In accordance with the recommendations of the EIA for the
present Project, a monitoring programme examining sediment quality will be instituted
to verify the EIA predictions and ensure that there is no build-up in
contamination adjacent to the pits.
Sediment chemistry has long been an important component of monitoring
programmes at the East of Sha Chau mud disposal complex. Since 1997 a comprehensive list of
Contaminants of Concern (COCs) comprising 8 heavy metals and 1 metalloid,
polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs),
organochlorine pesticides (eg DDT) and Tributyltin (TBT). These contaminants (which correspond to
the list of COCs in ETWBTCW 34/2002) in sediments should be measured in
the present monitoring programme and changes over time and distance should also
be examined.
The main objective of this task is to determine if there are
any changes and/or trends in the concentrations of contaminants in sediments
adjacent to the pits caused by disposal activities. This objective is most appropriately addressed through two
separate but intrinsically linked sub-tasks:
·
Near-field monitoring of sediment quality - conducted to examine near
field impacts of backfilling operations on the spread of contaminants from the
pits and to allow for rapid detection of any adverse environmental impacts and,
if necessary, changes to the operations plan.
·
Regional monitoring of sediment quality - conducted to analyse the
ambient conditions in the North Lantau
region and to investigate whether any impacts to marine sediments are occurring
due to the dispersion of contaminants from the active pits.
The impact hypothesis for this task is as follows:
There is no increase in sediment contaminant
concentrations over time at individual stations or a trend of increasing
concentrations with proximity to the active pit.
As a result of the separation of this programme into two
sub-tasks, two sets of null hypotheses should be tested:
Near-field monitoring of
sediment quality
H0 There is no increase in sediment
contaminant concentration in the area adjacent to the active pits as compared
to levels observed in the area under recently conducted, comparable monitoring
programmes.
Regional monitoring of
sediment quality
H0 There is no increase in sediment
contaminant concentration over time in the area of contaminated mud disposal activity.
H0 There is no increase in sediment
contaminant concentration with proximity to the active pits.
The designs for assessing the impacts of disposal of
contaminated mud in the active pits
on the sediment chemistry of remote and adjacent areas take into account the
following factors:
·
The
null hypotheses being tested;
·
Background
levels of contaminants in the region;
·
Predictions
taken from the EIA on sediment plume locations;
·
Spatial
variability in sediment chemistry;
·
Temporal
variability in sediment chemistry; and,
·
Expected
statistical treatment of the data.
·
As
mentioned in Section 1.7.2 the EM&A Manual is an evolving document
that should be updated to maintain its relevance as the Project
progresses. This includes the
relocation of monitoring stations to best suit the requirements of the
monitoring programme and to take into account other work that is occurring in
the direct vicinity of the active facility.
Sediment samples shall be collected on a monthly basis from
two sites in the active pit, two sites on the edge of the active pits and two
sites in close proximity to the pits (Figures 4.4a and 4.4b). Twelve replicates of composite samples
(ie 5 grab samples obtained using a cluster grab) will be collected from each
of the sites. Replicates have been
based on analysis of data conducted as part of the monitoring of CMP IVa
(Agreement No. CE 44/97). Under
this EM&A programme, Cumulative Running Mean Tests determined optimum
sample size for stabilising mean and standard error values was 12 samples for
sediment analysis. The technique
of clustering stations within one site has been proven to be an effective way
of testing hypotheses and removing the confounding effects of spatial variation
from the interpretation. The
number of stations within a site and the precise locations of the sampling
stations should be confirmed in advance of the commencement of disposal activities
and agreed with EPD subject to the detailed design of the disposal
facility.
Sediment samples should be collected twice during the dry
season and twice during the wet season at stations distributed throughout the North Lantau area. The stations should be located in three
discrete areas, with two sites in each area. The areas should be located at increasing distances from the
disposal operations (ie Near Field, Mid Field, Far Field and any additional sensitive
receiver sites indicated on Figures 4.4a and 4.4b). Twelve replicates of composite samples
(ie 5 grab samples obtained using a cluster grab) will be collected from each
of the sites. The exact positions
of the stations should be determined in advance of the commencement of disposal
activities and agreed with EPD.
Observed differences in the levels of contaminants should be
tested each month using analysis of variance (factors = Area and Site) followed
by Student Newman Keuls (SNK) multiple comparison procedures to isolate which
treatments differ from others.
Once a time series of data has been gathered, the data should be
re-analysed to examine the differences within and between the sites over
time. This should be achieved
using an analysis of variance with site, Area and Month as the factors.
For all of the analysis of variance techniques performed
during the monitoring programme, initial analyses should be performed to ensure
that the data complies with the specific assumptions of analysis of
variance. These assumptions state:
·
the
data within and among samples must be independent of each other;
·
the
variance within samples must be equal (tested through the use of tests such as
Levene's median test); and,
·
the
data among the samples must be normally distributed (tested through the use of
tests such as the Kolgomorov-Smirnov test).
Should the data not comply with these
assumptions then the appropriate transformation should be applied to the data
(eg, arc-sin for percentage data, log (x+1) for abundance data, or
rank transformation if necessary).
If, after transformation, the data are still non-compliant then
non-parametric equivalents to ANOVA such as Kruskal-Wallis tests should be
used.
The design of the regional monitoring programme should allow
the use of nested analysis of variance techniques to be employed. These techniques shall be used to
analyse the data at different spatial and temporal scales of replication. Statistical differences should be
tested at the following levels: between sites in each area and between each
area at each sampling time. An advantage
of this sampling design is that it removes the possibility of detecting
differences simply due to inherent variation over spatial scales in the active area and thus facilitates
clearer attribution to disposal operations. By replicating within each area, ie by sampling two sites in
one area, any statistically significant differences detected between areas are
more likely to be due to factors other than spatial variation (eg, disposal
operations). This approach is now
an internationally recommended technique for use in monitoring programmes ([1]). Multidimensional scaling ordination techniques shall also be
applied to the data.
Should significant increases be detected in the level of
contaminants in sediment samples, a review of the other monitoring parameters
should be undertaken. This review
shall focus on sampling stations in the vicinity of the sediment quality
monitoring stations where increases were detected to see if these can be
attributed to contaminant migration from the active pits.
Assessment of the statistical significance of the data, confidence in
the data and the presence of supporting data from other components of the
monitoring programme should be jointly assessed. If appropriate, changes to the operations plan should be
considered.
The parameters that should be measured in sediments
collected during the two sub-tasks and the rationale for each are given
below. The contaminants listed are
the "Contaminants of Concern" for which Lower and Upper Chemical
Exceedance Limits (LCEL/UCEL) exist.
(a) Total Organic Carbon (TOC) - an
indicator of organic load and the impact on bottom layer dissolved oxygen. TOC is an important factor influencing
the chemical partitioning and toxicity of hydrophobic organic compounds such as
PAHs, PCBs and pesticides. High
TOC often infers that hydrophobic contaminants are less bioavailable;
(b) Inorganic Contaminants - metals and
metalloids present in the disposed sediments which may be bioaccumulated;
(c) Polycyclic Aromatic Hydrocarbons (PAH)
- a class of organic compounds some of which are persistent and
carcinogenic. These compounds may
be bioaccumulated and stored in the fatty body tissues of mammals;
(d) Total Polychlorinated Biphenyls (PCB) -
a class of persistent man-made chemicals which tend to bioaccumulate through
the food chain and can cause reproductive failure and cancer;
(e) Organochlorine Pesticides (DDE & DDT)
- contaminants which are persistent, highly lipophilic (can be accumulated and
stored in fat), have high bioaccumulation and biomagnification potential, and
high toxicity to aquatic organisms; and,
(f)
Tributyltin (TBT) (in sediment
and interstitial water) -
moderately persistent toxic compound found in marine sediments which may be
bioaccumulated and cause growth abnormalities and reproductive failure.
(a) Percentage of Silt/Clay (% < 63mm) - organic contaminants and
metals bind more readily to finer particles than coarser particles due to their
larger surface area and consequent larger number of binding sites;
(b) Total Organic Carbon
(TOC);
(c) Inorganic Contaminants (1);
(d) Polycyclic Aromatic
Hydrocarbons (PAH) (2);
(e) Total Polychlorinated
Biphenyls (PCB);
(f) Organochlorine
Pesticides (DDE & DDT) (3);
and,
(g)
Tributyltin
(TBT) (in sediment).
All samples should be collected by an experienced sampling
team (with ISO 9002 certification), deployed on a survey boat equipped with
fully calibrated sampling equipment and precision navigational
instruments. All vessel
positioning should be accomplished with a calibrated Differential Global
Positioning System (DGPS), ensuring station location accuracy to < ± 1 m (95% confidence), with
sample position automatically logged and mapped by the navigation
computer. Where sample stations
are located in close proximity to the pit area, positioning should be further
validated by use of an echo sounder to detect whether the vessel is within the
boundaries of the pit.
At each sampling station the top 5 cm of
seabed sediment should be collected using a 5-component cluster grab sampler
which collects surficial sediments with a minimal disruption to the surface
layer and is designed to work effectively in soft sediment such as those found
in the area. The cluster grab
should be deployed once at each of the stations located within each sampling
area (eg Pit, Pit-Edge). The grabs
can customised and a fine mesh lid added, which ensures that the fine fluid
sediments on the surface of the seabed are retained in the sample. Utilisation of this cluster sampler
allows a large volume of sediment to be collected in a single deployment. Other similar samplers (eg Petit-ponar)
collect less sediment in each deployment and can have difficulty collecting
adequate samples in soft sediments, such as those within the study area,
thereby reducing efficiency and increasing collection time. The five-cluster grab should be
collected and combined, and the sample, labelled, double-bagged and stored in
an ice chest cooled to a temperature of 4oC with ice packs. The sediment sampler and all other
utensils should be rinsed with seawater after each sample has been collected to
avoid cross contamination between samples. On completion of the survey, all samples should be promptly
transported, in chilled containers, to the testing laboratory for analysis.
A broad range of contaminants should be analysed in sediment
samples including metals, metalloids, PAHs, PCBs, pesticides and Tributyltin in
both sediment and interstitial water.
The method detection limits should be consistent with previous
monitoring programmes at East of Sha Chau. Other QA/QC procedures to be implemented for marine sediment
analyses include:
·
Laboratory blanks - an analyte free matrix to
which all reagents shall be added in the same volumes or proportions as used in
the standard sample preparation to monitor contamination introduced in the laboratory
(organics and inorganics);
·
Batch duplicates - an intralaboratory split
sample randomly selected from the sample batch to monitor method precision
(intrabatch) in a given sample matrix (inorganics only);
·
Certified Reference Materials - analysis of a material with
a known concentration of contamination to determine the accuracy of results in
a given matrix (inorganics only);
·
Single Control Samples - a known, interference-free
matrix spiked with target analytes used to monitor laboratory preparation
techniques (organics only);
·
Duplicate Control Samples - multiple single control
samples designed to monitor preparation technique reproducibility
(organics).
Data Quality Objectives (DQOs) have been developed to
address precision, accuracy and analyte recovery.
Details of quality control specifications for inorganic
testing should be included in the updated EM&A Manual prior to commencement
of disposal activities.
Duplicates (1 in every 10 samples) should be used to
monitoring the precision of the analysis.
Results should be flagged for reference when:
·
For
all analytes, except metals, with concentration >4x Method Detection Limit
(MDL), the duplicate results have more than a 20% Relative Percentage Deviation
(RPD)
·
In
water samples, for metals with a concentration >4x MDL, the duplicate
results have more than a 15% RPD
·
In
sediment and biota samples, for metals with a concentration >4x MDL, the
duplicate results have more than a 25% RPD
·
For
all analytes with concentration <4x MDL, the duplicate results should be
reported as analysed and no bounds should be quoted
Standard and certified reference material (CRM) shall be
used to monitor accuracy and precision within and between batches: Results should be flagged for reference
if:
·
The
variation of the standard from its true value is more than ± 15% (for mercury: ± 20%).
Post digest spikes should be used to determined the recovery
of determinants in complex sample matrices. Results should be rejected if:
·
Spike
recoveries are more than ± 25% from the theoretical recovery for
waters, sediment and marine biota.
An exceptional case would be if the sample concentration is greater than
four times the spike value, the spike may be disregarded.
Samples should be analysed in lots of less than 20. In order to measure the laboratory
performance within each batch of samples, a single control sample (SCS), a
duplicate control sample (DCS) and a method blank (MB) should be processed
concurrently with the samples. A
SCS or DCS consists of an interference free control matrix that is spiked with
a group of target compounds representative of the method analytes.
Method blanks, also known as reagent, analytical, or preparation
blanks, should be analysed to assess the level of contamination that exist in
the analytical system and which might lead to the reporting of elevated
concentration levels or false positive data. For organic analyses, the concentration of target analytes
in the blank must be below the reporting limit for that analyte in order for
the blank to be considered acceptable.
Accuracy is expressed as the
average percent recovery of the SCS/DCS pair and precision is expressed as the relative
percent difference (RPD). For
control limits
that are not established due to insufficient data sets, the QC Acceptance
Criteria of US EPA Method 8080 and 8270A should be used as a supplement. Once enough data are collected, the
in-house control limits should then be calculated.
The accuracy and precision data for SCS and DCS should be
evaluated against laboratory established control limits. QC results falling outside the control
limits should be automatically flagged.
The acceptance criterion is that 100 percent of the precision and
accuracy values must fall within the control limits. If this criterion is not met, corrective action must be
taken. This may include repeat
sample analysis.
The relative percentage difference of SCS/DCS pair should be
compared to the limit set for each compound being monitored (Table 4.1). In normal instances, an RPD of less
than 20% is deemed to be acceptable.
For multianalyte organic tests, if greater than 20% of the
accuracy or precision results for the DCS are outside of the control limits,
the data are considered suspect and the samples associated with the
unacceptable DCS are reprepared and/or reanalysed.
Table 4.1 Quality Control Acceptance Criteria for Organic
Analyses
|
Target Analytes |
Percent Recovery Measured |
|
Naphthalene |
74
- 126 |
|
Acenaphthalene |
69
- 125 |
|
Acenaphthene |
73
- 119 |
|
Fluorene |
81
- 129 |
|
Phenanthrene |
74
- 131 |
|
Anthracene |
63
- 116 |
|
Fluoranthene |
73
- 134 |
|
Pyrene |
59
- 129 |
|
Benzo(a)anthracene |
77
- 136 |
|
Chrysene |
53
- 130 |
|
Benzo(a)pyrene |
51
- 103 |
|
Dibenzo(a,h)anthracene |
78
- 126 |
|
DDE |
73
- 121 |
|
DDT |
87
- 120 |
|
Total
PCBs |
79
- 127 |
|
Tributyltin |
80
- 115 |
D B
Detected, result must be greater than zero
([1]) AJ Underwood (1997) Experiments in Ecology: their logical design and interpretation using analysis of variance.
([2])
Cadmium
(Cd), Chromium (Cr), Copper (Cu), Lead (Pb), Mercury (Hg), Nickel (Ni), Silver
(Ag), Zinc (Zn) and Arsenic (As).
([3]) Acenapthene, Acenaphthylene, Anthracene,
Fluorene, Napthalene, Phenanthrene, Low Molecular Weight PAHs,
Benzo(a)anthracene, Benzo(a)pyrene, Chrysene, Dibenzo(a,h)anthracene,
Fluoranthene, Pyrene, High Molecular Weight PAHs and Total PAHs
([4]) Total Dichlorodiphenyl-trichloroethane
(DDT) and Dichlorodiphenylchloroethane (p,p'-DDE).