Vibrating Wire Piezometer Data

[RobPE]

I'm interested in how you all would go about interpreting vibrating wire piezometer data in the following scenario. Say a VWP reading indicates very slight pore pressure and was installed in a formation that is tight hydraulically speaking, so not much water was expected when drilling the hole leaving doubt as to whether or not the phreatic surface was intersected. In one scenario, you could say that the piezometric surface was barely intersected and assume hydrostatic pore pressure conditions for everything below the VWP. However, very very slight positive pore pressure might lead you to think that this assumption overestimates pressures below and that the reading is data noise more than anything leading you to assume dry conditions. Thoughts??

 

[dgillette]

Which is more likely, that you managed to put the piezo almost exactly at the elevation of the water table, or that there has been small zero shift, due to temperature, saturation of the sand pack around the piezo, or other cause? Does it vary with season? Has there been enough time since installation for the hole to fill with water seeping from this tight formation?

Regards,
DRG