siphon - suck out using a hose.
In detail and you might already know this:
Take a hose, fill the whole hose up with water. Use your thumps to cover both ends.
Put one end into the sump, the other end into a pail.
The end at the sump must be at a higher level than the end at the pail
Let go the thumb at the sump and then the thumb at the pail
the water will flow from the sump to the pail.
Move the hose in the sump to suck out all the dirt.