Groundwater sampling with a direct push rig is generally completed using a retractable groundwater sampler as shown in the figure. The sampler consists of a four foot enclosed stainless steel screen with a fine slot (.007 inch) size. The sampler diameter is approximately 1-3/4 inch. A disposable steel tip with an O-ring seal is placed in the end of the sampler while driving the sampler to the groundwater collection depth interval.
At the desired depth interval, the sampler and drive rods are pulled back to expose the stainless steel screen. Groundwater flows statically from the surrounding soils into the sampler screen.
The screen inner diameter is slightly less than 3/4 inch. A small diameter bailer (1/2 inch) or check valve sampler with 3/8 inch diameter tubing is generally used for groundwater sample collection. For depths less than 25 feet, a peristaltic pump can also be used for groundwater sampling. The bailer or tubing is lowered through the drive rods into the screened section of the sampler.
After collection of the groundwater sample, the sampler and drive rods are retrieved using the direct push rig. The sampler is decontaminated prior to using for subsequent groundwater sampling.