We need to test the ground to create a remediation strategy to confirm what we need to do, to ensure any contaminated soil is disposed of as hazardous waste to landfill. Appropriate measures are taken to eliminate risk from toxic gases and suitable foundations are used.
Cohesive soils
We found clays. Can you build on clay? We check first using a 'Pilcon hand vane'. It is stabbed into the clay and twist ed. The reading will confirm the shear strength.
0 to 40 is soft, you wouldn't build on this, 40 to 75 is firm, shouldn't be a problem and 75 to 150 is stiff, over 150 kilo pascals (kpa) is very stiff, so much so that you wouldn't be able to push the hand vane in.
So, we've got stiff cohesive sub soil... We'll wait for the results from the samples, issue to a structural engineer to design the foundations and we're good to go.
For house extension plans:
http://www.asandow.co.uk/HouseExtensionDesign.html