Trenches in the garden

Hi. I'm hoping somebody can give me some suggestions to solve a problem I have.
I have put together a trampoline in the garden for our kids only the garden is on a slope. To counter this I have dug two trenches for the legs to sink into which have levelled it out nicely. The problem is that when it rains the trenches develop little pools of water which turn in to mud when the trampoline is used.
Can anybody suggest something to put down as a base in order to stop this happening? I would like to fill the trenches in and put back the turf which I dug out in the 1st place eventually. Would this stop the mud churning up by stopping the water collecting in one place anyway? The ground is a bit clay-like but seems to drain fairly well at this end of the garden.

Here's hoping someone can help.

Ivan

Hi, wouldn't it be better to set some fence post holders into the garden?
Then fill in the trenches and replace the turf.
BTW, is it possible to post pictures of the garden? if not here try picassa (free, quick, easy) and use a link, because it's difficult to visualise what you mean.

Place a concrete block under each of the legs, put a 4" downpipe over each leg, so that it sticks out above the ground and goes all the way down to the concrete block, fill this pipe with pea shingle. Then fill the trenches back in.