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Advisory Council on the Environment

Report of the 65th Environmental Impact Assessment Subcommittee Meeting

(ACE Paper 48/2001)
For advice

INTRODUCTION

At its meeting on 26 November 2001, the Subcommittee considered the EIA report on the demolition of Kwai Chung incineration plant.

ADVICE SOUGHT

2. Members are requested to advise whether the EIA report should be endorsed.

VIEWS OF THE SUBCOMMITTEE

Demolition of Kwai Chung Incineration Plant
(ACE-EIA Paper 16/2001)

3. The Kwai Chung incineration plant was put into service as a municipal solid waste incinerator in 1978 and it ceased operation in 1997. The phasing out of the Kwai Chung Incinerator fulfills the Government policy set out in the "White Paper : Pollution in Hong Kong - A time to act" with significant environmental gains. If the premises of the plant are not demolished, they will progressively dilapidate and fall into disrepair, potentially causing problems to the surrounding environment and the general public. Demolition of the incinerator will release the site for future beneficial use.

4. The project will involve the demolition of all the buildings including a 150 m high chimney, the clearance of land and decontamination of contaminated soil. The Director of Environmental Protection has advised that the EIA report was suitable for public inspection.

Views and Recommendations of EIA Subcommittee

5. Members' concerns on the project were mainly on future land-use, the treatment of soil contaminated with heavy metal and reuse on site, the treatment of dioxin and furan contaminated ash waste, the demolition of the chimney, the removal of asbestos, landfill gas hazard, and engagement of consultants.

Future land-use

6. On the future land-use of the site, the project proponent indicated that the area was presently zoned for Government, Institution or Community purpose but the exact land-use had yet to be determined. Judging from its proximity to the sewage treatment plant, trunk road and port activities, the site would unlikely be used for residential purpose.

Soil contaminated with heavy metals

7. On member's concern about the treatment of soil contaminated with heavy metal and re-using the treated soil on site, the project proponent pointed out that the soil would be mixed with the appropriate amount of cement to form small blocks so as to immobilize the contaminants. Subject to the passing of the toxicity characteristic leachate procedures (TCLP) test, the blocks could be returned to the ground and there would be no need for future users to treat the soil. According to the proponent, the ground water in the site was not mobile, hence the impact on ground water in the area would be limited. To ensure safety, the project proponent would adopt for this exercise stringent standards in Holland which were meant for protecting groundwater to be used for drinking purposes. Furthermore, the project proponent pointed out that the level of soil contamination was not particularly high. The TCLP test would ensure the immobility of the heavy metals before reusing the soil on site. In addition, re-using the treated soil on site could help save the capacity of landfill.

Soil contaminated with petroleum hydrocarbon, etc

8. On the treatment of soil contaminated with petroleum hydrocarbons and polynuclear aromatic hydrocarbons, the project proponent indicated that it was not possible to treat the soil by the thermo destruction method given the existence of other co-existing contaminants in the soil. The soil contaminated with petroleum hydrocarbons would be disposed of at landfills.

Dioxin and furan contaminated ash waste

9. On the disposal of dioxin and furan contaminated ash waste, the proponent explained that they had not identified any standard international practice in the disposal of such contaminants. After discussion with authorities concerned, they decided to adopt a more cautious approach. The ash waste would be mixed with cement, sealed in polythene-lined steel drums and disposed at landfill. Before the actual treatment process, there would be a pilot mixing of the ash with progressively greater proportion of cement to find out the appropriate ratio to prevent the leaching of the contaminants. The process would be scrutinized by EPD in accordance with stringent standards. The treated ash waste would be further tested on the dioxin level before disposal at landfill.

10. On the possibility of exporting the contaminated ash to other countries for treatment and disposal, the project proponent pointed out that the estimated amount to be handled was only 20 m3 which was considered insignificant. If the treated ash waste failed to meet the TCLP test, it would be delivered to the Chemical Waste Treatment Centre in Tsing Yi for treatment. Since the proposed method was a practicable and robust solution, the project proponent did not consider that transferring the materials to other countries was a better option.

The demolition of the chimney

11. Regarding the demolition of the chimney, the project proponent indicated that they had considered the methods set out in the Draft Code for Demolition Practice in Hong Kong and decided that for safety reason they would adopt the top down conventional method. The blasting method which had been used for the Tsing Yi Chimney, located in a remote site without constraints in the surroundings, was considered the last resort. The project proponent also pointed out that a resident engineer would base on site, with experienced support staff, to carry out daily supervision of the demolition works, including the checking of scaffolding to ensure safety

12. On the possibility of deferring the demolition of the chimney to after a decision was made on the land-use, the project proponent explained that it would be too late to start the works when the land-use was determined because the demolition plus remediation works would take about three years. Furthermore, deferring the work would not be cost-effective.

Removal of asbestos

13. On the removal of asbestos, the project proponent explained that the works concerned would be carried out by Registered Asbestos Contractors according to methods prescribed in the Air Pollution Control Ordinance and the relevant code of practice. The safety of the workers would be regulated by the Occupational Health and Safety Ordinance. The workers would be required to put on protective uniforms and use safety equipment.

Landfill gas hazard

14. On landfill gas hazard, the project proponent pointed out that a standard qualitative assessment that was adopted in all other landfill gas assessment was made. On the basis of the assessment, various protection and precautionary measures would be adopted.

Consultancy for Design and Construction

15. On the issue of whether the same consultant would be engaged for the Design and Construction Consultancy, the Subcommittee noted that as far as the project and the independent environmental checking were concerned, the permit conditions of the project would specify that the two tasks could not be carried out by the same consultant.

Conclusion

16. The Subcommittee agreed to recommend the EIA report to the Council for endorsement without conditions while noting a member's urge for more caution in the treatment and disposal of dioxin contaminated ash waste and more proactive identification of chemical waste treatment for such contaminants.

EIA Subcommittee Secretariat
December 2001

 

 

 

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