There was plenty of balcony seating available to watch Probe Technology from Concord, NC, perform MIP logging at this equipment rental site.

Probe Technology, Concord, NC

A number of years ago, this project site in Charlotte, NC, located near a loading/unloading area next to a railroad spur, housed a chemical mixing/storage facility. The buildings and lot were then used as an equipment rental business where a large number of machines were moved in and out on a weekly basis. Working in the midst of these large, spider-like machines, Arlen Burney, owner of Probe Technology, Inc., in Concord, NC, brought in a Geoprobe® 54DT and an MIP (Membrane Interface Probe) System to locate possible areas of contamination in the subsurface. Although the chemical facility had been out of business for many years, lithologic changes and the distribution of chlorinated contaminants were easily observed using the EC (Electrical Conductivity) and MIP systems.

In addition to running the EC and MIP logs, Probe Tech’s field team took soil samples using the Macro-Core® soil sampler, soil vapor samples with the PRT system using both expendable points and the retractable drive point assembly, and groundwater samples using a Screen Point 15 sampler.

According to Arlen, “Our field team was easily able to locate high levels of chlorinated solvents near the railroad spur with the MIP System.” The field team provided the site owner with subsurface logs (two of which are shown below) that mapped the soil, soil gas, and groundwater plume in the subsurface. “We backed up and verified the data in the logs with a variety of samples,” Arlen added. “At the conclusion of the project, the MIP System and Probe Technology field crew proved to be an excellent team.”

	(left) This bird’s eye view shows one of the confined spaces EC (Electrical Conductivity) and MIP (Membrance Interface Probe) logs were obtained. After viewing the logs, the field crew followed up with Macro-Core® soil sampling, soil vapor sampling, and groundwater sampling using the Screen Point 15 sampler. The mobile lab, set-up in the rear portion of the white truck, helped the site crew quickly map the various contaminant plumes.
(right) Arlen Burney, foreground, owner of Probe Technology, Inc., operates the 54DT during MIP logging at a former chemical mixing/storage facility. The pre-strung rods for the MIP system are shown extended from the rear of Probe Tech’s mobile lab and MIP support vehicle.
Mapping the Plume: The two MIP logs shown below were obtained using a MP4510 MIP probe with an integrated electrical conductivity dipole. General lithologic changes and the distribution of chlorinated contaminates are observed in the subsurface by using the MIP.
MIP Log 03 shows a high conductivity down to 5 feet indicating the presence of silt-clay soils. Below the soil horizons, the conductivity drops abruptly to 20- to 40-milliSiemens per meter (mS/m) indicating an interface between the relatively fine-grained soils and the larger-grained sands and gravels. These changes are observed in the log until a depth of 32 feet where the conductivity indicates a larger-grained unit to the refusal of the bore location. The Electron Capture Detector (ECD) indicated the presence of chlorinated contaminants located in the larger-grained units, 18 to 29 feet and 31 to 45 feet. The finer-grained units served as barriers for the transport of the contaminants.	MIP Log 04 shows high conductivity down to 10 feet indicating silt-clay soils present. A drop to 40 to 50mS/m occurs from 9 to 12 feet indicating larger-grained units. Larger-grained units are also observed from 29 to 35 feet. These units are capable of being high permeable zones. The ECD in this log is saturated from 11 to 35 feet indicating very high chlorinated contamination. This location was terminated due to the fine-grained unit at 36 to 39 feet serving as a barrier for the contamination. The permeability of the fine-grained unit is orders of magnitude lower than that of the larger-grained units.

Find out more about the Membrane Interface Probe (MIP) System used in this article. Go to Geoprobe's Direct Sensing website: www.geoprobe-di.com.