Just looking at the picture it seams this is the lowest point in the drive so naturally that's where the water problem will be. When heavy rain occurs I'm guessing water will penetrate the building envelope and find its way under the house. There are two things you can do and both options are no where close to 50K.

Ring Council and find out if there is natural drainage in the area. e.g volcanic rock, they can look into the soakage plans while you wait on the phone. My guess is, that area is 85% clay by just looking at the picture so no soakage.

Option one is the more expansive one and will require council consent. You drill down until you hit rock (if available usually 30 meters), install a detention chamber and soakage-hole to manage the problem. When it rains water will be diverted into the soak hole (via cesspits) and overflow (when it cant cope) into the detention tank before it then drain down into the newly drilled hole. Council has proper drawings for this.

If no drainage is available then there is an exception to the rule that will allow you manage the problem within the boundary and overflow into the existing storm-water connection. This will probably apply. What ever you do make sure you use a Certifying Drainlayer for warranties, as-builds and insurance.

PM me and I can send you some more info in this regard  .

regards Plumber       

 

Hi,
Not sure if I'm a bit late in answering?

I would put a see snake (camera) down though the gully (sewer line) the pooling of water see if it looks or smells like sewage? to ease the mind of a broken pipe..

If not that,Can't tell by the photos it could be a burst water main under the drive under mining the drive causing the cracks..