The Castle Peak Power Company (CAPCO) has initiated a project for
emission control at the Castle Peak Power Station “B” units (CPB) (“Project”),
in response to the Hong Kong SAR Government (HKSARG)’s stated intent to reduce
emissions in Hong Kong. An Environmental
Impact Assessment (EIA) Study Brief was issued for the Project by the
Environmental Protection Department (EPD) in October 2005 (EIA Study Brief No. ESB-134/2005). In
compliance with one of the Study Brief requirements, a land contamination
assessment will be carried out for the Project Areas.
To accommodate the new development, extensive demolition works are
required to relocate a number of existing facilities, including:
·
CPB
Fuel Oil Day Tank (FODT, hereafter referred to as the aboveground fuel oil day
tank) and associated pipe works connecting with fuel oil pump house (FOPH) and
oil interceptor;
·
Dangerous
Goods (DG) stores; and
·
Intermediate
Pressure Reduction Station (IPRS), LPG compound and CO2 storage
tanks.
The preliminary Project Areas are shown in Figure 1.1a of the approved CAP (Annex E1a).
Environmental Resources Management (ERM) was commissioned by CAPCO to
conduct a land contamination assessment of the site, in accordance with the
Study Brief requirements. A
Contamination Assessment Plan (CAP) was prepared, submitted to and was approved
by the EPD (Annex E1a) and forms a basis of this assessment.
Site inspection including soil and groundwater
sampling and analysis was conducted to identify potential sources of
contamination from historical and on-going operations in this area in
accordance with the CAP.
1.2
Objectives of the Land Contamination Assessment
The main objectives of the land contamination
assessment were to establish the presence or absence of soil and groundwater
contamination and, if present, the degree of contamination.
1.3
Scope Of The Land Contamination Assessment
The scope of the assessment included the following:
·
to
review the available history of the site in relation to the potential for land
contamination;
·
to
review the available geology and hydrogeology information of the site;
·
to conduct
a site investigation programme through soil and groundwater sampling at twelve
strategic locations;
·
to
perform laboratory analyses of soil and groundwater samples for the target
analytical parameters; and
·
to report on the findings of the available information, the field
observations, the interpretation of laboratory analytical results, and the
assessment of potential contamination.
The remainder of this report is structured as follows:
·
Section 2
summarises the background information, including historical land uses, geology,
hydrogeology and the results of previous investigations at the site, if any;
·
Section 3 summarises the methodology used to carry out the land
contamination assessment;
·
Section 4 summaries the field activities and field
observations;
·
Section
5 presents the laboratory
analytical results for the samples collected; and
·
Section 6 provides the conclusions and recommendations.
Annexes to this report include:
·
Annex E1a Contamination
Assessment Plan
·
Annex E1b Borehole Logs
·
Annex E1c Groundwater
Monitoring Well Diagrams
·
Annex E1d Selected Photographs
·
Annex E1e Laboratory
Analytical Results
·
Annex E1f The Dutch
List
The
Project Areas are located
within the CPB,
situated on the coast of Tap Shek Kok in Tuen
Mun,
The
The
coastline is located approximately 350 to 500 meters to the south and southwest
of the Project Areas. The direction of groundwater flow
underlying the Project Areas is anticipated to be affected by the nearby tidal
motion and groundwater is likely to be recharged by seawater during high tides
and discharged to the sea during low tides.
Groundwater is not used for either domestic or industrial purposes at
the site or the adjacent areas.
The land uses in the immediate surroundings of the Project Areas
include:
North: The power
generation units of Castle Peak Power Station “A” (CPA);
South: The north coal
yard, the coastline is located approximately 350 m to the south;
East: The power
generation units of CPB and Green Island Cement Plant; and
West: The west coal
yard, the coastline is approximately 500 m to the west.
The
site investigation programme was designed in accordance with the Environmental
Protection Department (EPD)’s Practice
Notes for Professional Persons: Contaminated Land Assessment and Remediation ProPECC PN 3/94 (ProPECC PN3/94) and Guidance Notes for
Investigation and Remediation of Contaminated Sites of Petrol Filling Stations,
Boatyards, and Car Repair/Dismantling Workshops (Guidance Notes).
3.1
Soil Contamination Assessment
The soil contamination assessment was carried out through analysis of soil
samples collected from strategic locations at different depths in accordance
with the EPD-approved CAP.
Soil sampling was conducted through soil excavation or intrusive soil
drilling in accordance with the American Society for Testing and Materials’ (ASTM)
standards ([1]).
3.2
Groundwater Contamination Assessment
The
groundwater contamination assessment was carried out through the analysis of
groundwater samples collected from eight groundwater sampling wells. Groundwater well installation, well development
and sampling were carried out following the guidance for groundwater sampling
developed by USEPA for groundwater contamination investigation ([2]).
The
methodologies used for the laboratory analysis were as follows:
·
Total
petroleum hydrocarbons (TPH) for soil and groundwater samples by USEPA Method
8260 & 8015;
·
benzene,
toluene, ethylbenzene, xylene
(BTEX) for soil and groundwater samples by USEPA Method 8260;
·
polycyclic
aromatic hydrocarbons (PAHs) for soil and groundwater
samples by USEPA Method 8270;
·
Volatile
organic compounds (VOCs) for soil and groundwater
samples by USEPA Method 8260; and
·
Semi-volatile
organic compounds (SVOCs) for soil and groundwater
samples by USEPA Method 8270.
4.1.1
Underground
Soil boring and Sampling
Hand excavation and soil sampling was carried out at four trial
pits. Soil boring and sampling were
carried out at eight drilling locations.
The trial pits were excavated manually, and soil boring was conducted
using rotary drilling rigs. The
approximate locations of trial pits and boreholes are shown on Figure 3.1a of the approved CAP (Annex E1a).
Soil samples were collected from the trial pits and boreholes at designated
depths for visual inspection on the soil geological classification and signs of
contamination, on-site photo-ionisation detector (PID) testing for volatile
organic compound vapour and laboratory analysis. Soil sampling at the trial pits was performed
manually using a stainless
steel scoop. Soil sampling in the
boreholes was conducted using
split barrels following the standard penetration testing (SPT) procedures. Of note is that no soil sample was collected
from the depths where hard strata (ie boulders,
cobbles or bedrock) were encountered during the drilling or sampling. A summary of the soil boring and sampling
works is provided in Table 4.1a.
The four trial pits TP1, TP2, TP3 and TP4 were located near the boring
locations DH7, DH6, DH5 and DH4, respectively, and were excavated to depths
between 0.7 and 1.5 m bgl. Soil sampling for the depths near the ground
surface (ie 0.5 to 1.0 m bgl)
was not carried out at boreholes DH4 to DH7 but at the trial pits TP1 to TP4
instead.
Table 4.1a Soil
Boring and Sampling for the Land Contamination Assessment
|
Locations |
Total drilling depth (m bgl) |
Collected soil sample for PID
testing and laboratory analysis (m bgl) |
Remarks |
|
DH1 |
6.27 |
DH1 0.6 m |
Boulder/cobble/rock encountered from depth
0.6 to 6.27 m bgl. |
|
DH2 |
6.77 |
DH2 0.6 m |
Boulder/cobble/rock encountered from
depth 1.0 to 6.77 m bgl. |
|
DH3 |
7.07 |
DH3 0.8 m |
Cobble/granite encountered from depth 1.9
to 7.07 m bgl. |
|
DH4 |
6.81 |
No soil
sample collected |
Boulder/cobble/rock encountered from
depth 0.25 to 6.81 m bgl. |
|
DH5 |
6.80 |
No soil
sample collected |
Boulder/cobble/rock encountered from
depth 0.48 to 6.80 m bgl. |
|
DH6 |
7.15 |
No soil
sample collected |
Boulder/cobble/rock encountered from depth
0.6 to 7.15 m bgl. |
|
DH7 |
6.77 |
No soil
sample collected |
Boulder/cobble/rock encountered from
depth 1.38 to 6.77 m bgl. |
|
DH8 |
7.53 |
DH8 0.8 m |
Boulder/cobble/rock encountered from
depth 1.0 to 7.53 m bgl. |
|
TP1 |
1.5 |
TP1 1.5 m |
TP1 was located near DH7. |
|
TP2 |
1.1 |
TP2 0.8 m
(a) |
TP2 was located near DH6. |
|
TP3 |
1.1 |
TP3 0.9 m |
TP3 was located near DH5. |
|
TP4 |
1.0 |
TP4 0.7 m |
TP4 was located near DH4. |
|
Note: (a) One soil field duplicate sample (TP2 (duplicate))
was collected from this location. |
|||
The underground soil profiles observed during the drilling were recorded
are presented in the Borehole Logs,
Annex E1b.
All soil samples collected from the boreholes were placed immediately into laboratory
pre-cleaned sample bottles and stored with ice in a cooler on-site before
delivery to the laboratory for analysis.
ERM supervised the field drilling and soil sampling to meet the
requirements of the project QA/QC and appropriate decontamination procedures.
4.1.2
Groundwater Well Installation and Sampling
Groundwater was encountered at all eight boreholes
during the drilling. The boreholes were
converted into groundwater monitoring wells to
facilitate
groundwater sampling. In general,
groundwater monitoring wells were installed to approximately 2 m below the
measured groundwater levels using perforated u-PVC pipes. Diagrams showing details of the installed
groundwater wells are provided in the
Groundwater Monitoring Well Diagrams, Annex E1c.
After groundwater well installation, each well was
developed by removing at least five times the well volume by hand bailing. Groundwater samples were collected using new
dedicated Teflon bailers for each well.
A total of eight groundwater samples (exclusive of
QA/QC samples), marked as DH1 to DH8, were collected. All groundwater samples collected from the
wells were placed immediately
into laboratory pre-cleaned and pre-preserved sample bottles and stored with
ice in a cooler on-site before delivery to the laboratory for analysis.
ERM supervised the groundwater sampling to meet the requirements of the
project QA/QC and appropriate decontamination procedures.
4.1.3
QA/QC
Programme and Sample Delivery
A field QA/QC program was incorporated into the land contamination
investigation for the site. The program
consisted of collection of field QA/QC samples which included one soil field
duplicate sample, one groundwater field duplicate sample, three equipment blank
samples, and seven trip blank samples.
The field QA/QC samples collected or prepared are summarized in Table 4.1b.
Table 4.1b Collected
QA/QC Samples for the Site Investigation
|
QA/QC
sample |
Sample
ID |
Associated
sample |
|
Soil duplicate sample |
TP2 (duplicate) |
TP2 at 0.8m bgl |
|
Groundwater duplicate sample |
DH6 (duplicate) |
DH6 |
|
Equipment Blank samples |
EQ BLK 1 |
Soil samples TP1 1.5m, TP2 0.8m, TP3
0.9m, TP4 0.7m and DH9 0.8m. |
|
|
EQ BLK 2 |
Soil samples DH1 0.6m and DH2 0.6m. |
|
|
EQ BLK 3 |
Soil sample DH8 0.8m |
|
Trip blank samples |
Trip blank 1 |
Soil samples TP1 1.5m, TP2 0.8m, TP3
0.9m, TP4 0.7m and DH9 0.8m. |
|
|
Trip blank 2 |
Soil samples DH1 0.6m and DH2 0.6m. |
|
|
Trip Blank 3 |
Groundwater samples DH4, GH5, DH6, DH7,
DH9 and soil sample DH3 0.8m. |
|
|
Trip Blank 4 |
Groundwater samples DH1 and DH2. |
|
|
Trip Blank 5 |
Soil samples DH8 0.8m. |
|
|
Trip Blank 6 |
Groundwater sample DH3. |
|
|
Trip Blank 7 |
Groundwater sample DH8. |
All trip blank samples were pre-prepared in the laboratory, stored with
the samples in the sample coolers, and delivered with the samples to the
laboratory.
All soil and groundwater samples along with the field QA/QC samples were
delivery to the laboratory on ice in coolers on each sampling day.
4.2.1
Soil
At all land contamination investigation locations,
the ground surface generally comprised yellowish brown medium to coarse sand
from the ground surface to approximately 0.25 to 1.9 meters below ground level
(m bgl) following by cobbles, boulders or bed rocks
(granite) to the end of the drilling depths (ie 6 to
8 m bgl).
No evidence of soil contamination such as
staining, discoloration or abnormal odour was observed during the soil drilling
and sampling.
4.2.2
PID
Test Results
The photo-ionisation detector (PID) test
results for the soil samples are summarized in Table 4.2a.
Table 4.2a Soil Sample PID Test Results
|
Locations |
Soil sample (m bgl) |
PID test Results (ppm) |
Remarks |
|
TP1 |
TP1 1.5 m |
0.8 |
TP1 was located near DH7 |
|
TP2 |
TP2 0.8 m |
1.5 |
TP2 was located near DH6 |
|
TP3 |
TP3 0.9 m |
1.0 |
TP3 was located near DH5 |
|
TP4 |
TP4 0.7 m |
4.0 |
TP4 was located near DH4 |
|
DH1 |
DH1 0.6m |
2.0 |
|
|
DH2 |
DH2 0.6 m |
2.0 |
|
|
DH3 |
DH3 0.8 m |
0.5 |
|
|
DH8 |
DH8 0.8 m |
0.8 |
|
The
groundwater levels encountered during the drilling and measured at equilibrium
condition are provided in Table 4.2b.
Table 4.2b Groundwater
Level Measured at the Monitoring Wells
|
Groundwater Monitoring Well |
Groundwater Level Encountered During Drilling |
Groundwater Level Measured at Equilibrium Condition (m bgl) |
Groundwater Level Elevation |
|
DH1 |
2.38 |
2.38 |
2.67 |
|
DH2 |
2.55 |
2.55 |
2.57 |
|
DH3 |
3.70 |
4.19 |
2.81 |
|
DH4 |
4.70 |
4.70 |
1.31 |
|
DH5 |
4.62 |
4.76 |
1.25 |
|
DH6 |
4.60 |
5.00 |
1.23 |
|
DH7 |
4.72 |
4.72 |
1.95 |
|
DH8 |
5.50 |
5.51 |
1.56 |
|
Note: (a)
Groundwater
level elevations (meter above principal datum (mPD))
were estimated based on the ground level survey data and groundwater levels
measured at equilibrium condition. |
|||
Based
on the groundwater water levels measured and the local surface hydrology, the
shallow groundwater in the site area is anticipated to flow in a generally
southern or south-westerly direction.
However, the direction of groundwater flow underlying the site area is
likely to be affected by the nearby tidal motion.
No
evidence of groundwater contamination such as free floating products,
discoloration or abnormal odour was observed at the sampling locations during
the drilling, well development and groundwater sampling.
The analytical results for the soil and groundwater samples collected
from the Site are summarised in Tables 5.1a and 5.1b,
respectively, and are discussed in the following sections. The detailed results of the laboratory
analyses along with the QA/QC information are presented in Annex E1e.
The EPD’s ProPECC PN 3/94 has adopted the Dutch
Ministry of Housing, Planning and Environment Soil and Groundwater Standards (the ‘Dutch List’) as the criteria for assessing soil and
groundwater contamination in
As an initial screening tool for establishing a general understanding of
the degree and extent of soil and groundwater contamination, the Dutch List defines three different
levels, ie ‘A’, ‘B’ and ‘C’, for the concentration of
contaminants found in soil and groundwater.
The interpretation of the contaminant concentrations is as follows:
·
Concentrations
below ‘A’ and/or ‘B’ values refer to a situation in which the soil and/or
groundwater is considered ‘unpolluted’ and can fulfil all possible functions
and no further actions are required.
·
Concentrations
above ‘B’ but below ‘C’ values refer to a situation in which the soil and/or
groundwater is potentially contaminated and requires further
investigation. In
·
Concentrations
above ‘C’ are considered to represent significant contamination and cleanup
action is likely to be required.
In the absence of appropriate criteria applicable to industrial use, the
Dutch Intervention Values (DIVs), which are much more stringent criteria intended for
groundwater abstracted for drinking purpose, are used for comparison with the
measured results for substances in groundwater samples that are not included in
the Dutch List adopted in EPD’s ProPECC PN 3/94.
Table 5.1a
Analytical Results for Soil Samples (all results in mg/ kg-
dry weight) (a) (b)
|
Parameter |
Dutch ‘A’ |
Dutch ‘B’ |
Dutch ‘C’ |
Report Limit |
TP1 1.5 m |
TP2 0.8 m (e) |
TP3 0.9 m |
TP4 0.7 m |
DH1 0.6 m |
DH2 0.6 m |
DH3 0.8 m |
DH8 0.8 m |
|
Moisture Content (%) |
N/A |
N/A |
N/A |
0.1 |
6.9 |
4.5 |
6.6 |
5 |
10.1 |
8.5 |
7.7 |
4.3 |
|
TPH |
|
|
|
|
|
|
|
|
|
|
|
|
|
Gasoline (C6-C9) |
20 |
100 |
800 |
2 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
Light Diesel (C10-C14) |
N/A |
N/A |
N/A |
50 |
ND |
ND |
83 |
ND |
ND |
ND |
ND |
ND |
|
Heavy Diesel (C15-C28) |
N/A |
N/A |
N/A |
50 |
ND |
ND |
1,170 |
ND |
ND |
ND |
ND |
ND |
|
Heavy Oil (C29-C36) |
N/A |
N/A |
N/A |
50 |
ND |
ND |
605 |
ND |
ND |
ND |
ND |
ND |
|
Mineral Oil (c) |
100 |
1,000 |
5,000 |
N/A |
ND |
ND |
1,858 |
ND |
ND |
ND |
ND |
ND |
|
BTEX |
|
|
|
|
|
|
|
|
|
|
|
|
|
Benzene |
0.01 |
0.5 |
5 |
0.5 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
Toluene |
0.05 |
3 |
30 |
0.5 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
Ethylbenzene |
0.05 |
5 |
50 |
0.5 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
meta- & para-Xylene |
N/A |
N/A |
N/A |
1 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
ortho-Xylene |
N/A |
N/A |
N/A |
0.5 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
Total xylene (d) |
0.05 |
5 |
50 |
N/A |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
Chlorobenzene |
0.05 |
2 |
20 |
0.5 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
PAHs |
Various |
Various |
Various |
Various |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
Other VOCs |
Various |
Various |
Various |
Various |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
SVOCs |
Various |
Various |
Various |
Various |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
Notes: (a) Underlined and
Bold Results = concentration exceeds the Dutch “B”
values; Underlined, Bold, and Italic Results = concentration exceeds the Dutch
“C” values; (b) N/A
= not available; ND = not detectable. (c) Mineral
oil is sum of total detected results of light diesel, heavy diesel and heavy
oil. (d) Total
xylene is sum of m,p-xylene
and o-xylene. (e) Duplicate
samples were analysed for this sampling location. Higher results were
selected for presenting in the table where the two sample results differ from
each other. |
||||||||||||
Table 5.1b
Analytical Results for Groundwater Samples (a) (b)
|
Parameter |
Unit |
Dutch ‘A’ |
Dutch ‘B’ |
Dutch ‘C’ |
Report Limit |
DH1 |
DH2 |
DH3 |
DH4 |
DH5 |
DH6 (f) |
DH7 |
DH8 |
|
pH |
|
|
|
|
0.1 |
7.2 |
6.4 |
7.9 |
7.4 |
7.6 |
7.6 |
7.4 |
7.7 |
|
TPH |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Gasoline (C6-C9) |
mg/L |
10 |
40 |
150 |
20 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
Light Diesel
(C10-C14) |
mg/L |
N/A |
N/A |
N/A |
50 |
63 |
91 |
ND |
ND |
ND |
ND |
ND |
ND |
|
Heavy Diesel
(C15-C28) |
mg/L |
N/A |
N/A |
N/A |
100 |
1,460 |
2,590 |
1,590 |
712 |
1,400 |
733 |
1,560 |
125 |
|
Heavy Oil
(C29-C36) |
mg/L |
N/A |
N/A |
N/A |
50 |
ND |
78 |
1,490 |
368 |
1,720 |
79 |
62 |
79 |
|
Mineral Oil (c) |
mg/L |
20 |
200 |
600 |
N/A |
1,523 |
2,759 |
3,080 |
1,080 |
3,120 |
812 |
1,622 |
204 |
|
BTEX |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Benzene
|
mg/L |
0.2 |
1 |
5 |
5 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
Chlorobenzene |
mg/L |
0.02 |
0.5 |
2 |
5 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
Toluene |
mg/L |
0.5 |
15 |
50 |
5 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
Ethyl-benzene |
mg/L |
0.5 |
20 |
60 |
5 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
m,p-Xylene |
mg/L |
N/A |
N/A |
N/A |
10 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
o-Xylene |
mg/L |
N/A |
N/A |
N/A |
5 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
Total xylene (d) |
mg/L |
0.5 |
20 |
60 |
N/A |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
PAHs |
mg/L |
Various |
Various |
Various |
Various |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
|
Other VOCs (e) |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Chloroform |
mg/L |
N/A |
N/A |
N/A |
5 |
ND |
ND |
8 |
ND |
ND |
ND |
ND |
ND |
|
SVOCs (e) |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Dimethyl
phthalate |
mg/L |
- |
2 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
||
|
Diethyl phthalate |
mg/L |
- |
2 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
||
|
Di-n-butyl phthalate |
mg/L |
- |
2 |
44 |
132 |
66 |
31 |
459 |
47 |
57 |
46 |
||
|
Butyl benzyl phthalate |
mg/L |
- |
2 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
||
|
Bis(2-ethylhexyl)
phthalate |
mg/L |
- |
20 |
ND |
ND |
32 |
ND |
21 |
ND |
ND |
ND |
||
|
Di-n-octyl
phthalate |
mg/L |
- |
2 |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
||
|
Phthalates (sum) |
mg/L |
5 (g) |
- |
44 |
132 |
98 |
31 |
480 |
47 |
57 |
46 |
||
|
Notes: (a) Underlined and Bold
Results = concentration that exceed the Dutch “B” values; Underlined, Bold, and Italic Results = concentration that exceed the
Dutch “C” values. (b) N/A =
not available; ND = not detectable. (c) Mineral
oil is sum of light diesel, heavy diesel and heavy oil. (d) Total xylene is sum of m,p-xylene and
o-xylene. (e) Only
the compounds in the group that were detected in at least one sample are
shown. (f) Duplicate
samples were analysed for this sampling location. Higher results were
selected for presenting in the table where the two sample results differ from
each other. (g) Dutch
Intervention Value (DIV) of total phthalates was adopted to compare with the
measured results. |
|||||||||||||
5.2.1
Total
Petroleum Hydrocarbons (TPH)
TPH in the fractions of light diesel, heavy
diesel and heavy oil was detected in one soil sample collected from TP3 at a
depth 0.9 m bgl.
The sum of light diesel, heavy diesel and heavy oil for this soil sample
(1,858 mg/kg) exceeded the Dutch ‘B’
value for mineral oil (ie 1,000 mg/kg).
Benzene,
toluene, ethylbenzene and xylene
were not detected at concentrations exceeding the laboratory reporting limits
in any soil sample collected from the Site.
5.2.3
PAHs
No
target PAHs were detected at concentrations exceeding
the laboratory reporting limits in the soil samples collected from the Site.
5.2.4
VOCs
No target VOCs
were detected at concentrations exceeding the laboratory reporting limits in
the soil samples collected from the Site.
5.2.5
SVOCs
No target SVOCs
were detected above the laboratory reporting limits in the soil samples
collected from the Site.
5.3
Results for Groundwater Samples
5.3.1
Total
Petroleum Hydrocarbons (TPH)
Light diesel, heavy diesel and/or heavy
oil were detected in all groundwater samples collected from the Site. With the exception of the groundwater sample
from DH8, the sum of light diesel, heavy diesel and heavy oil fractions for the
groundwater samples ranged from 812 mg/L
to 3,120 mg/L
and exceeded the Dutch ‘ C’ value
(600 mg/L
for mineral oil). The sum of the light
diesel, heavy diesel and heavy oil fractions for the groundwater sample
collected from DH8 was 204 mg/L
which is marginally above the ‘B’
value (ie 200 mg/L)
for mineral oil.
5.3.2
BTEX
Benzene, toluene, ethylbenzene
and xylene were not detected at concentrations
exceeding the laboratory reporting limits in any groundwater sample collected
from the Site.
5.3.3
PAHs
No target PAHs
were detected at concentrations exceeding the laboratory reporting limits in
the groundwater samples collected from the Site.
5.3.4
VOCs
No VOCs were
detected in the groundwater samples collected from the Site at concentrations
exceeding either the laboratory reporting limits or the applicable EPD Dutch ‘B’ or ‘C’ values except chloroform at DH3. 8 mg/L
of Chloroform was detected at DH3 which is above the reporting limit of 5 mg/L.
5.3.5
SVOCs
Two SVOCs (di-n-butyl phthalate and bis
(2-ethylhexyl) phthalate were detected in the groundwater samples
collected. Di-n-butyl phthalate were
detected at concentrations ranging from 31 to 459 mg/L
in the groundwater samples from all groundwater wells whereas bis (2-ethylhexyl) phthalate were detected at
concentrations ranging from 21 to 32 mg/L
in the groundwater samples from DH3 and DH5.
The sum of phthalates for the groundwater sample from all groundwater
wells was higher than the DIV of 5 mg/L
for total phthalates.
5.4
QA /QC Sample Results and Data Usability
5.4.1
Field
QA/QC Sample Results
Assessment of field QA/QC sample results included
checking of relative percent difference (RPD) for field duplicate samples,
equipment blank and trip blank samples.
RPD Results
The relative percent difference (RPD[3])
was used to assess the sampling and laboratory reproducibility and
precision. The USEPA acceptable limits
for RPD are less than 30% for groundwater and less than 50% for soil. No RPD is required where the sample result is
below two times the method detection limits or below the method detection
limits.
The values of RPD calculated the detected
results for the soil duplicate samples (TP2 0.8 and DH9 0.8) were within the
50% acceptance limit.
The RPD values calculated for the
groundwater duplicate samples (DH6 and DH9) were within the 30% acceptance
limit.
Equipment and Trip Blank Sample Results
The results of the equipment or trip blank
samples are summarized in Table 5.4a.
Table
5.4a Summery of Detected QA/QC Sample Results
|
Sample ID |
Sample |
Detected parameter |
Detected result (µg/L) |
Laboratory report limit (µg/L) |
|
EQ
BLK3 |
Equipment
blank sample |
TPH
(C6 - C9 fraction) |
22 |
20 |
|
EQ
BLK3 |
Equipment
blank sample |
Toluene |
22 |
5 |
|
EQ
BLK3 |
Equipment
blank sample |
Phenol |
8 |
2 |
|
Trip
blank 4 |
Trip
blank sample |
Di-n-butyl
phthalate |
5 |
2 |
TPH (C6-C9 fraction), toluene, and phenol
were detected in the equipment blank sample (EQ BLK3), but was not detected in
the associated soil sample DH8 0.8m. The
equipment blank sample result, therefore, did not impact on the associated soil
sample results.
Di-n-butyl phthalate was detected in Trip
Blank 4 and in the associated groundwater samples (DH1 and DH2). The detected concentrations of di-n-butyl phthalate in the associated groundwater samples
DH1 and DH2 were 44 and 132 µg/L, respectively, which are more than 4 times
higher than the concentration detected in the trip blank. In accordance with the USEPA Region 1’s Data Validation Guidance, the detected di-n-butyl phthalate results in the trip blank did not
impact the sample results.
5.4.2
Laboratory
Internal QA/QC Sample Results
The laboratory QA/QC sample results
included surrogate recoveries, matrix spike sample, laboratory duplicate
samples and method blanks and met their respective requirements.
Based on the review of QA/QC sample
results, all laboratory results for the soil and groundwater samples are
considered useable.
Elevated concentrations of light diesel, heavy diesel and heavy oil were
detected in one soil sample collected from location (TP3) at a depth near the
ground surface (ie 0.9 m bgl). The detected TPH had the highest
concentration (1,170 mg/kg) for heavy diesel.
The total concentration of light diesel, heavy diesel and heavy oil in
this soil sample was 1,858 mg/kg and exceeded the Dutch ‘B’ value of 1,000 mg/kg.
No TPH was detected in any of other soil samples collected from the
site.
TPH including light diesel, heavy diesel, and heavy oil fractions was
identified in the groundwater samples collected from the wells DH1 and
DH2. Heavy diesel and heavy oil were
detected in the groundwater samples collected at the other six locations. Of the TPH fractions, diesel oil was detected
at the highest concentrations ranging from 100 to 2,590 mg/L.
The total concentrations of light diesel, heavy diesel and heavy oil for
all groundwater samples taken from the site (ranged from 812 to 3,080 mg/L) exceeded the Dutch ‘C’ value for mineral oil (ie 600 mg/L) with the exception of the sample from
DH8. The total of light diesel, heavy
diesel and heavy oil for DH8 (204 mg/L) marginally exceeded the Dutch ‘B’ value for mineral oil (200 mg/L).
Di-n-butyl phthalate was identified in the
groundwater samples collected from all wells (DH1 to DH8) and bis
(2-ethylhexyl) phthalate was detected in the groundwater samples from DH3 and
DH5. The sum of phthalates for the
groundwater sample from all groundwater wells was higher than the DIV of 5 mg/L
for total phthalates. It should be noted
that groundwater is not used for either domestic or industrial purposes at the
site.
6.3
Qualitative Risk Assessment
6.3.1
Potential
Source of TPH Contamination in Soil and TPH, Di-n-butyl Phthalate and Bis (2-ethylhexyl) Phthalate in Groundwater
The
The
The fuel oil day tank, which is located up gradient of the location
where soil TPH contamination was detected, is located above ground level and
was commissioned at the same time as the power station. The tank is surrounded by a concrete pavement
and is provided with secondary containment.
No oil spills and leakages have been reported at the tank and none were
observed during the site. An oil pipe
leakage near the fuel oil pump house was reported to the Marine Department and
the EPD in July 2004.
6.3.2
Chemicals
of Concern
The chemicals of concern are mainly TPH in the soil and groundwater and di-n-butyl phthalate and bis
(2-ethylhexyl) phthalate in groundwater.
The TPH included light diesel (C10-C14), heavy diesel (C15-C28) and
heavy oil (C29-C36) fractions.
6.3.3
Potential
Migration and Exposure
The potential transport mechanism for the TPH contamination in surface soil
at TP3 and TPH, di-n-butyl phthalate and bis (2-ethylhexyl) phthalate in the groundwater in the Site
area is the flow of shallow groundwater underneath the site which was measured
at about 1.3 to 2.5 mPD. The groundwater flow within the Site area is likely
influenced by tidal movements as the Site is located on a reclaimed area
approximately 100 to 400 m from the waterfront.
As the Site area is paved, and groundwater is not used for either
domestic or industrial purposes at the Site and in the adjacent areas, the
potential exposure to TPH, di-n-butyl phthalate and bis (2-ethylhexyl) phthalate in groundwater could only take
place during the demolition and construction stages of the Project. The potential exposure pathways include
dermal contact and accidental ingestion of the soil and groundwater.
6.3.4
Potential
Receptor
During the demolition of the facilities and the construction phases,
potential on-site receptors include workers involved in demolition and
construction actives who may be handling or come into contact with the
contaminated materials. Mitigations
measures are proposed in the Remediation Action Plan (RAP) to minimise worker
exposure during this period. No adverse
impacts are anticipated after the proposed measures have been implemented.
The site and the surrounding areas are used by
A site investigation was completed and the findings
are reported in this CAR. The land contamination assessment was
performed in accordance with
the procedures and requirements set out in the CAP. The CAP made reference to EPD’s
Practice Note for Professional Persons
(ProPECC PN 3/94) and Guidance Notes for Investigation and Remediation Contaminated Site of
Petrol Filling Stations, Boatyard and Car Repair/Dismantling Workshops.
The conclusions of the land contamination assessment are summarized
below.
TPH was detected at a concentration (1,858 mg/kg) which exceeded the EPD
Dutch ‘B’ value for mineral oil
(1,000 mg/kg) in a soil sample taken from one location (TP3), at a depth 0.9 m bgl. The detected TPH concentration was in the light diesel
(83 mg/kg), heavy diesel (1,170 mg/kg) and heavy oil fractions (605
mg/kg). Other than this, no TPH was
detected in any soil sample.
TPH in the fractions of heavy diesel and heavy oil were detected at concentrations
which ranged from 204 to 3,120 µg/L, exceeding the Dutch ‘B’ value (200 µg/L for mineral oil) in all groundwater
samples. Seven out of the eight
groundwater samples exceeded the Dutch
‘C’ value (600 µg/L for mineral oil).
As groundwater is not used for either domestic or industrial purposes at
the site and in the adjacent areas, remediation of groundwater contamination of
the Site is not considered necessary. If
groundwater is encountered during the construction of the Project, the groundwater
abstracted or collected should be recharged back to the site. Health and safety control measures will also
be implemented for the workers who may come into contact with contaminated
groundwater.
[3] RPD is
calculated from the detected results of field duplicate samples, which should
be higher than two times the detection limits.