It happens that Phil L formulated :
Andrew Haylett wrote:
We're having our driveway gravelled (standard hardcore + 15-20mm
gravel method). There are two drain covers, standard rectangular
shape/size. Our builder isn't sure how to handle this. They could be
left to stand proud of/level with the surface of the gravel, but I
suspect they would look better covered. If the latter, what is the
best approach? If we just use the same or similar covers but lowered,
the gravel will probably move off their flat, smooth surface too
easily. He suggested a screed tray with some sort of material in it
to provide grip for the gravel above. Does this sounds reasonable?
Is there any 'best practice' for this? Any experiences to share?

Andrew.

His suggestion of using trays is probably the best option, there is, however,
quite a lot of work in dropping the level of the manhole to take the inset
tray.
He'll need 2 or 3 inches of compacted grit in the bottom of each before
adding any MOT, to allow free drainage.

Also, you may not be able to find them at a later date unless you draw out a
plan now of where they lie in relation to each other and also the house,
boundaries etc - and put it somewhere safe!

If you have a rough idea of location, you can find them easily enough
with a cheapo metal detector - assuming they are metal of course.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk