The Dreaded "P" Site Classification

We have just received the contract from the builder, which includes a copy of the Soil Test report (Geotechnical Site Investigation). Our site has been classified as ‘P’ due to the depth of fill. From the three bore holes they drilled fill was encountered to a depth of 2000mm, 2200mm and 2100mm respectively.

The report states that “If certification is provided to confirm that the filling is compacted as per AS 3798 specifications to “controlled fill” standard as per AS 2870, then an engineer designed waffle footing system suitable for this site’s reactivity may be appropriate for an articulated brick veneer dwelling.

The waffle footing system may bear directly onto the compacted filling and shall be designed to account for a differential settlement of the fill by an Engineer experienced with the design of ‘rigid’ waffle footings.”

A couple of weeks after this Soil Test report was prepared, I supplied the builder with a copy of the document from the developer certifying that the fill was controlled in accordance with the standards.

Elsewhere in the soil report it is stated that “For the encountered soil profile and normal seasonable moisture conditions, we estimate that the characteristic surface movements to be less than 20mm”.  My interpretation of this is that the fill is classified as “S” (slightly reactive).