Solution for the Environmental
Protection of Soil and Underground Water
SEIICHI TERAKURA* 1

HIDEO SUZUKI* 1

SEIJI KOBAYASHI* 1

NAOYUKI KAMISHIMA* 2

TORU ETO* 3

SHIGEKAZU HATANO* 4

The Soil Contamination Countermeasures Law came into force in February 2003, and Mitsubishi Heavy Industries, Ltd. (MHI) was registered as a licensed survey institution. Thereupon, MHI started a large-scale soil survey
project and completed it in November 2003. Further, MHI completed on-site remediation of PCBs-contaminated soil,
for the first time in Japan, in March 2003, and subsequent work ordered by a private company was successfullycompleted in January 2004. MHI, answering the needs of society, deals with the whole process from survey to countermeasures, thereby offering solutions to soil and underground water environmental preservation.
(2) The presence of soil contamination is estimated.
(3) The survey plan (survey density etc.) is developed.
(4) The surface soil layer is surveyed to 2-dimensionallylocate the positions where pollution is present.
(5) The soil is 3-dimensionally surveyed in detail to obtain the depth of soil contamination.
(6) Based on the result of such survey, a countermeasure work plan is developed and carried out.
Thus, soil survey will proceed stage-by-stage basedon the result of each preceding stage. MHI has anestablished system to carry out a consistent operationfrom survey through to countermeasure implementation, thereby offering a total solution to thepreservation of the soil and underground water environment.
2.2 Status of the Soil Contamination Countermeasures Law enforcement
The status of the enforcement of the Soil Contamination Countermeasures Law as of 15 November 2003
shows that a total of 374 locations have been scheduled
to be surveyed, of which work at 205 locations has been
postponed, and 65 locations have been surveyed, with
reports submitted already or now under preparation.
Thus, although surveys at many locations have been
postponed, these locations will eventually be surveyed
in the future.
Further, some financial institutions have statedthat they would reduce to zero the valuations of someland properties in some specific areas listed on theirproperty ledger if soil pollution was discovered on theland. In the real estate business, soil survey is becoming essential before any transaction, so that thereal estate business conditions are drastically changing in connection with soil pollution due to theenforcement of the Soil Contamination Countermeasures Law.

1. Introduction
The history in Japan of soil pollution developing intosocial problems goes back to the Ashio Copper Mine Mineral Poisoning Incident, which took place in 1880. In the
1960s soil pollution by cadmium brought about serious
health problems, and in the 1980s cases of soil and underground water contamination by volatile organic
compounds (VOCs) such as trichloroethylene and dioxins etc. were discovered one after another.
In recent years, cases of discovery of contamination
have drastically increased as voluntary environment surveys have become more common for redevelopment of
ex-plant/factory sites, for acquisition of ISO 14000, or
for preservation and confirmation of the economic values of land properties to be acquired or sold.
The Soil Contamination Countermeasures Law wasenacted on 22 May 2002 and came into force on 15 February 2003, making soil survey compulsory andstandardizing the survey procedure, thereby opening a
new era for all phases of countermeasure procedure, including soil and underground water contamination
survey and remediation.

2. Survey based on the Soil Contamination Countermeasures Law
2.1 Soil Contamination Countermeasures Law
The purpose of the Soil Contamination Countermeasures Law is to protect peoples' health by defining the
subjects of survey for determining soil conditions and byproviding countermeasures to prevent danger to humanhealth caused by soil contamination.
The survey of soil is conducted by the following
procedure:(1) The history of the subject land property is surveyed
by using publicly available data and interview results.
*1 Kobe Shipyard & Machinery Works*2 Technology Planning Department, Technical Headquarters*3 Mitsubishi Jyuko Kankyo Engineering*4 Tsurui Chemical Co.,Ltd.

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 41 No. 4 (Aug. 2004)1

2.3 Approach to soil survey
MHI participated in the soil survey/remediation business in 2000 and was registered as a licensed survey
institution under the Soil Contamination Countermeasures Law in January 2003. During the period from June
2003 to November 2003, MHI carried out a soil survey
project of the largest class, based on the Soil Contamination Countermeasures Law.
This project was at an ex-factory site of approximately
180 000 m2, and was carried out as to all 25 pollutants
designated by the Soil Contamination Countermeasures
Law. This survey project is outlined in Table 1
1. Approximately 2 400 samples were analyzed in this survey. In
order to perform the survey fast, a self-moving boring1.
machine (Geoprobe) was used, as shown in Fig. 1
The project was completed successfully in a shorttime with full information control, employing past survey experience and comprehensive engineering
capability. Further, the method of the survey and thepossible health effects caused by industrial contamination, etc. were explained to the neighbors, and where
the survey discovered any contamination, a corresponding countermeasure plan was compiled.

operation rate. This method has the advantage that theland can be used immediately after excavating all thepolluted soil. Off-site soil remediation is the mainstream
method in the Netherlands, an advanced country as far
as soil remediation is concerned, and this method will
be adopted more often in Japan in the future.
Thus, low cost and short time treatment techniques
are being developed for practical application with VOCs
and heavy metal pollutants, but there have been no techniques easily acceptable by the public that are applicableto PCBs, which is difficult to deal with. Thus, the establishment of measures for dealing with PCBscontaminated soil has long been delayed.
3.2 PCBs-contaminated soil remediation technology
In July 2001, the Law for the Promotion of Environmentally Sound Destruction of PCB Waste came into force.
The demand for PCBs contaminated soil remediation is
expected to grow as a result of interaction between theacceleration of PCBs waste and enforcement of the Soil
Contamination Countermeasures Law.
At the present time, PCBs-contaminated soil
remediation techniques include the solvent extraction
system(1), a soil melting system, a base catalyzed decomposition system, an anaerobic thermal system, etc., andwidespread efforts are being made on the laboratory levelto adapt them to practical use.
MHI imported a solvent extraction method from theUnited States, which is considered to be publically acceptable as a PCBs-contaminated soil remediation
system. MHI successfully combined the solvent extraction system with its own solvent handling techniques
because MHI is a top manufacturer of solvent gas-treatment plant. As a result, MHI has built up its own
treatment system in compliance with the relevant Japanese laws and regulations and adaptable to Japanesesoil and contamination conditions.
The solvent extraction system extracts and separates
pollutants from soil by soaking the contaminated soil ina solvent. The stability of this method is high as the treatment is carried out at normal temperature and pressure,and the treatment cost is low.

3. Soil remediation work
3.1 Soil remediation technology
The techniques that are inexpensive, workable in ashort period of time and easily accepted by the public,
are required for soil remediation. Especially, much is
expected of both on-site soil remediation and off-site soil
remediation by low cost techniques.
On-site soil remediation can be conducted without
excavating polluted soil, but it used to require a longtime to complete in cases of soil contamination with
VOCs. Recently, however, a biological technology whichallows soil remediation quickly has been developed, and
MHI has started to study use of it.
On the other hand, off-site soil remediation can be
conducted at low cost using a large facility with a highTable 1 Outline of survey work
Item
Survey area
Substances
subject to survey

Remarks

180 000 m2
VOCs, heavy metals,
Alkyl mercury isagricultural chemicals,
not included.
etc.: 25 substances in all..
.

443 points
1 344 points
6 points

Each number of
excavation points
includes duplicatedpoints.

..
.

845 samples
1 524 samples
7 samples

The number of VOCs
analysis samples
for soil and soil gas
analysis.

Excavation points
VOCs
Heavy metals
Agriculturalchemicals, etc.
Analyzed samples
VOCs
Heavy metals
Agriculturalchemicals, etc.

Fig. 1 Self-moving boring machine (Geoprobe)

Details

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 41 No. 4 (Aug. 2004)

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Solvent
recovery
installation

Refinedsolvent tank

Solvent refining
installation

Discharged
solvent tank
Extraction ExtractionbinbinWater treatment
installation

Extracted
PCBs tank

Treatedwater

PCBs
treatment
facility

ExtractionbinCleaned soil

Contaminated soil

Fig. 2 Solvent extraction system treatment flow

Figure 2 shows the treatment flow of this system. Thissystem consists of the following three installations.
(1) Contaminated soil remediation installation
The contaminated soil remediation installation consists of extraction bins in which contaminated soil isfilled, a refined solvent tank to store the refined solvent, a discharged solvent tank to store the solvent
after extraction, and pumps. Contaminated soil isfilled into the extraction bins, the solvent is poured
in from the refined solvent tank, and the contaminated soil is soaked in the solvent in the extraction
bins to extract and separate the pollutants.
At this time, the water contained in the contaminated soil is also extracted. After extraction, thesolvent is discharged from the extraction bins andstored in the discharged solvent tank. By repetitionof this process, the contaminated soil can be cleaned
till the required cleanliness is reached.
This is a highly reliable system, without mechanical problems, since it adopts a simple extraction
method wherein the contaminated soil is not stirred
mechanically but remains still in place. Further, it iscapable of lot-by-lot treatment control.

(2) Solvent refining installation
The solvent refining installation consists of a solvent
refining tower and a PCBs enriching tower. Firstly, inthe solvent refining tower, the PCBs and water is separated from the discharged solvent containing PCBs andwater. After the solvent is refined, the solvent is sent to
the refined solvent tank for re-use. Secondly, in the PCBs
enriching tower, the pollutant is separated from the water so as to be concentrated and treated separately. The
separated water is discharged, treated in a water treatment installation and then discharged out of the system.
In the process of treatment, even a minute content
of PCBs cannot be allowed to remain in the solvent orin the separated water. MHI has successfully constructed a compact mobile-type refining installation thatremoves all PCBs, enabling economical on-site recyclingof the solvent.
(3) Solvent recovery installation
The solvent recovery installation consists of a blower,
condenser and activated carbon tower. Steam is sent to
the extraction bins to evaporate the solvent remaining
in the extraction bins, and the evaporated solvent isdrawn by the blower from the extraction bins, cooled andcondensed by the condenser and recovered by adsorbing
it in an activated carbon tower. The solvent absorbed by
activated carbon is separated by steam so that the carbon may be re-activated. The soil after remediation canbe used to backfill the original location.
This system has been employed successfully many times
in the United States, one of the most advanced countries
as regards soil remediation technology, and use of it has
been authorized by the Environment Protection Agency(EPA) of the United States. This system, depending on solvent selection, can also extract and separate agriculturalchemicals and dioxins. The contaminated soil has a complicated variety of soil quality, types of pollutants anddensities of co-existing materials. Economical, safe anddependable treatments are being proposed using systems
capable of fast and high accuracy evaluation, most suitable solvent, extraction treatment cycle and remediation
performance to subject soil, utilizing the compact andsimple real sample testing facility, as shown in Fig
Fig.. 3 .

Fig. 3 Actual soil sample testing facility

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 41 No. 4 (Aug. 2004)3

3.3 First on-site PCBs contaminated soil remediation
project in JapanIn March 2001, used high-voltage capacitors were foundto have been unlawfully dumped in Kita Ward of Kobe
City, and some soil was discovered to have been contaminated with PCBs that had leaked from the capacitors. In
fiscal 2002, a verification test(2)-(4) of this PCBs contaminated soil was completed, using the solvent extraction
system of MHI, this being the first on-site PCBs contaminated soil remediation work in Japan carried out as a joint
research project by MHI and the National Institute forEnvironmental Studies and the municipality of Kobe.
In order to confirm the safety of this treatment system
prior to the operation on site, a preliminary test was performed by analyzing the PCBs concentration at each
emission point (where PCBs may possibly leak in the worstcase) using laboratory testing equipment and actually
sampled contaminated soil. Table 2 shows the results. The
test of the actually contaminated soil verified the capability of the treatment system to consistently reduce theconcentration down to below the legal PCBs environmental quality standard for soil, and it also confirmed thatthe treatment system is capable of removing dioxins.
Based on the results of the preliminary test, the soil
remediation plant was installed on site, and on-site soil
remediation was started. Table 3 shows the results of theverification test by the solvent extraction system for all
47 lots of PCBs contaminated soil. The completion of thetreatment was determined when the soil treated cleared
the legal environmental quality standard for soil.
The solvent extraction treatment cycle was set withsome design margin to ensure sufficient soil remediation
after 8.4 cycles on average. Further, the safety of the treatment system as a whole was confirmed by periodical
monitoring of PCBs concentration, etc. at the verification
test equipment and surrounding environment, with results satisfying the established control target values. The
soil thus cleaned was used to backfill the original location.
During the on-site PCBs contaminated soil remediation
performed this time, precious data and know-how which
the laboratory tests could not provide were obtained, andthe actual soil remediation performance of the solvent extraction system and the negligible PCBs emission to theenvironment were confirmed. This test provided us witha foothold to start upgrading treatment performance andreducing treatment cost for various types of contaminatedsoil containing PCBs and dioxins, etc. by means of theselection of the solvent most suitable for the properties ofthe pollutants to be removed and the properties of thecontaminated soil, and by upgrading the solvent extraction system, and so forth.

Table 2 Results of preliminary test
Item

Soil before remediation

Test results

PCBs concentration in soil

(mg/kg)118

DXNs toxicity equivalent(pg-TEQ/g)

830

PCBs concentration in leachate (mg/L)
Soil after remediation

PCBs concentration in soil
DXNs toxicity equivalent

Discharged water

PCBs concentration

PCBs condensed liquid PCBs concentration
Tank vent gas

PCBs concentration

Remarks

Law Concerning Special Measures against Dioxins
Environmental Quality Standards for Soil
(1 000 pg-TEQ/g)
Environmental Quality Standards for Soil(not detected)

Not detected(mg/kg)0.1(pg-TEQ/g)

2.4(mg/L) 0.0005 - 0.0023(wt%)

Water separated from contaminated soil:
Discharged Water Quality Standards (0.003 mg/L)

18(mg/m3N)

0.00005

Exhaust Gas Quality Standards (Provisional)(0.15 mg/m3N)

Table 3 Results of verification test
Item

Test results

Remarks

92

Treated soil quantity (ton)Before remediation: average 88 mg/kg
Environmental Quality Standards for Soil(not detected)

PCBs concentration in soil after remediation (mg/L)

Not detectedin any lot(mg/L)

Less than 0.003

Water separated from contaminated soil etc.
Discharged Water Standards (0.003 mg/L)

Ventilation air of soil
handling building(mg/m3N)

Less than 0.0015

Exhaust Gas Quality Standards (Provisional)(0.15 mg/m3N)(mg/m3N)

Less than 0.0015

PCBs concentration in discharged water

Environment
monitoring PCBs
concentration

Tank vent gas

Downstream river/pond (mg/L)

Not detected

Environmental Quality Standards for
Underground Water (not detected)

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Technical Review Vol. 41 No. 4 (Aug. 2004)

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The successful on-site soil remediation resulted in thissystem receiving public acceptance so that MHI was able
to obtain a second project from a private company at another site. The installations used in the mentioned on-sitetest were moved to the second project site, and the onsite soil remediation for this project was commenced in
September 2003 and was completed successfully in January 2004.
3.4 PCBs contaminated soil remediation scheme
The solvent extraction system is now being employed
in a project to remove PCBs-derived dioxins from contaminated soil in Ota Ward of Metropolitan Tokyo. This
Ward had been designated for the first time within the
country as an area subject to the application of the Law
Concerning Special Measures against Dioxins.
In this project, which is scheduled to commence infiscal 2004, decisions have already been made to separate PCBs from the contaminated soil by the solvent
extraction method and to treat the separated PCBs by
MHI's hydrothermal decomposition system at a PCBs
treatment facility being prepared by Japan Environment
Corporation in Koto Ward.

Seiichi Terakura

Hideo Suzuki

Naoyuki Kamishima

Toru Eto

Thus, the MHI scheme for detoxication of PCBs contaminated soil using MHI's proprietary separation anddetoxication technology is now being recognized and more
widely employed.

4. Conclusion
MHI will continue to make efforts to reduce the costof soil survey with keeping the survey quality, and develop new technologies to upgrade soil treatment capacity
and reduce total cost by increasing the equipment size
and installation of off-site plants.
Further, MHI will expand its activities into not only
PCBs and dioxins but also poisonous substances which
are increasingly causing pollution problems, such as agricultural chemicals, and will apply to contaminatedsediment in addition to contaminated soil.
In the future, MHI, taking advantage of its capability to undertake the whole task of soil remediation fromsoil survey to countermeasures, will continue to propose
solutions to the preservation of soil and undergroundwater environment and so to contribute to the needs ofsociety in their own way.

References(1) Eto et al., Remediation of PCBs Contaminated Soil by Solvent Extraction Method, Technical Journal of Geo-Environmental Protection Center No.6 (2003) p.33
(2) Takigami et al., Remediation of PCBs Contaminated Soil by
Solvent Extraction Method and Monitoring, 9th Conference
for Contamination of Soil & Underground Water and Countermeasure No.139 (2003)(3)Sakai et al., Development of the Monitoring Technique inRemediation of PCBs Contaminated Soil - The First
Remediation Verification of PCBs Contaminated Soil in Japan -, The Monthly Journal of Global Environment April(2004) p.98
(4) Eto et al., The First Success in on-site Remediation for PCB
contaminated Soil, Mitsubishi Juko Giho Vol.41 No.1 (2004)
p.34

Seiji Kobayashi

Shigekazu Hatano

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 41 No. 4 (Aug. 2004)

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