Achingknees,
It can of course be very difficult to detect surface archaeological remains on gravel, depending on depth of alluvium and other factors - hence problems such as mercenary's unknown LBA settlement. However, it is far more difficult to evaluate the potential for Palaeoloithic material; nearly all of this is redeposited in gravel deposits, with only a handful of cases of primary deposition such as the mammoth butchery site at Lynford in Norfolk. Quarrying is usually the only way that finds of such material, primary and secondary, are ever found at all on dry land, but, of course, only as the deposits are being destroyed.
Add to this the overlapping responsibilities of English Heritage for Quaternary Archaeology and English Nature for Quaternary Geology and we have a big problem area. EN can and have funded excavations of Quaternary remains, such as the woolly rhino from Whitemoor Haye quarry in Staffordshire.
The Aggregates Levy Sustainability Fund has allowed EH and EN to fund a lot of research in this area, which is looking at a wide range of subjects including better detection and prediction of near-surface archaeology (in major river systems such as the Trent). There has also been a lot of research on the potential of primary and secondary Palaeolithic remains within gravels, including better means of predicting survival and determining potential. Lastly, there has also been a move to create a National Ice Age Network to improve the reporting of finds from quarrying and to provide resources for the archaeological and geological groups that have traditionally been involved in the discovery and reporting of such material. There is a good website for this at
http://www.iceage.bham.ac.uk/home.html
To get back to your original question, when I was involved with the ALSF a couple of years ago I was aware of only one case where a PPG 16 condition had been applied to Palaeolithic remains from quarrying, and that was a very occasional watching brief, where an archaeologist went to see what had turned up during quarrying. Not very satisfactory, but better than nothing. It will take some time for the research that is being done to influence planning controls, but it is encouraging that local government archaeologists are involved in most of these projects and leading some of them.
Weegie