9.
CONTAMINATED LAND ASSESSMENT
Introduction
9.1
Contamination can be defined as
"the introduction by man into the environment of substances or energy
liable to cause hazards to human health, harm to living resources and
ecological systems, damage to structures or amenity, or interference with
legitimate uses of the environment" (Holdgate 1979, and adopted by the
RCEP, 1984). The soil is a primary recipient, intended or otherwise, of many
waste products and chemicals used in modern society.
9.2
The Spur Line passes across a
range of landuses, including agricultural, residential, container storage,
industrial and fish farming areas. While there are no extensive areas of
contaminated land such as landfills, chemical stores, etc. across which the
Spur Line passes, there is potential for the presence of small industries or
storage sites to create an impact in the construction and operation of the Spur
Line. This contaminated land assessment has been written to present the
potential impact from the presence of contaminated land on the Spur Line
project in accordance with EPD Practice Note for Professional Persons
Concerning ProPECC PN 3/94 - Contaminated
Land Assessment and Remediation and the EPD Guidance Notes for Investigation and Remediation of Contaminated Sites
of: Petrol Filling Stations, Boatyards or Car Repair/Dismantling Workshops.
Methodology
9.3
This contaminated land
assessment includes the following steps:
(i) A
desktop study on the history of landuse along the Spur Line alignment (the
Desktop Study) which provides a clear and detailed account of the relevant past
land history and the present land uses along the alignment. This identifies
areas of potential land contamination.
(ii) A
site survey in order to identify potential 'hot spots' and pollutants for the
land contamination assessment.
(iii) Recommendations
for a schedule of 2 stage sampling, initially at potential “hot spots”
identified in the Desktop Study and during the site survey followed by grid
sampling if contamination is confirmed, and the laboratory analysis of
essential parameters. This should be carried out at the site investigation stage
of works to confirm the presence or absence of contamination.
(iv) Recommendations
on appropriate remedial action for several scenarios based on the range of
different types of contaminants which may be found during site investigations.
Any remedial action proposed will be beneficial not only in terms of preparing
the land for construction but will also alleviate potential impacts on
groundwater, water quality in river courses and the ecology of the area.
(v) The
application of the recommended sampling, analysis and remediation programme to
specific locations along the alignment to facilitate the implementation of the
Contamination Action Plan during the site investigation stage.
Study Area
9.4
The Study Area includes the direct track alignment and
the engineering works boundary (Figure 2.1). Three temporary works areas
have been earmarked at Lok Ma Chau, Kwu Tung and at the Sheung Shui Temporary
Housing Area. In the Lok Ma Chau area, fishponds will require temporary draining
and stabilisation with partial or complete infilling to create a base for
pier and station foundation works.
9.5
Most of the alignment passes
through rural areas dominated by agriculture. In these areas the potential for
contamination is minimal. However, around Sheung Shui and in Kwu Tung a number
of small industries and storage areas exist. At the Lok Ma Chau end of the
alignment are a number of container storage yards which may contribute to land
contamination.
9.6
The total alignment will include
viaduct across low-lying areas such as Long Valley and Lok Ma Chau fishponds
and at grade, cutting and embankment sections as it passes through Kwu Tung,
Pak Shek Au and Chau Tau. Details of the alignment are provided in Chapter 21. The type and
suitability of mitigation measures in a potentially contaminated site is
largely determined by whether the alignment is at grade, in a cutting, on
embankment or on viaduct.
9.7
Construction methods will
include foundation works for the viaduct supports and for Lok Ma Chau station
construction, bored piling works, and excavation of material along the sections
at grade and in cutting.
Risks to Health
9.8
A contamination assessment is
important because of the health risks posed to site workers on exposure to
contaminated soil or sediments, and contamination of groundwater during earth
moving operations, excavation or piling works. Workers could become exposed to
contaminants either directly e.g. skin contact during the work by inhalation of
dust or vapours, or through ingestion whilst eating or smoking on site.
9.9
If remediation is found to be
necessary at any point of the alignment it should be carried out to a suitable
level so as not to pose any future health risks to users of the site. As long
as there is no direct human - soil interface, it is likely that in many places
the sediments could remain in-situ or be remediated to a level sufficient for
its future use.
9.10
Contaminants of particular
concern due to their potential health risks include inorganics such as cyanides
and heavy metals, organics such as mineral oils, halogenated solvents,
polycyclic aromatic hydrocarbons and volatile aromatic hydrocarbons and
minerals such as asbestos.
9.11
Contaminants may also pose a
fire hazard or explosion risk if volatile gasses or flammable contaminants are
found.
Desktop Study
Industries Having the Potential to Cause
Land Contamination
9.12
Historically there is evidence
that the New Territories was the location for various light industries and
other landuses which change frequently but often have a potential to
contaminate the land. These include car repair yards, container storage areas,
livestock farms, paint and dye factories and other small scale industries. Many
of these small industries still operate today, although the density of
factories has reduced over recent years. In addition there are dumping grounds,
refuse collection points and illegal dumping areas which are likely to result
in some ground contamination. Many of these landuses fall within the areas of
the proposed alignment and, if unmitigated, give rise to concern for their
future landuse.
9.13
A number of industries
have been identified in ProPECC PN 3/94 as having the potential to cause land
contamination. These include:
·
oil installations (e.g. oil depots, oil filling
stations);
·
gas works;
·
power plants;
·
shipyards/boatyards;
·
chemical
manufacturing/processing plants;
·
steel mills/metal workshops; and
·
car repairing/dismantling
workshops.
9.14
This list is not exhaustive and
judgement is needed to determine if contamination is likely from other land
uses or industries. For example, there are several sites along the Spur Line
alignment where chemicals used to treat leather are stored. Such solvents are
known to be hazardous to the environment (LaGrega, 1994).
Land Ownership
9.15
There is a variety of ownership
along the alignment of the Spur Line. Across Long Valley there are many
agricultural lots, whilst in Kwu Tung many owner occupied small houses typical
of the New Territories are found. Significant Some areas of land along the alignment are
Government Land, particularly in the Lok Ma Chau and Sheung Shui areas. However, the latter
Government-owned areas are generally not the areas of potential contamination.
Landuse History
9.16
In order to assess potential
land contamination, the past landuse history and the present landuse of the
areas which will fall under the Spur Line alignment have been reviewed. Aerial
photographs have been used and landuse information has been obtained from the
District Land Offices in Yuen Long (DLO Yuen Long) and Fanling (DLO North).
Site Survey
Objectives and Methodology
9.17
The objectives of a site survey
for the land contamination assessment are to confirm any land-uses found in the
DLO records and to identify any other uses which may be illegal and not
recorded. The site survey has also been used to gather information on other
activities such as storage and management of hazardous substances.
9.18
Site inspections were carried
out on 17 May and 27 July 1999. No advance notice was given to land users in
order to obtain as authentic information as possible. A number of sites along
the alignment were disregarded due to information obtained during the desktop
study and site visits which indicated no likelihood of contamination. The
findings of the site survey are evaluated to identify potential "hot
spots" and parameters for further investigation in a sampling and analysis
programme.
9.19
Ground conditions were also
observed during the site surveys, to determine the ease of infiltration and
potential for underground dispersion of pollutants.
Results of Desktop Study and Site Visits
9.20
A full listing of the desktop study
results and the findings of site visits to each site are provided in Appendix
K. As some sites cover more than one lot, each site listed has been assigned
a letter. The sites are described from west to east along the alignment and
their location identified in Figures 9.1 9.2
9.3. The nature of the land in each lot, and the
activities being carried out which may potentially contaminate the ground,
are shown in Plates 9.1 to 9.32.
Not all lots could be photographed, however, a description of each lot is
given in the following tables. Table 9.1 lists lot numbers, their assigned
letter and whether each site is at grade, on viaduct or through cutting.
Table 9.1 Lot Numbers, Assigned Letters and Elevation
Letter |
Lot Number |
Elevation |
Letter |
Lot Number |
Elevation |
A (i) |
DD99/372 S.D RP - Northern Section |
Viaduct |
|
|
|
A (ii) |
DD99/372 S.D RP - Southern Section |
Viaduct |
|
|
|
B |
DD99/ 470 - 483, 486 - 493, 527, 545 - 548 |
|
|
|
Viaduct |
C |
DD96/352, 353, 354, 355, 423 |
|
|
|
Viaduct |
D |
DD96/ 428 |
|
|
|
Viaduct |
E |
DD96/2250 |
|
|
|
Viaduct |
F,
G |
DD 96/6 |
|
|
|
Viaduct |
|
|
Cutting |
|
|
Viaduct |
|
|
Cutting |
|
|
Viaduct |
|
|
Cutting |
|
|
Viaduct |
|
|
Cutting |
|
|
|
9.21
Table 9.2 summarises the results
of the desktop study and site visits. The table lists the registered landuse of
the site and the likely potential and extent of contamination. Appendix K
includes any permit numbers or Short Term Tenancy Agreements (STT) or Short
Term Waivers (STW) which cover the lots.
Table 9.2
Findings of Desktop Study & Site Visits and the
likely Potential for Contamination
Site and Lot No. |
Figure No. / Plate No |
DLO Registered Landuse |
Site Inspection |
Potential for Land
Contamination |
A DD99/372 |
Container vehicle park, open storage |
Confirmed landuse. Some petrol pumps, chemical waste
area |
Likely, rough surface, cracked concrete, storage of
chemical and hydrocarbons on site |
|
B DD99/470-483,
486-493, 527, 545-548 |
NA* |
Containers, open storage, storage of chemicals, oils
and solvents |
Likely, gravel and cracked surface and storage of
potential contaminants and scrap metals |
|
C DD96/352,
353, 354, 355, 423 |
NA* |
Sign said car repairs. Storage of many chemical
drums, most marked harmful |
Likely, evidence of spillage on ground. Concrete
cracked |
|
D DD96/428 |
NA* |
Disused/abandoned pig farm with chemical storage |
Likely, cracked surface and spillage evident |
|
E DD/96/2250 |
|
Storage of building materials |
Storage of large metal containers. No access was
allowed |
Unknown. Further clarification of activities and any
chemical storage required |
|
|
|
|
|
F,
G DD96/645 |
NA* |
Farm buildings, chemical storage, livestock waste
drums, site generally littered with waste |
Inventory of chemicals and pesticides used required.
Rough surface may have allowed some infiltration |
|
H DD96/702 |
NA* |
Car repairs/dismantling yard - no access allowed |
Likely but unknown. Probably hydrocarbon and heavy
metal waste. |
|
I DD96/704,
705, 709, 716 |
NA* |
Container lorries parking, some storage of old
chemical drums |
Possible but identification of past spillages would
be required. |
|
J DD96/698, 699 |
NA* |
Farm buildings. Some storage of chemicals and
livestock feeds |
Possible - further identification of chemicals and
feeds required |
|
K DD96/717,
718, 721 |
NA* |
|
|
|
L Gut
Land |
|
Permits for agricultural buildings and activities |
Several pig farms |
Possible - depending on chemicals used and stored. |
M DD95/786,
791, 792, 722 |
Illegal container storage |
Container and storage area with temporary
structures. Surface rough and some chemicals stored |
Possible - depending on whether any spillages have
occurred. |
|
N DD96/772 |
No registered landuse |
Metal recycling company. Many parked vehicles, rough
gravel surface. |
Possible - depending on whether spillages have
occurred |
|
O ( DD95/801 |
|
Sawmill and timberyard |
No access to site |
Unknown |
O (ii) DD95/801 |
|
Sawmill and timberyard |
Storage of timber. No chemical treatment is carried
out on site |
Unlikely. |
P DD95/803 |
|
NA* |
Storage area for adjacent factory. |
Possible form historic contamination as this was a
leather goods factory |
R DD95/803 |
NA* |
Car repairs/dismantling yard. Ground concreted and
vegetated |
Likely due to infiltration through cracked concrete
and vegetation |
|
S DD95/1994 |
Metal Works |
Disused metal workshop, concrete surface |
Unlikely due to concrete surface. But should not be
dismissed as this is a ProPECC PN 3/94 defined activity. |
|
T DD95/43-45,
53-59, 65-67, 70-74 |
NA* |
Access denied but site is fenced and appears to be
used as a repairs and maintenance site for Paul Y ITC |
Likely but activities carried out here must be
clarified |
|
U DD96/717,
718, 721 |
|
Rough
surface, many chemical drums stored and spillage noted over cracked concrete.
May be just outside works area but chemicals may also have been moved around
site. |
Initially
determine if the chemical storage area falls within the works area.
Contamination is likely at this point. Testing should also clarify whether
the drums have previously contaminated any other area of the site. |
Note NA* - No
information available from DLO
9.22
The main areas for concern are container storage
areas, particularly those in DD99 close to Lok Ma Chau (A and B), the chemical
storage area east of Pak Shek Au, (K), any car repair/dismantling yards and the
unknown risks posed by the former leather factory (P and Q).
9.23
The main contaminants are likely to be oils, organic
solvents and heavy metals. Some chemicals known to be hazardous were found.
These included methylene chloride, listed as a hazardous air pollutant (under
the US Clean Air Act, 1991). Many chloro alkanes are designated as priority
pollutants (Clean Water Act) and are on the Superfund Hazardous substances
list, as is chloroform which was found at site K. In addition to specific named
substances and chemicals there was much evidence of oil and petrol spillage,
piles of scrap metals and storage of unspecified chemicals.
Site
Appraisal
9.24
From the desktop study and site visit information
collected, it is possible to determine whether a contaminated land site
investigation is needed. This information was used to check against the set of
criteria described in Table 9.3 which is taken from the EPD Guidance Notes for Investigation and
Remediation of Contaminated Sites of: Petrol Filling Stations, Boatyards or Car
Repair/Dismantling Workshops. For this set of landuses if the answer to any
of the criteria is 'No', a full scale site investigation is recommended. A
positive answer to all criteria indicates that simplified site investigation
may be sufficient. The criteria can be used as guidelines or indicators for
different potentially contaminating landuses.
Table 9.3 Criteria for Adoption of Full-scale or
Simplified Site Investigation
Criteria |
Yes/No |
1. Length
of operation of the site is less than 5 years. |
|
2. There
is a practice of recording spill incidents or monitoring chemical storage. |
|
3. Waste
disposal is carried out in accordance with Government requirements |
|
4. Absence
of underground storage tank on site |
|
5. Absence
of surface contamination indicators which include: a) stained
areas b) uncontrolled
chemical drum storage c) cracked
concrete near storage of chemical drums d) unnatural
colours and odours; and e) abandoned
piping/mechanical components or cans. |
|
9.25
In the case of Spur Line, no
site along the alignment is known to have an underground storage tank. At
several sites where chemicals are stored, a negative answer is likely to
criteria 2 and 3 as most sites landuse is illegal and no DLO records are
available. At many of the sites there is evidence of spillage of chemicals,
uncontrolled chemical drum storage, cracked concrete or rough gravel surfaces,
all of which are criteria for full scale site investigations. On the basis of
this information, a Land Contamination Assessment Plan (CAP) is recommended.
The following section describes the CAP for the Spurline Project.
Land Contamination Assessment Plan (CAP)
9.26
This section summarises the results of the desktop
study and site inspection and proposes a sampling and analysis programme based on
the data collected. The sampling programme should be carried out during the
site investigation stage.describes the approach to be taken in the
development of the CAP. A detailed CAP showing the locations of the boreholes
and defining depths to be sampled and parameters to be sampled, will be
presented as a separate document to EPD for approval.
Site
Investigations
9.27
A site investigation should be
approached in a systematic way bearing in mind the purpose and the level of
detail which is required. The main topics, as defined by EPD (1999) are:
·
Physical site conditions, including geology,
topography, soil type and physical properties, drainage and groundwater.
·
Likely contaminants - previous
site use.
·
Extent and severity of
contamination, the concentrations, depth, spatial distribution of contamination
in both soils and groundwater.
·
Effects on users, including the
nature and level of contamination with regard to future use.
·
Potential environmental harm.
·
Hazards during construction.
9.28
The subsurface geology and
groundwater flow are important as petroleum hydrocarbons in particular can
float and migrate some distance. This could impact other drainage waters around
the Spur Line alignment and cause modification of BODs5, SS and other
important parameters. Many of the areas where potential contamination sites
were identified, are located on flat, low-lying land, not far above the water
table. There is therefore potential for contaminants to enter the groundwater
in these areas.
9.29
Table 9.4 below lists the lot
numbers and the main activities at each site identified. Likely contaminants
associated with different site activities are listed in Table 9.5. The level of
contamination and the extent of contamination need to be determined through a
formal sampling and analysis programme and the most suitable methods for clean
up of the site determined.
Table 9.4
Lots along the Spur Line and Potential Contaminating Landuses
Site |
Fuelling Areas |
Servicing /Parking Areas |
Paint Shop |
Fitting out/ repairs |
Coating/ steel treatment |
Vehicle Breaking |
Chemicals or waste storage |
Drainage and soakaway systems |
Agricultural Activities |
Unknown |
A |
√ |
√ |
√ |
√ |
√ |
√ |
√ |
√ |
|
|
B |
√ |
√ |
√ |
√ |
√ |
√ |
√ |
|
|
|
C |
|
|
|
|
|
|
√ |
|
|
|
D |
|
|
|
|
|
|
√ |
|
√ |
|
E |
|
|
|
|
|
|
|
|
|
√ |
F |
√ |
|
|
|
√ |
|
√ |
|
|
|
G |
|
|
|
|
|
|
|
|
√ |
|
H |
|
√ |
|
|
|
|
|
|
|
√
Vehicle repairs etc likely |
I |
|
√ |
|
√ |
|
|
√ |
|
|
|
J |
|
|
|
|
|
|
|
|
√ |
|
K |
|
|
|
|
|
|
√ |
|
|
|
L |
|
|
|
|
|
|
|
|
√ |
|
M |
|
√ |
√ |
√ |
|
√ |
√ |
|
|
|
N |
|
√ |
|
|
|
|
√ |
|
|
|
O (i) |
|
|
|
|
|
|
|
|
|
√ |
O (ii) |
|
|
|
|
|
|
√ |
|
|
√ |
P |
|
|
|
|
|
|
√ |
|
|
|
R |
|
√ |
√ |
√ |
|
|
√ |
|
|
|
S |
|
|
|
√ |
√ |
|
√ |
|
|
|
T |
√ |
√ |
√ |
√ |
√ |
√ |
√ |
|
|
|
U |
|
|
|
|
|
|
√ |
|
|
|
Table 9.5
Activities found along the Spur Line and their likely
associated contaminants
Contaminant |
Fuelling Areas |
Servicing/ Parking Areas |
Paint Shop |
Fitting out/repairs |
Coating/steel treatment |
Vehicle Breaking |
Chemicals or waste storage |
Drainage and soakaway systems |
Agricultural Activities |
Others |
Metals (all) |
√ |
√ |
√ |
√ |
√ |
√ |
√ |
√ |
√ |
√ |
Lead |
√ |
√ |
√ |
|
|
|
|
|
|
|
Chromium |
|
√ |
|
|
|
|
|
|
|
|
Zinc |
√ |
|
√ |
|
|
|
|
|
|
|
Copper |
√ |
√ |
|
|
|
|
|
|
|
|
Cyanides |
|
|
|
√ |
√ |
|
√ |
√ |
|
√ |
Organic Contaminants |
|
√ |
√ |
√ |
√ |
|
√ |
√ |
√ |
√ |
Simple aromatics |
√ |
√ |
|
√ |
√ |
√ |
√ |
|
|
√ |
Organic solvents |
√ |
√ |
√ |
√ |
√ |
|
√ |
|
|
√ |
Polyaromatic hydrocarbons |
|
√ |
|
|
√ |
√ |
√ |
|
|
√ |
Fuels/oils |
√ |
√ |
|
√ |
|
√ |
√ |
√ |
√ |
√ |
Biocides |
|
|
|
√ |
√ |
√ |
√ |
√ |
√ |
√ |
Oily sludges |
|
√ |
|
√ |
√ |
√ |
√ |
√ |
√ |
√ |
Microbacteriological |
|
|
|
|
|
|
√ |
√ |
√ |
√ |
Acids |
|
|
|
√ |
√ |
√ |
√ |
√ |
|
|
NOTE:
Simple aromatics includes
benzene, toluene, ethylbenzene, xylene etc
Organic solvents includes
non-halogenated and halogenated solvents
Fuels/oils includes Total
Petroleum Hydrocarbons
Acids includes sulphuric and
hydrochloric
SOURCE: EPD
(1999)
Voelcker
Science (1999)
Preliminary
Methodology for Evaluation of Contaminated Land
Selection of sampling locations
9.30
From the desktop study and site
visit information collected, the need for a contaminated land site
investigation was determined. This
information was used to identify areas of potentially contaminated land. The approach taken
to
be taken in the CAP in
selecting suitable locations for sampling and analysis tookmust take into account the following
factors:
•
The extent to which the
potentially contaminated land site overlapsped
with the KCRC Scheme boundary.
•
The form of the railway alignment
at the location of each site (viaduct, cutting or embankment/at grade).
•
The location of boreholes being
conducted for the GeotechnicalSite Investigation (S.I.)as part of the site investigation works.
9.31
The sections of each potentially
contaminated land site which fall within the Spur Line Scheme Boundary are
shown on Figures 9.4 –1 to 9.6-3 and tabulated in Table 9.6. The figures also show the limits of the
viaduct, cutting and embankment sections along the alignment. The
locations of those boreholes that are within the potentially contaminated sites
and will be used for sampling and analysis under the Contaminated Action Plan
(Stage 1) are highlighted. These
boreholes have been located to coincide as far as possible with the locations
of identified “hotspots” during site visits.Boreholes which are defined as
part of the SI should be located, as far as possible, at “hotspot” locations defined in
the CAP. These
“hotspots” are generally locations where staining has been noted from vehicles,
chemical storage areas, or spillage.
9.32
Also included on the drawings are
other boreholes from which samples will be taken and retained at the same time
as sampling from Stage 1 boreholes.
These samples will only be tested if the Stage 1 samples indicate contamination. Figures 9.7 to 9.187. Show further details of monitoring locations for
Stage 2 of the CAP investigation, if samples from Stage 1 are found to be
contaminated according to the Dutch List criteria. These figures show the grid locations for sampling under
Stage 2 of the CAP, and locations for sampling in the viaduct sections of the
railway alignment. Where these locations are within buildings (such as in farm
sites), no samples will be taken unless analysis of locations outside the
buildings have been taken and are shown to be contaminated. The number of boreholes and/or
trial pits needs to be defined in the CAP and approved by EPD as part of the Stage 1 sampling. If samples from these locations
are contaminated according to the Duch hint criteria (Appendix K), Stage 2
sampling is required. Stage 2 sampling takes the form of grid sampling
according to ProPECC PN 3/94.
9.33
Where the sites are beneath a
viaduct section of the railway, samples will
should
be taken from
boreholes close to the proposed pilecaps.
If further testing is required, this will be limited to the pilecap
locations as shown on Figures 9.7 to 9.187. The
remainder of the area around the pilecap will not be excavated and will
therefore not require investigation.
and
other areas where significant ground disturbance or excavation may occur. If changes are made to the interface of the
viaduct/cutting or viaduct/embankment sections during the detailed design
stage, the principles described in this section regarding number and location
of samples in each type of railway section should be followed.
9.34
Where no boreholes are available
for sampling close to the potentially contaminated site, a trial pit willshould be dug within the site of interest at a suitable
“hotspot”. In some cases, access
could not be gained during the site visits and the location of the trial pit
will need to be defined when the land has been
resumedaccess has been obtained.
Sampling methodology
9.35
Prior to a borehole being
constructed, it is usual practice to dig an inspection pit up to 3m deep to
verify the presence or absence of utilities. An environmental scientist with experience in contaminated
land assessment should be on site to monitor the first few boreholes to confirm
that the samples are being taken at the right locations and in the correct
manner. A visual inspection of the
trial pits will also enable the environmental scientist to make a visual
assessment of the likelihood of severe contamination.
9.36
It is preferable that samples are
taken from the trial pit as a visual assessment of the ground material can be
made more readily than a borehole and the exact sample depth can be
verified. If contamination is
suspected at the base of the trial pit, samples willshould be taken at a greater depth from the borehole. In
locations where there are several boreholes being dug for geotechnical
investigations, but only selected boreholes have been chosen at the “hotspots”
for Stage 1 contamination assessment, samples will also be taken from the other
boreholes at similar depths, and retained in cool conditions (at 4oC)
until results have been obtained for the initial “hotspot” samples.
9.37
Table 9.6 describesThe CAP should describe the locations and number of
boreholes and trial pits to be sampled, the number of samples to take and the
parameters to be tested.
From site visits, it is likely that In
all cases, Total Petroleum
Hydrocarbons (TPHs) will be
analysed in all
cases. In selected samples, metals, cyanide
and organics (chlorinated and non-chlorinated solvents, aromatics and
polyaromatic hydrocarbons (PAHs)) will be included in Stage 1 sampling. In sites such as container yards,
organics are unlikely less likely to be a problem. and are therefore
not included in the parameter list. However, in chemical storage
sites organics are one of the main potential contaminants. The result of these analyses will help to fine tune the
testing required for Stage 2 sampling and analysis.
9.38
At
Stage 2, additional samples should be taken in the same area if the potential
“hot spot” samples are shown to be contaminated. These additional samples will
be taken on a grid sample basis as outlined in ProPECC PN 3/94 and the Contaminated Sites Investigation Remediation
Guidance Notes. The locations covered by the grid at the potentially
contaminated sites will be shown in the CAP.
Table 9.7
Grid Sampling to be Conducted if
“Hot-spot” Sample Indicates
the Presence of Contamination
9.39
The proposed analysis programme
is summarised below:
Two Stage
Analysis Programme
Sampling methods
9.40
There are several methods that
can be used to obtain samples of potentially contaminated material within the
ground. These are listed below:
·
Hand methods - usually for depths up to 0.5m by manual
excavation or up to 5m with a hand auger. This usually produces only small,
disturbed samples.
·
Trial pits - can be used up to
about 53m depth. Allows easy
collection of large samples.
·
Light cable percussion boreholes
- traditional method for geotechnical soil investigations. Can penetrate to 50m
depth and allow easy water monitoring or gas wells to be inserted.
·
Power auger drilling - very quick method, however
samples are limited to around 6 m depth and are disturbed.
9.41
Trial pits are the most widely
used technique, especially when sampling is required to depths of less than 3m.
Care should be taken to avoid underground services. It is likely that a
combination of boreholes and trial pits can be used for the Spurline iInvestigations.
9.42
For
borehole sampling, samples will be collected from the top, middle and bottom
(above rockhead) of the borehole as recommended in BSI DD175. The depth of the
samples will depend on the field sampling data. For trial pit sampling, samples
will be taken at three depths (e.g. 0.5m, 1.5m and 3m). If contamination is
evident at 3 m depth, additional samples at greater depths should be collected.
Where groundwater is encountered, groundwater samples should also be taken and
records kept of the ground water level in the trial pit. Photographic records
should be kept of each borehole and trial pit to show the gradient of pollution
into the ground and the appearance of each sample. The presence of any free product floating on the
top of the groundwater and the thickness should be recorded. The floating layer
should be removed/recovered and analyzed.
9.43
All
soil samples should weigh not less than 0.5 kg and must be representative of
the location at which they are taken. Samples should
be handled in an appropriate manner so as to avoid cross contamination, and
should be stored between 0 - 4ºC. Cooling of samples containing volatile
contaminants is especially important. All samples should be properly labelled
and any excess sample kept for further testing if necessary. Sample containers should be
thoroughly cleaned between sampling of individual samples. It is important for
the sampling person to avoid direct or indirect contact with potentially
contaminated materials.
9.44
All
samples should be well contained, sealed, properly labelled and any excess
sample kept for further testing if necessary.
Parameters
to be Tested for Contamination
9.45
The
parameters to be tested at each proposed sampling location are shall be based on the
expected contaminants related to the land use. Prior to sampling, an
examination of the site should be made by an environmental scientist responsible
for the sampling, to confirm whether additional or alternative analyses are
required
apart from those listed in Table 9.6to those listed in the CAP.
9.46
Waste automotive oils which may
be detected at container sites are composed of an organic base with additives to increase
performance. Additional compounds
such as chlorinated solvents may be present in the waste oils due to blending
of used oils during storage. The presence of such suspected carcinogens and
mutagens is the basis of concern about waste oils in the environment. The
sampling programme recommends that in Step 1 only total petroleum hydrocarbons
(TPH) are tested for as recommended in ProPECC PN 3/94 (Appendix III). If necessary, Polyaromatic hydrocarbons
(PAHs) and Benzene, Toluene, Ethylbenzene and Xylene (BTEX) will be required to
be determined if Step 2 of the analysis programme is to be implemented.
9.47
For
the inorganic analysis heavy metals (including Cd, Cr, Cu, Hg, Ni, Pb and, Zn etc)
should be determined in addition to cyanides and sulphates.
Analytical Laboratory and
Methodology
9.48
The
laboratory for chemical analysis for the land contamination assessment should
achieve HOKLAS accreditation for environmental testing of sediment trace
metals: Cd, Cr, Cu, Ni, Pb, Zn and Hg and preferably for TPH, PAHs and BTEX.
9.49
The
methodology should be compatible with international standard methods. Detection
limits should be to standards listed in Table 9.8.
Table
9.8
Detection
Limits of Parameters to be analysed
GroupNo. |
Parameter |
Detection
Limit (mg/kg dry soil) |
1 |
Metals: Cd, Cr Cu Hg Ni Pb Zn |
0.2 20 10 0.1 10 10 40 |
2 |
Total
Petroleum Hydrocarbons (TPH) |
20 |
3 |
Benzene Toluene Ethylbenzene Xylene |
0.002 0.01 0.01 0.01 |
4 |
Polyaromatic
Hydrocarbons (PAH) |
0.2 |
9.50
The preliminary sampling number and locations will
be reviewed and a detailed land contamination
assessment plan will be submitted for approval by the Director in accordance
with the requirements set out in the ProPECC Practice Note 3/94 “Contaminated
Land Assessment and Remediation” prior to on-site assessment before
commencement of works.
Evaluation of Potential Impacts
9.51
The interpretation of analytical
results should be considered by comparing the data with the Dutch Indicative
List which is recommended by EPD in ProPECC PN 3/94 for interpretation of the
analytical results.
9.52
The soils, geology, groundwater
and climate of Hong Kong are different to those of the Netherlands. The
reference values have been developed for use under these specific conditions.
The adsorption of pollutants to soil colloids may be different under such
conditions and therefore pose a different toxicity risk.
9.53
Appendix K contains the
Dutch list which should be considered carefully in terms of application to the
Hong Kong environment. It can be used as an indicative measure of levels of
contamination, qualitatively based on like groups of contaminants, known
landuses and possible pollutants.
Remediation
Measures to be Considered in the Remediation Action Plan (RAP)
9.54
Following approval of the CAP by
EPD and completion of the sampling and analysis programme, a Contaminated
Assessment Report (CAR) will be produced. The CAR will detail the results of
the implementation of the CAP and evaluate the extent of the potential
contamination on the site. Suitable means of minimizing the environmental
impact from these areas of contamination should be defined. If remediation of
the land is required, the type of remediation should be identified in a
Remediation Action Plan (RAP).
9.55
The selection of an appropriate
remediation technique for a site is dependent on a number of factors including:
(i) the
type of contamination;
(ii) the
extent of contamination;
(iii) the
time available and speed of each technique;
(iv) cost
effectiveness;
(v) the
future use of the site;
(vi) availability
of expertise and equipment.
9.56
There are a range of options
available for treating contaminated land sites and new techniques are
constantly being developed. The main methods in use are:
·
Retention and isolation of material on-site using an
appropriate form of cover, barrier or encapsulation system.
·
Physical, chemical or biological
treatment to eliminate or immobilise the contaminants.
·
Removal of material from the site for disposal
elsewhere.
9.57
ProPECC Note PN 3/94 also
includes recovery trenches or wells for removal of leaked oil and soil venting
for volatile organic compounds (VOCs). It suggests that "wherever
possible, in-situ remedial measures should be adopted". This policy should
be followed as far as possible in order to prevent increasing the pressure on
landfills.
9.58
Table 9.9 describes several
techniques which would may be applicable to contamination expected
within the works of the Spur Line.
Table 9.9
Remediation techniques which could be used at sites
along the Spur Line
Type of Contamination |
Technique |
Oil - surface layers |
Bioremediation - in-situ or on site degradation of organic pollutants to harmless CO2
& water using microbes. Ranked I by Haiges (1989). Other
bioremediation techniques include adding cotton which absorbs the oils.
Bacteria which occur naturally in the cotton then degrades the oils before
decomposing the cotton into the soil and enriching it. Soil washing/flushing
– addition of a surfactant/solvent and flushing
in-situ or washing excavated soil. The oils and fluids separate out and the
oily waste can then be bioremediated. |
Oil - above
groundwater or at depth in the soil. |
Recovery trenches or
wells – used to constrain groundwater flow so that oils
settle and can be skimmed off. A dual pump system uses a deep pump in the
groundwater to create a depression cone into which the free floating product
will migrate. This can then be pumped off. The dual pump system is ranked I
by Haiges. Other techniques include simpler pumps which extract both oils and
water which can then be separated at the surface.. |
Heavy hydrocarbons and
oily sludges |
Thermal treatment - soil is excavated, sorted and fed into a rotary kiln thermal unit
and heated until combustion occurs. The clean soil is then cooled and
moistened and can be replaced. |
Cyanides |
Incineration – similar thermal heating and combustion as for heavy hydrocarbons.
Care must be taken to ensure that air emissions achieve required standards. |
Heavy Metals |
Soil washing – soil is passed through sieves and scrubbers using water or
oxidising chemicals which leach the contaminants out. The sludge residue can
then be disposed of at a chemical waste treatment plant. Discharge of was Stabilisation – contamination can be permanently isolated using lime, cement,
thermoplastic or soluble silicate reagents to chelate metal ions to soil
colloids. The soil is excavated, sorted and injected with the reagent before
replacing and compacting to high density. |
Volatile Compounds |
Soil Venting – contaminant are removed through extraction wells using a vacuum which
enhances chemical movement from soil particles to air pockets. Air Sparging – mainly used to remove volatiles from groundwater by injecting air into
the saturated zone and transferring the contaminants to the vadose zone from
which they can be vented. |
Microbiological |
Incineration – to eliminate any toxic micro-organisms or bacterias, such as
anthrax spores, the only consistently dependable method is incineration. |
Broad spectrum of
contaminants |
Excavation and
Landfilling – best used for shallow contaminants
and one off excavations. Because of limits on contaminants that can be
disposed of in landfills (based on TCLP)* pre treatment may be required by
another method (e.g. bioremediation) prior to disposal. |
NOTE:
Haiges (1989) rated techniques from 1 (best) to 8 (worst) for treatment of oil contaminated soils on the basis of technical feasibility, achievable treatment levels, adverse impacts, cost and time taken.
* TCLP - Toxicity Characteristic Leaching Procedure Limits - as outlined
in the Guidance notes issued by EPD (1999).
Application
of Contamination Action Plan to Spur Line
9.59
From the desktop study, site survey and generic
methodology for sampling and analysing pollutants from potentially contaminated
sites, a number of sites along the Spur Line alignment have been identified as
being potentially contaminated.
9.60
Prior to the completion of the CAP and CAR, an
estimate has been made of the quantity of contaminated land which may be
present at each site (Table 9.10). This is based on site visits, the extent of
the area used at each site, and the assumption that the contamination has
penetrated to a depth of approximately 1 m from the ground surface. Where
viaduct occurs, it is assumed that only the area around the viaduct support footing
pile cap will
be impacted during construction (each footing pile cap is assumed to be 2.56.0 m diameter with an
additional 2.0 m allowed for the works area.) HoweverIn the embankment and cutting
sections, the whole width of the viaduct (32 m) may be impacted and
has therefore been included in the calculation. Where quantities of material
are too small to make physico-chemical or biological treatment cost-effective,
disposal of the material may be considered.
9.61
The total quantity of contaminated land is estimated
at this stage of the assessment, to be up to 5635,000 m³. This volume
needs to be confirmed through implementation of the CAP and the sampling and
analysis programme during site investigation, at which time the quantities
requiring remediation or disposal will be more accurately defined.
9.62
Where volumes are relatively small and/or contaminant
level is low, disposal may be a preferable option. Where volumes are large
and/or contaminant levels are high, remediation techniques should be considered
as a cost effective and environmentally favourable option.
Table 9.10
Main Activities at Each Site, Contaminants Likely to be
Present and Possible Extent of Contamination
Site |
Main Activities |
Estimated quantity (m³) |
Main Contaminants Likely to be present |
A |
Container Storage |
8 and EVA = |
Metals, |
B |
Container Storage |
|
Metals, |
C |
Chemical Store |
1, |
Organics, oils, metals, solvents |
D |
Pig Farm |
|
|
E |
Building Materials Storage |
200 m³ |
Metals |
F, G |
Farm Buildings |
5000 m³ |
|
H |
Car Repairs/ dismantling |
300 m³ |
Metals, cyanides, |
I |
Containers
|
2000 m³ |
Metals, |
J |
Farm Buildings |
1000 m³ |
|
K |
Chemical Storage |
1300 m³ |
Organics, solvents,
metals, oils |
|
Pig Farms |
10000 m³ |
|
M |
Container Storage |
100 m³ |
Metals, |
N |
Metal Recycling |
- |
Metals, TPH |
O (i) |
Sawmill and
Timberyard |
<100 m³ |
Unknown activities |
O(ii) |
Sawmill and
Timberyard |
100 m³ |
|
P |
Storage |
- |
Organics, solvents,
metals, oils, bacteria spores |
R |
Car Repairs/ dismantling |
- |
Metals, cyanides,
organics, fuels/oils, acids |
S |
Metal Works |
- |
Metals |
T |
Vehicle Maintenance
|
300 m³ |
Metals, cyanides,
organics, fuels/oils, acids |
U |
Chemical Storage |
1500 m³ |
Metals, o |
Total volume (m³) |
|
|
Precautionary
Measures to be taken during Construction
9.63
The following measures should be implemented to
minimise risks to workers during remediation works, excavation of soil,
construction of viaducts, blasting of the cutting, piling works or construction
of the stations. These measures will also mitigate against transferring
contamination to groundwater, to surface water courses or to the air.
·
Site workers should wear gloves, masks, and other
protective clothing where exposure to vapours or contaminated soil may be
encountered.
·
Contaminated materials should be moved with bulk earth
movers to prevent human contact.
·
Adequate washing facilities should be provided and
smoking/eating should be prohibited in the area.
·
Contaminated sediments which have been stockpiled or
are being transported should be covered with tarpaulin.
·
Leakage of pollutants or leaching from excavated soil
should be prevented by storing on an impermeable surface.
Temporary
Works Areas
9.64
There are several temporary works areas in the Sheung
Shui area which have previously been used as container parking areas. The site
inspection showed that, as is typical of such landuses there has been some
leakage of oils and lubricants. However, these sites should not pose a health
risk during their use in the construction phase provided there are no earth
moving activities at the sites. The leaked oil can be covered with a layer of
gravel or sawdust to soak up the leaks, and the materials disposed of appropriately.
Other Projects in the Study Area
9.65
The recently publicized Kwu Tung SGA under the NENT
Planning Study also has the potential to be impacted by contaminated land. The
findings and recommendations of the Spur Line EIA should be taken into account
in the EIA for the SGA, to minimize environmental impacts.
Summary
9.66
This contaminated land assessment includes a desktop
study on relevant past and present landuses, a site survey, an assessment on
the findings and recommendations on a schedule ofof the approach to the sampling / analysis of
essential parameters and appropriate remediation measures. Application of the
sampling/analysis programme to specific sites identified to have potential
contamination along the Spur Line alignment is included. A Contaminated Land Assessment Plan (CAP) will be
submitted separately to EPD for approval. This will outline the methods for sampling and
analysis of the identified potentially contaminated sites, and criteria for
evaluation.
9.67
No underground storage tanks or extensive areas of
contaminated land have been identified in this assessment within the works area
of the alignment. The main areas for concern are container storage areas,
particularly those in DD99 close to Lok Ma Chau (A and B), the chemical storage
area east of Pak Shek Au, (K), any car repair/dismantling yards and the unknown
risks posed by the former leather factory (P and Q). The main
contaminants are likely to be oils, organic solvents and heavy metals.
9.68
Remediation measures for different types of
potentially contaminated land are recommended, however, the small quantities
which have been identified for several sections of the alignment make
remediation too costly to be effective, and disposal should be considered. It
is estimated that the quantity of material in areas of potential contamination,
which requires treatment or disposal is approximately 535,000 m³. These quantities
and the degree of contamination need to be confirmed at the site investigation
stage. Following the
implementation of the approved CAP, a Contamination Assessment Report (CAR) and
Remediation Action Plan (RAP) will be prepared to recommend the methods of
remediation or disposal to be followed. This assessment indicates that
potentially contaminated material excavated during the construction of the alignment,
does not present an insurmountable environmental impact to the Project.
REFERENCES
Holdgate,
M.W., (1979) A Perspective of
Environmental Pollution, University Press, Cambridge.
Royal
Commission on Environmental Pollution (RCEP), (1984), 10th Report: Tackling Pollution - Experience and Prospects, Cmnd
9194, HMSO, London.
LaGrega
M.D., Buckingham P.L & Evans J.C. (1994), Hazardous Waste Management, McGraw-Hill, Singapore.
Cairney
T (ed) (1993), Contaminated Land:
Problems and Solutions, Chapman & Hall, London.
EPD
(!999), Guidance Notes for Investigation
and Remediation of Contaminated Sites of: Petrol Filling Stations, Boatyards or
Car Repair/Dismantling Workshops. Report EPD/TR1/99
Voelcker Science (1999) Guide to Contamination Packages
HSE (1998), Protection
of Workers and the General Public during Development of Contaminated Land.
http://www.ContaminatedLAND.co.uk/ - Pages on Past Industrial uses, Causes of
Contamination, Standards and Guidelines, Remediation Techniques
British Standards Institution (1988), Draft for
Development DD175: 1988 Code of Practice
for the Identification of Potentially Contaminated Land and its Investigation, BSI,
London.
Kelly R.T. (1980) Site Investigation and Material
Problems, in: Reclamation of Contaminated
Land, B21-B2-13, Society of Chemical Industry.
Haiges L et al. (1989)
Evaluation of underground fuel spill clean-up technologies, in Haztech International Conference, San
Francisco.
ProPECC
PN 3/94. Environmental Protection Department. Practice Note for Professional
Persons: Contaminated Land Assessment and Remediation.