The Geoprobe system can be utilized to perform subsurface soil, water or vapor surveys. It is capable of obtaining and analyzing soil samples, obtaining and analyzing groundwater samples, installing small diameter monitoring wells, pre-packed monitoring wells, piezometers, sparging implants, and injecting Oxygen Release Compounds (ORC).

Advantages of the Geoprobe's direct-push sampling capabilities include:

• Multiple sampling alternatives - groundwater, soil, or soil gas

• Flexible range of sample intervals

• No waste disposal problems

• Minimal disturbance to samples

• Minimizes need for permanent sampling points

• Minimal intrusion to site

• Increased speed of site characterization

• On-site analysis and results

The availability of on-site analytical data results in cost savings over the conventional approach (sample, ship to the lab, and analyze) because:

• Contaminant plume mapping can be performed immediately, even in the field.

• Plume delineation is possible in the first phase of the investigation.

• Laboratory analytical costs are minimized via optimal sampling locations.

The Geoprobe requires a staff of two for safe and efficient operation and direction of the investigation. Atlatl's typical project team would include one of our three trained GC operators (Engineer or Scientist) and a probe operator (Hydrogeologist, Engineer, or Technician, depending on the site).

Soil-Gas Survey - The Geoprobe system can be used to collect soil-gas samples through disposable post-run tubing, which runs from the tip of the probing unit to a purging pump located in the rear of the Geoprobe van. Figure 2 shows the post-run tubing system commonly utilized in a soil-gas survey. The gas samples are drawn from a sampling port using a gas-tight syringe. The gas sample is directly injected into the GC by the operator. The on-board computer and APEX software collect the data and produce a chromatogram. The APEX software integrates the chromatogram and computes the gas component concentrations, utilizing data from a calibration standard. The results are printed within minutes and are available for review by the operator. The chromatograms are saved on the computer memory so that can be summarized at the end of the project.

This quick availability of analytical results allows on-site personnel to pin-point contamination sources and position subsequent probe points to clearly determine the horizontal and vertical extent of the contamination. This method of investigation has the following advantages over conventional methods:

The Geoprobe is small and very mobile; the system will not interfere with overhead power lines or business operations, and can be moved quickly.

• The system will not generate drill cuttings which require disposal.

• The system can collect soil-gas, soil, and water samples for analysis.

• The availability of on-site analytical results allows optimum location of subsequent probe points for quick and accurate definition of horizontal and vertical extent of contamination.

The precision of the on-board laboratory, coupled with the system's ability to advance numerous probes each day, can result in a large amount of data being collected and interpreted each day. As much as a twenty-fold increase in data collection can be realized over conventional drilling and sampling methods. The system is cost effective, discreet, and reliable.

Soil Sampling - Soil samples can be collected using several different-sized sampling devices. Atlatl is equipped with Geoprobe’s Large Bore and Macro-Core Closed-Piston Soil Sampling equipment. The details and specifications for each of the types of soil sampling equipment can be found in Figures 3 and 4. The type of soil sampling equipment utilized on a project will depend on the amount of soil sample required, soil conditions at the project site and the objective of the project. Soil samples can be collected in clear plastic (PTEG), teflon (PTFE), brass, and stainless steel liners, depending on project requirements. These liners can easily be capped and sent to a laboratory for analysis.

Groundwater Sampling - Groundwater samples can be collected utilizing Screen Points, Mill-Slotted Well Points, Tubing and Check Valves, Mini Bailers, and Screen Implants. The method to be chosen for groundwater collection depends on the aquifer characteristics, sample contaminants and the objectives of the project. Atlatl is equipped to provide any of the above groundwater sampling methods. In most cases, the depth to groundwater is less than 35 feet, and a peristaltic pump may also be utilized to extract groundwater. Figures 5 and 6 show the equipment utilized in the above groundwater sampling methods.

After obtaining groundwater samples, the on-board GC can be used to analyze the water samples in the field. The water samples are placed in a 40-ml VOA vial and are then equilibrated in a temperature-controlled incubator. The GC operator then obtains a vapor sample through the septum in the vial and injects it into the GC. The data collection and interpretation is similar to that of the soil-gas survey, with the exception that a water-borne calibration standard is used.

Small Diameter Monitoring Wells – Atlatl has the ability to install small diameter monitoring wells. Atlatl is equipped with Geoprobe’s 2.125-inch probe rods and has the ability to install a small diameter well with Geoprobe’s pre-packed screen system or a standard well completion without pre-packed screen as shown in Figure 7. The type of well completion will depend on the soil characteristics and the objective of the project.

Some of the advantages of small diameter monitoring wells are as follows:

Subsurface Disturbance

The smaller diameter boring has less surface area than a larger diameter boring, thereby reducing the area for surface water to enter the borehole, which is the main purpose of the Bentonite seal.

Economics

Installation of small diameter wells cost approximately 1/3 of the cost of a 2" monitoring well. Well materials are less expensive and installation can be completed in 1-2 hours.

Reduced installation expense allows additional investigation points, increasing out confidence in identifying the extent and magnitude of groundwater contamination.

Sampling Costs:

Sampling procedures require the removal of three well volumes prior to sampling. Small diameter wells have smaller well volume, thereby reducing sample time and project costs.

Waste Generation

Direct push sampling creates little or no drill cuttings, reducing the problem and expense of cutting disposal.

Piezometer/Sparger Implants - Atlatl has the ability to install 3/4 inch PVC or steel piezometers using the Geoprobe system. The type and size of piezometer to be installed depends on the soil characteristics and the objective of the project. Piezometers can be used to determine groundwater flow direction, and to monitor contaminant migration. Atlatl can also install sparger implants for in-situ gas sparging systems. A typical piezometer and sparger implant are shown in Figure 8.

Injection of Oxygen Release Compounds (ORC) – Atlatl has the ability, experience and expertise required to inject ORC as part of the remediation of a site. Atlatl utilizes Geoprobe rod accessories and grout pump (GS-1000) to inject ORC at desired depths and intervals as shown in Figure 9.