Today we officially started work on the workshop/studio. We marked out the bore-holes (14) of them, and managed to drill 5 of them.
The workshop is 6m x 9m, with a little alcove on the north side. There are 14 bore holes, each 600mm in diameter and 1m deep.
It took us a while to get the whole thing square – bit of high school trigonometry came in to play – but it should be right now 
This is the new auger I bought to do the job. I was planning on hiring a Dingo with a posthole digger and auger, but when I worked it out, buying on and using it 4 times (bore holes then veranda post holes for the workshop, and the same again for the house), was cheeper than hiring a Dingo 4 times.
As it turned out, the day I has booked to hire the dingo (yesterday) was lousy weather, so I would not have got value out of the hire ($360). And to in hindsight, there is no way we could have dug all 14 holes in one day, so we would have had to hire the Dingo a second time. So those two hires paid for the new auger.
Once I have done the house, I can easily sell the auger.
The soil report indicates that the depth of the fill on the block varies from 500mm to 1000mm. Everywhere we have dug so far, anywhere on the block where there is fill, has not exceeded 500mm of fill depth. It will be interesting to see what the inspector says about the hole depth. According to the slab engineering, we need to go down 1000mm – 1100mm and a minimum of 100mm into the founding soil. Well, we are 500mm into the founding soil at 1m depth.
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We dig about 150 – 200mm at a time. If you dig deeper, you are starting to strain the post hole gearbox with an auger this size. Lift the auger out when it is stationary or going slow so you don’t throw the dirt everywhere. That way, you can scrape the dirt off the auger into a bucket to sum into a wheelbarrow. Its actually easier to do this than to clean up the dirt off the ground afterwards. There is still some cleanup, but not as much. We don’t want the dirt on the ground, cause it will get in the way when we fill the piers.
Notes for next time:
Setup and use hurdles to layout the slab. The hurdles stay in the ground till you have built the formwork. That way, everything is consistent and its easy to place string lines whenever you need them. The only thing to remember here is to place the hurdles far enough out so you can swing the tractor without knocking them over.
Be VERY accurate on the placement of the auger – get it right where the middle of the hole is supposed to be. The rafts sit over the top of the piers, so if the piers are out, the rafts will be out.
It takes about 45 mins to dig and clear each hole.
Stockpile the dirt from the holes (don’t put it in a garden yet). You will probably need to use it to top up the slab flats.