Morrison Construction's open minded approach to the remediation of contaminated sites is backed by experience built up over the six years since the company's civil engineering division began land remediation operations. Close attention to the whole process of remediation is behind the division being able to claim it is the first civil engineering contractor in the UK to be certified to international environmental management system BS EN ISO 14001:1996.
Divisional director David Bull says that achieving certification was a challenge but also a measure of Morrison's commitment to sustainable remediation.
The company is firmly committed to partnering and a holistic approach to the brownfield sites it works on. 'Involving everyone in the process, from client to consultant and specialist suppliers means we can come to the right solution about how best to get rid of contamination and cleanse sites.'
Two ground remediation techniques favoured by Morrison are bioremediation and encapsulation. Bioremediation involves using bacteria and fungi to break down organic compounds found in the earth such as hydro-
carbons and oil.
Encapsulation is the process of retaining contaminated material under a layer of clay which seals the waste so pollutants cannot enter the atmosphere or leach into groundwater. Cementitious grouts can be injected under the capped layer, forming a hardstanding base which is often suitable for building development.
There are a number of constraints which have to be overcome before landfill can be completely superseded, says Bull. 'The new techniques such as bioremediation can be quite costly and can take many months before contaminants are nullified,' he says.
Techniques carried out on site can take as little as three weeks where common contaminants are found, but there are also 'hot spots' where contaminants such as phenol or mercury must be taken away to landfill.
Bull explains that Morrison recently incorporated encapsulation as part of a wider reclamation contract which involved demolishing a number of buildings. Its pounds4M reclamation contract at the 1.6ha derelict ABB carriage works in York involved on site crushing of hardstanding, building foundations and floors. Crushed concrete was used to form a hardcore layer to cap contaminated land, allowing building on top.
'We made sure the site was safe by carrying out periodic monitoring after the job was completed using boreholes for sampling. Most of the big players in the sector have laboratories and test facilities and we are no different. We work in conjunction with one laboratory to
improve the technology continually,' says Bull.
On obtaining ISO 14001 certification Bull says: 'We had to demonstrate our regard of the surrounding environment and people when conducting our operations and that the future targets we would set ourselves were realistic and we could work towards them.
'We have looked at adapting systems on a few occasions, especially groundwater remediation. We modified a system of filtration of contaminated water through lagoons so that only completely clean water enters the water course,' he says.
Bull explains that the demand for remediation is increasingly being driven by landowners
making enquiries themselves. Statutory cleaning, whereby landowners are forced by the local authorities to clean up dangerous sites, is not as prevalent.
'There seems to be more pressure on landowners for a betterment of the community, not just because they have to clean their land by law. Regulations are in place and do work, but we are seeing a changing culture in recent times that owners do not want to see their brownfield sites deteriorate further,' said Bull.
Mike Walter writes for Barrett, Byrd Associates.