3 Air QualIty Assessment

3.1 Introduction

This section presents the air quality impact assessment for the Project during the construction and operation phases. Air Sensitive Receivers (ASRs) and the potential sources of impacts have been identified and the impacts evaluated. Mitigation measures are also recommended where necessary.

3.2 Legislative Requirement and Evaluation Criteria

The principal legislation for the management of air quality in Hong Kong is the Air Pollution Control Ordinance (APCO) (Cap. 311). Under the APCO, the Hong Kong Air Quality Objectives (AQOs), see Table 3.1, stipulate the statutory limits for air pollutants and the maximum allowable numbers of exceedances over specific periods.

Table 3.1 Hong Kong Air Quality Objectives (mg m^-3) ^(a)

Air Pollutant	Averaging Time
	1 Hour ^(b)	24 Hour ^(c)	3 Months ^(d)	1 Year ^(d)
Total Suspended Particulates (TSP)	-	260	-	80
Respirable Suspended Particulates (RSP) ^(e)	-	180	-	55
Sulphur Dioxide (SO2)	800	350	-	80
Nitrogen Dioxide (NO2)	300	150	-	80
Carbon Monoxide (CO)	30,000	-	-	-
Photochemical Oxidants (as ozone (O3)) ^(f)	240	-	-	-
Lead (Pb)	-	-	1.5	-
Notes: (a) Measured at 298K (25°C) and 101.325 kPa (one atmosphere) (b) Not to be exceeded more than three times per year (c) Not to be exceeded more than once per year (d) Arithmetic means (e) Suspended airborne particulates with a nominal aerodynamic diameter of 10 micrometres or smaller (f) Photochemical oxidants are determined by measurement of ozone only

In addition, the Technical Memorandum of Environmental Impact Assessment Ordinance (EIAO-TM) also stipulates an hourly TSP criterion of 500 mg m^-3 for the construction dust impact.

3.3 Existing Conditions, Air Sensitive Receivers and Background Air Quality

3.3.1 Existing Condition

The L4 & L5 Flue Gas Desulphurisation Retrofit is at the existing HEC Lamma Power Plant. The existing air quality in the immediate vicinity is dominated by the gaseous emissions from the existing HEC Lamma Power Plant.

3.3.2 Air Sensitive Receivers (ASRs)

We are using the same set of 69 Wind Tunnel receptors/Air Sensitive Receivers (ASRs), including several co-located at different heights, as in the EIA of a 1,800MW Gas-fired Power Station at Lamma Extension ([1]) (hereafter called “Approved EIA (1999)”) and the Project Profile for Lamma Power Station Conversion of Two Existing Gas Turbines into a Combined Cycle Unit (hereafter called “Project Profile (2000)”) ([2]). The full list is presented in Table 3.2 and a map showing their locations covering the Lamma and Cheung Chau islands as well as relevant areas of the Southern and Central & Western Districts of Hong Kong Island is shown in Figure 3.1.

Table 3.2 Air Sensitive Receivers (ASRs)

No.	Location	Receptor Height^(a)	No.	Location	Receptor Height^(a)
1	Yung Shue Wan	30	36	HKU Quarters	145
2	Pak Kok San Tsuen	10	37	Mt Davies	220
3	Ko Long	50	38	Queen Mary Hospital	170
4	North Lamma	50	39	Queen Mary Hospital	255
5	Pak Kok Tsui,	10	40	Smithfield	90
6	Pak Kok Tsui	60	41	Smithfield	190
7	Pak Kok Tsui	110	42	Telegraph Bay	10
8	Lo Tik Wan	20	43	Telegraph Bay	110
9	Lo Tik Wan	70	44	Baguio Villa	70
10	Lo Tik Wan	120	45	Baguio Villa	130
11	Tai Wan To, Beach	10	46	High West	470
12	Lo Tik Wan, Sea	0	47	HKU	100
13	Kat Tsai Wan	10	48	HKU	200
14	Lamma Quarry W	70	49	Chi Fu Fa Yuen	130
15	Lamma Quarry E	30	50	Chi Fu Fa Yuen	245
16	Lamma Quarry E	80	51	Overthrope	490
17	Lamma Quarry E	130	52	Wah Fu estate	50
18	Ngai Tau	20	53	Wah Fu estate	120
19	Tit Sha Long	20	54	Sherwood’s Bluff	430
20	Sok Kwu Wan	0	55	Admiralty	90
21	Ling Kok Shan	210	56	Admiralty	190
22	Sea shore, Lamma South	10	57	Wah Kwai Estate	50
23	Mt Stenhouse	320	58	Wah Kwai Estate	160
24	Tai Kok	110	59	Mt Kellet	400
25	Ha Mei Tsui	10	60	South Horizons	10
26	Sea shore, Lamma South	20	61	South Horizons	150
27	West Lamma Channel	0	62	Aberdeen Centre	40
28	West Lamma Channel	0	63	Aberdeen Centre	135
29	Sea, Cheung Chau West	10	64	Lei Tung Estate	50
30	Cheung Chau	50	65	Lei Tung Estate	155
31	Green Island	0	66	Wong Chuk Hang	30
32	West Lamma Channel	100	67	Wong Chuk Hang	90
33	Honey Villa	70	68	Ocean Park	70
34	Honey Villa	145	69	Ocean Park	30
35	HKU Quarters	50
Note: (a) metres above sea level

3.3.1 Background Air Quality

The EPD Guidelines on Assessing Total Air Quality Impacts ([3]), suggested using in the assessment of the cumulative concentrations the background levels of 21 μg m^-3 and 59 μg m^-3 for SO₂ and NO₂ , respectively in urban areas, and 13 μg m^-3 and 39 μg m^-3 for rural/new development sites. However, in the previous EIA studies for the Lamma Power Station, the Approved EIA (1999) and the Project Profile (2000) which form a basis for this assessment, a more conservative approach was adopted, based on a detailed analysis of the monitoring data from the HEC network on Hong Kong Island South and the EPD Air Quality Monitoring Station (AQMS) at Central/Western.

For the assessment of the maximum 1 hour average concentrations the background levels were assumed at 23 μg m^-3 and 49 μg m^-3 for SO₂ and NO₂, respectively, for ASRs located on Lamma, Cheung Chau and Hong Kong Island South, based on the maximum hourly average for a ‘typical day’ for data recorded at the HEC monitoring network, in 1993 -1996. Higher values of 33 μg m^-3 and 80 μg m^-3 for SO₂ and NO₂, based on the monitoring data from the EPD AQMS at Central/Western were adapted for a number of receptors located in urban areas.

In order to check whether the above assumptions made several years ago remain still valid, we checked the recent trends in the annual SO₂ and NO₂, concentrations at the Central/Western AQMS and from the HEC network available from the EPD ([4]). The results are summarised in Table 3.3.

As can be seen, the levels of NO₂ have not significantly changed over the last several years, especially at the HEC network which is more relevant to this study, so the background values adopted in our previous studies remain valid. Note that the SO₂ background concentration is not used in the present study to demonstrate the AQO compliance but only for the comparison of the ‘before’ and ‘after’ cumulative concentrations.

Table 3.3 Trends in Air Quality, HEC Monitoring Network and the Central/Western AQMS

Average annual concentration (μg m^-3)	1993-1996	1997	1998	1999	2000	2001	2002	2003
SO2 HEC	10	9	9	10	10	13	12	11
Central/Western	15^(a)	18	14	17	18	21	20	18
NO2 HEC	28	28	25	26	27	29	26	25
Central/Western	47^(a)	58	52	56	53	54	46	52

Note (a): 1996 only

We will therefore use the following background levels (see Approved EIA, 1999 & Project Profile, 2000):

· 33 μg m^-3 and 80 μg m^-3 for SO₂ and NO₂, for Receptors 31, 32, 40, 41, 47, 48, 55, and 56; and

· 23 μg m^-3 and 49 μg m^-3 for SO₂ and NO₂, respectively, at all other receptors.

It should be noted, that with the recent emission reduction commitments from the HKSAR and Guangdong Governments, an improvement of air quality is anticipated over the next several years, so our background levels assumptions, including the background ozone concentrations used for estimations of the NO_x to NO₂ conversion, will become even more conservative.

3.4 Construction Air Quality Impact Assessment

Dust nuisance is the key concern during the construction of the Project. Demolition of the existing Nos 4 and 5 Light Oil tanks with each of 250m³ storage capacity, 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. Although dust emission and gaseous emission are not expected to affect the nearby ASRs during construction phase, the dust control measures stipulated in the Air Pollution Control (Construction Dust) Regulation should still be implemented to ensure compliance with the Regulation. Hence, no adverse air quality impact is envisaged from the construction of the Project.

3.5 Operational Air Quality Impact Assessment

3.5.1 Objective of the FGD Retrofit

The L4 & L5 Flue Gas Desulphurisation Retrofit is a project aiming at a significant improvement of air quality in the direct vicinity of the Lamma power station and in the wider region. 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 from units L4 and L5 will be reduced as a result of the project:

· SO₂ emission reduction by about 90%; and

· Particulate emission reduction by about 30%.

More details on the L4 & L5 emission levels before and after the retrofit are provided in Section 3.5.2 (Table 3.6).

A comparative assessment of the cumulative SO₂ worst-case hourly average concentrations at 69 ASRs will demonstrate the scale of anticipated improvements of air quality in the study area.

The NO_x emissions will not be reduced nor increased by the project, however changing of the stack exhaust parameters may result in a re-distribution of NO_x in the vicinity of the power station. The cumulative concentrations of NO₂ after the retrofit will also be estimated and their AQO compliance assessed at all ASR locations.

Since the project involves a reduction in particulate emissions, it can be expected that the RSP emissions from the Units L4 and L5 retrofitted with FGD will not result in any exceedance of AQOs for RSP. More details are presented in Section 3.5.5.

3.5.2 Assessment Methodology

The approach in the comparative study for SO₂ and the assessment of the project impact on the NO₂ concentrations is based on the wind tunnel test methodology, and involves a careful interpretation of the results obtained in the previous wind tunnel test studies for the Lamma Power Station.

Wind Tunnel Test Methodology

In general, wind tunnel air quality studies involve placing a physical model of the emission sources and surrounding terrain in a wind tunnel, emitting a passive tracer from the sources and measuring its concentrations at a number of receivers inside the wind tunnel for different wind speeds and directions. The raw results come in the form of Concentration Ratios expressing the rate of dilution of the pollutant from a source to the identified receptor for a given wind speed and direction. The concentration ratios depend on the source and receptor locations and the source characteristics, such as release height and exit temperature and velocity, but do not depend on the emission levels of particular pollutants.

The next step of a wind tunnel modelling study is a numerical analysis which, taking into account the emission levels and combining emissions from separately tested sources, translates concentration ratio values measured at each receptor to real-world concentrations of different air pollutants.

Previous Wind Tunnel Tests

A comprehensive set of wind tunnel tests was conducted in 1998 by ERM’s sub-contractor, RWDI of Guelph, Ontario, Canada in support of the Approved EIA (1999). The same test results formed also a basis for the Air Quality Assessment presented in the Project Profile (2000). However, while the 1998 tests assumed that the whole Power Station operates at a load of 2,794 MW, the results presented in the Project Profile (2000) were scaled up to a maximum load of 3,050 MW.

Emission Sources Tested in Wind Model

The parameters of sources tested in the 1998 RWDI wind tunnel tests and relevant to this study are listed in Table 3.4.

Table 3.4 Parameters of Exhaust Sources

Source ID	Units	SO2 emissions mg/Nm^3	NOx emissions mg/Nm^3	PM emissions mg/Nm^3	Efflux Temp ^oC	Efflux Velocity m/s
A	L1, L2, L3	1910	1200	125	120	15
B	L4, L5, L6	1910 (L4&L5) 191 (L6)	1200 (L4&L5) 660 (L6)	125 (L4&L5) 85 (L6)	80	15
C	L7 & L8	200	411	50	80	15
D1	GTs	290	185	12	390	32
D2	CC (GT5/7)	10	90	5	80	15

Source B, including units L4, L5 and L6 is of particular interest. Note that while the L4&L5 emissions listed in Table 3.4 reflect the situation before the FGD retrofit, the Source B was, as stated in the original report (RWDI, 1998)[5], tested with the efflux temperature of 80 ^oC for all units, under a worst case assumption of using the lowest efflux temperature as per unit L6 in the previous assessment. This worst case assessment incidentally reflects the efflux temperature expected after the present FGD retrofit.

Load Scenario

For the comparison of the air quality impacts before and after the FGD retrofit we are assuming the Lamma Power Station operating at a maximum load of 3050MW, following the approach adopted for the Project Profile (2000), before the commissioning of the new units at Lamma Extension, with the distribution of the load between the units as shown in Table 3.5.

Table 3.5 Assumed Loading Schedule (MW)

Source C		Source B			Source A			Source D2	Source D1	Total
L8	L7	L6	L5	L4	L2	L1	L3	GT5/7	GTs
350	350	350	350	350	250	250	250	365	185	3050

Note that this would be the worst-case scenario, since it is expected that by the time the FGD retrofit is completed, a part of the load from the coal-fired units will be shifted to the newly commissioned gas-fired units at Lamma Extension, which will result in a further reduction of air pollutant emissions.

Past Modelling Scenarios and their Relevance to the Present Study

Of the modelling scenarios tested in the past, The Scenario 2 presented in the Project Profile (2000), that included Exhaust Sources A, B, C, D1, and D2 (see Table 3.4) and assumed the total load of 3050MW distributed between units as shown in Table 3.5 is most relevant to this assessment. All the assumptions and source parameters adopted in Scenario 2 for units L1-L3, L6-L8 and GT 2-7, are also valid for this study.

The only differences concern the parameters of Units L4 and L5 (Source B) and are summarised in Table 3.6.

Table 3.6 Assumed Parameters of Exhaust Source B (Units L4, L5 and L6)

Scenario	SO2 emissions mg/Nm^3	NOx emissions mg/Nm^3	PM emissions^(a) mg/Nm^3	Efflux Temp ^oC	Efflux Velocity m/s
Before the Retrofit	1910 (L4&L5) 191 (L6)	1200 (L4&L5) 660 (L6)	125 (L4&L5) 85 (L6)	110 (L4&L5) 80 (L6)	15
After the Retrofit	200 (L4&L5) 191 (L6)	1200 (L4& L5) 660 (L6)	85	80	15
Scenario 2^(b)	1910 (L4&L5) 191 (L6)	1200 (L4& L5) 660 (L6)	n/a	80^(b)	15

Notes:

a: Particulate matter (PM) emissions are not used in this assessment and are included here for the sake of completeness only

b: Even that Scenario 2 of Project Profile (2000) was based on the Source B parameters before the FGD retrofit, in the actual wind tunnel testing (RWDI, 1998) the source B assumed the worst case efflux temperature of 80 ^oC.

The detailed results of the Scenario 2 are provided in Tables A1-5c and A1-5d of Project Profile (2000). They include the predicted cumulative concentrations of SO₂ and NO₂ at each receptor, contributions of each source (A, B, C, D1+D2) to the total and some other supplementary information. This will be the principal source of information for this assessment, subject to corrections accounting for different Source B emissions before and after the retrofit.

Marine Emissions

Besides the reductions in the SO₂ and particulate emissions, the project will result in a slight increase in the marine traffic, due to the increased needs for the limestone and gypsum transportation. Currently, the limestone shipments for the L6, L7 and L8 FGD plants involve about 44 barges of 700 to 3,000 tonnes per year. Similarly, the gypsum by-product is transported out by about 53 barges of 700 to 3,000 tonnes. With the L4 and L5 FGD plants operational, these transportation needs will increase by 66%. However, it is planned that the number of barge shipments per year will not increase, but only the barge sizes will increase to meet the additional demand. Note that the coal transport involves about 66 shipments per year using ships of 50,000 to 70,000 MT. Since the NO_x emission factors are roughly proportional to the ship engine power, assuming that it is proportional to the ship size, it can be estimated that the limestone/gypsum transport currently accounts for only about 1% of the total marine NOx emissions associated with the operation of Lamma Power Station, and this contribution would remain below 2% after the L4&L5 FGD Plants become operational.

Therefore, in the context of much heavier existing marine traffic associated with other operations of the Lamma Power Station, the significant SO₂ and particulate emission reductions from the power plant and relatively low cumulative SO₂ and NO₂ concentrations predicted (See Tables C1 and C2) for the receptors located in the West Lamma Channel and close to the loading berths, the effects of the slightly increased emissions from the use of larger barges are considered insignificant.

3.5.3 Cumulative SO₂ Concentrations Before and After the Retrofit – A Comparative Study

Source B Corrections for Changes in Emissions

As explained above, our quantitative assessment is based on the results of Scenario 2 of Project Profile (2000) and involves appropriate scaling of the obtained during that study contributions of Source B to the total pollutant concentration at each ASR. The scaling coefficient used is explained below.

SO₂ before the Retrofit

As can be seen in Table 3.6, the SO₂ concentrations before the retrofit can be taken directly from the results of Scenario 2 (Project Profile, 2000) i.e. Table A1-5c of that report.

SO₂ after the Retrofit

The retrofit will result in significant reductions of L4 & L5 SO₂ emissions. Therefore the Source B contribution to the total at each receptor obtained from Table A1-5c needs to be appropriately scaled down. Based on the emission data provided in Table 3.6, the scaling coefficient is:

(2 x 200 + 191) / (2 x 1910 + 191) = 0.147

Results

The impacts of the L4&L5 FGD Retrofit on the Source B contribution and cumulative SO₂ concentrations at the ASRs listed in Section 3.3.2 are summarised in Table C1 in Annex C.

As can be seen, the FGD retrofit will result in a significant reduction of the worst-case 1-hour average SO₂ concentrations. The reduction, of up to 263 μg m^-3 and up to 55% of the total cumulative concentration will occur in the whole area studied with the exception of a few receptors located close to the power station, which are not affected by the Source B emissions.

Note that, as explained in Section 3.5.2, the concentrations before and after the retrofit were based on the same wind tunnel tests assuming the L4 & L5 efflux temperature of 80 ^oC, which reflects the conditions after the retrofit. Since the actual efflux temperature before the retrofit is higher, this assumption may slightly affect the accuracy of our predictions of the SO₂ concentrations before (but not after) the retrofit. However, it is believed, that in general, the scale of the air quality improvements related to SO₂ has been predicted correctly.

3.5.4 Cumulative Concentrations of NO₂ After the Retrofit

The NO_x emissions will remain unchanged after the retrofit, so their redistribution due to the lower plume rise may result in the increase of the NO₂ concentrations at some receptors (and possibly their decrease at other locations). Therefore, the cumulative NO₂ concentrations at Air Sensitive Receivers after the retrofit needs to be predicted and their compliance with the relevant Air Quality Objective (AQO) assessed.

However, as explained in the previous sections, such assessment had already been performed in the past. As can be seen from Table 3.6, all NO_x emission and efflux parameters of Scenario 2 (Project Profile, 2000) are exactly the same as those reflecting the situation after the retrofit in the present study. Therefore the cumulative NO₂ concentrations predicted under Scenario 2 of Project Profile (2000), included in Table A1-5d of that report, can be directly applied here.

Distance Correction

The original results of (RWDI, 1998) were obtained assuming a constant NO_x to NO₂ conversion factor of 0.20. When applying these in the Project Profile (2000), in order to make the NO₂ prediction more accurate, a correction factor was introduced to account for a different distances between the source and receptors. The correction is based on the Janssen formula ([5]) that links the conversion rate to the prevailing meteorological conditions, distance to the receptor and the background ozone concentrations.

The set of average Janssen’s formula coefficients used in the Project Profile (2000) assessment was applicable to summer conditions, wind speeds of 5 to 15 m/s and ozone concentrations ranging from 39 to 59 μg m^-3. In order to check if these 2000 assumptions remain valid, we have examined the recent ozone trends at two AQMS stations close to the project site, i.e. at Central/Western and Tung Chung. The annual average ozone concentrations at these locations are listed in Table 3.7. As can be seen, the concentrations at both stations are well within the range of applicability of our Janssen’s formula coefficients. Note that also the background ozone level of 57 μg m^-3 recommended for the rural/new development areas by the EPD’s Guidelines on Assessing the 'TOTAL' Air Quality Impact included in Appendix B-2 of the Study Brief falls within the range of validity of these coefficients. Furthermore, Table 3.7 does not show a strong increasing trend in ozone concentrations, which in the coming years are expected to decrease due to the HKSAR and Guangdong commitments on reducing the NO_x and VOC emissions. Therefore, the same distance correction coefficients as used in Project Profile (2000) will be applied in this study as well.

Table 3.7 Trends in Ozone Concentrations

Average annual concentration (μg m^-3)	1996	1997	1998	1999	2000	2001	2002	2003
Central/Western	29	27	30	37	34	35	32	44
Tung Chung				43	37	41	42	43

Results

The cumulative NO₂ concentrations at each receptor, derived from the Project Profile (2000) data are listed in Table C2 of Annex C.

From the data presented in Table C2 it is evident that the worst-case cumulative NO₂ concentrations after the FGD retrofit will remain well below the AQO of 300 μg m^-3, with the concentration at the worst-affected Receptor 29 at Cheung Chau within 88% of the AQO. It should be stressed that the retrofit does not cause an increase in NO_x emissions, but only different plume dispersion characteristics, i.e. the re-distribution and not increase of the pollution under the worst-case meteorological conditions. For the longer time scales and wider area, the FGD retrofit at units L4 and L5 would remain neutral with respect to the NO₂ pollution, so the quantitative assessment of averaging periods longer than 1 hour was not necessary. It was also confirmed in the Approved EIA (1999) that the one hour average is the more critical parameter to be considered when compared with the AQO.

3.5.5 RSP Assessment

Since neither the Approved EIA (1999) nor the Project Profile (2000) reports addressed the RSP concentrations which were considered of secondary importance, we cannot apply the same assessment methodology as for the SO₂ and NO₂ concentrations. The worst-case hourly particulate concentrations after the retrofit can however be estimated by appropriate scaling of the SO₂ results presented in Table A1-5c of Project Profile(2000).

Since the resulting RSP concentrations are low, we will present such detailed estimates for the worst-case Receptor 29 only. For that receptor, the worst-case SO₂ hourly concentrations were reported in the Project Profile (2000) as 674 μg m^-3 ,with sources A, B, C, D1 and D2 contributing 301, 262, 27, 74, and 9 μg m^-3 , respectively. To convert these SO₂ concentrations to their particulate equivalents, appropriate scaling factors based on the stack emissions of SO₂, and RSP can be applied. As can be seen from Table 3.6, such a factor for Source B, equal to the ratio of PM emissions after the retrofit to SO₂ emissions before the retrofit is 3x85/(2x1910+191) = 0.064. In a similar way, using the data provided in Table 3.4, the coefficients for sources A, C, D1, and D2 can be calculated as 0.065, 0.25, 0.041, and 0.5, respectively. The worst case PM concentration at Receptor 29, resulting from the Lamma Power Station emissions can therefore be estimated as: 301x0.065 + 262x0.064 + 27x0.25 + 74x0.041 +9x0.5 = 50.6 μg m^-3. Assuming as the worst case that all the particles emitted are in the form of RSP (less than 10 μm in diameter) and taking the background RSP concentration as 53 μg m^-3_, based on the 2003 annual average at Central/Western AQMS, we can obtain the worst case one hour RSP concentration at the worst-affected Receptor 29 as 103.6 μg m^-3 which constitutes only 58% of the AQO for the 24 hour averages. The assumption that all particulates emissions are in the form of RSP will make this result even more conservative .

Therefore, the RSP emissions from the Units L4 and L5 retrofitted with FGD, will not result in any exceedance of AQO for RSP.

3.6 Mitigation Measures

3.6.1 Construction Phase

The following dust control measures stipulated in the Air Pollution Control (Construction Dust) Regulation are recommended:

· The area at which demolition work takes place should be sprayed with water prior to, during and immediately after the demolition activities so as to maintain the entire surface wet;

· Dust screens or sheeting should be provided to enclose the structure to be demolished to a height of at least 1 m higher than the highest level of the structure;

· Any dusty materials should be wetted with water to avoid any fugitive dust emission;

· All temporary stockpiles should be wetted or covered by tarpaulin sheet to prevent fugitive emissions;

· All the dusty areas and roads should be wetted with water;

· All the dusty materials transported by lorries should be covered entirely by impervious sheet to avoid any leakage; and

· The falling height of fill materials should be controlled.

3.6.2 Operational Phase

Since the project will significantly reduce SO₂ and Particulate emissions and the NO_x emissions from the L4 and L5 Units will remain unchanged, no mitigation measures are required. Nevertheless, it should be noted that HEC is conducting feasibility study to look into various options including the retrofit of low NO_x burners to Units 4&5 boilers to reduce the overall NO_x emissions from Lamma Power Station.

3.7 Summary of Environmental Outcomes and Conclusions

3.7.1 Construction Phase

Dust from demolition and construction activities is the key concern during the construction of the Project. Demolition of the existing Nos 4 and 5 Light Oil tanks with each of 250m³ storage capacity, 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 the small scale of construction works and with the implementation of the dust control measures stipulated in the Air Pollution Control (Construction Dust) Regulation, no adverse air quality impact is envisaged from the construction of the Project.

3.7.2 Operational Phase

The re-assessment of the previous wind tunnel modelling data has confirmed that the FGD retrofit project at units L4 and L5 of the Lamma Power Station will lead to significant reductions of the worst-case hourly SO₂ concentrations for most ASRs throughout the area studied.

Since the operation of the FGD plants will also result in reduction of emissions of particulate matter (PM), it is expected that the environmental benefits of the FGD retrofit with respect to the RSP concentrations would be similar in nature, but lower in magnitude than those for SO₂.

A quantitative assessment of the cumulative NO₂ concentrations after the retrofit demonstrated that they will remain AQO-compliant throughout the study area. The highest NO₂ concentration predicted after the retrofit, 264 μg m^-3 at Cheung Chau is still well below of the AQO of 300 μg m^-3.

3.7.3 Environmental Monitoring and Audit (EM&A) Requirements

Due to the small scale of the demolition and construction works of the Project, and no adverse impacts predicted, no EM&A is required for the Construction Phase.

Since the Project will bring a general air quality improvement, no additional EM&A activities are required, besides those already in place, such as those required by specific process licenses for the operation of the existing Lamma Power Station.

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^{([1]) http://www.epd.gov.hk/eia/register/report/eiareport/eia_00998/index.htm}

^{([2]) http://www.epd.gov.hk/eia/register/profile/latest/e_dir37.pdf}

^{([3]) http://www.epd.gov.hk/epd/english/environmentinhk/air/guide_ref/guide_aqa_model_g2.html}

^{([4]) http://www.epd-asg.gov.hk/english/report/aqr.php}

[5] ^{Wind Tunnel Modelling for the Additional Generating Facilities at Lamma Power Station Hong Kong. Report for ERM – Hong kong Ltd. RWDI, September 1998}

^{([5]) Janssen L.H.J.M. et al. A Classification of NO Oxidation Rates in Power Plant Plumes Based on Atmospheric Conditions. Atmospheric Environment, 22, 43-53, 1988}