ok lets start from the beginning
you have said it is 10' high. Is it holding back 10' of ground?
What is this ground? is it clay sand, rock? all these will have different
characteristics on what weight they have, how much slump they give with
different amounts of water in them.
Is the retaining wall on the boundary of your property? If so check with
your local authority. In most areas boundary walls NOT onto a highway can
only be at 2 metres (6') without permission. At that point almost certainly
the local authority will want to see how the calculations were produced.
Next problem and possibly the most difficult one if you are intending to do
the work yourself is how do you hold up 10' high verticle face of ground for
you to build a wall against it. In many ground conditions if you cut a
trench 10 deep it will collapse, possibly not as you cut it but as you are
down there trying to lay bricks. Note if the wall/ground you are holdin up
is 10' high then the foundation will go deeper. Dangerous conditions. Of
course there are many ways of dealing with this, Pilling, battering the
slope back are two that come to mind.
As I said if your dimensions are anywhere near correct then 10' is a serious
problem unless you have it checked by a person on site. Ground conditions
are the all important thing here and for that you cannot describe clearly
enough on here