In reply to Mr Rix's letter (NCE last week), site investigation should indeed comprise more than 'just' sinking exploratory holes and doing tests. It should always start with a desk study or preliminary sources report.
Unfortunately the Highways Agency and many other clients do not always live up to their own published best practice and consultancy is now largely satisfying job numbers and cost centres rather than common sense.
There is also a simple test which may offer a direct assessment of whether stabilised soil will swell: the soaked CBR with swelling gauge.
J Gray, Warwicks, jericgray@hotmail. com