InterPhase's Standard Operating Procedure For Soil Gas Sampling
|Direct-push sampling technology refers to samplers that are inserted into the ground without the use of drilling to collect soil, soil gas, and groundwater samples. This technology produces no drilling wastes or soil cuttings and does not require use of drilling fluids or water. InterPhase utilizes Geoprobe 5400, 4200, 540M, 4220 (Kawasaki Mule) and the Deep Sampling Direct-push system and direct-push tools. These tools are able to collect samples at depths greater than 50 feet, depending on soil conditions. InterPhase provides the following direct-push services:|
|-Discrete soil sampling
-Continuous soil core sampling
-Grab groundwater sampling
-Installation of small diameter monitoring wells
-Soil gas sampling to depths of over 50 feet under ideal conditions
InterPhase provides sampling and real-time chemical analysis of volatile organic compounds (VOCs) in soil gas or ambient air. These methods have been designed to maximize accuracy and minimize contamination. the methods meet or exceed level III QA/QC requirements and are in accordance with the California Regional Water Quality Control Board (CRWQCB) Well Investigation Program (WIP).
Soil Gas Sampling
Sampling probes, consisting of 3-foot sections of flush-threaded, 1 1/4 inch hardened alloy steel rod tipped by an expendable steel point, are driven into the ground to the target depth. The probe is withdrawn to release the expendable tip and allow soil gas flow. Soil gas samples are collected by filling a syringe from an unbroken virgin length of 1/4 inch polyethylene tubing installed within the bore of the probe. The tubing is connected via an adapter to the tip of the deepest probe rod.
Soil Gas Sampling Apparatus
InterPhase uses the "Post-Run" method of sampling. This means that sampling tubing is not carried in the probe rod during probe driving, but rather inserted down the borehole once the appropriate sample depth is reached. Sampling probe rod consists of 1 to 2-inch hardened steel. Gas samples are collected from the point holder adapter mounted on the distal (deep) end of the sampling train. A stainless steel adapter is connected to 1/4-inch clean, virgin polyethylene tubing, lowered down the bore of the probe string, and mated to the point holder adapter. O-ring connections enable the system to deliver a
|vacuum-tight seal to assure that the sample is collected at the bottom. To ensure a representative sample, discrete volumes of gas are purged to rid the tubing of atmospheric air and to allow subsurface air to enter. The volume of gas removed is determined by the volume of tubing employed and the analytical results of purge volume tests (if performed). Unlike groundwater sampling, purging of a soil gas probe is designed to remove only the ambient air in the system.
After allowing the system to return to atmospheric pressure, a syringe needle is inserted through the wall of the silicon tubing attached to the aboveground end of the sample tubing. A 10-cc aliquot of soil gas is withdrawn from the probe. Duplicate samples are collected as needed.
Summary of Analytical Method for Soil Gas Samples
Sol gas samples are analyzed within 30 minutes of collection in order to preserve the integrity of the vapor sample. Analytes are identified by their respective elution times through the selected columns and detectors. Retention or elution times are compare d with external standards injected in a gaseous, organic, or aqueous phase. The analysis is best described by EPA Methods 8010/8015/8020, analyses for volatile chlorinated hydrocarbons, aromatic species, methane (low concentrations), common solvents such as ketones and alcohols, and substances such as gasoline, diesel, and JP fuels.
Other sampling components include:
-Gasoline and diesel powered AC generators
-Air sampling sorbents, indicator tubes, and low volume pumps
-Rotron and Fuji blowers used for vapor monitoring
-Manometers, pressure and flow gauges, valves, hoses, bushings and other hardware required for air permeability testing