10                     Conclusions and Summary of Environmental outcomes

10.1               Introduction

This Section summarises the environmental outcomes associated with the construction and operation of the proposed biodiesel plant at TKOIE.

10.2               Air Quality

10.2.1         Construction Phase

The Project Site has been formed and is currently vacant.  No major earthworks will be required for the site formation works and only minor excavation works will be required for the construction of the foundation works and site utilities.  The storage tanks and process equipment will be pre-fabricated off-site and assembled on site using hydraulic and tower cranes and hence minimal dust will be generated from this activity.  Dust generated from the minor excavation works and concreting works for the construction of site buildings will be minimal.

The jetty will be constructed in form of a piled deck and no dredging of marine sediment will be required.  Marine piles will be drilled through the existing rubble mound seawall to the competent bearing strata by a piling rig placed on a temporary steel platform.  Concrete infill to piles will be undertaken prior to placement of trellis beam and pre-cast concrete panels.  The dust and air emissions generated from the marine works will be minimal.

With the implementation of dust suppression measures stipulated under the Air Pollution Control (Construction Dust) Regulation and the adoption of good site practices, no adverse construction dust impact is anticipated.  Dust monitoring during the construction phase is therefore considered not necessary.

Monthly site audits will be undertaken to ensure the implementation of recommended dust control measures and good site practices during construction phase.

10.2.2         Operational Phase

The stacks of the boiler and biogas flare (if in operation), and the exhaust of the Process Building are the major emission sources associated with the operation of the biodiesel plant.  Nitrogen dioxide (NO2), carbon monoxide (CO), sulphur dioxide (SO2), non-methane organic compounds (NMOC) are the principal emission of concerns of the boiler and biogas flare stacks, and methanol and acetyldehyde (as one of the impurities of methanol) are the principal emissions of concerns for the exhaust of the Process Building.  The assessment indicates that the operation of the proposed biodiesel plant together with the existing air emission sources in the TKOIE, will not cause adverse air quality impacts at the identified Air Sensitive Receivers (ASRs).  The predicted concentrations of pollutants are well below the respective criteria.

The potential odour impact due to the discharge of exhaust air from the final air scrubber of the on-site wastewater treatment plant has been evaluated.  After scrubbing, the odour concentration will be significantly reduced. The predicted odour concentrations at the identified ASR are well below the odour criterion.  The operation of the biodiesel plant will not cause adverse odour impacts to the identified ASRs. 

The concentrations of NOx, CO, SO2 and NMOC in the flue gas of the stacks of the boiler and biogas flare (if in operation) and the concentrations of methanol and acetyldehyde from the exhaust pipe of process building will be monitored for during the operation of the biodiesel plant.

Odour concentration at the stack of the final air scrubber will be monitored for the first two years of operation of the biodiesel plant and odour patrols along the Project Site boundary will also be carried out to confirm that the operation of biodiesel plant will not cause adverse odour impacts.

With the implementation of proper design, the recommended mitigation measures and monitoring programme, it is concluded that the construction and operation of the biodiesel plant will not cause adverse air quality impacts and will comply with the EIAO-TM requirements.

10.3               Noise

10.3.1         Construction Phase

The predicted construction noise levels at the identified NSRs range from 48 dB(A) to 64 dB(A) and 48 to 55dB(A) for residential premises and an educational institution, respectively.  These levels are well below the noise criteria of 75 and 70 dB(A) for domestic premises and educational institutions, respectively.   Therefore, the identified NSRs within the Study Area will not be adversely affected by the construction of the Project.    Good construction site practices (see Section 5.7) will be implemented by the Contractor to further minimise the noise impact.

Noise monitoring during construction phase is considered not necessary.  However, monthly site inspections will be carried out to audit the compliance of the Contractor with regard to noise control and to recommend further mitigation measures if found to be necessary.

10.3.2         Operational Phase

The operational noise impact assessment was undertaken based on a set of conservative assumptions.   To minimise potential noise impact to NSRs, all noisy equipment in the fat preparation plant, wastewater treatment plant, steam boiler room and process building will be located within completely enclosed buildings or complete noise enclosures.  Due to the large separation distances between the identified NSRs and the noise sources at the biodiesel plant, the predicted noise levels at the NSRs due to the operation of the biodiesel plant range from 40to 49 dB(A) and 36 to 45 dB(A) during the day-time and night-time periods, respectively.  These noise levels comply with the corresponding day-time and night-time noise criteria of 60 and 50 dB(A).           

In view of the predicted insignificant noise impact during the operational phase, noise monitoring work is considered to be not necessary.

10.4               Water Quality

10.4.1         Construction Phase

The construction works for the Project will mainly be land-based.   With respect to the nature and relatively small scale of the land based construction activities, the potential water quality impacts are considered minimal with the implementation of the good practices outlined in ProPECC PN 1/94 Construction Site Drainage”.

The proposed jetty (50m long and 26m wide) will be in a form of a reinforced concrete deck supported by the marine piles.  No dredging or reclamation works will be required.  A total of about 60 piles (approximate diameter of 1 m each) will be constructed.     Bore piles will be driven through the existing rubble mound seawall.   The water quality impacts due to the piling activities will be minimal and no adverse water quality impact is anticipated. 

The cross-sectional area of each pile underwater has been estimated to be 0.8m2.  It is estimated that the volume of each pile underwater will range from 0.8 m3 to 9.6m3.  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.   It is not expected that the piles will result in any adverse impact to the water flow regime at the jetty during the operational phase.

As no adverse water quality impact is anticipated, no water quality monitoring is considered necessary during the construction phase.    

10.4.2         Operational Phase

A surface water drainage system will be provided to collect stormwater runoff from the Project Site.   Clean stormwater runoff will be segregated from potential contaminated areas.  The stormwater from the potential contaminated areas will be collected and diverted to the on-site wastewater treatment plant for treatment.    

Wastewater from the biodiesel production process will be collected and treated prior to discharge to the foul sewer leading to the Tseung Kwan O Sewage Treatment Works.  

Bund wall will be provided at the tank farm (including the storage tank of the raw materials/products) and the process tanks within the Process Building to contain any spillage of materials (the wall is designed to hold 110% of the largest tank) within the bunded area.  The floor of the bunded area will also be paved with concrete and coated with waterproofing material.  It will effective prevent any spill from seeping into the soil.  The bunded area will be provided with a sump pit(s) with a manually controlled valve/penstock which is normally close.   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.  All surface water discharged from the bunded area will pass through an oil interceptor before discharge into the stormwater drainage system of the TKOIE.  No surface water will be automatically drained from the bunded area. 

All materials to be used and stored on site (except for the gas oil) are biodegradable and hence the potential for land contamination or environmental pollution due to the spillage during handling and transfer, and leakage of tanks will less severe.   Nevertheless, the plant/equipment and tank farm are designed to comply with relevant local regulations and standards.  Measures have been put in place to prevent spillage of materials during handling and transfer.    For example, 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 during the transportation of biodiesel off the site, retainer booms will be deployed around the barge and the contaminated areas to prevent the spillage spreading.   An outline emergency response plan related to pollution prevention and management has been prepared which will form the basis of the detailed plan.    A detailed plan which will detail emergency actions will be prepared during the detailed design stage.     

Based on the above and with the provision of appropriate mitigation measures, no adverse water quality impacts are anticipated.   Stormwater and effluent discharged from the site will be monitored to ensure the discharge will comply with the requirements of the Water Pollution Control Ordinance Licence.

10.5               Marine Ecology

10.5.1         Construction Phase

No dredging or reclamation works will be required.  Permanent loss of a small stretch ([1]) of low ecological value marine habitat at the artificial seawall is expected due to the marine works for jetty construction.  Pile surfaces can, however, serve as artificial habitats for the settlement and recolonisation of marine assemblages.  Residual impacts are expected to be low.

As no adverse water quality impact is expected due to construction activities, there will be no secondary impacts to ecology.   It is considered that environmental monitoring is not required.  Nevertheless, monthly site inspections will be undertaken to ensure that the recommended mitigation measures on water quality are properly implemented such that secondary adverse impacts on marine ecological resources can be avoided and minimised.

10.5.2         Operational Phase

As no adverse water quality and hydrodynamic impacts are expected due to the operation of the biodiesel plant, the potential impacts to marine ecological resources are expected to be minimal.   No adverse impacts to marine ecology are expected.  

No monitoring and audit will be required during the operational phase.

10.6               Risk  Assessment

A quantitative risk assessment (QRA) has been conducted for the operational phase of the Project.  The potential risks to the off-site population have been estimated based on the population levels (including the planned population at the vacant land adjacent to the biodiesel plant).  The assessment shows that the principal hazards to the public are related to catastrophic failures of the biodiesel and methanol storage tanks.  Potential explosion of methanol vapours in the process area that can result from a methanol leak also contributes to the overall risk levels. Other hazardous scenarios considered were found to pose lower risks to the off-site population.

The overall risk levels estimated for the operational phase of the Project are relatively low.   Individual risk levels at the Project Site boundary are predicted to be well below the criterion of 1 x 10-5 per year ([2]).  The societal risks expressed in the form of a FN curve lie within the “acceptable” region of Hong Kong Risk Guidelines. Therefore the Hazard to Life criteria stipulated in Annex 4 of EIAO-TM are met.

It is recommended that the mitigation measures recommended in Section 8.9 should be audited during the detailed design stage and before the operation of the plant to ensure that:

·           they have been properly incorporated into the design of the plant;

·           control and management measures are clearly described in the detailed Emergency Response Plan; and

·           be properly installed and implemented.

10.7               Environmental Outcomes

The environmental impact assessment (covering air quality, noise, water quality, marine ecology and hazard to life) has concluded that no unacceptable environmental impacts are envisaged due to the construction and operation of the Project.  No long-term unacceptable impact on the environment is anticipated. 

10.8               Environmental Benefits

The proposed biodiesel plant will use multi-feedstock which consists of waste cooking oil (WCO), oil and grease recovered from grease trap waste (GTW), PFAD (a distillate from palm oil)  and animal fats.   It not only offers a convenient recycling outlet for GTW and WCO but also converts the oil and grease recovered from these wastes into useful products.    The Project also offers a cleaner alternative to diesel fuel to the Hong Kong market.

 

 



([1])      A total of approximately 48 m2, which is about 3% of the total area of the jetty will be loss due to marine piling.

([2])      As seen from the Figure 8.2b, the 1.0 ´ 10-5 per year individual risk contour does not extend beyond site boundary.  Individual risk from the biodiesel plant is therefore considered acceptably low.