3. SITE INVESTIGATION

The objectives of the land contamination investigation are to

i) identify subsurface geological conditions and groundwater movement;

ii) identify the contaminants present;

iii) locate their distribution over the site area; and

iv) determine their concentrations both on and below the surface.

Detailed planning of the investigation is necessary to ensure cost-effectiveness.

3.1 Subsurface Geological Conditions and Groundwater Movement

It is important to know the subsurface geology and groundwater flow at the site Some substances, particularly petroleum hydrocarbons, can float on top of groundwater and migrate some distance away from the sources of leaks or spillage. Selection of remediation methods also depends on subsurface geology, e.g. low permeability soil may not be amenable to soil venting. Investigation of subsurface conditions should be done through borehole sampling (see 3.3(i)). Types of soil at different depths are revealed by the samples collected. Experienced field personnel should be employed to record the strata log and the depth to groundwater table at each borehole.