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Miniature Pumps in the Cone Penetrometer Tip for Groundwater and Soil Sampling (Cone Sipper)

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AR #1730
AR #2362
AR #2429

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Tech ID: 381
Project Overview
Miniature pumps have been developed by the Savannah River Technology Center (SRTC) for use with Cone Penetrometer Technology (CPT) probes to obtain groundwater samples. Previously-available commercial samplers for use with CPT were cumbersome and subject to routine operational failures. Use of these samplers requires removal of all cone penetrometer push rods from the ground to deploy the bailer type of sampler. Depending on the depth of investigation, this process can take several hours, and each sample requires that the sampler be deployed to depth and then retrieved for sample collection at the surface. The miniature pumps developed eliminate most of the problems associated with water sampling by the Cone Penetrometer.

Miniature pumps installed at the tip of a cone penetrometer allow depth discrete semicontinuous sampling of groundwater during a cone penetrometer push. By installing these pumps in the cone penetrometer, the need to exit and re-enter the hole is eliminated resulting in a significant time savings (30 to 60 minutes) for each sample collected.

Technology Description
 The Cone Sipper is a groundwater and soil vapor sampling device designed to be used with a cone penetrometer truck (CPT). It is a gas lift pump that uses alternating vacuum/pressure and miniature valves to move liquid or gas samples. The probe is advanced into the subsurface with the CPT and can be used to collect samples at multiple depths in a single borehole. Samples are brought to the surface via small-diameter plastic tubes and the device can be purged for reuse in situ by injecting distilled water, air, or inert gas. The main advantage of the Cone Sipper over other groundwater samplers is that it eliminates the need for retrieval and decontamination of the sampler between sampling intervals. Its simple construction, using just three remote-controlled valves, ensures reliable operation.

The first version of this pump incorporated a single electrically operated valve on the sample inlet line. This design was shown to be capable of delivering a sample from a depth of 180 ft below ground surface when it was tested in a hollow penetrometer body at Savannah Rivers Site (SRS). The initial results indicated that design changes could be made to improve the reliability and sample integrity. Subsequently, a second version was developed which functions by pulling a slight vacuum on the vacuum/pressure line that will draw the groundwater in through the filter on the outer edge of the penetrometer body. The vacuum is held until the chamber is full. The vacuum is replaced by pressure, usually nitrogen or air, and the sample trapped in the chamber is gently blown to the surface through the sample line. After the desired sample is obtained, the sampling system and associated tubing can be flushed by using pure water and/or gases pushed down through the backflush line. The check valve in the back flush line has a high cracking pressure compared to the sample inlet and outlet check valves so it stays closed during normal sampling operations.

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