We were obviously aware that the center of the site was higher than the sidewalk (formally validated by a survey) and our design took advantage of this to provide interesting steps up to the front door. We also wanted to ensure the sliders out to the patio did not require a step down, so the house is designed on two levels, with the kitchen and dining/living area being 1 foot lower than the rest, something which cannot be seen from the outside. To achieve this, we knew we would need some soil to be taken out.
Our builders concerns related to the nature of the soil -- '' a lot of organic matter" -- and why our lot had that "domed" perspective when the others nearby did not. So he suggested a soil test, which involves soil engineers drilling and taking core samples. The results were not good for a slab-based house, particularly one in an earthquake zone, and were advised to have the soil compacted.
This involved his folks, using special rented machines, digging out the soil and recompacting back in layers, with the soil engineers retesting at each stage. A costly, non-budgetted, item which added 4-5 weeks to the timeline.
This picture illustrates what went on. We gather that the neighbors thought were building a basement!
