In its simplest form the advice provided consists of an assessment of the presence of soil, groundwater and gaseous contaminants within materials encountered during site investigations. Undertaken in conjunction with a desk study, that provides the information to target areas at most risk of being contaminated from past activities, the likelihood of encountering unforeseen conditions can be reduced.

Recent experience at Cromer Waste Water Treatment Centre where a secondary treatment facility is being constructed has shown that a detailed desk study in conjunction with a phased ground investigation can identify and zone areas of contaminated ground. At Cromer the desk study revealed that:

• the existing Treatment Centre occupies the site of a former Town Gas Works
• the planned development falls within the area of a number of structures from the former gas works
• the structures were identified as a fuel oil tank, separating pits, tar tank, gas holders and associated buildings
• earlier investigations and construction works on site had not revealed all contamination and substructures within the present development area

The desk study enabled the subsequent combined geotechnical and environmental site investigation to focus on the location of the old gas works buildings and hazards associated with the processes and activities that took place. Such a focussed approach enabled a cost effective combined investigation to identify sources of contamination. Interpretation of the investigation and analytical results then enabled contamination pathways and targets to be assessed.

Following the site work a report was produced that, in addition to considering the geotechnical issues, identified the presence and severity of contamination on site and also discussed the implications with respect to;

• the planned construction
• risks to construction workers and future site users
• groundwater / pollution potential
• the general environment
• remedial measures
• re-use and off site disposal of materials

Key issues revealed by the investigation were the presence of an area of hydrocarbon contamination within the building footprint. The levels of hydrocarbon were such that some materials were classified as Special Waste. Subsequent close involvement of A F Howland Associates in the initial construction works has enabled the volumes of wastes removed to tip as Special Waste to be reduced. Supervision of the removal of the difficult waste has enabled a significant cost saving to be made.