How to support/underpin cracked foundation for garden wall.

[John A M]

I have a 2 foot garden wall (double course) which I intend to strip down to the founds which are 150mm deep.Then build a 5 foot wall. However there is a crack in the wall & 2 foot to the left of that is a crack in the foundation. There is a waste water drain running under the wall aound where the crack in the foundation is. The wall has been up for about 40 year or so. Overall lengthe of the wall will be 20 metres.
Can the damage be underpinned to allow the laying of new bricks?