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Cautionary tales


Small private housing developer discovers gasworks legacy too late

In April 1998 a housing developer bought a plot of land in north London on which it planned to construct a small number of private residential dwellings.

A site investigation was commissioned and three boreholes were sunk to 10m into the underlying London Clay. As part of the investigation, five near-surface samples were analysed for chemical contamination. These indicated the samples were at non-hazardous levels and the report pronounced the site clean and 'suitable for housing'.

Belatedly, and in reverse order to normal procedure, a desk study was carried out. Published maps dating back to Victorian times indicated the site had been occupied by a gasworks, and later as a vehicle depot. Still the consultant did not revise its advice regarding the suitability of the site for housing.

It was not until the excavation of a tar tank during foundation preparation that attention was paid to the history of the site and ground contamination. Problems were compounded when a second tank was found under the site cabin during investigation work.

The key points from this saga are that clients still do not give due regard to the need for best value for money. Furthermore the need for a desk study as an essential element of any investigation is not always accepted or understood by clients or some of their consultants.

Failure on both counts in this case has lead to a six month delay in the programme, which has seriously eroded profitability of the small development. It has also lead to significant costs being incurred by the local authority, which is concerned about public health.

The developer is not happy with the advice received - but has he learnt the need for appropriately qualified consultants to carry out planned investigations in accordance with best practice?

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