KIRTLAND AIR FORCE BASE ALBUQUERQUE, NEW MEXICO ...

APPENDIX B
easily be penetrated with this method. Hydraulic pounding equipment can also be used to drive the rod.
In some cases, due to hard or cobbly soil, the presence of a concrete pad, or a depth requirement beyond
that obtained by hand, the hole must be advanced with some type of drilling apparatus (i.e., hand auger,
rock drill, pothole digger, etc.). As an alternative to pounding a probe, a hole can be augered using hand
or powered equipment.
A sampling hole depth of a least 2 ft is required to ensure the exclusion of ambient air and provide
adequate contaminant detections. Advancing the sampling hole to greater depths will facilitate the
detection of contamination in deeper soil intervals and groundwater. For most sites with soil
contamination or relatively shallow groundwater, a depth of 3 to 4 ft provides adequate detection
capabilities with a reasonable number of samples each day. Typically, if the holes can be advanced
manually, an average of 15 to 25 samples can be collected daily. If the holes are advanced with the use
of powered equipment, an average of 10 to 20 samples can be collected daily.
After the sampling hole is advanced, a sampling probe is placed in the hole. The sampling probe may
have an open end or slots to allow gas flow into the probe. The slots or open end must be protected from
becoming plugged. Some methods combine the pounding and sampling probe in a single unit. For
sampling holes with a diameter of less than 1-inch, soil should be packed around the probe to minimize
the introduction of ambient air into the hole. For larger diameter sampling holes, a packer, preferably an
inflatable one, should be used to exclude ambient surface air.
After the sampling probe is in place, the soil gas is drawn to the surface using a vacuum pump. The
pump can be hand or power operated. Several sampling probe volumes should be removed to purge the
probe of ambient surface air. The gas is then collected using a syringe or pumped into a bag or bottle.
The sample collection container must be clean, inert, and have appropriate seals. Sampling bags should
be made of Tedlar ® , sampling bottles should be amber glass with Teflon ® seals, and syringes should be
gas-tight glass and Teflon ® . To prevent contamination of the sample from the pump, the sample should
be collected upwind of the pump. The sample is then either analyzed onsite with a portable GC or sent to
the onsite lab.
Sampling Equipment Decontamination
To avoid cross-contamination and the possibility of false positive readings, the sampling probes and
sample collection equipment should be decontaminated between each use. The probes can be washed
with Liquinox ® or other laboratory-type detergent and rinsed with deionized water. If this too is found to
be inadequate, the sampling equipment can be heated to volatilize any remaining organic compounds.
Sampling equipment should never be decontaminated with solvents since the solvents and contaminants
in the solvents will interfere with subsequent analyses. By periodically analyzing two ambient air
samples, one collected with the sampling equipment (called a probe blank) and one collected without, the
soil gas team can confirm the effectiveness of the decontamination by comparing the two analyses (they
should be identical).
Sample Analysis
The most common methods available to analyze soil gas samples are: (1) field analysis with a portable
gas chromatograph, and (2) onsite laboratory analysis with a laboratory-grade gas chromatograph.
Kirtland AFB
SOPs for Field Investigations B-103 April 2004