Laserfiche WebLink
<br />Soil Investigations for Data Collection in the Delta <br />Initial Study/Proposed Mitigated Negative Declaration 13 <br /> <br />*Source: Geoprobe 2019 <br />Figure 6. Track-Mounted Cone Penetrometer Testing Rig <br />2.1.3 On-Land CPT Investigation Methods <br />To conduct a CPT, a cone-tipped rod with a diameter of 1 to 2 inches is pushed through <br />the ground to measure various parameters including tip resistance, side friction, pore <br />pressure, inclination, and shear wave velocity of the soil layers. While advancing the <br />cone, bentonite may be used to reduce friction. The method to perform the deeper <br />CPTs uses an automatic bentonite injection system to keep the friction low on the <br />drilling string, allowing for CPTs of approximately 200 feet deep. The bentonite drilling <br />fluids will be contained and removed from the Impact Area after completion. At various <br />depths, the cone may be stopped, and testing will be performed, including pore <br />pressure dissipation and shear wave velocity testing. During shear wave velocity <br />testing, a source signal is induced in the ground using a small hammer and tapping on a <br />beam pressed against the ground. <br />The duration of CPT investigation activities for the 103 CPTs will be up to 4 days for <br />each Impact Area.