7
Land Contamination
7.1.1
Contaminated land refers to the land which has
been polluted by hazardous substances as a result of industrial operations
carried out on the site over a number of years. These contaminants if present,
may pose hazardous risks or cause adverse effects to the land users and the
nearby environment. The implications of land contamination associated with the
widening of Tuen Mun Road (TMR) at Tsing Tin Interchange were assessed in
accordance with Section 3.4.4.2(iii)
of the EIA Study Brief (ESB-127/2005) in this section.
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 Workshop” issued by
Environmental Protection Department (EPD) provides guidance on land
contamination assessment. The Guidance Notes make reference to criteria
developed in the Netherlands
(the “Dutch Guidelines”) which are most comprehensive and are widely used for
contaminated site assessment. The
Dutch “B” levels under the Dutch Guidelines stipulated in the ProPECC Notes No.
3/94 shall be adopted for assessing soil contamination.
7.2.2
Further consideration of contamination issues is
provided in 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).
7.3
Assessment
methodology
7.3.1
In order to identify and evaluate the potential
contamination impacts associated with the Project, the following tasks have
been undertaken:
l
Desktop study to review the current and historical land
uses; and
l
Site inspection to confirm the existing land uses.
7.3.2
In addition, the following sources of information
have been collated and reviewed:
l
Aerial photographs from Lands Department;
l
Ground investigation (GI) reports from Civil
Engineering Development and Department (CEDD) Geotechnical Information Library;
and
l
Records and photographs from site visits.
Geology and Hydrogeology
7.4.1
A review of previous GI reports undertaken at or in
the vicinity of the Project boundary was conducted to obtain available
information about the geological and hydrogeological conditions of the Project
site. The following GI reports are reviewed:
l
Tuen Mun New Town
Geotechnical Report on Reinforced Earth Alternative by Scott Wilson
Kirkpartrick & Partners (CEDD’s Geotechnical Information Unit Report
No.13643)
l
Final Ground
Investigation Data Report of PTI Area Under Contract No. DD-210 by Maunsell
Consultants Asia Ltd. (CEDD’s Geotechnical Information Unit Report No35267)
l
Fieldwork Report
(Volume 7 of 8) Under A.S.D. Term Contract No. TCC E321 by I-P Foundations Ltd.
(CEDD’s Geotechnical Information Unit Report No29248)
l
Geotechnical
Report on Road Embankments Addendum Under Contract 12/TM/82 by Scott Wilson
Kirkpartrick & Partners (CEDD’s Geotechnical Information Unit Report
No.10345)
7.4.2
With reference to the GI reports, the general
geological sequence around the Project site was mainly fill, marine deposit,
alluvium and completely to highly decomposed rock. The immediate top layer of
the fill was mainly yellowish grey silty sand with gravel. The top layer of
soil was determined to be around 0.5m-3m.
7.4.3
According to the groundwater levels recorded in some
of the reviewed GI reports, the groundwater level varied from +6.23mPD near Brillant
Garden to +2.8mPD near the
Tsing Tin Interchange. The general groundwater pattern likely flows from east
to west i.e. from Siu Hong to Ho Tin. It was anticipated that the groundwater
level was around 1m
to 5m
below ground at the Project site.
Site History
7.4.4
Historical aerial photographs (Table 7.1)
covering the study area was reviewed to evaluate any land use changes
associated with potential contamination implication within the Project
boundary.
Table 7.1 Reviewed
Historical Aerial Photographs
|
Year
|
Ref. No.
|
Height (ft)
|
|
1949
|
5045
|
5800
|
|
1974
|
10320
|
4000
|
|
1978
|
23595
|
4000
|
|
1980
|
32353
|
4000
|
|
1984
|
55535
|
4000
|
|
1985
|
CN925
|
4000
|
|
1990
|
A22820
|
4000
|
|
1998
|
CN21427
|
4000
|
|
2006
|
CW1367
|
4000
|
Source
of historical aerial photographs: Survey and Mapping Office, Lands Department.
7.4.5
The findings of the review of historical aerial
photographs are summarized as follows:
Year 1949-1980
Ÿ
The earliest aerial photograph relevant to assessment area was taken in 1949. As shown in the aerial photograph of 1949, only Castle
Peak Road was constructed and the surrounding environment of the assessment area was mainly
occupied by farmland. TMR was noted in 1978 aerial photograph and was found to
be surrounded mainly by residential buildings and open area.
Year 1984-1985
Ÿ
Tsing Tin Interchange was found under
construction in the period from 1984 to 1985. The surrounding areas of the
Project site were mainly residential areas.
Year 1988-2006
Ÿ
No apparent change in the site
layout was found in the period from 1988 to 2006. Parks, housing estates,
hospital and school were found around the Project site.
7.5.1
A site inspection was conducted on 11 May 2007 to
identify any contamination hotspots within the Project boundary. All accessible
areas were inspected as far as practicable to collect information about the
current activities undertaken within the Project site. Photo-documentation was
also undertaken if possible and provided in Appendix 7.1. Findings of
the site inspection are summarised as follows:
7.5.2
TMR was found at the south of the Tuen Mun River
Channel. As observed, the areas around Tsing Tin Interchange were found to be
mainly surrounded by parks, playground and residential buildings. A secondary
school was also found at the western part of the Project site. Since the areas
within/in vicinity of the Project site have been mainly used for institution
and community uses, it is therefore unlikely to have potential land
contamination impacts from these land uses.
7.5.3
During the site inspection, a petrol filling station
was found located at the interchange of San Tak Street and TMR (approximately 30m
away from the Project boundary), however, it was observed that the petrol
filling station was kept in tidy and the ground was well paved with concrete.
As discussed in Section 7.4.3,
the general groundwater pattern of the Project site likely flows from east to
west (i.e. from the direction of alignment to that of the filling station),
potential land contamination impacts from this petrol filling station to the
Project site are not expected.
7.6.1
Based on the findings from the desktop studies and
site inspection, no contaminated sites were identified within/in vicinity of
the Project boundary. No adverse environmental impacts on land contamination
for the Project are anticipated.