7 Land Contamination

7.1 Introduction

7.1.1 This section reviews the potential environmental issues associated with land contamination for all land lots/sites within the study boundary due to their past or present land uses. Where appropriate, areas which are suspected as potential contamination sites and would be identified for further assessment in the subsequent construction phase of the proposed drainage improvement works in Sai Kung River, Pak Kong River and Ho Chung Channel.

7.2 Environmental Legislation, Policies, Plans, Standards and Criteria

7.2.1 The Practice Note for Professional Persons ProPECC PN3/94 “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” issued by the Environmental Protection Department (EPD) provide guidance on land contamination assessment. In Hong Kong, the “Dutch List” is generally referenced as the criteria for assessing soil and groundwater contamination under the ProPECC PN3/94.

7.2.2 Provision for consideration of contamination issues is also 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).

7.2.3 The following legislation, documents and guidelines also cover or have some bearing upon land contamination and the handling, treatment and disposal of contaminated waste in Hong Kong.

· Water Pollution Control Ordinance (WPCO);

· Waste Disposal Ordinance (Cap. 354);

· Waste Disposal (Chemical Waste) (General) Regulation (Cap. 354); and

· Code of Practice on the Packaging, Labelling and Storage of Chemical Wastes, Environmental Protection Department (1992).

7.3 Assessment Methodology & Criteria

7.3.1 The assessment methodology was developed in accordance with the Practice Note ProPECC PN3/94 “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” issued by EPD. Under the ProPECC PN 3/94 and the Guidance Notes, evaluation of the following issues should be made before any construction works being carried out in the subject site. They include:

i) Preliminary review of the present and historical land uses to evaluate the likely level of potential for soil/groundwater contamination;

ii) Identification of the nature of potential contaminants;

iii) Evaluation of potential environmental impacts, risks, hazards or health concerns arising from the proposed river/channel improvement works; and

iv) Overview of possible remediation and mitigation measures for the site, where necessary, in order to remedy the site to the satisfaction of the EPD.

7.3.2 During the course of the study, the following tasks with respect to land contamination assessment have been undertaken:

· Desktop study (including review of Hong Kong Government Survey Maps, Hong Kong Geological Survey Maps (Series: HGM20) – Sheets no. 7, 8 and 11 and The Geochemical Atlas of Hong Kong by R J Sewall, 1999).

· Review of historical aerial photographs taken along the three rivers

· Acquisition of relevant information from government departments

· Site inspection

7.4 Description of the Environment

Baseline Condition

7.4.1 As detailed in Sections 1 and 2, the principle works of this Project are improvement of the three watercourses in order to prevent flooding problems in Sai Kung Town Centre, Pak Kong and Ho Chung. The existing Sai Kung River flows through Sai Kung town centre in a box culvert before entering Inner Port Shelter. The Pak Kong River currently runs alongside Hiram’s Highway before entering a road crossing to Hebe Haven. The Ho Chung Channel runs along Ho Chung Road before passing under Hiram’s Highway to Hebe Haven in the South. Based on reviewing the contemporary and historic Hong Kong Government Survey Maps and site appraisal carried out in November 2002, the surrounding areas of the three rivers are mostly undeveloped sites, either rural in nature with mainly agricultural lands or villages/squatter houses scattered on the nearby lands. A number of vehicle repairing/maintenance workshops were also identified close to the Pak Kong River. As potential contaminants including heavy metals, petroleum oils, acids and solvents could be released to the environment due to localised spillages/leakages from the above mentioned activities, these land uses may give rise to potential concerns for land contamination and warrant this contaminated land study.

Land Zoning

7.4.2 The Pak Kong & Sha Kok Mei Outline Zoning Plan (OZP No. S/SK-PK/7) gazetted in February 2004 was reviewed and the OZP showed that the proposed land uses along the study boundary of Sai Kung River and Pak Kong River are mostly zoned for ‘Recreation’, ‘Agricultural’, ‘Village Type Development’ and ‘Green Belt’. For the Ho Chung Channel, the information obtained from the Ho Chung Outline Zoning Plan (OZP No. S/SK-HC/6) gazetted in July 2004 also revealed that the lands adjacent to the Ho Chung Channel are zoned for Green Belt, agricultural and Village Type Development. As observed from the site visits, vehicle repair workshops which encroach upon the proposed Pak Kong River alignment are located at the areas currently zoned for ‘Recreation’ and ‘Green Belt’.

Site Geology and Superficial Geological Deposits

7.4.3 According to the Hong Kong Geological Survey Map (Series: HGM20) – Sheets No. 7, 8 and 11 on the solid geology across the Sai Kung area, the inferred solid geology of the subject area is mainly identified to be undivided and coarse ash crystal tuff of Tai Mo Shan Formation. Not much variation is identified for the superficial geology beneath the three rivers. A layer of alluvium, which consists of well-sorted to semi-sorted clay/slit, sand and gravel from the Pleistocene and Holocene eras of the Quaternary age is shown underlying the three rivers and its surrounding areas. The subsurface geology is important in connection to surface contamination. Any contaminants, especially those associated with petroleum hydrocarbon products such as gasoline, fuels and oils, may enter the soil through spills and easily migrate through the underground medium if the soil matrix consists of high content of sand and gravel. For the subject site with alluvial deposit, the nature is generally with low permeability and the ability of potential contaminant migration through this horizon would be relatively low.

Site History

7.4.4 A review of historical aerial photographs (Table 7.1) covering the study area has been undertaken. The aim of this review is to evaluate land-use changes and development of specific properties closely along Sai Kung River, Pak Kong River and Ho Chung Channel.

Table 7.1 Historical Aerial Photographs Reviewed

Year	Photograph References	Height (feet)
1976	12309, 12331, 12898	6000, 6000, 4000
1979	25642, 25729, 25678	2500, 2500, 2500
1981	39518, 36524, 37331	2500, 2500, 4000
1984	57430, 57427, 57424	4000, 4000, 4000
1986	A05250, A04162, A05256	3800, 2000, 3800
1989	A16889, A16901, A16357	4000, 1500, 2000
1991	A25909, A26761, A25732	2000, 2000, 2500
1993	A35506, A35501, A35779	4000, 4000, 1500
1995	CN10846, CN 10934, CN10966	2500, 2500, 2500
1999	CN23106, CN23112, CN23115	2800, 4000, 2500
2001	CNW32821, CW32602, CW30728	4000, 1400, 1500

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

7.4.5 As revealed from the historical aerial photographs from 1976 to 2001, most of the areas adjacent to the Sai Kung River were agricultural lands. Village houses adjacent to the proposed river boundary were built in late 1970s and since then no significant change was observed along the Sai Kung River. For Ho Chung Channel, a large number of village houses and the ATV Studio which is currently still in operation were found along the Channel. Apart from some new village houses be recently built opposite to the Ho Chung Village as well as the road construction works opposite to the Sai Kung Central Primary School in 2001, neither major development nor contamination-related industry was found along the Ho Chung Channel in the recent decade. For Pak Kong River, few locations have been identified to have potential contaminating sources during the site visits as mentioned above.

7.4.6 The aerial photographs further confirm that there are two locations, namely Sites A and B, were noticed to have land use changes leading to potential land contamination implication. The locations are shown in Figure 7.1. The findings of the historical aerial photograph review in respect of Pak Kong River are summarised as follows:

Year 1976

· Mainly farmland and open spaces were observed along the Pak Kong River.

Year 1981

· Some small houses were built at the location of Site A but exact activities being carried out at the site could not be recognised due to the small resolution of the photograph.

Years 1984 and 1986

· No significant change was observed.

Year 1989

· Workshops at both Sites A and B were developed.

Year 1993

· No significant change in terms of land use was noticed at both sites since 1993.

7.4.7 As shown in the above records, land-use changes were initiated since late 1980s. Most of the obvious changes were from vegetated lands to car repairing workshops of which might cause potential land contamination although the scale may be generally localised. Historical records of chemical spillage and registration of Chemical Waste Producers (CWP) within the study area were sought by sending inquiry letters to several Government Departments. Details are shown in the following section.

Acquisition of Relevant Information from Government Departments

Environmental Protection Department (EPD)

7.4.8 Inquiry letter has been sent to EPD to acquire information about the registered Chemical Waste Producer(s) within the Study Area and records of accidents of spill/leakage of chemicals within the Study Area.

7.4.9 According to the information provided by EPD, there were 4, 21 and 25 registered/de-registered Chemical Waste Producers (CWPs) found near Sai Kung River, Pak Kok River and Ho Chung Channel respectively. However, there were no records of chemical spill/leakage within the Study Area.

7.4.10 Most of the CWPs on the list were vehicle repair workshops. As noted, some of the CWPs were in a considerable distance from the project boundary and some were either not found at the address provided by EPD or already surrendered, only one of which in proximity to the project worksite likely had a potential for contaminated land concerns. Details of the CWP are tabulated in Table 7.2. It should be noted that this CWP had already been identified as potential contaminated site during the site visits. Location and relevant photographs are shown in Figure 7.2.

Table 7.2 Details of Chemical Waste Producer (CWP) Within the Study Area

Nearby River	CWP	Business	Status
Pak Kong River	Wah Shing Motor Repair Factory	Repairing of Motor Vehicle	Existing CWP

Fire Services Department (FSD)

7.4.11 Inquiry letter had also been sent to FSD to acquire information about current and past registration of dangerous goods stored within the Study Area and records of spillage/leakage of dangerous goods stored within the Study Area. According to the information provided by the FSD, there were no available records of application for storage of dangerous goods nor any known spillage/leakage of dangerous goods within the Study Area.

Lands Department (LD)

7.4.12 Inquiry letter had been sent to Lands Department to acquire information about the current and past land uses within the Study Area. Response from LD indicated that there was no available information regarding land uses within the Study Area.

7.5 Identification of Environmental Impacts

7.5.1 Based on the information obtained from the site visits conducted in November 2002, activities related to land contamination were not identified in or near to Sai Kung River and Ho Chung Channel. However, there were two potential contaminated workshops, mainly vehicle repairing workshops, identified near Pak Kong River. Site inspection, photo-documentation and interview with the site personnel were carried out as far as possible. Details of the two potential contaminated workshops are listed in Table 7.3 and their locations are illustrated in Figure 7.2.

Table 7.3 Potentially Contaminative Land Uses Near Proposed Work Boundary of Pak Kong River

Workshop Reference Number	Name of Company	Nature of Trade
Workshop - A	- Wah Shing Motor Car Repairing Factory	Repairing of lorry engines
Workshop – B	- Wing Chong Car Repair	Repairing of car engines

Workshop - A: Wah Shing Motor Repairing Factory

· This motor repair workshop has been operated for more than 10 years as revealed by the site personnel and historical aerial photographs. It located at the area adjacent to the riverbank of Pak Kong River. As observed during the site visits, activities of engine repairing and maintenance for heavy goods vehicles had been carried out in the site. Physical evidence of contamination was identified as heavy oil stains were noted on the paved ground. This might be caused by the local spillage of engine oils/lubricating oils during repairing or direct leakage from the parking vehicles. A lot of equipment for motor maintenance was observed inside the working hut of the workshop. This workshop has been registered as a Chemical Waste Producer with EPD. As told by the site personnel, the chemical waste would be stored in a 220 litre lid drum inside a chemical waste storing room with size of approximately 1.5m x 1.5m. Based on the nature of the industry and the general site observation, further investigation for contaminated land is recommended for this workshop.

Workshop – B: Wing Chong Car Repair

· As shown in the review of historical aerial photographs, this car repair workshop being relatively smaller in scale than the Wah Shing Motor Repairing Factory has been operated for about 14 years. It located just next to the Pak Kong River with land location number of Lot DD 217 989 6A. The business nature of this workshop is engine repairing for private cars and mini-vans. During the site inspection, oil stains were observed at a few locations and the ground was not well paved. Interview had been carried out with the site personnel and they expressed that chemical waste generated from this site would be usually transferred to the chemical waste storage drum of Wah Shing Motor Car Repair Factory. Due to the nature of business and its long history of operation, further investigation for contaminated land is also recommended for this workshop.

7.6 Site Investigation for Land Contamination

7.6.1 The proposed drainage improvement works at Pak Kong River include (1) reconstruction of one footbridge and one vehicular crossing to 3-cell box culverts, and (2) construction of a retaining wall for the purpose of stabilizing the existing riverbank adjacent to the Hiram’s Highway. In regard to this, site clearance, excavation, construction of concrete structures would be carried out within the defined site boundary.

7.6.2 As aforementioned, the findings of the site inspection and desktop study indicated that there are two potential contaminative workshops located within the proposed site boundary of Pak Kong River. Activities mostly car repairing/servicing were undertaken by such workshops and stains were generally observed on the ground of the sites. Potential sensitive receivers which may come into contact with excavated contaminated soils are mainly construction workers via the principal exposure routes of (1) inhalation of dust, (2) direct ingestion through poor hygiene practices, such as eating or drinking on site as well as (3) dermal contact with the contaminated materials. As there may have potential adverse effects on the health and safety of workers during construction of Project, a detailed site investigation would be recommended for those areas falling within the Project boundary in order to assess the degree and extent of potential land contamination. Contaminated soil should be remediated before construction work could be started at the concerned areas.

7.6.3 As shown in Figure 7.2, there are two workshops, including Workshop A - Wah Shing Motor Repairing Factory and Workshop B - Wing Chong Car Repair, with part of the site areas encroaching upon the proposed drainage work area of Pak Kong River. The major concern associated with these workshops would be of lube oil, engine oil and/or solvents that could be inaptly be disposed of by workers or leaked from vehicles causing contamination in the site and its vicinity. According to EPD’s “Guidance Notes for Investigation and Remediation of Contaminated Sites of Petrol Filling Stations, Boatyards, and Car Repair / Dismantling Workshops” and “ProPECC PN3/94”, site contamination assessment and remediation, where necessary, are required to avoid or minimise any risks or hazards associated with the sites prior to any construction works taken place. In regard to this, two potential zones, namely SI-1 and SI-2, are confined for conducting site contamination investigation, as shown in Figure 7.3.

7.6.4 Based on the requirement stated in EPD’s “Guidance Notes for Investigation and Remediation of Contaminated Sites of Petrol Filling Stations, Boatyards”, a full-scale site investigation is required as both workshops A and B have been operated for more than 5 years. Due to inaccessibility of the workshops for full site inspection, location of contamination hotspots could not be accurately determined at this stage. Instead, only approximate number of sampling locations required for the Areas SI-1 and SI-2 are estimated based on the confined potential areas recommended for carrying out site investigation. Table 7.4 shows the preliminary Contamination Assessment Plan (CAP) which summarises the identified activities, possible contaminants, number of sampling locations and testing parameters suggested for further investigation.

7.7 Prediction and Evaluation of Impacts

7.7.1 As illustrated above, there are some land uses in the vicinity of the proposed work limit of Pak Kong River that could feasibly result in land contamination. Considering the nature of business and the general site practice of the workshops, two potentially contaminative zones have been identified at which car repairing/servicing workshops impinging upon the proposed alignment of the River was found. As observed during the site visits, area-wide land contamination would not be likely in terms of the appearance of current site condition and scale of the business. Localised contamination due to the potential incidence of spillage/leaking from maintenance and dismantling of equipment within the study boundary would be more likely encountered. As a whole, the overall contamination concerns would be limited to the works area within the project boundary and significant impact would not be anticipated taken into account the scale of the workshops.

7.7.2 Due to the possibility of land-use changes and variable future site conditions caused by different factors such as weather and business operation, a full site inspection is required by the future Environmental Team to review the validity of the preliminary CAP and define the exact sampling locations and sampling parameters for further site investigation. The inspection should be undertaken immediately after the site was resumed for this project. An updated CAP shall then be prepared after the site inspection in accordance with EPD’s “Guidance Notes for Investigation and Remediation of Contaminated Sites of Petrol Filling Stations, Boatyards, and Car Repair/Dismantling Workshops” and endorsed by EPD prior to commencement of the site investigation.

7.7.3 Upon receipt of EPD’s approval on the updated CAP, the actual site investigation for land contamination impact assessment shall be conducted accordingly before any construction work started at the identified contaminated sites. Soil and groundwater samples shall be collected and tested as described in the approved CAP to provide site-specific information for the assessment. A Contamination Assessment Report (CAR) shall be compiled to document the findings and shall include interpretation of laboratory testing results in accordance with the ProPECC Note No. 3/94 and comparison of the findings with relevant standards, such as the Dutch guidelines or other international practices as appropriate. If land contamination is confirmed, a Remediation Action Plan (RAP) shall be drawn up to formulate necessary remedial measures and potential water quality impact to the river shall be also addressed if necessary in the remediation measures. The subsequent CAR and RAP shall be endorsed by EPD before implementation of any remedial technology. The contaminated sites should be remediated before commencement of any construction work at the concerned sites which may disturb the ground. The duration of remediation should be taken into account by the Project Proponent or the Contractor as part of the construction programme.

7.7.4 In terms of remediation measures, examples of available practical methods widely adopted for decontamination at small sites are listed below:

· Excavation & disposal;

· Soil venting/Air sparging; and

· Recovery trenches or wells.

7.7.5 In assisting the formulation of appropriate remedial measures, the Guidance Notes for Investigation and Remediation of Contaminated Sites of Petrol Filling Stations, Boatyards, and Car Repair/Dismantling Workshops suggest the following factors to be taken into consideration when evaluating different available remediation methods:

i) degree and extent of the contamination;

ii) anticipated future use of the site;

iii) nature of the contaminants;

iv) soil characteristics; and

v) time available for remediation.

7.8 Residual Environmental Impact

7.8.1 After any necessary remediation of contaminated soil being carried out, the concerned site is expected to meet the acceptable standards and no adverse residual impact would be envisaged.

7.9 Mitigation Measures

7.9.1 Mitigation measures are proposed for handling of the contaminated materials in order to minimise (1) the potentially adverse effects on the health and safety of construction workers and (2) the impacts arising from the disposal of potentially contaminated materials. These measures include:

· Construction workers' potential contact with contaminated materials should be minimised by using bulk earth-moving excavator equipment;

· Exposure to any contaminated materials should be minimised by wearing appropriate clothing and personal protective equipment such as gloves and masks (when interacting directly with suspected contaminated material), providing adequate hygiene and washing facilities and preventing smoking and eating during such activities;

· Stockpiling of contaminated excavated materials on site should be avoided as far as possible;

· The use of contaminated soil for landscaping should be prohibited unless there is proper treatment of soil;

· Vehicles containing any excavated materials should be suitably covered to limit potential dust emissions or contaminated wastewater run-off, and truck bodies and tailgates should be sealed to prevent any discharge during transport or during wet conditions;

· Only licensed waste haulers should be used to collect and transport any contaminated material to an appropriate disposal site and procedures should be developed to ensure that illegal disposal of waste does not occur;

· The necessary waste disposal permits should be obtained, as required, from the appropriate authorities, in accordance with the Waste Disposal Ordinance (Cap 354), Waste Disposal (Chemical Waste) (General) Regulation (Cap 35), as required;

· Records of the quantities of wastes generated and disposed of should be maintained; and

· In accordance with good construction practice, silt traps should be used to reduce the impact to drainage caused by suspended solids arising from disturbed ground, or any construction materials such as cement and gravel. Wastewater, surface runoff or extracted groundwater should be disposed of in accordance with the WPCO.

7.10 Environmental Monitoring and Audit Requirements

7.10.1 Since two potential zones have been confined for further investigation due to the presence of potential contaminative workshops located within the proposed alignment of Pak Kong River, a review of the preliminary Contamination Assessment Plan (CAP) would be required by the future Environmental Team at a later stage when full site inspection is available after the land is resumed for the Project. Such revised CAP should be submitted to EPD for approval.

7.10.2 Site investigation for contamination at the potential contaminated zones shall follow the requirements laid out in the approved CAP. A Contamination Assessment Report (CAR) and Remediation Action Plan (RAP) if necessary, shall 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.

7.10.3 The land contamination investigation and the reporting may take 3 to 6 months to complete. If contamination is found, remedial actions for contaminated soil are required which may take another 6 months or more to complete. The Project Proponent shall take into account the time required for land contamination study at the identified areas. These identified areas should be handled as the first priority after land resumption. The CAP, investigation works, CAR and RAP shall be carried out as soon as the land is available for study. Construction work might only be carried out at these areas if the investigation results, which are obtained either after contamination assessment (according to CAP) or after the remediation work (according to RAP), are found acceptable.

7.11 Conclusions

7.11.1 An account of the present and historical land uses along the proposed drainage improvement areas of the three river channels indicated that activities related to land contamination impact was not identified in or near to Sai Kung River and Ho Chung Channel. However, two workshops associated with contaminating uses were noted to be present near Pak Kong River, and the main type of activities was related to vehicle repairing works.

7.11.2 Considering the potential land contamination impact to site workers during construction of the Project, a detailed site investigation was recommended for those areas falling within the project boundary after land resumption. According to the preliminary design of Pak Kong River, only partial areas of two identified workshops were found located within the project works area with implication of land contamination impact. A preliminary Contamination Assessment Plan (CAP) has been prepared for further investigation.

7.11.3 Due to the possible changes of land use and site conditions, a review of the CAP would be required by the future Environmental Team at a later stage after land resumption. Such revised CAP should be submitted to EPD for approval. It is considered that the potential residual impacts would not be significant provided that any identified contaminated land would be remediated to the acceptable standards prior to the site clearance/excavation works, and the mitigation measures recommended would be properly implemented during the construction stage of the Project.