Land quality – managing ground conditions

4.1.6Detailed Investigation (sites where hazards are identified or suspected)

Where hazards are identified or suspected, a Detailed Investigation of the site shall be conducted under the supervision of a consultant or specialist acceptable to NHBC to determine and report on the nature and extent of the conditions.

A Detailed Investigation should be carried out where hazards are identified or suspected:

  • from the outset
  • from the initial results of the desktop study and walkover survey, or
  • from the Basic Investigation.

A consultant or specialist acceptable to NHBC should be appointed to:

  • design and supervise the Detailed Investigation
  • present all the factual data obtained from the Detailed Investigation.

In addition to the Basic Investigation, the Detailed Investigation should adopt a clearly defined, structured approach, gathering information which considers the:

  • immediate site and the adjacent area
  • possibility of future development in the vicinity of the site
  • nature of the development
  • complexity of the ground conditions
  • extent of influence of the proposed foundations
  • presence of soil gas (if there is any possibility a full gas investigation should be carried out and include flow measurements)
  • surface water and ground water conditions, soils and geology, and site history.

The problems and liabilities which have to be managed in order to develop the site should be clearly communicated in the Detailed Investigation report.

Further investigation should be conducted if the Detailed Investigation has not satisfactorily addressed all of the original objectives.