AEA Technology to manage the SIReN project co-ordinating long-term research to further the understanding of MNA and develop its practical application.
The results of MNA research on the SIReN site will be disseminated widely within the contaminated land community and to potential stakeholders, enhancing confidence and best practice in the methodology. Any researchers wishing to use the SIReN site should first express their interest with a member of the project management team. Anyone submitting projects is also encouraged to develop their projects through CL:AIRE to ensure optimum dissemination of the results.
Natural attenuation of organic contamination by biological and physico-chemical processes takes place in the natural environment. These same processes also occur on contaminated sites and groundwater. To be considered as a legitimate remediation technique these natural processes need to be fully understood and monitored on contaminated sites that by implication need to be well characterised by a thorough site investigation.
This technique has been termed monitored natural attenuation (MNA) and can be an effective remediation technique when compared to engineering methods or expensive disposal at landfill sites. Whilst considerable research into MNA has taken place in the USA, Canada, Holland and Germany this has usually involved the study of the saturated zone in unconsolidated aquifers. Little research has been carried out into those MNA processes that occur in the unsaturated zone or consolidated hard rock aquifers such as the Permo-Triassic sandstone or Cretaceous chalk which are important aquifers in the UK. Therefore, it is important that there is a greater understanding of MNA in the context of UK geological environments and associated aquifers.