Soil and Groundwater Contamination Survey and Countermeasure Technologies

Category of Tchnology	Survey	Soil Gas Survey Method
Media	Soil Gas
Contaminants	Volatile Chlorinated Organic Compounds (TCE, PCE, etc) Semi Volatile Chlorinated Organic Compounds (PCB, etc) Volatile Hydrocarbon (Benzene, etc)
	Applied (Demonstrated) Substances	Volatile Chlorinated Organic Compounds
Scope	Concentration Range	Detective sensibility will be 10 ppbv if 100 ml of soil gas is poured into 1 ml of hexane.
	Hydrogeological Conditions	Unsaturated	Permeable Layer
	Chemical Soil Properties
	Other Remarks	Contaminants are absorbed by hexane on-site for gas chromatographic analysis.  This is a relatively sensitive survey method available for analysis by ordinary research institutions, allowing identification of individual substances.
Technology Description	Classification
	Status	Fully Commercialized Soil and Groundwater Countermeasure Test Study (Performed 1993)
	Outline of Technology	Soil gas is taken by a gas-tight cylinder from the bottom of small holes dug for the purpose, and volatile substances in the gas is absorbed by hexane contained in a mini vial on-site, then to be taken to laboratory for gas chromatographic analysis. Generally, some deciliters of gas is taken and absorbed to some milliliters of hexane, although the volume depends on the concentrations in the gas.
	Required Pre- and Post-treatment
	Enhance Effectiveness through Combination	Linear survey method, to which the soil-gas method is applied, for surveying the plume containing contaminated groundwater and for searching the contaminant source.
	Case History	Work time at the site is mostly used for pouring the gas into hexane.  The time can be saved by using a large number of gas sampling devices. The soil gas test surveys in two areas, where the contaminant sources were identified in advance, have proven that it is possible to detect the contaminated gas at spots 22 m to 29 m away from the contaminant source.  This method ranks between the gas detection tube method and high sensitivity methods, such as “Mobilabomethod, in terms of the analysis sensitivity.
	Application Examples	This soil-gas survey technology is widely used to locate the contaminant source and to measure the concentrations, ranging from low to high, in areas where the gas is highly contaminated within a plant site, etc.
	Limitations	Fixing the gas contents to hexane is the most time-consuming part of the work.  It also takes time to get results of the laboratory analysis of the sampled materials.
	Properties of Treated Soil	-
Schematic Flow Process	Sampling of Soil Gas and Absorption of Volatile Components to Hexane
Applicability	In Situ Applicability	Possible
	Ground Structures	Applicable even if Ground Structures are Present *
	Required Excavation	Sampling holes should be about 2 cm to 3 cm in diameter and about one meter deep.
	Groundwater Extraction	None
	Required Space	Space for soil gas sampling work.
	Operational Time	-
	Installation Time	On-site work time is comparable to that of the gas detection tube method.  Laboratory analysis takes time.
	Maintenance and Control Requirements	-
	Additional Remarks	* Concrete floors must be dug separately by cutters.
Secondary Impacts to Environment	Secondary Treatment Required?	-
	Effects on Living Environment
	Additives	-
	Possibility of Contaminant Spreading	None
	Secondary By-products	-

• Understanding the Contamination Survey and Countermeasure Technology Description Sheet
• Where to make contact

Soil Environment Management Division, Water Environment Department, Environmental Management Bureau, Ministry of Environment
Tel: +81-3-5521-8319
E-mail: MOE@env.go.jp