The construction and operation of the Project has the potential to cause
adverse water quality impact to the receiving water bodies if not properly
managed. This section examines the
potential impacts on the nearby water resources due to construction activities
(particularly piling works for the jetty), effluent discharge from the on-site
wastewater treatment works, surface water runoff and potential spillage of raw
materials and biodiesel products.
Consideration is given to identify practicable means and/or mitigation
measures to avoid marine pollution incidents arising from loading and unloading
of materials at the jetty and on-site storage of raw materials and biodiesel
products.
The regulatory requirements and standards to protect water quality are
as follows:
·
Water Pollution Control Ordinance (WPCO) (Cap. 358);
·
Environmental
Impact Assessment Ordinance (Cap. 499. S.16), Technical Memorandum on
Environmental Impact Assessment Process (EIAO-TM), Annexes 6 and 14;
·
Technical Memorandum Standards for Effluents Discharged
into Drainage and Sewerage Systems, Inland and Inshore Waters (TM);
·
Practice Note for Professional Persons on Construction
Site Drainage (Prop PECC PN 1/94); and
·
6.2.1
Water Pollution Control Ordinance (WPCO)
The WPCO is the legislation for the control of water pollution
and water quality in
The assessment area (thereafter referred to as the Study Area) is
located inside the Junk Bay WCZ and is in close proximity to the Eastern Buffer
WCZ (see Figure
6.2a). The WQOs for the Junk Bay WCZ and
Eastern Buffer WCZ, which are presented in Tables 6.2a and 6.2b, respectively, are
hence applicable as evaluation criteria for assessing compliance of any effects
from the discharges of the Project.
Table 6.2a Water Quality Objectives for Junk Bay
Water Control Zone
|
Water
Quality Objectives |
Junk Bay WCZ |
|
A. AESTHETIC
APPEARANCE |
|
|
(a) Waste discharges shall cause no objectionable odours or
discolouration of the water. |
Whole
Zone |
|
(b) Tarry residues, floating wood, articles made of glass, plastic,
rubber or of any other substance should be absent. |
Whole
Zone |
|
(c) Mineral oil should not be visible on the surface. Surfactants
should not give rise to a lasting foam. |
Whole
Zone |
|
(d) There should be no recognisable sewage-derived debris. |
Whole
Zone |
|
(e) Floating, submerged and semi-submerged
objects of a size likely to interfere with the free movement of vessels, or
cause damage to vessels, should be absent. |
Whole
Zone |
|
(f) Waste discharges shall not cause the water to Whole Zone contain
substances which settle to form objectionable deposits. |
Whole
Zone |
|
B. BACTERIA |
|
|
(a) The level of Escherichia
coli should not exceed 610 per 100 mL, calculated as the geometric mean of
all samples collected in one calendar year. |
|
|
(b) (Repealed L.N. 451 of 1991) |
- |
|
(c) The level of Escherichia
coli should not exceed 1000 per 100 ml, calculated as the running median of
the most recent 5 consecutive samples taken at intervals of between 7 and 21
days. |
Inland
waters |
|
C. COLOUR |
|
|
Waste
discharges shall not cause the colour of water to exceed 50 Hazen units. |
Inland
waters |
|
D. DISSOLVED
OXYGEN |
|
|
(a) Waste discharges shall not cause the level of dissolved oxygen
to fall below 4 mg L-1 for 90% of the sampling
occasions during the year; values should be calculated as the water column
average (arithmetic mean of at least 3 measurements at 1 m below surface,
mid-depth and 1 m above seabed). In addition, the concentration of dissolved
oxygen should not be less than 2 mg L-1 within 2 m of the seabed
for 90% of the sampling occasions during the year. |
Marine
waters excepting Fish Culture Subzones |
|
(b) The dissolved oxygen level should not be less than 5 mg L-1 for
90% of the sampling occasions during the year; values should be calculated as
water column average (arithmetic mean of at least 3 measurements at 1 m below
surface, mid-depth and 1 m above seabed). In addition, the concentration of
dissolved oxygen should not be less than 2 mg L-1 within
2 m of the seabed for 90% of the sampling occasions during the year. |
Fish
Culture Subzones |
|
(c) Waste discharges shall not cause the level of dissolved oxygen
to be less than 4 mg L-1. |
Inland
waters |
|
E. pH |
|
|
(a) The pH of the water should
be within the range of 6.5-8.5 units. In addition, waste discharges shall not
cause the natural pH range to be extended by more than 0.2 units. |
Marine
waters (L.N. 451 of 1991) |
|
(b) (Repealed L.N. 451 of
1991) |
- |
|
(c) The pH of the water
should be within the range of 6.0-9.0 units. |
Inland
waters |
|
F. TEMPERATURE |
|
|
Waste
discharges shall not cause the natural daily temperature range to change by
more than 2.0oC. |
Whole
Zone |
|
G. SALINITY |
|
|
Waste
discharges shall not cause the natural ambient salinity level to change by
more than 10%. |
Whole
Zone |
|
H. SUSPENDED SOLIDS |
|
|
(a) Waste discharges shall
neither cause the natural ambient level to be raised by 30% nor give rise to
accumulation of suspended solids which may adversely affect aquatic
communities. |
Marine
waters |
|
(b) Waste discharges shall not
cause the annual median of suspended solids to exceed 25 mg L-1. |
Inland
waters |
|
I. AMMONIA |
|
|
The
ammonia nitrogen level should not be more than 0.021 mg L-1,
calculated as the annual average (arithmetic mean), as unionized form. |
Whole
Zone |
|
J.
NUTRIENTS |
|
|
(a)
Nutrients shall not be present in quantities sufficient to cause
excessive or nuisance growth of algae or other aquatic plants. |
Marine waters |
|
(b) Without
limiting the generality of objective (a) above, the level of inorganic
nitrogen should not exceed 0.3 mg L-1, expressed as annual water column average
(arithmetic mean of at least 3 measurements at 1 m below surface, mid-depth
and 1 m above seabed). |
Marine waters |
|
K.
5-DAY BIOCHEMICAL OXYGEN DEMAND |
|
|
Waste discharges shall not cause the 5-day
biochemical oxygen demand to exceed 5 mg L-1. |
Inland
waters |
|
L.
CHEMICAL OXYGEN DEMAND |
|
|
Waste discharges shall not cause the chemical oxygen
demand to exceed 30 mg L-1. |
Inland
waters |
|
M. DANGEROUS SUBSTANCES |
|
|
(a)
Waste discharges shall not cause the concentrations of dangerous substances
in the water to attain such levels as to produce significant toxic effects in
humans, fish or any other aquatic organisms, with due regard to biologically
cumulative effects in food chains and to toxicant interactions with each
other. |
Whole Zone |
|
(b)
Waste discharges of dangerous substances shall not put a risk to any
beneficial uses of the aquatic environment. |
Whole Zone |
|
N-O (Repealed L.N. 451 of 1991) |
Whole Zone |
Table 6.2b Water Quality Objectives for Eastern
Buffer Water Control Zone
|
Water Quality Objectives |
Eastern Buffer WCZ |
|
A. AESTHETIC
APPEARANCE |
|
|
(a) There
should be no objectionable odours or discolouration of the water. |
Whole Zone |
|
(b) Tarry
residues, floating wood, articles made of glass, plastic, rubber or of any
other substances should be absent. |
Whole Zone |
|
(c) Mineral
oil should not be visible on the surface. Surfactants should not give rise to
a lasting foam. |
Whole Zone |
|
(d) There
should be no recognisable sewage-derived debris. |
Whole Zone |
|
(e) Floating,
submerged and semi-submerged objects of a size likely to interfere with the
free movement of vessels, or cause damage to vessels, should be absent. |
Whole Zone |
|
(f) The
water should not contain substances which settle to form objectionable
deposits. |
Whole Zone |
|
B. BACTERIA |
|
|
(a) The
level of Escherichia coli should
not exceed 610 per 100 mL, calculated as the geometric mean of all samples
collected in a calendar year. |
Fish Culture Subzones |
|
(b) The
level of Escherichia coli should be
less than 1 per 100 mL, calculated as the geometric mean of the most recent 5
consecutive samples taken at intervals of between 7 and 21 days. |
Water Gathering Ground Subzones |
|
(c) The
level of Escherichia coli should
not exceed 1000 per 100 mL, calculated as the geometric mean of the most
recent 5 consecutive samples taken at intervals of between 7 and 21 days. |
Other inland waters |
|
C. COLOUR |
|
|
(a) Human
activity should not cause the colour of water to exceed 30 Hazen units. |
Water Gathering Ground Subzones |
|
(b) Human
activity should not cause the colour of water to exceed 50 Hazen units. |
Other inland waters |
|
D. DISSOLVED
OXYGEN |
|
|
(a) The
level of dissolved oxygen should not fall below 4 mg L-1 for 90% of the sampling occasions during the whole
year; values should be calculated as water column average (arithmetic mean of
at least 3 measurements at 1 m below surface, mid-depth and 1 m above
seabed). In addition, the concentration of dissolved oxygen should not be
less than 2 mg L-1 within 2 m of the
seabed for 90% of the sampling occasions during the whole year. |
Marine waters excepting Fish Culture Subzones |
|
(b) The
level of dissolved oxygen should not be less than 5 mg L-1 for 90% of the sampling occasions during the year;
values should be calculated as water column average (arithmetic mean of at
least 3 measurements at 1 m below surface, mid-depth and 1 m above seabed).
In addition, the concentration of dissolved oxygen should not be less than 2
mg L-1 within 2 m of the seabed for 90%
of the sampling occasions during the whole year. |
Fish Culture Subzones |
|
(c) The
level of dissolved oxygen should not be less than 4 mg L-1. |
|
|
E. pH |
|
|
(a) The pH
of the water should be within the range of 6.5-8.5 units. In addition, human activity
should not cause the natural pH range to be extended by more than 0.2 units. |
Marine waters |
|
(b) Human
activity should not cause the pH of the water to exceed the range of 6.5-8.5
units. |
Water Gathering Ground Subzones |
|
(c) Human activity
should not cause the pH of the water to exceed the range of 6.0-9.0 units. |
Other inland waters |
|
F. TEMPERATURE |
|
|
Human activity should not cause the natural daily temperature range to
change by more than 2.0oC. |
Whole Zone |
|
G. SALINITY |
|
|
Human activity should not cause the natural ambient salinity level to
change by more than 10%. |
Whole Zone |
|
H. SUSPENDED
SOLIDS |
|
|
(a) Human
activity should neither cause the natural ambient level to be raise by more than
30 % nor give rise to accumulation of suspended solids which may adversely
affect aquatic communities. |
Marine waters |
|
(b) Human
activity should not cause the annual median of suspended solids to exceed 20
mg L-1. |
Water Gathering Ground Subzones |
|
(c) Human
activity should not cause the annual median of suspended solids to exceed 25
mg L-1. |
Other inland waters |
|
I. AMMONIA |
|
|
The un-ionized ammoniacal nitrogen level should not be more than 0.021
mg L-1, calculated as the annual average (arithmetic mean). |
Whole Zone |
|
J. NUTRIENTS |
|
|
(a) Nutrients should not be present in
quantities sufficient to cause excessive or nuisance growth of algae or other
aquatic plants. |
Marine waters |
|
(b) Without limiting the generality of objective
(a) above, the level of inorganic nitrogen should not exceed 0.4 mg L-1, expressed as annual water column average
(arithmetic mean of at least 3 measurements at 1 m below surface, mid-depth
and 1 m above seabed). |
Marine waters |
|
K. 5-DAY BIOCHEMICAL OXYGEN DEMAND |
|
|
(a) The 5-day biochemical oxygen demand should
not exceed 3 mg L-1. |
Water Gathering Ground Subzones |
|
(b) The 5-day biochemical oxygen demand should
not exceed 5 mg L-1. |
Other inland waters |
|
L. CHEMICAL OXYGEN DEMAND |
|
|
(a) The chemical oxygen demand should not
exceed 15 mg L-1. |
Water Gathering Ground Subzones |
|
(b) The chemical oxygen demand should not
exceed 30 mg per litre. |
Other inland waters |
|
M. TOXIC SUBSTANCES |
|
|
(a) Toxic substances in the water should not
attain such levels as to produce significant toxic, carcinogenic, mutagenic
or teratogenic effects in humans, fish or any other aquatic organisms with
due regard to biologically cumulative effects in food chains and to
interactions of toxic substances with each other. |
Whole Zone |
|
(b) Human activity should not cause a risk to
any beneficial use of the aquatic environment. |
Whole Zone |
6.2.2
Technical Memorandum for Effluent
Discharges into Drainage and Sewerage Systems, Inland and Inshore Waters (TM)
All discharges from the Project are required to comply with the Technical
Memorandum for Effluents Discharged into Drainage and Sewerage Systems, Inland and
Inshore Waters (TM) issued under Section 21 of the WPCO. The
TM defines discharge limits for
different types of receiving waters.
Under the TM, effluents
discharged into the drainage and sewerage systems, inshore and inshore waters
of the WCZs are subject to pollutant concentration standards for particular
discharge volumes. Any new discharges
within a WCZ are subject to licence conditions and the TM acts as a guideline for setting discharge standards for
inclusion in the licence. Any sewage
from the proposed construction and operational activities should comply with
the standards for effluent discharged into the foul sewers, inshore waters or
marine waters of the
6.2.3
Environmental Impact Assessment Ordinance
(Cap. 499. S.16), Technical Memorandum on Environmental Impact Assessment
Process (EIAO-TM)
Annexes 6 and 14 of
the Environmental Impact Assessment
Ordinance (Cap. 499. S.16), Technical Memorandum on Environmental Impact
Assessment Process (EIAO-TM)
provide general guidelines and criteria to be used in assessing
water quality issues.
6.2.4
Practice Note for Professional Persons on
Construction Site Drainage (ProPECC PN 1/94)
The ProPECC PN 1/94 issued by the EPD provides some basic
environmental guidelines for the handling and disposal of construction site
discharges to prevent or minimise construction impacts on water quality.
Whilst the technical circulars are non-statutory, they are generally
accepted as best guidelines in
6.2.5
Chapter 9 of the Hong Kong Planning Standards and Guidelines (HKPSG)
provides guidance for including environmental considerations in the planning of
both public and private developments. It
applies both to the planning of permanent or temporary uses which will have
potential to cause significant changes to the biophysical environment or which
are sensitive to environmental impacts. Section
5 in Chapter 9 of the HKPSG provides additional information
on regulatory guidelines against water pollution for sensitive uses such as
aquaculture and fisheries zones, bathing waters and other contact recreational
waters.
6.3
Assessment Methodology
The Study Area was
defined as the area within 500 m of the Project Site boundary.
The construction
method and sequence described in Section 3 were reviewed to assess the remoteness of the construction
works from existing and committed Water Sensitive Receivers (WSRs) within the
Study Area. The WSRs were identified
according to guidance provided in the EIAO-TM
and HKPSG.
The construction
sequence, duration and activities, and the operation activities were reviewed
to identify activities with the potential to impact on the identified WSRs and
other water courses.
Following the
identification of WSRs and potential water quality impacts, the scale, extent
and severity of potential net (ie unmitigated) construction and operation
impacts were evaluated, taking into account all potential cumulative effects
including those of adjacent projects, with reference to the WPCO criteria.
Where net water
quality impacts exceed the appropriate WPCO criteria, practical water
pollution control measures/mitigation proposals were identified to ensure
compliance with reference to the WPCO criteria. Water quality monitoring and audit
requirements were developed, if necessary, to ensure the effectiveness of the
water pollution control and mitigation measures.
6.4
Water Quality
Sensitive Receivers and Baseline
Conditions
6.4.1
Existing Conditions
The Project Site is located at the
seafront of the TKOIE which is situated in the southeast of the Tseung Kwan O
New Town, Sai Kung District in
There are no natural streams and rivers
either passing through the Project Site or within the catchment of the Project
Site. A few seasonal streams were
recorded within Study Area in another catchment near Fat Tong Chau which is
located to the south of the Project Site.
They are classified as seasonal streams because they were found to have
limited water flows during the wet season and no water flows during the dry season. In addition, the Project Site is not situated
with the secondary contact recreation area, in accordance with the WPCO.
The ecological impact assessment was
detailed in Section 7. Ecological
surveys were conducted along the seawall of the TKOIE and the natural shoreline
at Fat Chau Tong. Based on the surveys
results, the assessment concluded that there were no species of high ecological
value within the Study Area.
6.4.2
Water Sensitive Receivers (WSRs)
In order to evaluate the water quality impacts resulting from the construction
and operation of the biodiesel plant, the WSRs have been identified in
accordance with the EIAO-TM and HKPSG.
The WSRs identified in the Study Area include:
·
Inshore waters in
·
Surface water including seasonal streams.
6.5
Evaluation of Impacts during Construction Phase
6.5.1
Piling Works for
the Jetty
The jetty in a
form of piled deck will be constructed (see Figure 2.2b) for berthing of marine
vessels. No dredging of marine sediment
will be required for the construction of the jetty. Marine piles will be driven through the
existing rubble mound seawall (see Figure 2.2c) to competent bearing strata
by a hydraulic hammer piling barge. During the construction of the existing rubble mound
seawall, the sediments below the seawall have been removed and backfilled with
marine sand. The materials to be
excavated from the bore pile will consist of rock and sand. No sediment will be excavated.
A temporary working platform will be constructed by
placing steel piles on the seawall and then welding steel planks on top. The casing of the pile will be drilled
through the existing seawall to the rock head.
The rock fill will be removed and the marine sand will be airlifted
under pressure through the top of the casing and channelled
to a sedimentation tank located on
land. The top of the casing will be
covered with canvas to prevent spillage of material during removal of the sand
fill. After settling the sands, the effluent
will be discharged to stormwater drain.
A disposal license will be applied under the Water Pollution Control Ordinance (WPCO) for the discharge and the
licence conditions will be complied
with prior to discharge. The settled
sand will be reused on-site.
Silt curtain will
be installed around the marine piling area to contain any suspended mud and
sediments generated during the piling works.
It is expected that the marine piling will cause limited disturbance to
the existing seawall and is unlikely to cause unacceptable impacts to the water
quality in
Concrete infill to
piles will be undertaken prior to placement of trellis beam and pre-cast
concrete panels. It is estimated that
the construction of the jetty will take about 6 months, including 2 months for
pile installation and 4 months for jetty deck construction.
6.5.2
Sewage and General
Refuse generated by Workforce
Sewage and general
refuse will be generated from construction workforces. An adequate number of
portable toilets will be provided on site to ensure that sewage from site staff
is properly collected. The portable
toilets will be desludged and maintained regularly by a specialised
contractor. Recyclable materials (ie
paper, plastic bottles and aluminium cans) will be separated for recycling as
far as possible, in order to reduce the amount of general refuse to be disposed
of at landfill. An adequate number of
enclosed waste containers will be provided on-site to ensure waste is fully
contained. No adverse water quality
impacts associated with the handling and disposal of sewage and general refuse
generated by the construction workforce are envisaged.
6.5.3
Surface Runoff and
Drainage
Construction site
runoff will be the major source of water quality impacts associated with the
land based construction activities. As
discussed in Section 3.3.2, the
construction of the biodiesel plant will only involve minor earthworks.
The construction
of the superstructure has a low risk of generating contaminated runoff since
drainage systems will be well established before the commencement of
construction works and as portable toilets will be used and will be serviced
regularly by a specialised contractor for off-site disposal. With the implementation of general good site
practice in accordance with the Practice
Note for Professional Persons on Construction Site Drainage (ProPECC PN1/94), the land based
construction activities will not cause adverse water quality impacts.
6.6
Evaluation of Impacts during Operation Phase
6.6.1
Presence of Jetty
The proposed jetty (50 m long and 26 m wide) will have a reinforced
concrete deck and will be supported by marine piles. A total of about 60 piles, of approximate diameter
of 1m, will stand underneath the deck of the berthing facility. The cross-sectional area of each pile
underwater has been estimated at 0.8 m2 and the depth underwater
will be in the range 10 m to 12 m. It is
estimated that the volume of each pile underwater will be in the range 8 m3
to 9.6 m3. Although there may
be localised effects due to the physical resistance of the piles, the water
flow through the piled structure will generally be maintained. In view of the small cross-sectional area
occupied by the piles, the closeness to the shore, and an average and maximum
current speeds at the study area of about 0.07 m s-1 and 0.37 m
s-1 respectively ([1]), the marine
piles will not have adverse impact to the hydrodynamic system or marine water flow
regime at the jetty during the operational phase. The layout of the marine piles and the jetty
is designed to minimise influence to the seawater flow around the jetty.
The maximum draft
of the loaded barges (1,000 tonne barges) for the transportation of biodiesel,
PFAD and methanol is about 4m. The water
depth at the jetty is about 10m (see Figure 2.2c) and therefore there will be
sufficient water depth for the access of the barges without the need to dredging
during operation.
6.6.2
Wastewater
Generated From the Operation of the Facility
With reference to other biodiesel plants of similar scale, the number of
personnel for the operation of the proposed biodiesel plant will be approximately
20 during the day and 8 at night. If
necessary, additional personnel will be hired for maintenance and repair
works. The small amount of sewage
generated by the site staff (a maximum of about 1.5 m3 per day ([2])) will be
collected and discharged to the foul sewer of the TKOIE which leads to the TKO
Sewage Treatment Works.
It is estimated that a total of about 170,000 m3 per year (or
about 515 m3 d-1 or 515 tpd) of wastewater will be generated from feedstock
pre-treatment and the
glycerine dewatering processes. As advised
by the Hong Kong Science and Technology Parks Corporation ([3]), the capacity of the sewerage system of the TKOIE is
in excess of 20,000 m3 d-1 and hence will have sufficient
capacity to handle the anticipated flow of the effluent discharged from the
plant (ie daily discharge of 515 m3 d-1 from the Project
which is about 2.6% of the existing capacity).
It should be noted that a
number of land lots at the TKOIE have not been occupied. In addition, the discharge of the treated effluent
could be carried out on a continuous basis so that the flow will be minimal
(about 6 litres/sec). The effluent
discharge from biodiesel plant will not have an adverse impact on the
downstream sewers. A review by the
Design Engineer shows that the foul sewers downstream of the biodiesel plant
will have sufficient capacity to handle the hourly flow of the effluent
discharge from the wastewater treatment plant.
The wastewater generation from the biodiesel pre-treatment and
production processes will contain trace amounts of oils and fats (such as
triglycerides and free fatty acids) and will have a high COD concentration
(about 9,400 mg L-1 to 15,000 mg L-1). The on-site wastewater treatment plant will be
designed based on these characteristics and to comply with the standards for
effluent discharged into foul sewer.
The key components
of the wastewater treatment plant will include an oil-water separator, a
dissolved air flotation (DAF) system, an Internal Circulation (IC) Reactor (an
anaerobic treatment that utilises the upflow anaerobic sludge blanket (UASB)
technology), an aerobic treatment system and a secondary clarifier. The IC Reactor is an anaerobic treatment
technology that can effectively reduce the organic loading of the wastewater
especially for wastewater with high organic matter content. The effluent from the IC Reactor will be
transferred to the aeration tanks for further treatment. The suspended solids in the treated effluent
from the aeration tanks will be settled in the secondary clarifier so that the
effluent will meet the standards for effluent discharged into foul sewer
leading to the TKO Sewage Treatment Works.
The sludge will be
dewatered to at least 30% dry solids in order to comply with the landfill
acceptance criteria. It is estimated
that about 1.3 tpd of dewatered sludge will be generated and stored in enclosed
containers prior to landfill disposal.
The filtrates from dewatering process will be fed back to the aeration
tank for treatment. The dewatered sludge
will be delivered to landfill by trucks.
All wastewaters generated from the site
(including the wastewater from the GTW pre-treatment, process water from
biodiesel production and wash water from the GTW reception area ([4]), etc) will be
collected and treated at the on-site wastewater treatment plant prior to
discharge to foul sewer leading to the TKO Sewage Treatment Works. The effluent quality will comply with the
discharge standards stipulated in Table 1
of the Technical Memorandum on Standards
for Effluents Discharged to Drainage and Sewerage Systems, Inland and Coastal
Water published by the EPD. No
adverse water quality impact
resulting from the operation of the biodiesel plant is anticipated.
6.6.3
Surface Runoff and
Drainage
The operation of
the biodiesel plant has the potential to cause adverse water quality impacts if
site runoff, wastewater and material storage are not properly managed. The following control measures have been
incorporated in the design of the plant.
Control of
Leakages from the Tank Farm /
Bund wall will be provided at the
tank farm (including the storage tank of the raw materials/products) and the
process tanks within the
Stormwater runoff
of the bunded area (see Figure 3.2f) will pass through an oil
interceptor (see Figure 3.2i) before discharge into the
stormwater drainage system of the TKOIE (see Figure 3.2h).
During rainstorm, the valve of the sump
pit of the bunded area of the tank farm will be manually open to allow an
appropriate flow to pass through the oil interceptor. The water discharged from the oil interceptor
will be checked to ensure that the effluent comply with the discharge standards
prior discharge to the stormwater system.
The sump pit will also be equipped
with a level switch instrument to detect the water level. The sensor will be connected to an alarm of
the PCS-system. Spill/leak within the bunded area will be cleaned up
immediately. If a large spill/leak is
detected, the materials will be pumped out and reuse, where appropriate. Otherwise the material will be disposed of as
a chemical waste to the Chemical Waste Treatment Centre. If the leak is from the GTW and WCO storage
tanks, the materials will be pumped to other GTW storage tank or to the
wastewater treatment plant for treatment.
All storage tanks
will be hydro-tested with water (according the designed test pressure) before
used. The tanks will be provided with
leak detection system. The integrity of
the tanks will be inspected regularly in accordance with relevant building regulations.
Control of
Leakages from the
After
installation, the pipelines will be tested (pressure test with water). There will be no connection (eg flanges and
valves) on the pipe bridge as the pipes on the pipe bridge will be welded. Flanges and valves will only be located
within/above a bunded area (eg
To prevent the pipe bride against any traffic
collisions, the bottom line of the bridge will be at least 4.5m above ground
level. At the site entrance, a “height
check/control” will be installed to ensure that vehicles taller than 3m will
not been allowed to enter the site unless it is escorted by senior site
operator. The columns of the pipe bridge
at the street level will be protected by barriers and sufficient clearance from
the road.
Control of
Pollution during Loading/Unloading Operations at the GTW Unloading Area and
Jetty
At the GTW loading and unloading stations, the
following control measures will be implemented:
·
Dry couplings
will be used to connect the pipes with the truck or barge;
·
The GTW unloading
area will be paved with concrete and the drainage will be separated from the
stormwater drainage system. The drainage
will be connected to the wastewater treatment plant. For the unloading area at the jetty area,
gate valve of the sump pit of the bunded area of the dry coupling will be
closed to ensure any spillage will be contained and collected. This avoids direct discharge of any spill to
the stormwater drainage system.
·
Emergency stops
of loading and unloading will be installed at all stations.
·
The loading and
unloading operation is carried out by trained staff personnel.
With the implementation of the proposed pollution
control measures and site drainage, no adverse water quality impacts arising from site
runoff, wastewater and material storage are expected.
6.6.4
Spillage of Raw
Materials and Biodiesel Plants
There is potential
for spillage of biodiesel, PFAD and methanol during the loading/unloading
operations at the jetty area. Dry
coupling will be used to connect two loading/unloading pipes or a flexible hose
to a transfer pipe in order to avoid any leakage of the materials at the
joint. The loading/ unloading area will
be bunded to contain any potential spillage of materials. In addition, the operations will be
undertaken at the paved loading/ unloading station and will be manned by
trained staff and closely monitored with flow control equipment. Any spillages will be contained and the spill
be absorbed by appropriate absorbents.
The area will be properly washed and the wastewater will be conveyed to
the on-site wastewater treatment plant for treatment.
For accidental spills that
could occur during transportation of biodiesel from the site, retainer booms
will be used to create a warp around the barge and the contaminated areas to
prevent the spillage spreading. Unlike other petroleum products, the raw
materials and biodiesel products are biodegradable and potential impacts
arising from a small amount of uncaptured spilled materials to the marine environment
will be minimal.
An outline emergency response plan related to
prevention of pollution is presented in Annex
F. A detailed emergency response
plan will be developed prior to
the commencement of the operation of the biodiesel plant. In case of accidental spills, the emergency
response plan will be implemented to confine the area affected and clean up the
spillage immediately, hence minimising potential impacts on the marine
environment.
Proposed mitigation measures for containing
and minimising water quality impacts are summarised below.
6.7.1
Construction Phase
Piling Activities
Silt curtain will
be installed around the marine piling area to contain any suspended mud and
sediments generated during the piling works.
Silt removal
facilities such as silt traps or sedimentation facilities will be provided to
remove silt particles from groundwater (if pumping is required) ([5])
to meet the requirements of
the TM standard under the WPCO. The design of silt removal
facilities will be based on the guidelines provided in ProPECC PN 1/94. All drainage facilities and erosion and
sediment control structures will be inspected monthly and maintained to ensure
proper and efficient operation at all times and particularly during rainstorms.
Construction Site Run-off and Drainage
Good site practices outlined in ProPECC PN 1/94 “Construction Site Drainage” will be followed as far as practicable
in order to minimise surface runoff and the chance of erosion, and also to
retain and reduce any suspended solids prior to discharge. These
practices include the follows:
·
Silt
removal facilities such as silt traps or sedimentation facilities will be
provided to remove silt particles from runoff to meet the requirements of the TM standard under the WPCO. The design of silt removal
facilities will be based on the guidelines provided in ProPECC PN 1/94. All drainage facilities and erosion and
sediment control structures will be inspected monthly and maintained to ensure
proper and efficient operation at all times and particularly during
rainstorms.
·
Careful
programming of the works to minimise surface excavations for the construction
works during the wet season. If excavation of soil cannot be avoided
during the wet season, exposed slope surfaces will be covered by a tarpaulin or
other means. Other measures that need to be implemented before, during,
and after rainstorms are summarised in ProPECC
PN 1/94.
·
Exposed
soil surfaces will be protected by paving or fill material as soon as possible
to reduce the potential of soil erosion.
·
Open
stockpiles of construction materials or construction wastes on-site of more
than 50m3 will be covered with tarpaulin or similar fabric during
rainstorms. These materials will not be placed in the seawall area.
General Construction Activities
·
Debris
and refuse generated on-site will be collected, handled and disposed of
properly to avoid entering the nearby WSRs. Stockpiles of cement and
other construction materials will be kept covered when not being used.
·
Oils
and fuels will only be used and stored in designated areas which have pollution
prevention facilities. All fuel tanks and storage areas will be provided
with locks and be sited on sealed areas, within bunds of a capacity equal to
110% of the storage capacity of the largest tank. The bund will be
drained of rainwater after a rain event.
Sewage generated from On-site Workforce
·
Temporary
sanitary facilities, such as portable chemical toilets, will be provided
on-site. A specialised contractor will be responsible for regular
collection and appropriate disposal of the sewage and maintenance of these
facilities.
6.7.2
Operational Phase
Accidental Spillage of Raw Materials and
Biodiesel Products
Should a spill arise, the following
actions will be taken:
·
Within the loading/unloading area:
The bunded loading and unloading area will be paved with an impermeable
surface and spills will be contained by appropriate absorbent materials. The spill area will be properly washed. The contaminated wastewater will be
transferred to the on-site wastewater treatment plant for treatment.
·
Spillage on site: The spill will be contained and removed by using appropriate absorbent
or dispersant. The spillage area will be
cleaned up immediately. The wastewater
will be collected and treated at the on-site wastewater treatment plant.
·
During transportation:
Retainer booms will be used to create a wrap around the barge and the
contaminated areas to prevent the spillage spreading. Absorbents will be used to absorb the waste
in the confined area.
An outline emergency response plan is
presented in Annex F which forms the
based for a detailed plan which will be developed prior to the commencement of the operation
of the biodiesel plant. The detailed
plan will stipulate the detailed actions to be taken in case accidental spills
occurred and prevent any spillages from discharge into the sea.
The training for the staff will include all
possible risks, which can be occurred when handling different materials (eg
methanol, acids and bases, biodiesel, etc) and the necessary clean up
procedures. Training will make reference
to the MSDS (Material safety data sheets) so that the staff will be fully
conversant with the potential risks and environmental implications associated
with spillage of materials.
There will be no
other construction activity in the vicinity of the site during the construction
of the Project and hence it is expected that there will be no cumulative
impacts on the surrounding water bodies.
The capacity of the sewerage system in the TKOIE is in excess of 20,000
m3 d-1 and can therefore accommodate the daily discharge
of 515 m3 d-1 of treated effluent from the Site ([6]) during operation.
The Project is hence unlikely to contribute to cumulative water quality
impacts with other plants operating during this period.
With the full implementation of the recommended
mitigation measures for the construction and operational phases of the Project,
no unacceptable residual impacts on water quality are expected. It is
recommended that regular site audits of the implementation of the recommended
mitigation measures be undertaken during the construction phase.
6.10
Environmental Monitoring and Audit
The impact assessment indicates that there
will be no adverse water quality impacts on the WSRs within the Study
Area. Environmental monitoring of water quality during the construction
phase is therefore not required. Monthly
site inspections will be carried out during construction to ensure that the
mitigation measures listed above are properly implemented. The site audit frequency will be increased to
weekly intervals during the piling works.
During the operation phase, the quality of the stormwater/effluent will be monitored
at the terminal manholes of the stormwater and foul water drainage systems on a
monthly basis. Parameters to be
monitored will include:
·
Stormwater discharge from the site: oil and grease and suspended
solids; and
·
Treated effluent from the wastewater treatment plant: Parameters listed in Table 1 of the Technical
Memorandum on Standards for Effluents Discharged to Drainage and Sewerage
Systems, Inland and Coastal Water or those specified in the WPCO licence.
6.11.1
Construction Phase
The construction works for the Project
will mainly be land-based and the construction for the jetty will involve
piling activities. Water quality impacts
will be minimal during the construction phase of the Project provided that good
practices are implemented. No water
quality monitoring is thus considered necessary during the construction phase. Nevertheless, monthly site inspections will
be undertaken to ensure that the recommended mitigation measures are properly
implemented.
6.11.2
Operational Phase
During the operation of the biodiesel
plant, a surface water drainage system will be provided to collect the road runoff
and to facilitate drainage of runoff during rainstorms. The stormwater runoff from the bunded area
will be intercepted and passed through an oil interceptor prior to discharge
off-site. Sewage generated by the site
workforce will be collected and discharge to the foul sewer. Wastewater generated from the GTW
pre-treatment works and biodiesel process will be collected and treated at the
on-site wastewater treatment plant prior to discharge to the foul sewer leading
to the TKO
Sewage Treatment Works. A detailed emergency response plan will be
developed to set out the actions to be taken in case a spillage occurs and
prevent any spillages from discharging into the sea. Based on the above and with the provision of
appropriate mitigation measures, no adverse water quality impacts are
anticipated. To ensure compliance with
the effluent discharge standards, the quality of the stormwater/effluent will
be monitored at the terminal manholes of the stormwater and foul water drainage
systems on a monthly basis.