8. Land Contamination Assessment
8.1. Introduction
8.2. Environmental
Legislation, Policies, Plans, Standards and Guidelines
8.3. Description of
the Environment
8.4. Description of
Assessment Methodology
8.5. Identification,
Prediction and Evaluation of Environmental Impacts
8.6. Mitigation of
Adverse Environmental Impacts
8.7. Good Site
Practices
8.8. Definition and
Evaluation of Residual Environmental Impacts
8.9. Identification
and Evaluation of Operational Phase Environmental Impact
8.10. Environmental Monitoring
& Audit
8.11. Conclusions and
Recommendations
This chapter presents the assessment of potential land contamination impact associated with the Project. The assessment has taken into consideration the historical and present land usage at the Subject Site for potential contamination source.
Relevant legislation and guidance notes regarding the assessment of land contamination include:
·
Section
3.4.7, and Appendix F of the EIA Study Brief (ESB-243/2012)
·
Sections
3.1 and 3.2 of Annex 19 of the Technical Memorandum on Environmental Impact
Assessment Process (EIAO (TM))
·
Guidance
Manual for Use of Risk-based Remediation Goals (RBRGs) for Contaminated Land
Management
·
Practice
Guide for Investigation and Remediation of Contaminated Land
·
Guidance
Note for Contaminated Land Assessment and Remediation
8.3.1. The Subject Site is located at the existing ash lagoons in Tsang Tsui, Tuen Mun, overlooking the Deep Bay in the north-western New Territories. The Subject Site within area of approximately 30,000m2 (3 hectares) located at the west portion of the Middle Ash Lagoon, was leased to China Light & Power Company Ltd. (CLP) for the storage of pulverized fuel ash (PFA). A location plan of this potential site is shown in Figure 1.1.
8.3.2. Other than the Subject Site, the remaining Middle Ash Lagoon area will be taken over by the Environmental Protection Department (EPD) as an extension of WENT Landfill (WLES). According to the approved EIA report from EPD for the Development of the Integrated Waste Management Facilities (IWMF) Phase 1 (application no. EIA 201/2011), the area directly to the east of the Subject Site is one of the potential sites for the IWMF Phase 1. Further to the east in the East Lagoon, a Sludge Treatment Facilities (STF) development is currently under construction.
8.3.3. The baseline environmental condition of current site area consists of a pool of water over PFA. Thus, any form of land contaminants would be likely found within the PFA constituents. Barring any future change in usage of the site as PFA storage by CAPCO, the environmental condition with respect to the source of land contamination would be subjected to the PFA disposed of at the Subject Site.
8.4.1. In accordance with the prevailing guidance manual/note and practice guide regarding land contamination assessment, the land contamination assessment is focused on the potential soil and groundwater contamination due to former land uses for anthropogenic activities.
8.4.2. The historical land use of Subject Site has been for the storage of water and PFA since the 1980s. A site walkover checklist obtained from Annex C1 of Practice Guide for Investigation and Remediation of Contaminated Land is attached in Appendix 8.1. The site walkover checklist was conducted by the current site owner, and confirmed that as the sole user of the Subject Site, no known contaminations were identified on site, and no chemicals were found on site beside that of PFA. In addition, aerial photos of Subject Site are attached in Figures 8.1-8.4. As the figures show and prove, the Subject Site has been filled with water since 1980s, confirming that there have not been anthropogenic activities for well over 30 years.
8.4.3. Moreover, CLP has constructed protective liners at the onset to prevent leakage of the stored water and PFA. In light of the given statuses regarding the history and current land use, it is determined that there is no land contamination at Subject Site. Nevertheless, good site practices should be enforced during the decommissioning and construction periods.
The major activities involved with the decommissioning and construction of the Project include filling, excavation and levelling works. The decommissioning process is expected to include the deposit of a 1m thick layer of general fill to the mixture of PFA on-site. The use of general fill on top of the PFA will form a stable ground available for future developments on Subject Site. Filling works will also be involved in modifying and expanding the access road. Potential leakage of chemical fuels and lubricant oils from the machinery used for excavation and filling works may contribute to contamination on site. It is anticipated that such chemical spills will be minimal, and would not pose adverse environmental impact on the site.
As no adverse environmental impacts are expected to arise from the decommissioning and construction works, the Contractor will be required to perform good site practices primarily to prevent leakage of stored PFA and water, and secondly to minimize impact on the health of site workers.
8.7.1. A protective liner has been previously installed and maintained by CLP. Responsible personnel shall be requested to maintain the protective liner during decommissioning and construction works throughout the Project programme, so as to prevent leakage of the stored water and PFA.
8.7.2. Other good site practices are recommended during decommissioning and construction works. Some of these precautionary measures are listed as follows:
· Proper personal protective equipment (PPE) if contact with stored PFA/water is necessary; and
· Prevention of workers from ingestion of stored PFA/water.
Residual environmental impact is the net impact remaining with the mitigation measures in place. With the incorporation of good site practices, residual land contamination impact during the decommissioning and construction phase is not expected.
As defined in Section 2.5, operational phase shall be defined as the period when the decommissioning works as detailed in Section 2.6 are completed. The operational phase of the Project shall be an idle buildable land to cater any future developments by the government. Since the operational phase does not involve any equipment operation or human activities, adverse environmental impact from land contamination is not expected.
No environmental monitoring and auditing relating to land contamination are required during decommissioning and construction works.
An assessment of land contamination is conducted based on historical and current land use. Based on the assessment, it is determined that there is no impact from land contamination.