Soil and Groundwater Contamination Survey and Countermeasure Technologies

Category of Tchnology	Treatment	In Situ Extraction Technology
Media	Groundwater, Soil Gas
Contaminants	Volatile Chlorinated Organic Compounds (TCE, PCE, etc) Volatile Hydrocarbon (Benzene, etc)
	Applied (Demonstrated) Substances	Trichloroethylene (TCE)
Scope	Concentration Range	High recovery rate achievable at high concentration sites
	Hydrogeological Conditions	Saturated Unsaturated	Permeable Layer
	Chemical Soil Properties
	Other Remarks
Technology Description	Classification
	Status	Under Demonstration Soil and Groundwater Countermeasure Test Study (Performed 1997)
	Outline of Technology	beneath buildings through horizontal wells, utilizing a method similar to the installation of gas pipelines.The drilling head uses a high-pressure water jet to drill a pilot hole. The position of the drilling head can be monitored by a transmitting signal from the drilling head and an above ground receiver, as well as the summarized and processed data from an internal inclinometer. The drilling direction could be directed and monitored.  After completing the pilot hole, the screened extraction well will be pulled in it’s final position, to extract soil gas or groundwater by suction.
	Required Pre- and Post-treatment	Soil Vapor Extraction (SVE) and groundwater pumping need a treatment of the extracted media, congruent to the standard vertical SVE or “pump-and-treatapplications.
	Enhance Effectiveness through Combination
	Case History	This method is applied for countermeasures of TCE and PCE contamination in soil and groundwater. An SVE application with a screen length of 15 m developed a radius of influence of 4 to 5 m by a soil gas extraction rate of 2 m3/min. After an operation time of 1080 h, a total amount of 4.6 kg TCE was recovered. Although it was possible to pump groundwater with a double jet pump, high recovery rates couldn’t be archived due to a low groundwater level.
	Application Examples	The installation method for the horizontal wells is usually used for the installation of gas supply pipes. In other countries it is also used as a remediation technique in a wider range.
	Limitations	Directed horizontal drilling has the potential to install an extraction well in the source zone, but foundation structures, underground structures like pipelines, and gravel layer may inhibit the described drilling method.
	Properties of Treated Soil	-
Schematic Flow Process	Soil and Groundwater Remediation by Horizontal Well
Applicability	In Situ Applicability	Possible
	Ground Structures	Applicable even if Ground Structures are Present
	Required Excavation	Partial excavation
	Groundwater Extraction	If applied for groundwater treatment, groundwater extraction is necessary.
	Required Space	4 m x 8 m for installation of the drilling rig and working space
	Operational Time
	Installation Time	9 hours for a well with 92 mm casing diameter and 96 m of total well length.
	Maintenance and Control Requirements	Monitoring of groundwater- and soil gas extraction rates and recovered contaminant concentrations is required.
	Additional Remarks	Effluent Water Treatment    Off-gas Treatment Waste Treatment
Secondary Impacts to Environment	Secondary Treatment Required?	Effluent Water Treatment    Off-gas Treatment Waste Treatment
	Effects on Living Environment	Noise
	Additives	Water
	Possibility of Contaminant Spreading	The establishment of the pilot hole by a high-pressure water jet might cause migration of contaminants, but the used water volume is only about 16 l/m2 and it is supposed that the impact will be small.
	Secondary By-products	None

• 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