Peter Atchison

Geosynthetic specialist

PA Geotechnical

Aspects of Development on Contaminated Land

In today's litigative society it is increasingly important for funders and developers to be aware of the risks that they take and to limit these so far as is possible by close involvement and awareness in their projects. Nowhere is this situation more complicated and indeed more feared than in the area of developing on contaminated land. As Government edict directs us toward increasing re-use of "Brownfield sites" financial drivers make this more attractive and yet the difficulties of ascertaining and limiting risk seem to increase at the same rate.

This shouldn't and indeed needn't be so. There is increasing information and advice being made available by the Environment Agency allowing appropriate specialist advisors to identify, and limit risks. Site investigation information is now a primary requirement before any land purchase or development plan. This is all extremely laudable and indeed a recent and major change from the "buyer beware" situation of only ten years ago. Yes indeed the buyer still needs to be aware but typically is far more able to be so than at any time in the last ten years.

None the less the increasing complexity of the risk model, increased legislation in the form of Part 2A and contaminated land trigger levels make this an ever moving and increasingly complicated area. No wonder that clients are still risk averse and that even with the proliferation of professional advisors that are there to assist with the process, it is difficult, if not impossible to accurately limit and quantify one's risk. Add to this, the likely situation of legislation changing during the lifetime of the development; possible contaminant changes due to outside influences and you can see why this area is still one of the most feared and misunderstood of the development sector.

It needn't be so, however, as in all things a little knowledge of current trends, both legislative and solutions provision can massively increase the balance of power in the direction of the developer / funder. Whilst it is entirely appropriate to utilise the experience and expertise of professional advisors in this as in other areas of one's work, a level of knowledge of the sector can massively increase value in this sector. Much as a knowledge of the workings of the motor car is useful in gaining best value and service from a garage (and avoiding being overcharged for unnecessary work) so a working knowledge of the contamination issues in development can make best value use of both time and importantly money in reducing the all important risk.

So what can the intellectually alert client do to limit his risk and effect best value from his development team? Firstly, it is important to be aware that different rules apply to different contamination issues. Much of this is simply due to the slow pace of putting in place new trigger levels for a vast array of different contamination compounds. Secondly, remember that post remediation proving is perhaps the best way of controlling risk and of demonstrating its long-term reduction. Remember that the Site Investigation report is a little like an MOT test. It can only identify the situation on a particular day or over a given period of time. The effect of the construction itself can massively affect the long-term situation on the site.

Currently the consultancy profession (often under the instruction of their insurers) are limiting themselves to the provision of a report on the Status Quo. Advice as to the system to be used to remediate the various elements of contamination found is fraught with difficulties and implies long-term liability as to its performance. This aspect is increasingly being left with the main Contractor or more worryingly his sub contractors to share through Collateral warranties. In the event of a problem, the difficulty of proving whether it was design, materials or installation that was at fault gives each party a reduced level of accountability and potentially leaves the client with less cover than he believed.

Nowhere is this situation more evident than in the area of gas contamination (predominantly Landfill or naturally occurring Methane gas). Unlike heavy metals, VOCs and the like, gas contamination levels tend to fluctuate with time, be affected by atmospheric conditions such as barometric pressure and be particularly likely to alter as a direct effect of the construction process itself. Advice and design solutions in this area tend to date back over seven to ten years and indeed the main legislative documentation is over ten years old. Developments in the area of activated and assisted systems have been slow to take off. Clients have been concerned as to their reliability and more importantly, fear of perceived blight on their building in the event of subsequent on-sale. The fear of reliability is perhaps valid, certainly some of the early extraction systems of the 1990's were plagued by unreliable motors and over-sensitive alarm systems; causing untold false alarms and building evacuation. The industry has improved and current active systems (particularly those utilising positive pressurisation principles) are so reliable as to come with "fit for purpose" insurance backed guaranties.

The Issue of "blight" is more difficult to understand. It is difficult, if not impossible to hide the fact that the site is (or was) contaminated. With a basic, passively protected, un-monitored system, any future purchaser is entirely at the mercy of the original design and construction efficiencies which are by the nature of time "dated" may not meet current (or future guidelines) and are unproven as to their performance (except that the building has not had a catastrophic failure as it still stands!) With an active or supported system, proven constantly by sub slab monitoring points the current performance can be identified, confirmed, and the long term protection passed to the new owner by assignment of the protection policy. Is it any wonder that once they understand the principles involved, fund holding clients are taking more interest in the systems used to protect their developments and investments?

The same is true of other less mobile contaminants such as VOCs which may have been dealt with by techniques such as bioremediation, off site removal and /or containment/exclusion using membranes. Here, once again, materials have come on a long way over the last twenty years. The ubiquitous Polythene barriers of ten years ago whilst "state of the art" then have been superseded in some aspects by more modern materials, aimed specifically at certain sectors of the contamination market.

So how does the prudent development client control his risks? By keeping abreast of the main developments in the market and being aware of the advantages and limitations of the various solutions. Also by studying the current and future legislation and being conscious of the real risks associated with some of the contaminants being identified. Professional advisors are of course integral in this but by being aware that even professionals have their limitations and indeed that they are as interested in reducing their risks as you are, then an informed client can more easily obtain "best value" out of his spend.

Eventually one accepts that the only real way to avoid risk entirely is to develop "Greenfield" sites or to remove all possible contamination to landfill. As legislation, cost drivers and environmental impact make this more and more impractical a small amount of time-spent investigation the actual effects of the various issues raised in say a SI can reap dividends in both project costs and ultimate risk reduction.

So what does the future hold? Whilst it is perhaps prudent to realise that much of the contamination that we are currently protecting ourselves against has been around for a good number of years, (much of it dating back to the industrial revolution), we are only now in a position to identify both the issues and solutions. This trend will continue and as we develop better detection techniques so are we able to identify the risk factors and come up with means of defraying this risk. Current legislation is being constantly updated as research is completed into toxicity levels and exposure risks. One thing is certain, we will need to demonstrate not only a realistic level of protection against known contamination at construction but also to have taken into account the possibility of future contamination trends, be they increasing or decreasing. More concerning perhaps is the current advice that we should also be anticipating future levels set by the regulator, that these may well change and that we should be in a position to have anticipated or increase our protection levels accordingly. One thing is certain; this is an ever increasing and complex area and will continue to be so for a long time to come

Peter Atchison August 2002

Peter Atchison is a geosynthetic specialist with over 20 years experience in geomembrane and associated products. As a consultant he specialised in contaminated land issues and now runs a company offering technical and commercial consultancy support to manufacturers and providers of specialised materials and services aimed at the sector. He is involved in both standards setting and advice to the legislative process through involvement in a number of committees. The opinions expressed above are the authors own and do not necessarily reflect those of neither his clients nor the professional bodies of which he is a member.