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                                      Air Quality

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.

9.2                                      Land Contamination

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                                      Water Quality

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                                      Waste Management

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


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                                      Noise

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.

9.7                                      Conclusion

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.