We just received our soil survey and I'm more than a little worried about the notes regarding rock at each of the bore holes.
We have a $3.5k (paid for) additional provision for rock that was added as a variation post-contract - are the results of this soil report and only having a small provision for rock going to present a problem (ie. are we going to be up for a -lot- more than the 3.5k)?
The bit that's worrying me is the "refusal" on rock at relatively shallow depths and the notes regarding potential difficulties with excavation at the end of the report.
Soil survey results shown below:
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Horizon, Soil Description, Hole 1, Hole 2 , Hole 3
A, Clay/Silt mix - Brown - Poorly compacted, 0-200, 0-150, 0-150
B, Clayey Silt - Dark Brown/Grey - Firm - Low Plasticity, 200-300, 150-200, 150-200
C. Silty Clay - Dark Brown/Grey - Very Stiff - High Plasticity - Refusal on rock at holes 1, 2 and 3 (possible floaters), 300 - 1100, 200 - 1000, 200 - 1000.
This site is classified as "H" under AS 2870-1996
Note: Rock/floater encountered at shallow depth. Excavation with light machinery may be difficult.
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On a different note it does appear that we have good stiff clay at a relatively shallow level, so while our geosite estimations factored in 19 piers at 1800mm depth the concrete piers calculation/footings plan details 17 piers (11 external, 6 internal) at 1300mm depth (600mm founding into natural B horizon clay).
Will this have an impact on our site costs (perhaps for the better) as we don't need as many piers as was originally estimated and they appear to not as deep, or am I reading that particular section of the engineering/footing plans incorrectly?