8
LAND CONTAMINATION
IMPACT
This chapter presents the findings of the land
contamination assessment of the impacts from the Assignment during the
construction phase.
A Contamination Assessment Plan (CAP) has been prepared
which set out the requirements and methodologies for a land contamination
assessment along the CKR alignment and was endorsed by EPD on 23 September 2008
(appended in Appendix 8.1). A total of 10
boreholes (including 7 in the West Portion and 3 in the East Portion) were
proposed in the endorsed CAP to identify the potential land contamination
issues along the CKR alignment.
A total of 74 soil and 7 groundwater samples were
collected from these 10 boreholes. The analytical testing results of the soil
and groundwater samples collected were presented in the Contamination
Assessment Report (CAR) and Remediation Action Plan (RAP) which was submitted
to EPD in November 2010 (appended in Appendix 8.2).
Based on the testing results, exceedances
of the relevant Risk-Based Remediation Goal (RBRG)
values have been identified in 3 boreholes (PBH4, PBH5 and PBH7). Hence, a
confirmatory investigation involving 7 boreholes (including 5 in the West
Portion and 2 in the East Portion) was proposed in the CAR/RAP to delineate the
extent of the contamination detected.
Subsequently, additional at-grade works areas have been
proposed and a Supplementary CAP (appended in Appendix 8.3)
was prepared and submitted to EPD separately to address the latest changes and
also to cover the confirmatory investigation works proposed in the CAR/RAP. The
Supplementary CAP was endorsed by EPD in February 2012.
A total of 8 boreholes were proposed in the
Supplementary CAP including 7 boreholes for the confirmatory investigation and
1 borehole for the additional works area. However, due to site constraints,
only 5 boreholes have been partially or fully completed from which a total of
41 soil samples were collected. All the collected samples were analysed by a HOKLAS accredited laboratory for all
parameters listed in the Supplementary CAP. A Supplemented CAR/RAP presenting
the findings of the SI works has been submitted to EPD for retention in January 2013 (appended in Appendix 8.4).
Legislation
and non-statutory guidance for carrying out the land contamination assessment
is as follow:
·
Technical
Memorandum on Environmental Impact Assessment Process (TM-EIAO);
·
Practice
Guide for Investigation and Remediation of Contaminated Land;
·
Guidance Notes for Contaminated Land Assessment and
Remediation; and
·
Guidance Manual for Use of Risk-Based Remediation Goals
(RBRGs) for Contaminated Land Management, EPD.
The assessment of the potential
land contamination concerns along the CKR alignment has been carried out by
reviewing the relevant information such as geological information, aerial
photos and site survey. Potentially contaminated sites have been identified
based on the information reviewed.
8.3.1
Geology
The geological profile of the
proposed CKR alignment is shown in the endorsed CAP in Appendix 8.1. The materials
encountered during the SI works consists of fill, fill derived from marine
deposit, marine deposit and alluvium.
8.3.2
Historical Information
With the aid of selected aerial
photos between 1967 and 2008, the historical landuse
along the CKR alignment has been reviewed and the findings are summarised in
below.
West Portion (Yau Ma Tei)
From the aerial photos covering
areas near the Yau Ma Tei Typhoon Shelter, areas along the West Portion of the
proposed CKR alignment is mainly occupied by residential buildings. Reclamation
in the old Yau Ma Tei Typhoon Shelter to form a new reclaimed land and the new
typhoon shelter was completed in 1992. West Kowloon Highway Interchange was
constructed in 1990s. The land that will be affected by the Assignment has not
undergone much change since the completion of the reclamation and is mainly
open space and open car parks. No former shipyard sites were found within the
project boundary of the Assignment.
Central Portion (Ho Man Tin)
Landuse identified along the Central Portion of the proposed
CKR alignment is mainly natural terrain and residential use. The Housing
Authority Mock-up Centre was already constructed in 2000 and remained
unchanged. No other major change in landuse was
observed.
East Portion (To Kwa Wan/ Ma Tau Kok/ Kai Tak)
Landuse identified along the East Portion of the proposed CKR
alignment include Kai Tak Airport, Hong Kong & China Gas Company Ltd (HKCG)
Ma Tau Kok Gas Works (North Plant & South Plant), Bus Terminus/ Car park,
Ma Tau Kok Ferry Pier, Kapok Industrial Building, and EMSD Sung Wong Toi
Vehicle Repair and Maintenance Workshop which were constructed before 1967. Kai
Tak Airport ceased operation since 1997. The HKCG Ma Tau Kok Gas Works (South
Plan) was demolished in the 1990s and the site was developed into residential
use in 2007.
Site survey was conducted to
confirm findings of the desktop study and to identify other landuse
along the proposed CKR alignment which may cause potential soil and groundwater
contamination. The potentially contaminative landuse
identified during the site survey include:
·
Liquefied Petroleum Gas (LPG) Filling Station
·
Open Car Park Areas (Flyway Carpark)
·
CLP Yau Ma Tei Substation
·
Ma Tau Kok Gas Work
·
Kowloon City Bus Terminus
8.5
Future Landuse and Activities
The RBRGs was categorised into
four different post-restoration landuse, namely
“Urban Residential”, “Rural Residential”, “Industrial” and “Public Parks”, to
reflect the actual settings which people could be exposed to contaminated soil
or groundwater. Definitions of the four post-restoration landuse
categories are given in EPD’s Guidance
Note for Contaminated Land Assessment and Remediation and RBRGs Guidance Manual.
Considering the future landuse
of CKR which will either be intended for public open spaces or roads, RBRGs
(Public Park)[1]
would be adopted. Yet, the assessment
has covered all four landuse categories in case the
excavated contaminated soil was used as public fill for unidentified
after-uses.
For the additional works area,
since the future landuse has not yet been confirmed,
the most stringent set of RBRGs (the lowest RBRGs values) will be adopted for
data analyses.
8.6
Potentially
Contaminated Sites
Based on the selected aerial photos and information collected from the site survey, 8 potentially contaminated sites have been identified. Details of the potentially contaminated sites are summarised in Table 8.1 below.
Table 8.1:
Potentially Contaminated Sites
|
Landuse with Potential Land Contamination Concern |
Potential Sources of Contamination |
Site Investigation Requirement |
Remarks |
|
West Portion |
|||
|
Liquefied Petroleum Gas (LPG) Filling Station |
Potential contamination due to the on-site underground storage tanks (USTs) for LPG |
No |
The site is located 50m away from the project boundary and there is little chance of land contamination by nature of the storage and activities on-site |
|
Open Car Park Areas (Flyway Carpark) |
Possible spillage/ leakage of fuel |
No |
No chemicals were used on-site. The car park is asphalt paved and no evidence of spills/ leakages were likely. |
|
CLP Yau Ma Tei Substation |
Potential contamination due to chemical wastes |
Yes |
- |
|
East Portion |
|||
|
Ma Tau Kok Gas Work |
Potential contamination from the on-site diesel USTs |
Yes |
- |
|
Kowloon City Bus Terminus |
Potential contamination from fuel |
Yes |
- |
|
Area adjacent to the To Kwa Wan Vehicle Inspection Centre |
Possible spillage/ leakage of fuel |
Yes |
- |
|
EMSD Sung Wong Toi Vehicle Repair and Maintenance Workshop |
Release of oils and fuels and lubricants from vehicles, vehicle and equipment maintenance and refuelling. Use of chemicals and solvent in maintenance activities. Motor vehicle painting and storage and portable containers. |
No |
Remediation work is in progress under another consultancy service[1] |
|
Former Kai Tak Airport |
Historical leakage of aviation fuel |
No |
Site cleaned up by CEDD (former TDD)[2] |
Note:
[1]
Agreement No.: 2P10CT10 Consultancy for Decontamination and
Remediation Works for Sung Wong Toi Vehicle Repair and Maintenance Workshop and
Kowloon Bay Vehicle Servicing Station
[2]
CEDD and TDD denote “Civil Engineering and Development
Department” and “Territory Development Department” respectively.
A Contamination Assessment Plan (CAP) has been prepared which set out the requirements and methodologies for a land contamination assessment along the CKR alignment and was endorsed by EPD on 23 September 2008. Site investigation (SI) proposed in the endorsed CAP were conducted in 2009 at 10 boreholes (including 7 in the West Portion and 3 in the East Portion as shown in Figure 8.1 and Figure 8.2) in accordance with the requirements stipulated in the endorsed CAP (Appendix 8.1). A total of 74 soil and 7 groundwater samples were collected from these 10 boreholes. All the samples collected were analysed by a HOKLAS accredited laboratory for all parameters listed in the endorsed CAP.
A CAR/RAP (Appendix 8.3) was submitted to EPD in November 2011 to summarise and
present the testing results of the SI works. Based on the testing results, exceedances of the relevant Risk-Based Remediation Goal (RBRG) values have been
identified in 3 boreholes (PBH4, PBH5 and PBH7). Locations of these boreholes
are shown in Figure 8.3 and Figure 8.4. In order to
delineate the extent of the contamination detected, a confirmatory
investigation involving 7 boreholes (including 5 in the West Portion and 2 in
the East Portion as shown in Figure 8.3 and Figure 8.4) was proposed in the CAR/RAP.
Subsequently,
since additional at-grade works areas have been proposed, a Supplementary CAP
(appended in Appendix 8.2) was prepared and submitted to EPD separately to address the
latest changes. The Supplementary CAP was endorsed by EPD in February 2012.
A total of 8 boreholes were proposed in the endorsed Supplementary CAP including 7 boreholes for the confirmatory investigation proposed in the CAR/RAP and 1 borehole for the additional works area (as shown in Figure 8.3 and Figure 8.4). SI works for these boreholes were conducted in 2011 and 2012.
However, due to site constraints, only 5 out of the 8
boreholes proposed in the endorsed Supplementary CAP have been completed or
partially completed. A total of 41 soil samples were collected from these 5
boreholes and all the samples were analysed by a
HOKLAS accredited laboratory for all parameters listed in the endorsed
Supplementary CAP. Based on the testing results of the soil samples collected
from these 5 boreholes, no RBRGs exceedances have
been detected. A Supplemented CAR/RAP presenting the findings of the SI works
has been submitted to EPD for retention on January 2013 (appended in Appendix 8.4).A summary of the SI works conducted is given in Table 8.2.
Table 8.2: Summary
of SI Works Conducted
|
Borehole ID |
Locations |
Purpose of the Boreholes |
Remarks |
|
SI works in 2009 |
|||
|
PBH0/PBH0A |
West Portion |
Borehole locations for land contamination assessment of the
CKR alignment |
- |
|
PBH1 |
- |
||
|
PBH2 |
- |
||
|
PBH3 |
- |
||
|
PBH4 |
Exceedances of RBRGs detected |
||
|
PBH5 |
Exceedances of RBRGs detected |
||
|
PBH6 |
East Portion |
Borehole locations for land contamination assessment of the
CKR alignment |
- |
|
PBH7 |
Exceedances of RBRGs detected |
||
|
PBH8 |
- |
||
|
SI works in 2011 and 2012
(for confirmatory investigation and the additional works area) |
|||
|
WBH1A |
West Portion |
Borehole locations for confirmatory investigation |
- |
|
WBH2A |
- |
||
|
WBH3 |
- |
||
|
WBH4 |
Sampling completed to 1.50 mbgl[1]
as oppose to the proposed 20.00 mbgl due to
underground utility encountered. |
||
|
WBH5 |
Could not be completed due to concrete slab encountered. |
||
|
EBH1 |
East Portion |
Borehole locations for confirmatory investigation |
Sampling completed to 0.50 mbgl as
oppose to the proposed 20.00 mbgl due to
underground utility encountered. |
|
EBH2 |
Could not be completed due to constraints of site access |
||
|
EBH3 |
Borehole location for land contamination assessment of
additional works area |
Could not be completed due to constraints of site access |
|
Note:
[1] “mbgl”
denotes meter below ground level.
8.8
Identification and
Evaluation of Land Contamination
For the SI works conducted in 2009, no exceedances of RBRGs were detected except for 3 soil samples collected from PBH4, PBH5, and PBH7 where exceedance of the RBRGs for Lead or PCBs have been identified. As summarised in Table 8.3 below, the contamination detected exceeded the RBRGs for “Urban Residential” and “Rural Residential” but not “Industrial” and “Public Park”. Locations of these contaminated boreholes are shown in Figure 8.1 and Figure 8.2.
For
the SI works conducted in 2011 and 2012, based on the available testing
results, no exceedances were detected in any of the
soil samples collected.
Table
8.3: Summary of Soil Samples with
RBRGs Exceedance
|
Borehole ID |
Locations |
Sample Depth (mgbl) |
Contaminants |
Concentrations (mg/kg) |
|
PBH4 |
West Portion |
3.00 – 3.95 |
PCBs |
0.5 |
|
PBH5 |
7.00 – 7.95 |
Lead |
570 |
|
|
PBH7 |
East Portion |
7.00 – 7.95 |
Lead |
490 |
Note:
1.
RBRGs for Lead – Urban residential:
258mg/kg; Rural Residential: 255 mg/kg; Industrial: 2290 mg/kg; Public Park:
857mg/kg.
2.
RBRGs for PCBs – Urban residential:
0.236mg/kg; Rural Residential: 0.226mg/kg; Industrial: 0.748; Public Park –
0.756mg/kg.
8.9
Possible Soil
Contamination Extent
As discussed above, RBRGs exceedances have been detected in PBH4, PBH5 and PBH7. However, only PBH4 and PBH7 are located within the CKR cut-and-cover section, PBH5 is located outside the CKR alignment and does not fall within the excavation extent, hence the contaminated soil identified at PBH5 would not be excavated.
Contamination extent has been estimated for PBH4 based on the available testing results from WBH1, WBH2 and WBH3 which are intended to investigate the coverage of contamination detected at PBH4. Since only marginal exceedance of the RBRGs limit of PCBs was detected in PBH4, and the PCBs level detected at WBH1, WBH2, and WBH3 were all below detection limit (i.e. <0.1mg/kg), it could be reasonably assumed that the contamination detected at PBH4 was relatively localised. Hence, a circular area with a radius of 5m centred at PBH4 is considered adequate to cover the contamination extent at PBH4. The contamination extent is depicted in Figure 8.5.
Based on the contamination extent, it is estimated that approximately 157m3 of contamination soil would be excavated from PBH4. The estimation of the contaminated soil quantity to be excavated is summarised in Table 8.4 below.
Table
8.4: Estimated Quantity of
Contaminated Soil
|
Contaminated Borehole |
Radius of the Contaminated Zone (m) |
Estimated Vertical Extent of Contamination (m)[1] |
Estimated Area of the Contaminated Zones (m2) |
Estimated Quantity of Contaminated Soil (m3) |
|
PBH4 |
5 |
2.0 (2.5m – 4.5m) |
78.5 |
157 |
|
|
|
|
Total: |
157 |
Note:
[1]
In estimating the vertical extent of contamination, the full
depth of soil sampling (i.e. 1m) is taken as contaminated. Besides, a depth of
0.5m above and below the sampling depth will also be taken as contaminated as a
conservative estimate.
For PBH7, since the SI works could not be completed for boreholes EBH1 and EBH2, which are intended to confirm the extent of the contamination detected at PBH7, the contamination extent of PBH7 could not be determined at this stage.
Similarly, since SI works could not be completed for EBH3, the potential land contamination issues at the additional works area could not be evaluated at this stage.
8.10.1
Confirmatory Investigation at WBH4 and WBH5
The purpose of WBH4 and WBH5 is
the same as WBH1, WBH2 and WBH3 which is to confirm the extent of contamination
detected at PBH4. Since no RBRGs exceedances were
identified in all the available testing results from WBH1, WBH2 and WBH3, the exceedance detected at PBH4 could reasonably be regarded as
localised contamination. As the purpose of confirming the contamination extent
at PBH4 has already been achieved, subject to agreement with EPD, WBH4 and WBH5
would be cancelled.
8.10.2
Confirmatory Investigation at EBH1 and EBH2
At this stage, SI works could
not be completed for EBH1 and EBH2 due to underground utility and site access
constraints respectively. The SI works at these two boreholes would need to be
carried out at a later stage e.g. after possession of site and utility
diversion by the construction contractor.
8.10.3
Land Contamination Assessment at EBH3
Due to site access constraints,
SI works at EBH3 could not be conducted at this stage and therefore would need
to be carried out at a later stage e.g. after possession of site by the construction
contractor.
Following the completion of the remaining SI works at EBH1, EBH2 and EBH3, the Project Proponent would prepare and submit a Second Supplementary CAR/RAP to EPD to present the findings of the remaining SI works and to recommend specific remediation measures, if required. Upon completion of the remediation works, if any, a Remediation Report (RR) would be prepared and submitted to EPD for agreement prior to commencement of the construction works.
8.11
Soil Remediation Options & Recommendations
It is currently estimated that
approximately 157m3 of contaminated soil will be generated during
the construction phase of the Assignment. Considering the small quantity
involved and that the level of contamination detected did not exceed RBRGs (Public
Park) which is a more representative
landuse for CKR, on-site reuse of the contaminated
soil within the boundary of CKR, such
as using to backfill in non-pedestrian use area under new flyover, would be recommended as the remediation option for the
contaminated soil. A Remediation Action Plan (RAP) presenting the remediation
option recommended has been prepared and submitted to EPD for agreement in May
2012 (appended in Appendix 8.4).
Although the above estimation
is subject to findings of the remaining SI works which would be re-scheduled at
a later stage e.g. after possession of site and utility diversion by the
construction contractor, the contamination issue is anticipated to be surmountable
with the supportive view that the contamination identified are relatively
localised, likely contaminants are generic and easily remediated as remediation
methods available in the market are well established and nature of the possible
contaminants can be dealt with by sufficient local remediation experience.
A land contamination assessment has been conducted for
the Assignment. Background information including geological conditions and
selected aerial photos has been reviewed and site survey has been conducted to
identify the potentially contaminated sites along the proposed CKR alignment.
Based on the testing results collected from the SI works
conducted in 2009, exceedances were detected at 3
boreholes including PBH4, PBH5 and PBH7. Based on the confirmatory
investigation conducted in 2011 and 2012, the contamination extent at PBH4 has
been determined and the quantity of contaminated soil to be generated from PBH4
was estimated at 157m3.
Considering the small quantity
of contaminated soil to be generated from PBH4 and that the level of
contamination detected did not exceed RBRGs (Public
Park) which is a more representative
landuse for CKR, on-site reuse of the contaminated
soil within the boundary of CKR, such as using to backfill in non-pedestrian
use area under new flyover, would be
recommended as the remediation option for the contaminated soil. A Remediation
Action Plan (RAP) presenting the remediation option recommended has been
prepared and submitted to EPD for retention in January 2013.
Investigation of contamination extents at PBH5 is not required as this borehole is located outside the CKR alignment and does not fall within the excavation extent. For PBH7, since the SI works could not be completed for boreholes EBH1 and EBH2 which are intended to confirm the extent of the contamination detected at PBH7, the contamination extent of PBH7 could not be determined at this stage.
The potential for land contamination issues at EBH1, EBH2, and EBH3 will be confirmed by site investigation after site possession and utility diversion by the construction contractor. Following the completion of the remaining SI works, the Project Proponent would prepare and submit a Second Supplementary CAR/RAP to EPD to present the findings of the SI works and to recommend specific remediation measures, if required. Upon completion of the remediation works, if any, a Remediation Report (RR) would be prepared and submitted to EPD for agreement prior to commencement of the construction works.
Nevertheless, the contamination
issue is anticipated to be surmountable with the supportive view that the
contamination identified are relatively localised, likely contaminants are
generic and easily remediated as remediation methods available in the market
are well established and nature of the possible contaminants can be dealt with
by sufficient local remediation experience.
[1]
Considering the future
landuse of CKR,
the corresponding
RBRGs
would be
“Lower of
Industrial or Public Park”.
Taken
into account the respective RBRGs criteria for the two parameters concerned
(i.e. Lead and PCBs),
RBRGs (Public Park)
would be adopted.