Agreement No. CE 35/2006(CE)

Kai Tak Development Engineering Study

cum Design and Construction of Advance Works

– Investigation, Design and Construction

 

 

Decommissioning of the Former Kai Tak Airport

Other than the North Apron

Environmental Monitoring and Audit Manual

 

 

Contents

 

 

2............ land contammination. 7

2.1        Introduction. 7

2.2        Removal of Free Product Encountered during Excavation. 7

2.3        Confirmation Sampling / Testing for Soil Excavation. 8

2.4        Confirmation Sampling / Testing for Biopiling. 10

2.5        Confirmation Sampling / Testing for Solidification / Stabilization. 11

2.6        Environmental Mitigation Measures and Safety Measures. 12

 

 

List of Tables

Table 2.1.......... Event and Action Plan for Removal of Encountered Free Product during Excavation

Table 2.2.......... Event and Action Plan for Confirmation Sampling / Testing for Soil Excavation

Table 2.3.......... Concerned Action Levels for Soil Excavation

Table 2.4.......... Event and Action Plan for Confirmation Sampling / Testing for Biopiling

Table 2.5.......... Concerned Cleanup Targets for Biopiling

Table 2.6.......... Event and Action Plan for Confirmation Sampling / Testing for Solidification / Stabilization

Table 2.7.......... Concerned Cleanup Targets for Solidification / Stabilization

 

List of Drawings

Drawing 2.1       Contaminated Zones Proposed for Excavation

 

List of Appendices

Appendix A       Iimplementation Schedule of the Recommended Mitigation Measures

 


2                          land contammination

2.1                    Introduction

2.1.1               The EIA study has recommended excavating the contaminated soil from the proposed excavation zones within the Study Area for carrying out soil treatment at the proposed decontamination works area located at the northern part of the South Apron of the former Kai Tak Airport (as shown in Drawing 1.3).

2.1.2               TPH free product was encountered during the site investigation in the ex-GFS apron area.  It has been recommended in the EIA Report that any free product encountered during excavation at the ex-GFS apron area should be skimmed, containerised and collected by a licensed chemical waste collector for final disposal.  In this regard, it has also been recommended in the EIA Report that confirmation sampling / testing be carried out to ensure complete removal of any free product encountered during excavation.

2.1.3               As recommended in the EIA Report, confirmation sampling / testing shall be carried out by the ET for: (i) soil excavation (to ensure complete excavation of contaminated soil); (ii) biopiling (to ensure attainment of cleanup targets); and (iii) solidification / stabilization (to ensure attainment of cleanup targets). In addition, the IEC should carry out independent checking on the above confirmation sampling / testing for not less than 10% of total numbers of samples and the scope shall cover sampling works and laboratory analysis by an independent Hong Kong Laboratory Accreditation Scheme (HOKLAS) accredited laboratory.

2.1.4               In addition, in order to minimise the potentially adverse environmental impacts arising from the handling of potentially contaminated materials, environmental mitigation and safety measures have been recommended in the EIA Report during the course of decontamination works.

2.2                    Removal of Free Product Encountered during Excavation

                Monitoring and Confirmation Sampling / Testing Requirements

2.2.1               Where TPH free product is encountered at groundwater surface during excavation at ex-GFS apron area, the free product shall be skimmed off from the groundwater surface.  The skimmed free product shall be drummed properly and collected by a licensed chemical waste collector.

2.2.2               Skimming of free product shall continue until there is no detectable free product on the groundwater surface (the usual detection limit of an oil / water interface probe is about 1.5mm).  A confirmation sample of groundwater shall then be collected at the surface of the groundwater and analysed for TPH by a HOKLAS accredited laboratory.

Compliance Assessment and Event / Action Plan

2.2.3               Removal of all encountered TPH free product is considered complete when: (i) there is no detectable free product present on the surface of the groundwater where free product has been encountered and (ii) the TPH concentration of the confirmation sample is below 213 mg/L (‘allowable’ TPH concentration derived from risk-based assessment in the EIA Report).  Skimming of free product should be continued until all encountered free product has been removed.  The Event and Action Plan for the removal of encountered free product is given in Table 2.1.

Table 2.1                            Event and Action Plan for Removal of Encountered Free Product during Excavation 

Event

Action

Action Party

Detectable free product is present on the surface of groundwater at excavated area(s) (the usual detection limit of an oil / water interface probe is 1.5 mm).

Skimming of free product should be continued until no detectable free product is present on the groundwater surface.

Contractor

TPH concentration in the confirmation groundwater sample is higher than 213 mg/L (‘allowable’ TPH concentration derived from risk-based assessment in the EIA Report).

Skimming of free product shall be continued until the TPH concentration in the confirmation groundwater sample is below 213 mg/L.

Contractor

 

 

2.3                    Confirmation Sampling / Testing for Soil Excavation

                Sampling and Testing Requirements

2.3.1               After excavation, confirmation samples should be undertaken at limits of excavation to confirm that all contaminated soils have been excavated.  The confirmation samples shall be analysed by an HOKLAS accredited laboratory and if the analytical results are below the relevant Dutch B/C levels, removal of contaminated soil shall be considered complete. If the analytical samples exceed the relevant action levels, more soil shall be excavated (either with 0.5m increment in vertical or 1m in horizontal direction depending on whether the exceeding confirmation sample is collected from a sidewall or excavation base), and additional confirmation samples shall be collected and analysed until all confirmation samples are below the relevant action levels.

2.3.2               For small excavation areas (i.e. for excavation zones A - I, L, N - Q as shown in Drawing 2.1), one confirmation sample shall be collected from the excavation pit bottom and one from each sidewall of the excavation pit.  The depth of sampling shall be based on depth of the original site investigation (SI) sample result that triggered excavation in that area.  If there are any visible indications of impact, samples shall be collected from the apparent impact zone(s).

2.3.3               For larger excavation areas (i.e. for excavation zones J, K and M as shown in Drawing 2.1), confirmation samples shall be collected from sidewalls of the excavation with a lateral spacing of not more than 15m.  At least one confirmation sample shall be collected from each sidewall.  Depth of sidewall samples shall be based on the depth of the original SI sample result that triggered excavation in that area.  Confirmation samples from the bottom of lager excavation pits shall be collected on grid spacing not larger than 15m by 15m (i.e. one sample per approximately every 225m2).  In all cases, if there are any visible indications of impact, samples shall be collected from the apparent impact zone(s).  

Compliance Assessment and Event / Action Plan

2.3.4               If the analytical results of the confirmation samples are below the concerned action levels for soil remediation, removal of the contaminated soil shall be considered complete.  If the analytical results exceed the relevant action levels, more soil shall be excavated either laterally or vertically depending on whether the exceeding confirmation sample is from a sidewall or excavation base, and additional confirmation samples shall be collected and analysed until all confirmation samples are below the relevant Action Levels.  The Event and Action Plan for confirmation sampling / testing for soil excavation is provided in Table 2.2.

 

Table 2.2                            Event and Action Plan for Confirmation Sampling / Testing for Soil Excavation 

Event

Action

Action Party

The concentration of the chemical(s) that triggered the excavation exceed the relevant Action Levels for soil remediation (as tabulated in Table 2.3 below).

i) More soil shall be excavated either laterally or vertically depending on whether the exceeding confirmation sample is from a sidewall or excavation base.

 

ii) Additional confirmation samples shall be collected and analysed until all confirmation samples are below the relevant Action Levels.

Contractor

 

 

 

 

 

 

Contractor

 

Table 2.3                            Concerned Action Levels for Soil Excavation

Contaminant

Action Level (mg/kg) *

TPH (adopt standard for Mineral Oil)

1,000

Benzene

0.5

Toluene

3

Ethylbenzene

5

Xylenes

5

Polynuclear Aromatic Hydrocarbons (PAHs) (as listed below)

20

i) Naphthalene

5

ii) Phenanthrene

10

iii) Anthracene

10

iv) Fluoranthene

10

v) Benzo(a)pyrene (also known as 1,2-Benzopyrene)

1

vi) Pyrene

10

Lead

150

Copper

100

Arsenic

30

Remarks:

* The action level adopted is the Dutch B level provided in the Practice Note ProPECC PN3/94 “Contaminated Land Assessment and Remediation” issued by Environmental Protection Department.

 

 

 

 

 

 

2.4                    Confirmation Sampling / Testing for Biopiling

                Sampling and Testing Requirements

2.4.1               The objective of the biopile closure assessment is to collect soil samples for testing in order to ensure that the soil contaminant levels in the biopiles are below the cleanup targets for TPH / VOCs / SVOC.  Furthermore, for soil to be treated subsequently by solidification / stabilization, the levels of the concerned metals will also be analysed to provide the baseline conditions.

2.4.2               Confirmation samples shall be collected with sampling frequency of one sample per 100m3 soil treated.  The samples shall be collected at representative locations distributed evenly throughout the biopile and at various depths within the biopile.  Sample locations within the biopile shall be documented accurately so that the analytical results can be correlated with locations within the biopile.

2.4.3               Access to the sampling locations should be though opening of heat bonded cover panels. These openings shall be closed after each access.  Extracting the soil samples shall be accomplished using a hand auger or other methods approved by the ER.

2.4.4               All soil samples shall be analysed in an HOKLAS accredited laboratory for TPH, VOCs and SVOC and the concerned metals.

Compliance Assessment and Event / Action Plan

2.4.5               If the analytical results of the confirmation samples are below the concerned cleanup targets for biopiling, cleanup of the contaminated soil shall be considered complete.  Individual soil lot which has demonstrated meeting the cleanup target could be removed from the biopile provided the lot would not affect the operation of biopile or would not be affected by adjacent soil lots still under treatment.  If the analytical results exceed the relevant cleanup targets, the concerned biopile treatment system shall have to be restarted to fully decontaminate the soil.  The Event and Action Plan for confirmation sampling / testing for biopile closure assessment is given in Table 2.4.

Table 2.4                            Event and Action Plan for Confirmation Sampling / Testing for Biopiling 

Event

Action

Action Party

Exceedance of any cleanup targets for the contaminants (as tabulated in Table 2.5 below).

Concerned biopile treatment system shall be restarted to fully decontaminate the soil.

Contractor

 

Table 2.5                            Concerned Cleanup Targets for Biopiling 

Contaminant

Action Level (mg/kg)*

TPH (adopt standard for Mineral Oil)

1,000

Benzene

0.5

Toluene

3

Ethylbenzene

5

Xylenes

5

Polynuclear Aromatic Hydrocarbons (PAHs) (as listed below)

20

i) Naphthalene

5

ii) Phenanthrene

10

iii) Anthracene

10

iv) Fluoranthene

10

v) Benzo(a)pyrene (also known as 1,2-Benzopyrene)

1

vi) Pyrene

10

Remarks:

* The action level adopted is the Dutch B level provided in the Practice Note ProPECC PN3/94 “Contaminated Land Assessment and Remediation” issued by Environmental Protection Department.

 

2.5                    Confirmation Sampling / Testing for Solidification / Stabilization

                Sampling and Testing Requirements

2.5.1               Following solidification / stabilization treatment for metal-contaminated soil and curing of the solidified soil, confirmation sampling / testing shall be undertaken to ensure that the cleanup targets have been attained. 

2.5.2               Confirmation samples shall be collected with sampling frequency of one sample per 100m3 of treated material.  Each sample shall be a composite sample collected at 5 locations throughout the treated soil pile, and the same volume of sample shall be collected at each of the locations so that the composite sample is not biased.

2.5.3               Confirmation samples shall be analysed in an HOKLAS accredited laboratory for the concerned soluble metals using Toxicity Characteristics Leaching Procedure (TCLP) in accordance with USEPA Method 1311.

2.5.4               In order to ensure the soil will be solidified in the solidification process, all the soil treated with solidification / stabilization shall be tested for unconfined compressive strength.  All the treated soil shall have unconfined compressive strength of at least 150 pound-force per square inch (psi) (1 MPa), with reference to USEPA guideline (USEPA 1986) for hazardous waste solidification / stabilization requirement.

Compliance Assessment and Event / Action Plan

2.5.5               The “Universal Treatment Standards” (UTS) shall be used for interpretation of the TCLP test results to assess if the cleanup targets have been attained.

2.5.6               If either the cleanup targets or the target unconfined compressive strength have not been achieved, the treated material shall be crushed and returned to the solidification / stabilization process.  The Event and Action Plan for confirmation sampling / testing for solidification / stabilization treatment is given in Table 2.6.

Table 2.6                            Event and Action Plan for Confirmation Sampling / Testing for Solidification / Stabilization 

Event

Action

Action Party

Respective cleanup targets (as tabulated in Table 2.7) of any confirmation samples have not been attained.

The treated material shall be crushed and returned to the solidification / stabilization until the respective cleanup targets have been achieved.

Contractor

Unconfined compressive strength of 150 pound-force psi (1 MPa) has not been attained for all confirmation samples

The treated material shall be crushed and returned to the solidification / stabilization until the respective cleanup targets have been achieved.

Contractor

Table 2.7                            Concerned Cleanup Targets for Solidification / Stabilization 

Contaminant

Cleanup Target (mg/L as TCLP) *

Lead

0.75

Arsenic

5

Copper

7.8**

Remarks:

* Reference to Universal Treatment Standards (UTS) of U.S. Resource Conservation and Recovery Act (RCRA) in Title 40 of the Code of Federal Regulations (CFR) Parts 268.

** It should be noted that the UTS standard for copper is unavailable. To determine the UTS for copper, a comparison has been made between Drinking Water Standards for the USEPA and the USEPA Federal Register. It was found that the 2 sets of standards differ by a factor of 6 (for Chromium) to 2950 (for Cyanide). Using a more conservative approach, the factor of 6 is taken. Therefore, the UTS for copper is taken to be the Drinking Water Standard value of 1.3 mg/L times a factor of 6, giving a value of 7.8mg/L.

 

2.6                    Environmental Mitigation Measures and Safety Measures

2.6.1               In order to minimise the potentially adverse environmental impacts arising from the handling of potentially contaminated materials, the following environmental mitigation measures are proposed during the course of the site remediation:

Free Product Recovery

·            The skimmed free product should be drummed properly, stored in a designated drum storage area with containment and collected by a licensed chemical waste collector for proper disposal. In general, the storage of skimmed free product should comply with the requirements in the Waste Disposal (Chemical Waste) (General) Regulation including the type of drum and containment measures.

Excavation and Transportation

·            Excavation profiles must be properly designed and executed.

·            Stockpiling site(s) shall be lined with impermeable sheeting and bunded.  Stockpiles shall be properly covered by impermeable sheeting to reduce dust emission.  If this is not practicable due to frequent usage, regular misting shall be applied.  Watering shall be avoided on stockpiles of contaminated soil to minimise contaminated runoff.

·            Stockpiles shall be properly covered by impermeable sheeting to minimize contaminated runoff from the stockpiles.

·            Excavation and stockpiling shall be carried out during dry season as far as possible to minimise contaminated runoff from contaminated soils.

·            Supply of suitable clean backfill material is needed after excavation.

·            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.

·            Speed control for the trucks carrying contaminated materials should be enforced.

·            Vehicle wheel and body washing facilities at the site’s exist points shall be established and used.

Biopiling

·            To avoid fugitive emissions of dust or any air pollutants from the biopile(s) and to minimise runoff from the stockpiled soils, the stockpiled soils at the biopiles shall be covered by impermeable sheeting such that not longer than 5m of the biopile is exposed to open air.

·            Impermeable sheeting shall be placed at the bottom of the biopiles and leachate collection sump shall be constructed along the perimeter of the biopiles to prevent leachate from contaminating the underlying soil/groundwater. All leachate generated from the operation of biopiling shall be collected and recycled to the biopile.

·            The vented air from the biopile(s) shall be connected to blower and carbon adsorption system for treatment before release to the atmosphere.  Exhaust air from the blower and carbon adsorption system shall be monitored for VOCs regularly.

·            Spend activated carbon of the carbon adsorption system shall be replaced at appropriate intervals such that the VOCs emission rate from the system is acceptable.

·            Silencers shall be installed at the biopile blowers to minimise noise impact.

·            Contaminated runoff from biopile(s) shall be prevented by constructing a concrete bund along the perimeter of the biopiles.

Solidification / Stabilization

·            Mixing process and other associated material handling activities should be properly scheduled to minimise potential noise impact.

·            Mixing of contaminated soils and cement / water / other additive(s) should be undertaken at a solidification plant to minimise the potential for leaching.

·            Runoff from the solidification / stabilization area should be prevented by constructing a concrete bund along the perimeter of the solidification / stabilization area.

2.6.2               In order to minimise the potentially adverse effects on health and safety of construction workers during the course of site remediation, the Occupation Safety and Health Ordinance (OSHO) (Chapter 509) and its subsidiary Regulations shall be followed by all site personnel working on the site at all times. In addition, the following basic health and safety measures should be implemented as far as possible:

·            Set up a list of safety measures for site workers;

·            Provide written information and training on safety for site workers;

·            Keep a log-book and plan showing the contaminated zones and clean zones;

·            Maintain a hygienic working environment;

·            Avoid dust generation;

·            Provide face and respiratory protection gear to site workers;

·            Provide personal protective clothing (e.g. chemical resistant jackboot, liquid tight gloves) to site workers; and

·            Provide first aid training and materials to site workers.

2.6.3               The implementation for the recommended land contamination mitigation measures is presented in Appendix A.  In the event of exceedances or complaints, the ET and / or the Contractor shall be responsible for reviewing the effectiveness of these measures and for proposing, designing and implementing alternative measures as appropriate.