– Peter Bogle, Chief Executive, HPCHA
"We knew the ground conditions. The structure of the homes took into account the conditions and that's why there was piling.
That's why there are concrete beams.
That's why the timber frame and the structure has held out well when a hole opened up under one of the houses; the house didn't collapse into it."
– Dr Clive Edmonds, Peter Brett Associates
"You have a solid steel cone which you're driving into the ground with a hammer and you're measuring the blow counts of that hammer.
The numbers give us the feedback of whether the ground is hard or soft, for example if the blow count is 1 or 2 its clearly weak. If it's ten then it's clearly much firmer, much harder."
It's nearly two weeks since a ten metre wide and 6 metre deep sinkhole opened up in Hemel Hempsted.
Forty eight homes in the surrounding housing estate had to be evacuated and are still empty today.
Watch Martin Stew's report:
The sinkhole has been temporarily filled with concrete whilst engineering geologists assess whether the ground is now safe. They're now probing in sixty locations to see how firm the ground is from the surface to a depth of fifteen metres.
The developer who build the homes five years ago says he is hopeful people can move back into 44 of the 48 properties soon.
He says the timber design of the homes build on concrete foundations means they have stood up well to the damage.
The other four homes could require serious underpinning and early estimates show it could be at least three months before people can move back in.