| Use: | Detecting and monitoring VOCs in the unsaturated zone. |
Description:
Manually or pneumatically driven probes are a nondestructive method for collecting samples from a moving stream of gas or they can be permanently installed in a borehole. A 3/8-inch diameter hole is driven into the ground to a depth of four to five feet using a commercially available slam bar. Soil gas can also be sampled at other depths by the use of a longer bar or bar attachments. A 1/4-inch O.D. stainless steel probe is inserted into the hole. The hole is then sealed around the top of the probe using modeling clay. The gas contained in the interstitial spaces of the soil is sampled by pulling the sample through the probe using an air sampling pump. The sample may be stored in tedlar bags, drawn through sorbent cartridges, or analyzed directly using a direct reading instrument. The air sampling pump is not used for Summa canister sampling of soil gas. Sampling is achieved by soil gas equilibration with the evacuated Summa canister.
Power-driven sampling probes may be utilized when soil conditions make sampling by hand unfeasible (i.e., frozen ground, very dense clays, pavement, etc.). Commercially available soil gas sampling probes can be driven to the desired depth using a power hammer.
Analytes:
| 1. Non-Halogenated VOCs | 3. Halogenated VOCs |
Media:
| Soil: | Ground Water: | Surface Water: | Gas/Air: |
| Not Applicable | Not Applicable | Not Applicable | MINIMUM |
Caution must be taken to make sure that the correct depth is being sampled due to site specific factors such as moisture conditions, porosity, ground water depth, and analyte specific factors such as solubility, volatility, and degradability. VOC samples may be disturbed due to pumping action of the probe
| Maximum Depth: | Up to 100 feet. Depends on the density of subsurface material and method of penetration/coring. Probes used with cone penetrometer rigs can reach depths of 100 to 150 feet with favorable soil conditions. Depths can be increased if hole is drilled before insertion. Coring depth limits are based on drilling method used. Vendor information indicated that depth is limited to level of the water table. In addition, soil permeability can affect depth. |
| Production Rate: | Sample is available quickly. |
| Investigation Derived Waste Volume: | Small volume of waste. |
| Technology Status: | Commercially available and routinely used field technology. |
| Certification/Verification: | Technology has not participated in CalEPA certification and/or CSCT verification program. |
| Relative Cost per Sample: | Least expensive. |
Limitations:
ASTM Standards:
| D 5314 - 92 | Soil Gas Monitoring in the Vadose Zone. |
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