9
conclusion: Summary of Environmental Outcomes
The L4 & L5 FGD Retrofit Project will result in
significant reductions of the SO2 and particulate emissions which will lead to improvements of the local
and regional air quality.
Despite the net environmental benefits, the
construction and operation of the Project could also result in some negative
environmental impacts which have been subject of a detailed assessment under
this Study. They are summarised and discussed in the following sub-sections.
9.1.1
Construction
Phase
Dust nuisance is the key concern during the
construction of the Project.
Demolition of the existing Nos 4 and 5 Light Oil tanks, civil works of
the retrofitting of FGD Plants to two existing 350MW coal-fired Units L4 &
L5 are the major construction works of the Project. Due to small scale of the Project and a distance from the
ASRs, no dust impact is anticipated.
In addition, only limited number of diesel-driven equipment will be
operated on site, therefore, impact from construction equipment is not
expected.
9.1.2
Operational
Phase
Except
for a slight increase of emissions associated with marine traffic due to
increased reagent and by-product shipping, the operation of the project will
not introduce any additional emissions of air pollutants, while the SO2 and particulate emissions will
be significantly reduced.
The
following reductions of emissions from units L4 and L5 are anticipated as a
result of the project:
·
SO2 emission reduction by about 90%;
and
·
Particulate emission reduction by
up to 30%.
Results
of a comparative assessment of the cumulative SO2 worst-case hourly average
concentrations at 69 ASRs demonstrate the scale of anticipated improvements of
air quality in the study area.
Since the project involves a reduction in
particulate emissions, it can be expected that the RSP concentrations will be
decreased throughout the study area as a result of the project, and that the
reductions will be similar in nature but smaller in magnitude than those
predicted for SO2.
The NOx emissions will not be reduced
nor increased by the project, however changing of the stack exhaust parameters
may result in a re-distribution of NOx in the
vicinity of the power station. The cumulative concentrations of NO2 after the retrofit have been
estimated and their AQO compliance demonstrated for at all ASR locations.
Two above
ground oil storage tanks with associated pipelines and one oil separation sump
are to be demolished to provide space for installation of the FGD plants. A land contamination assessment was
carried out at these areas following the methodology and procedures prescribed
in the contamination assessment plan (CAP) by the EPD. The land contamination assessment
included soil and groundwater sampling, laboratory analyses for target
parameters, preparation of contamination assessment report (CAR) and
preparation of remediation action plan (RAP).
Total
petroleum hydrocarbon (TPH) was detected in one out of 15 soil samples and five
out of six groundwater samples at concentration exceeding the EPD Dutch B value
for mineral oil and implied a TPH contamination at the Site. Remediation measures and procedures for
TPH contamination were recommended for the Site for the demolition operation,
and the details are provided in the RAP.
Depending
on the results of confirmation soil samples collected for remediation, the
recommended remediation measures for soil include excavation, testing, in-situ
treatment (ie soil venting/biopiling) and on-site reuse. As groundwater is
not used for either domestic or industrial purposes at the Site and in the
adjacent areas, remediation of TPH in the groundwater of the Site is not
considered necessary. However, the groundwater encountered
and /or abstracted during the demolition programme should be collected, appropriately stored on-site and
recharged back to the underlying ground.
With the
implementation of the remedial measures in the RAP, the hazard and
environmental impacts associated with the potential land contamination and
handling and treatment of the contaminated soil and ground water are considered
acceptable.
9.3.1
Construction Phase
Since there will be no
wastewater generated by the demolition of oil tanks and the excavated top soil
will not be stored on site and will be removed offsite soon after the
excavation due to limited site works area, it is anticipated that the
construction runoff will not be significant. Therefore unacceptable water quality impacts due to surface
runoff are not expected.
Similarly, as the existing
toilet facilities of the Power Station will be provided for use by the
workforce, adverse impacts to water quality as a result of the sewage effluent
generated by the workforce are not anticipated.
9.3.2
Operational Phase
Potential source of impacts to water quality from the
operation of the FGD plants are as a result of filtrate generated from the
dewatering of gypsum slurry.
In line
with the existing practice adopted for the Units L6, L7 & L8 FGD plants,
operational plant effluent from the proposed FGD plant will be reused as far as
possible for preparation of limestone slurry, conditioning of PFA for offsite
transportation, etc. to minimise discharge to the existing WWTP.
Referring to the past
record (October 2004 to September 2005) at the sampling point of the Rejected
Treated Water Storage Tank, the effluent generated is well below the licence limit.
As the L4 & 5 FGD would adopt
the same wet limestone-gypsum process, similar properties of effluent would be
generated. Since the existing WWTP
has spare capacity to cater for the additional wastewater produced from the
proposed retrofit project, it is expected that effluent from the WWTP to the
Ash Lagoon will meet the requirements in the WPCO licence
for the Ash Lagoon Decantrate Tower.
9.4.1
Construction
Phase
The key potential impacts during the construction
phase are related to management of demolition materials, excavated materials
and construction waste.
A total
of about 600 m3 contaminated soil will be excavated for on-site treatment and disposal
in accordance with the
EPD’s Guidance
Notes for Investigation and Remediation of Contaminated Sites of Petrol Filling
Stations Boatyards, and Car/Repair/Dismantling Workshops, May 1999. The remediation actions
could involve excavation, testing, on-site treatment (ie soil
venting/biopiling) and on-site reuse.
A total of about 29 tonnes of scrap steel will be
produced during demolition of oil tanks and the associated fixtures/
appendages. All the scrap steel
will be delivered off-site by barge for recycling.
A total of about 3,400 m3 of surplus public fill will be
generated from the demolition and construction works. The public fill will be reused as fill for the reclamation
of the Lamma Power Station Extension.
About 15 m3 of construction waste will be disposed of at landfills.
Small
quantities of chemical wastes (less than 100 litres per month), sewage (a
maximum of 3.6 m3 per day) and general refuse (a maximum of 39 kg per day) will be
generated during the construction phase.
With the implementation of the mitigation measures
recommended, the potential environmental impacts arising from storage,
handling, collection, transport and disposal of wastes should be able to meet
the criteria specified in the EIAO-TM. No unacceptable waste management impact is anticipated.
9.4.2
Operational
Phase
Gypsum
During the FGD operation wastewater from absorber
will be produced and gypsum will be generated as a by-product. It should be noted that high quality
commercial grade gypsum is produced from the operation of the existing FGD
plants at Lamma Power Station. The
gypsum to be generated from the new FGD units will also be commercial grade.
Gypsum is a useful construction material in
building industry and the demand for gypsum is high in both Hong Kong and
mainland China.
A total of 46,000 tonnes gypsum will be produced
per year during the operation of new FGD plants (L4 and L5). Under existing contract arrangement,
the limestone suppliers are required to collect an equivalent amount of gypsum
produced from the FGD Plants and no gypsum will be stored on-site. This arrangement has worked satisfactorily
for the existing FGD plant. The
same contract arrangement will therefore be used for the new FGD plant.
Additional Sludge from WWTP
The existing WWTP has spare capacity to handle the
additional wastewater produced from the new FGD plants. It is expected that a maximum 12 m3 hr-1 of wastewater will be produced
from the new FGD plants and an additional 1,200 tonnes per year (or about 3.3
tonnes per day) of sludge will be produced from the WWTP.
In line with current operation, the sludge
generated from WWTP will be off-taken by the limestone suppliers together with
the gypsum by barges. All sludges
will be reused for production of building materials (ie plaster board) in
China.
Industrial Waste
From the operational experience of the existing FGD
plant, the amount of waste generated from the maintenance of the FGD plant is
minimal (in the order of a few kg per month).
Chemical Waste
With reference to the operational experience of the
existing FGD plant at Lamma Power Station, the amount of chemical waste to be
generated from the maintenance of the plant is minimal (in the order of several
litres per month).
9.5.1
Construction
Phase
The proposed Project is in small scale. Additionally, in the view that the
residential developments are shielded from construction noise to varying
degrees by the intervening hill (Kam Lo Hom) and the existing plants, and
considerable separation distance between the NSR and the Project, the noise
generated during the construction stage is not expected to be a concern.
9.5.2
Operational
Phase
Based on the noise data collected from the existing
operating units in the Lamma Power Station, the facade noise levels at the
identified NSRs (Hung Shing Ye/Tai Wan To) have been predicted. Results indicate that the identified NSRs will be
subject to noise level of 38 dB(A), which will comply with the stipulated noise
criterion of 45 dB(A). For the NSR
at Ko Long, which is located the north of the proposed plants, the existing
buildings and terrain act as barriers and significantly reduce the noise levels
due to the new plant, and therefore these NSRs will be subject to even lower
noise level than the NSRs at Hung Shing Ye and Tai Wan To.
The additional equipment to be installed will have
insignificant contribution when compared with the cumulative operational noise
of the Lamma Power Station.
Therefore, the plant noise associated with the retrofit plant is not
expected to give rise unacceptable environmental impacts.
9.6
Landscape and Visual Considerations
Since its location within a large existing
facility, the proposed retrofit works will not have any negative impact on the surrounding landscape, and will have a very low
visibility.
The Project will result in significant reductions
of the SO2 and particulate emissions which will lead to improvements of the local
and regional air quality.
The detailed impact assessment concluded that both
during the construction and operational phases, no adverse environmental
impacts are envisaged in the areas of air and water quality, waste management,
noise impacts and visibility.
Planned demolition of two above ground oil storage
tanks with associated pipelines and one oil separation sump raised concerns of
possible land contamination issues. Their investigation is the subject of the
separate documents Contamination Assessment Plan (CAP), Contamination
Assessment Report (CAR) and Remediation Action Plan (RAP) that are included in
Annexes to this Report.