Soil Contamination Countermeasures

Hyogo Prefectural Government Agricultural & Environmental Affairs Department

Environmental Management BureauWater & Air Quality Control Division

Water Quality GroupIINO Hiroo　飯野　博夫

2014.6.25 JICA Training

Contents

1 VOC (Volatile Organic Compounds)

contamination countermeasures (Plants) 　2 Heavy metal contamination countermeasures (urban area)

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○ VOC(Volatile Organic Compounds) contamination spreads out deep into the ground, contaminates the underground water and lasts for a long time

○ Heavy metal contamination remains in the surface layer but sometimes it is difficult to differentiate the nature-derived and artificial ones

○ Once the land is contaminated, remediation measures take a lot of money and time

○ Soil contamination makes a difference in land price 　(Once soil contamination is found, the land value is estimated as almost zero)

Summary of soil contamination countermeasures

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Difference made in soil contamination by substances

・ VOC contamination spreads out deep into the ground and contaminates the underground water

・ Heavy metal contamination remains in the surface layer

Most heavy metals

Volatile organic compounds

aquifer

Hardly-permeable layer

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〔 The beginning of the revelation of contamination〕　 1983 　 The Ministry of Health and Welfare ordered all prefectures to

investigate water supply for TCE (Trichloroethylene) etc.　　　　　　　 Oihara 0.407mg/L, Okidai 0.076mg/L　 　　　　　　（ WHO guideline 　 0.03mg/L ）

1 VOC (Volatile Organic Compound) contamination countermeasures (Plants)

〔Water supply source problem〕　 Dec. 1983 Stopped water supply from the source of the area 　　　

Adjacent cities supported by supplying water from their source Jan. ～ 1984 Installed purification (aeration) apparatus to the source

〔Underground water investigation〕　 Dec. ～ 1983 Conduct well water survey in the neighborhood （ Maximum concentration 10mg/L ） Jan. ～ 1984 Transfer of households using well water to public water

system

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Distribution of Trichloroethylene concentration (unit: ppb)

Jan – March 1984

Manufacturing CRT (cathode ray tube)

Usage of TCE

・ Amount

　 Monthly 12 – 14t

‘( Annually 140-160t)

・ Period

　 From 1970 to 1983

Contaminated soil remediation work (excavation process ）Apr. ～ June 1984 　 Excavated and removed about 1,000m3

8Chronological change of distribution of soil contamination

1984.5.7 1985.5.16

〔Monitoring investigation of the neighborhood〕　　・ Chose 20 typical wells as fixed point observation and conducted follow-up

investigation　　・ The spread of contamination rapidly declined after the removal of the contaminated

soil 　　　　　

1984.11.2

9Chronological change of Trichloroethylene concentration in shallow and deep wells in the plant

〔 Countermeasures taken in the plant 〕　　　　　Feb.1984 　 Switched from Trichloroethylene to 1,1,1-TrichloroethaneLater 　　 ・ Started to pump contaminated wells （ shallow wells & deep wells ）　　　　　　 ・ Trichloroethylene concentration declined after switching the raw

materials　　　　 　　 ・ Trichloroethylene concentration declined rapidly after the removal

of contaminated soil

Rem

ova

l of contam

inated soil

shallow well

Deep well

Sw

itch m

ate

rials

TC

E concentration

10Changes of Trichloroethylene concentration in deep wells

〔 Countermeasures taken at deep wells 〕　　　　・ The highest concentration measured is about 6mg/L at the latest survey　・ The concentration of other deep well is declining due to pump water

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○ The excavation of contaminated soil and pump underground water methods were effective for shallow wells inside and outside of the plant

○ However, decline is slow for the concentration of deep wells in the plant and maintains the high level around 6mg/L as in the latest survey

○ Lot of time and labor is necessary to remediate once contaminated soil & underground water. This reminds us of the difficulties of solving this problem

Summary & Challenges

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2 Heavy metal contamination countermeasure (Urban area)

・ Kawanishi city is located in the metropolitan area and its suburbs like Osaka or Kobe

・ Central North Area is situated in the center part of the city　（ Area about 24ha ）

・ The area expanded once thanks to the local leather industry but now it is in decline

Future initiatives toward redevelopment

Kawanishi

Central North Area

Osaka

Kobe

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Jan.1983 Mar. 2002

Central North Area （ Full view ）

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Image of Redevelopment of Central North Area

A bird’s eye view

Seseragi no michi (A path along a shallow)

(provisional name)

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〔 Soil Contamination Investigation〕　 In the past Used hexavalent chromium at leather plants

　 Feb.2003 　 Enforced Soil Contamination Countermeasures Law○ Close the plants before law enforcement → exempt from this law （ No obligation for investigation ）○ Close the plants after law enforcement → subject to this law ( Obliged for investigation )

※ It is necessary to make clear the current contamination condition for the future site substitute hereinafter→ Gave guidance to conduct voluntary survey in accordance with the law for the areas both within and out of the range of law enforcement and to increase the number of items to be analyzed

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Soil Investigation Results (Kawanishi city & business operators)

・ As a result of investigation of about 97,000m2, about 18,630m2 was contaminated in area

・ Target substances were Hexavalent Chromium compounds, Lead, Arsenic, Fluorine and Boron and their compounds

・ No contamination was detected in the water quality survey of underground and water way in the area

・ Countermeasures like excavation & removal etc. were taken for soil estimated to be contaminated artificially

Soil investigation points

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1 Conduct soil contamination status investigation of areas not surveyed yet

2 Before conducting site substitute in redevelopment projects etc., be sure to trace back the history of soil contamination and usage still farther(There are cases that current residential house used as plant using hazardous substance in the past)

3 The heavy metal soil contamination of this area is difficult to identify the source of pollution; nature-derived or artificial

Problems and Challenges