11.              Land contamination

 

Introduction

 

11.1          This section reviews the potential environmental issues associated with land contamination and assesses its implications for the proposed land uses at the site in accordance with the EIA Study Brief Clause 3.4.5.1. 

 

Environmental Legislation & Standards

 

11.2          Two publications issued by the Environmental Protection Department (EPD), ProPECC PN 3/94 - Contaminated Land Assessment and Remediation and Guidance Notes for Investigation and Remediation of Contaminated Sites of: Petrol Filling Stations, Boatyards, and Car Repair / Dismantling Workshops, provide guidance on land contamination assessment.  In ProPECC PN 3/94, it makes reference to the criteria developed in the Netherlands (known as “Dutch List”).  Although there is currently no standard for the clean-up of contaminated soil and groundwater in Hong Kong, the Dutch B level of the Dutch List is normally used as the clean-up target for soil in Hong Kong.  Where groundwater concentrations exceed the Dutch B level, a risk-based assessment is usually required to establish the nature and extent of remediation required.

 

11.3          Provisions for consideration of land contamination issues are given in the Section 3 “Potential Contaminated Land Issues” of Annex 19 “Guidelines for Assessment of Impact on Sites of Cultural Heritage and Other Impacts” of the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM).

 

11.4          The legislation and guidelines relevant to the issue of land contamination, due to the handling, disposal and treatment of contaminated waste in Hong Kong are listed as follows:

 

·             Waste Pollution Control Ordinance (WPCO)

·              Waste Disposal Ordinance (Cap. 354)

·              Waste Disposal (Chemical Waste) (General Regulation (Cap 354), and

·               Code of Practice of the Packaging, Labelling and Storage of Chemical Waste, EPD (1992)

   

Assessment Methodology & Criteria

 

11.5          The objective of the land contamination assessment is to identify and evaluate the potential of ground contamination within the Study Area.  In order to accomplish the objective, the following tasks have been undertaken:

 

i)                    A desktop study to review the current and historical land uses along the alignment of proposed elevated roads.  The study aims to provide a clear and detailed account of the relevant past land history and the present land uses along the alignment, which identifies the contaminated areas with a potential to cause contamination.

ii)                  Identification of works associated with the construction of elevated roads that may have impact on the contaminated sites caused by handling, collection and disposal of the contaminated materials.

iii)                 A review of environmental information in relation to potential contamination have been requested from the Fire Services Department (FSD), Local Control Office (LCO) of the Environmental Protection Department (EPD) and Lands Department (LandsD).

iv)                Site reconnaissances to confirm the existing land uses.

 

11.6          In addition, the following sources of information have been collated and reviewed:

 

i)                    Contemporary and historic Hong Kong Government Survey maps

ii)                  Aerial photographs

iii)                 Hong Kong Geological Survey Solid and Superficial Geology Series Maps

iv)                Historic records of chemical storage / spillage within the Study Area

 

Baseline Conditions & Sensitive Receivers

 

11.7          The Study Area of the land contamination assessment includes the area along the alignment of the proposed elevated roads and existing roads proposed to be widened/modified.

 

11.8          Preliminary information reveals that there are several sites with potential contaminative land uses within the Study Area, the location of these areas is shown in Figure 11.1 and their existing land uses are described below:

·     Site A: an area used as vehicle parking area, open storage area with several vehicle repairing / servicing workshops

·      Site B: Highways Department – Lok Ma Chau Maintenance Yard

·      Site C: an area adjacent to an open storage area, which construction works under Drainage Services Department’s Eastern Main Drainage Channel (EMDC) is being conducted

·      Site D: a site vehicle parking area

·      Site E: an area used as car parks, open storage area and vehicle repairing / servicing workshops 

 

11.9          The review of the Hong Kong and Kowloon Geological Survey Map Sheet 2 indicates that the superficial deposits at Study Area consist of alluvium predominately.

 

Site History

 

11.10      The site history information of the Study Area was obtained by reviewing relevant historical aerial photographs.  Table 11.1 summarizes the aerial photographs which have been reviewed.

 

Table 11.1          Historical Aerial Photographs Reviewed

Year

Height (feet)

Photograph Reference No.

1987

4,000

A09732

1989

4,000

A18205

1990

1,900

A22669

1993

4,000

A36429

1995

3,500

CN11878

1997

3,000

CN16700

1999

1,000

CN23515

2001

2,700

CW31404

2003

3,500

CW46729

             Source of aerial photographs:       Survey and Mapping Office, Lands Department

 

11.11      The changes of land uses at the Study Area are described below:

·         In 1987, the Study Area was occupied by fish ponds and farmland

·         In 1989, San Tin Highway was being constructed in the Study Area

·         In 1990, the construction of San Tin Highway had been completed.  There were no significant human activities / construction took place at the area immediately adjacent to the Highway (including Sites A to E)

·         In 1993, human activities took place in some sites of the Study Area, as listed below:

·         Site A was an area mainly used for container storage and long vehicle parking.  Moreover, the area seemed to be unpaved as observed in the photo 

·         There was construction activity at Site B

·         Site C was used as a container yard and long vehicle parking area.  Moreover, a number of workshops were located in the area.  The area seemed to be unpaved as observed in the photo

·         Site D was an unpaved road

·         Site E was used as an area for vehicle parking, open storage yard and workshops.  The area seemed to be unpaved as observed in the photo   

·         In 1995, some site offices had been built at Site B and some areas at Site B were used for vehicle parking.  However, there was no significant change of land use observed at other sites

·         In 1999, site D was used as a site office.  However, there was no significant change of land use observed at other sites compared to 1995

·         In 2001, part of Site A area had been used for private car parking, while Site D was used as a vehicle parking area.  However, there was no significant change of land use observed at Site B, Site C and Site E

·         In 2003, Site C was no longer an area used for long vehicle parking area and container storage yard.  Site C was observed to be a bare ground from the photo

 

Historical storage / spillage of contaminants      

 

11.12      According to the information provided by FSD, there is no record regarding storage or leakage of dangerous goods within the Study Area for the past 20 years.

 

Existing Land Uses

 

11.13      Information of existing land uses in the Study area was obtained from Lands Department and site reconnaissances conducted on 1 April 2003 and 18 September 2003. 

 

11.14      Based on the site reconnaissance conducted on 1 April 2003, it is confirmed that there are private car parking area and several vehicle servicing / repairing workshops located at Site A.  A site office of Highways Department is located at Site B.

 

11.15      Another site reconnaissance was conducted on 18 September 2003.  It was observed that construction works were being conducted at Site C.  By observation, the excavated soil seemed not to be heavily contaminated.  However, some localised red stains were observed in the soil.  Moreover, it was confirmed that Site D is paved and is no longer used as site office.  There were a few site vehicles parked in the area.  For Site E, since site entry was not allowed, observation could only be made at the entrance of the site.  It was observed that the site consisted of a large area for open storage, car-parking area and several vehicle servicing / repairing workshops. Moreover, ten to fifteen vehicles were observed parked at the entrance of Site E, which the ground was paved.  However, detailed operations of the workshops could not be observed.   

Sensitive Receivers

 

11.16      Construction workers are more likely to be exposed to any potential contaminated material than the future users of the land within the Study Area.  It is because the construction workers could be exposed to potential contaminants during excavation and preparation of foundation works.  Depending on the nature of the contaminants, hazards during preparation of foundations and subsurface services could be significant.  The principal exposure routes for workers include:

 

·          ingestion of contaminated soil through eating, drinking or smoking on site;

·         dermal contact with contaminated spoil; and

·         inhalation of contaminants if they are volatile.

 

Identification of Environmental Impacts          

 

Identification of Potential Source of Impact

 

            Site A

 

11.17      According to the site history information, Site A has been used as container storage and long vehicle parking area since 1993.  In the site reconnaissance, it was observed that private car parking area and vehicle repairing / servicing workshops were located at the site.  The information gathered from interviews with personnel on site indicates that the vehicle repairing / servicing workshops at Site A have been in business before year 1996.  Observation and communication with relevant personnel indicated although no large amount of chemicals and petroleum oils were stored within the area, paints, hydraulic oil, lube oil, solvents and acid batteries were used in the workshops.  Moreover, localized, small-scale oil stains on bare ground were observed.  It is considered that land contamination at the site is likely.

 

11.18      The main expected contaminants from container storage area, long vehicle parking area, vehicle repairing / servicing workshops are fuels, paints, solvents, petroleum oils, and possibly acids.  The potential contaminants associated with the above land uses are listed in Table 11.2.

 

Table 11.2Potential Contaminants associated with historic and present land uses at Site A 

Land Uses

Potential Contaminants

Vehicle Repairing / Servicing Workshops

benzene, toluene, ethylbenzene, xylene (BTEX), petroleum hydrocarbons, solvents, paints, acids (from acid batteries)

Container Storage Area / Long Vehicle Parking Area

BTEX, petroleum hydrocarbons, acids (from acid batteries)

 

 

Site B

 

11.19      According to site history information, Site B has been used as a site office of Highways Department since 1995.  During the site reconnaissance, it was observed that there were a vehicle parking area and several site offices at Site B.  Based on observation on site and information gathered from site office personnel, no chemicals were stored and no vehicle repairing works was undertaken on site.  According to site office personnel, any waste generated on site was handled and disposed properly.  Therefore, it is considered that land contamination at Site B is unlikely.

 

Site C

 

11.20      According to the site history information, Site C has been used as an area for container storage, long vehicle parking and vehicle repairing / servicing workshops since 1993.  According to information gathered from aerial photo review and site reconnaissance, the site was no longer used as open storage and long vehicle parking area in 2003.  Moreover, construction works under Drainage Services Department’s San Tin Eastern Main Drainage Channel (EMDC) Project were being conducted on site during site reconnaissance. 

 

11.21      It should be noted that prior to the commencement of construction works, contamination investigation works at Site C had been carried out and the contaminated soil had been treated/disposed of as suggested in the endorsed Remediation Action Plan (RAP)[1].  Therefore, there should be no further land contamination concern present at Site C.

 

Site D

 

11.22      Based on the site history information obtained from aerial photographs, Site D was an unpaved road in 1993 and the site became a site office in 1997.  In 2001, no site office was located in the area and remained as an area for vehicle parking.     

 

11.23      During the site reconnaissance, it was observed that a few site vehicles were parked in this paved area.  No workshop, vehicle cleaning area or oil stain was observed at site.  Based on the information obtained, it is considered that land contamination at Site D is unlikely.

 

            Site E

 

11.24      According to information gathered from aerial photographs review, Site E has been used as an area for long vehicle parking, open storage and vehicle repairing / servicing workshops since 1993.  As observed from the aerial photos, Site E was not paved in 1999.  Entry of the site was not allowed during the site reconnaissance.  Therefore, observation can only be made at the entrance of the site and it was observed that the site is paved.  Moreover, a vehicle parking area, open storage area and several vehicle repairing / servicing workshops were observed within the site. 

 

11.25      It is considered there is a possibility that the soil at Site E is contaminated because aerial photographs indicated that the site was unpaved and it is used as open storage area and vehicle parking area.  The main expected contaminants from vehicle parking area are fuels, petroleum oils and possibly acids.  The potential contaminants associated with the above land use are listed in Table 11.3.

 

 

Table 11.3Potential Contaminants Associated with Historic and Present Land Uses at Site E

 

Land Uses

Potential Contaminants

Container Storage Area / Long Vehicle Parking Area

BTEX, petroleum hydrocarbons, acids (from acid batteries)

Vehicle Repairing / Servicing Workshops

benzene, toluene, ethylbenzene, xylene (BTEX), petroleum hydrocarbons, solvents, paints, acids (from acid batteries)

 

11.26      To conclude, there is a potential concern of land contamination at Site A and Site E while it is considered that land contamination at Sites B, C and D is unlikely.

 

Identification of Potential Impact

 

11.27      In accordance to the above sections, Site A and Site E are considered to be areas having potential land contamination.  The relevant land uses in the area include:

·         container storage area;

·         long vehicle parking area; and

·         vehicle repairing / servicing workshops.

 

11.28      The potential contaminants identified are: benzene, ethylbenzene, toluene and xylene (BETX), petroleum hydrocarbons, fuels, solvents, paints and acids.  The implications of potential land contamination are listed as follows:

 

i)     There could be potential adverse effects on the health and safety of workers on site during construction.  Site workers maybe exposed to contaminated materials by means of incidental ingestion of contaminants, dermal contact with contaminated soil and groundwater during excavation, and inhalation of volatile contaminants in soil.

ii)   Disposal of potentially contaminated soil arise from site clearance, excavation, construction works, which prior agreement from EPD should be sought.   

 

Prediction & Evaluation of Impacts

 

11.29      The primary potential source of land contamination impact for the Project is the potential contaminants arisen from the past and present land uses at Site A and Site E.  As sections of proposed elevated roads and roads proposed to be widened/modified will pass through the site area, land contamination impact would arise from excavation works.  Visual observation in site reconnaissances indicated that oil stains and contamination are not widespread in the site areas.  However, the vertical extent of any contamination in subsurface could not be evaluated.  The migration (if any) of contaminants is considered to be limited because of the presence of alluvial material in the site area.

 

11.30      Although detailed information concerning construction method is not available at this investigation stage, it would be considered that only limited amount of soil material would be excavated and disposed of.  Therefore, it is considered that the impacts related to health effects on construction workers and disposal of contaminated material would be surmountable.

 

 

Mitigation Measures

 

11.31      As it is considered that land contamination impact is likely at Site A and Site E, a land contamination assessment should be conducted at these site areas prior to the commencement of site clearance/excavation works.  Figure 11.2 showed the proposed potential zones for conducting site contamination investigation.  The land contamination assessment would include sampling and analysis of soil / groundwater to confirm the presence and level of contamination (if any) in the area.  The information obtained from the assessment would be used to determine the appropriate handling and disposal requirements of the excavated materials.

 

11.32      The sampling and analysis of soil and groundwater should be conducted in accordance with EPD’s requirements.  A Contamination Assessment Plan (CAP) should be submitted to EPD for endorsement prior to conducting the contamination assessment works at Sites A and E under the design and construction stage of the Project.  Based upon an endorsed CAP, a contamination assessment should be conducted and a Contamination Assessment Report (CAR) should then be compiled for EPD’s approval.  If contamination is identified during the preparation of CAR, a Remediation Action Plan (RAP) should be submitted to EPD for approval and site clean up works should be conducted before construction works of the Project.

 

11.33      The following environmental and safety precautionary measures should be implemented and reviewed during the construction of elevated roads, in order to minimize the potential health impact on the site workers:

 

·        Site workers should wear appropriate personal protective equipment (i.e. gloves, mask) when exposed to potential contaminated soil and groundwater;

·        Eating, drinking and smoking should be prohibited in contaminated areas to avoid advertent ingestion of contaminants;

·        Stockpiling of contaminated soil should be avoided as far as possible.  If this cannot be avoided, the stockpile of contaminated material should be segregated from the uncontaminated ones.  Moreover, the contaminated materials should be properly covered with appropriate material (e.g. tarpaulin) to avoid leaching of contaminants, especially during heavy rainstorm;

·        Bulk earth moving equipment should be utilized as much as possible to minimize handling and contact of contaminated materials of the workers;

·        Adequate washing facilities should be provided on site;

·        If disposal of contaminated soil and groundwater is needed, the Contractor should dispose of the contaminated soil according to the requirements agreed by EPD  

 

Residual Environmental Impact   

 

11.34      With the implementation of the recommended mitigation measures for the assessment of the presence and extent of contamination, handling and disposal of the identified (if any) contaminants, no residual impact was anticipated during the construction works for the proposed elevated roads and road widening/modification works.

 

 

 

 

Environmental Monitoring and Audit (EM&A) Requirements

 

11.35      Two potential zones have been proposed for further investigation due to presence of potential contaminative land uses located within the Project boundary.  A CAP should be submitted to EPD for endorsement prior to conducting the contamination assessment works.   Contamination assessment at the potential contaminated zones should follow the requirements laid out in the CAP.  A CAR and RAP, where necessary, should be prepared based on the results obtained from the site investigation and submitted for EPD’s approval. Details of the requirements are provided in a stand-alone EM&A Manual.

 

 



[1]    Maunsell Consultants Asia Ltd. (2002). Design of Ecological Mitigation Measures and Landscaping Works and Assessment of Land Contamination for Eastern Main Drainage Channel for San Tin – Contamination Assessment Report (CAR) / Remediation Action Plan (RAP). Agreement No. CE 49/2000.