1                                  Introduction

1.1                            Background to the Study

The Castle Peak Power Company (CAPCO) has initiated a project for emission control at the Castle Peak Power Station ?units (CPB) (roject?, in response to the Hong Kong SAR Government (HKSARG) stated intent to reduce emissions in Hong Kong.  An Environmental Impact Assessment (EIA) Study Brief was issued for the Project by the Environmental Protection Department (EPD) in October 2005 (EIA Study Brief No. ESB-134/2005).  In compliance with one of the Study Brief requirements, a land contamination assessment will be carried out for the Project Areas (he site?.  To accommodate the new development, extensive demolition works are required to relocate a number of existing facilities, including:

·       CPB Fuel Oil Day Tank (FODT, hereafter referred to as the aboveground fuel oil day tank) and associated pipe works connecting with fuel oil pump house (FOPH) and oil interceptor;

·       Dangerous Goods (DG) stores; and

·       Intermediate Pressure Reduction Station (IPRS), LPG compound and CO2 storage tanks.

Environmental Resources Management (ERM) was commissioned by CAPCO to conduct a land contamination assessment of the site, in accordance with the Study Brief requirements.  A Contamination Assessment Plan (CAP) was prepared, submitted to and was approved by the EPD and forms a basis of this assessment.

The preliminary Project Areas are shown in Figure 1.1a of the approved CAP.

Site inspection including soil and groundwater sampling and analysis was conducted to identify potential sources of contamination from historical and on-going operations in this area, in accordance with the CAP.

A Contamination Assessment Report (CAR) summarising the results of the investigation works and recommending further investigation was prepared (Annex E1).

1.2                            Objectives of the Action Plan

This Remediation Action Plan (RAP) presents the results obtained during the contamination investigation at the Project Areas and proposes remediation actions.  The objective of the plan is to reduce the opportunity for exposure to contaminants during the construction of the Project.

1.3                            Scope of the Remediation

The scope of the remediation will include:

·       Sampling and testing and, where applicable, treatment and handling/management of the excavated contaminated soils; and

·       Preparation of a decontamination verification report upon completion of the demolition, construction and any necessary decontamination works.

1.4                            Structure of the RAP

The remainder of this document is structured as follows:

Section 2    summarises the site investigation results; and

Section 3    presents contamination remediation action plan for the Project Areas.

The document is accompanied by the CAR in Annex E1.

 

2                                  Contamination Assessment background Information

This Section presents the summary of the results of the site investigation works.  The full details of the methodology used for the soil and groundwater sampling works, details of field observations such as visual observations made during the investigation programme and the analytical results from soil and groundwater analyses are provided in the CAR, Annex E1.

2.1                            Site Investigation Programme

The Site Investigation (SI) was conducted as described in the CAR and consisted of drilling of eight boreholes (DH1 to DH8) and four trial pits (TP1 to TP4), the installation groundwater sampling wells where groundwater was encountered (ie DH1 to DH8), soil and groundwater sampling, laboratory sample analysis and a field QA/QC programme.  The locations of the boreholes and trial pits are presented in Figure 3.1a of the approved CAP.

The SI programme was designed and carried out in accordance with the EPD Practice Notes for Professional Persons: Contaminated Land Assessment and Remediation ProPECC PN 3/94 and the Guidance Notes for Investigation and Remediation of Contaminated Sites of Petrol Stations, Boatyards, and Car Repair/Dismantling Workshops, 1999.

2.1.1                      Field Observations

The underground soil profiles observed during the exploration were recorded using boring logs (see Annex E1b of the CAR).  No obvious sign of hydrocarbon staining, discoloration or odour was observed in any underlying soil samples and/or groundwater.  No free oil product was observed on the groundwater surface.

2.1.2                      Soil Sample Results

A soil sample taken from TP3 at a depth 0.9 m below ground level (m bgl), had a reported total TPH concentration of 1,858 mg/kg  ([1]).  .  This level exceeds the Dutch ?level for mineral oil (1,000 mg/kg).  The concentration was below the Dutch ? value for mineral oil of 5,000 mg/kg.  No soil sample was collected at a deeper level at the adjacent borehole location (DH5) as the underlying geology comprised of boulders and fractured granite rock from 0.5 meter below ground level (m bgl) to the end of drilling at 6.8 m bgl.  TPH was not detected in any other soil samples collected from the Project Areas.

No target volatile organic compounds (VOCs) including Benzene, Toluene, Ethyl Benzene and Xylene (BTEX) and semi-volatile organic compounds (SVOCs) were detected at concentrations exceeding the laboratory reporting limits.

2.1.3                      Groundwater

The static groundwater levels were between 2.4 to 5.5 m bgl (or 1.23 and 2.7 mPD).  Based on the groundwater water levels measured and the local surface hydrology, the shallow groundwater in the Site area is anticipated to flow in a generally southern or south-westerly direction and may be influenced by tidal motion in the nearby coastal area.

Light diesel, heavy diesel and/or heavy oil were detected in groundwater samples collected from the Site.  The sum of light diesel, heavy diesel and heavy oil concentrations in the groundwater samples from DH1 to DH7 ranged from 812 (g/L to 3,120 (g/L and exceeded the Dutch ?value of 600 (g/L for mineral oil.  The sum of the light diesel, heavy diesel and heavy oil fractions in the groundwater sample collected from DH8 was 204 (g/L which is marginally above the ?value (ie 200 (g/L) for mineral oil.

No free-floating oil product was observed on the groundwater surface.

VOCs and other SVOCs were not detected in the groundwater samples except di-n-butyl phthalate and bis (2-ethylhexyl) phthalate.  Di-n-butyl phthalate were detected at concentrations ranging from 31 to 459 (g/L in the groundwater samples from all groundwater wells whereas bis (2-ethylhexyl) phthalate were detected at concentrations ranging from 21 to 34 32 (g/L in the groundwater samples from DH3 and DH5 ([2]).  The phthalates in groundwater however does not represent a risk for this specific Site as there is no abstraction of groundwater for any use and there is no exposure to groundwater under normal circumstances.

2.2                            Assessment of Land Contamination Extent

TPH in Soil at TP3

The concentration of TPH [light diesel (C10-C14), heavy diesel (C15-C28) and heavy oil (C29-C36)] in soil at TP3 at 0.9 m bgl exceeded the Dutch ?value but was below the Dutch ?value.  As no TPH was detected in soil at the other sampling locations, the TPH detected contamination was considered to be localised.  As an extremely worst-case approach, it is The estimated that amount of potentially contaminated soil within the Project boundary is 50 m3 of soil to be excavated near TP3 may be contaminated by TPH.

TPH, Di-n-butyl Phthalate and Bis (2-ethylhexyl) Phthalate in Groundwater

TPH (light diesel, heavy diesel and heavy oil) contamination at above Dutch ?and ?levels has been reported in all the groundwater samples (DH1 to DH8).  The TPH concentrations detected in the samples from wells DH1 and DH2 were primarily attributable to the light diesel and heavy diesel fractions.  TPH concentrations at DH3 to DH8 were primarily attributable to the heavy diesel and heavy oil fractions.  Phthalates were found in the groundwater samples from all groundwater wells (DH1 to DH8) but this does not represent a risk since groundwater is not abstracted for any use at this Site and there is no exposure to groundwater under normal circumstances.

The FODT was located above the ground, has been provided with secondary containment systems and no oil spills and leakages have been reported or observed during the site investigation works in this area.  An oil pipe leakage near the fuel oil pump house was reported to the Marine Department and the EPD in July 2004.

The potential transport mechanism for the TPH, di-n-butyl phthalate and bis (2-ethylhexyl) phthalate contamination in the groundwater at CPB is the flow of shallow groundwater, which was measured at about 1.23 to 2.7 mPD.  The groundwater flow within CPB is likely to be influenced by tidal movements as the site is located on a reclaimed area approximately 100 to 400 m from the waterfront.

As CPB is paved, and groundwater is not used for either domestic or industrial purposes at CPB and in the adjacent areas, the potential exposure to TPH in groundwater could only take place during the demolition and construction stages of the Project.  The potential exposure pathways include dermal contact and accidental ingestion.

With the implementation of appropriate environmental, health and safety control measures (as described in Section 3), no potential adverse impacts are anticipated during the demolition and construction activities.

2.3                            Evaluation of Construction Methods for FGD Plant

2.3.1                      Tanks and Oil/Water Separator Sump Demolition

To accommodate the installation/construction of the proposed Selective Catalytic Reduction (SCR) and Limestone Flue Gas Desulphurisation (LS-FGD) equipment, demolition works are required to relocate a number of existing facilities, as described in Section 1.1.

In addition gypsum storage facilities are proposed to be constructed within the western coal storage yard.

The demolition works will take about eight months and are currently scheduled to commence in early 2007.  Excavations for the construction of foundations are anticipated to commence in around third or fourth quarters of 2007.

 

The FODT and the oil separator serving it will be washed/decontaminated prior to demolition.  This will also enable the materials to be disposed as non-contaminated construction and demolition wastes.

A total of about 835 tonnes of scrap steel will be produced from the demolition of the fuel oil day tank, LPG and CO2 tanks, pumps and the associated fixtures/ appendages such as pipeline, spiral stair and catwalk attached to the tanks.  The steel sheets of the facilities will be cut into small panels for easy transportation.  All the scrap steel will be transported off-site by barges or lorries for recycling.

A total of 1,830 m3 of uncontaminated reinforced concrete (after applying a bulking factor of 1.4) will be generated from the demolition of the fuel oil day tank retaining walls, DG stores, LPG switch room and vaporiser, LPG tank foundation and pipe trenches.  The concrete is not contaminated and will be separated from other waste to avoid contamination.  The concrete (C&D materials) will be reused on-site for the subsequent construction within the northern and western coal yard areas or sent to public filling facilities /other reclamation sites for reuse.

2.3.2                      Excavated Materials

Non-Contaminated Excavated Materials

Excavation works would be required for the construction of the piles and shallow foundations to support the new facilities.  A total of about 30,000m3 (after applying a bulking factor of 1.2) of excavated materials (assumed to be mainly soft materials) will be generated from the demolition of the existing facilities and excavation for the construction of the foundations for new facilities.

After excavating the in-ground foundations and concrete structures, the area will be backfilled with the excavated uncontaminated soil and imported fill materials to the existing grade.  In addition, excavated soil will be reused as far as practicable in the Project Area located within the existing north coal yard which will need to be raised from the existing +5 to +6 mPD to approximately +7 mPD.

Potentially Contaminated Excavated Materials

Excavation works will be required at the TP3 area for the construction of the foundations of an FGD absorber.  An estimated total of 50 m3 of potentially contaminated soil (after applying a bulking factor of 1.2) will be excavated and treated before reuse within the Project or disposal.

The excavated potentially contaminated soil will be managed in accordance with the EPD ProPECC PN 3/94 and Guidance Notes for Investigation and Remediation of Contaminated Sites of Petrol filling Stations, Boatyards, and Car/Repair/Dismantling Workshops.  The proposed strategy for the excavation, testing, remediation and disposal is presented in the following Section 3.

 

3                                  Remediation Actions

Following the completion of the land contamination site investigation at the Project area, the following remediation programmes are proposed.

3.1                            Soil Excavation and Confirmation/Verification Sampling

The only soil contamination identified during the SI programme described in Section 2.1 is the TPH contamination observed in soil samples at TP3.  According to the arrangements in the current construction plan discussed in Section 2.3.2, only minor excavation works for the construction of the foundations of the FGD facilities are expected to be required.   Moreover, the existing ground level at the TP3 location as well as its neighbourhood area will have to be raised by backfilling with filling materials (excavated or imported) for the installation of the emissions control facilities.  

For the remediation of petroleum hydrocarbon contaminated soil to be excavated at TP3, the following steps are proposed:

·       Excavation of 50 m3 soil around TP3 for construction of bored piles and pile caps.

·       Temporary stockpiling of the excavated materials from TP3.

·       The temporary stockpile will be contained in a container covered by HDPE sheet on top.

·       Conducting verification sampling for TPH contamination in the soil around the excavated parcel.  The soil samples will be obtained at each boundary of the excavation parcel at 0.5m, 1m and 1.5 m bgl.

·       Bioremediation by applying nutrient to the soil will be employed for the on-site treatment of contaminated soils at a location within the Project boundary.  Suitable kinds of nutrient will be added to the soil and the soil will be turned regularly to ensure sufficient air goes into the soil to undergo biodegradation.

·       Where the treated soil showed TPH concentrations below the Dutch ?value, the treatment is considered completed and the soil can be used as fill materials on-site or disposed of as fill materials at the public fill bank.

·       If disposal to the public fill bank is required, vehicles containing any excavated materials will be suitably covered to limit potential dust emissions or wastewater run-off, and truck bodies and tailgates will be sealed to minimise the risk of a discharge during transportation or during wet conditions.

·       Records of the quantities of soil generated for off-site disposal will be maintained.

·       A decontamination verification report will be prepared upon the completion of the decontamination works.

3.2                            Groundwater Handling

Groundwater was found to be contaminated in the groundwater samples collected from all wells with the total TPH at concentrations ranged from 204 to 3,120 (g/L.   Di-n-butyl phthalate were detected at concentrations ranging from 31 to 459 (g/L in the groundwater samples from all groundwater wells whereas bis (2-ethylhexyl) phthalate were detected at concentrations ranging from 21 to 34 32 (g/L in the groundwater samples from DH3 and DH5.  There is no abstraction of groundwater at this Site for any use.

As such, it is proposed that the following control measures are implemented during the demolition and excavation to minimise potential environmental impacts from the groundwater contamination.  The following steps are proposed:

·       Cleaning of the FODT and the oil separator serving it prior to demolition.  Oily water and sludge collected from the cleaning should be treated at the on-site wastewater treatment facility.  Oily water and sludge collected from the cleaning should be collected and disposed of as chemical waste at Government chemical waste treatment facility.

·       Only licensed waste contractors shall be used to collect and transport any chemical waste.  The necessary waste disposal permits will be obtained, as required, from the appropriate authorities, in accordance with the Waste Disposal Ordinance (Cap 354) and Waste Disposal (Chemical Waste) (General) Regulation (Cap 354C), as required.

As groundwater is not used for either domestic or industrial purposes at the site or in the adjacent areas, remediation of groundwater is not considered to be necessary for the Project to proceed.  If groundwater is encountered during the construction of foundations, the groundwater abstracted or collected will be recharged back to the site.   

3.3                            Health and Safety Control Measures

The remediation work will involve soil excavation, soil stockpiling and soil sampling.  To minimise the contacts of the workers with the contaminated materials and to ensure a safe work environment during the remediation works, the following control measures are proposed:

·       Prior to commencing any remediation works, a health and safety risk assessment should be performed for the remediation works to identify potential work related hazards and prepare appropriate control measures.

·       Appropriate Personal Protective Equipment (PPE) such as safety hat, chemical protective gloves, masks (for both dust and vapour), eye goggles, protective clothing and protective footwear should be provided to staff who would be involved in the contaminated area (TP3) remediation works.  No works should be allowed without the suitable PPE.

·       The workers should inspect and check their PPE before, during and after use.  In cases where any of the PPE is impaired, the workers should stop work immediately and inform their supervisor.  The workers should not be allowed to re-start their work until the impaired PPE is replaced.

·       The workers should always maintain basic hygiene standard (eg hand wash before leaving the contaminated work area).  The workers should also be responsible for cleaning and storing their own PPE in a secure place before leaving the site.

·       Eating, drinking and smoking should be strictly prohibited within the contaminated area.

·       The designated site management representatives must be informed if any workers feel uncomfortable physically or mentally during the remediation works.  All workers should leave the work areas and the works should be temporarily suspended until the reason for the uncomfortable feeling has been identified.

·       The works should be stopped or discontinued when Typhoon Signal No. 3 or Rainstorm Warnings are hoisted.  All stockpile materials (if any) should be covered immediately by tarpaulin or other similar protective and waterproof materials.

·       Bulk earth-moving excavator equipment should be used to minimise construction workers? potential contact with contaminated materials.

 


Contents

1                      Introduction                                                                                              1

1.1                   Background to the Study                                                                                 1

1.2                   Objectives of the Action Plan                                                                         1

1.3                   Scope of the Remediation                                                                                 2

1.4                   Structure of the RAP                                                                                       2

2                      Contamination Assessment background Information       3

2.1                   Site Investigation Programme                                                                        3

2.2                   Assessment of Land Contamination Extent                                                  4

2.3                   Evaluation of Construction Methods for FGD Plant                               5

3                      Remediation Actions                                                                               7

3.1                   Soil Excavation and Confirmation/Verification Sampling                      7

3.2                   Groundwater Handling                                                                                  8

3.3                   Health and Safety Control Measures                                                         89

 

Annex E1     Contamination Assessment Report

 



([1])        Expressed as the sum of light diesel (C10-C14) (83 mg/kg), heavy diesel (C15-C28) (1,170 mg/kg) and heavy oil (C29-C36) (605 mg/kg).

([2])        The sum of phthalates for the groundwater sample from all groundwater wells was higher than the corresponding Dutch Intervention Value (DIV) of 5 (g/L.