7 Predicted Environmental Impacts & Mitigation Measures

Transcription

1 7 Predicted Environmental Impacts & Mitigation Measures 7.1 Overview Asphalt plants are comprised of some basic environmental pollution sources. As is the case with any development project, this project will have certain inescapable environmental impact. The aim of this Environmental Impact Assessment (EIA) would be to assess the possible impacts and propose mitigating measures which will be implemented during the design, construction and operational phase. The figure below presents an overview of the different stages involved in the life cycle of the project. Figure 7.1: Stages in Life Cycle of Project 36 P a g e

2 7.2 Construction Phase In order to ensure proper operation of the plant, the construction of a relevant infrastructure is necessary. The asphalt plant set-up would require conventional reinforced concrete bases on which the mechanical equipments will be fixed. The equipments will be in modular form which will be assembled on site with the help of cranes and special trucks. Thus there will be very little on-site fabrication. As already mentioned in section 4.5, the infrastructure of the asphalt plant is being set-up in a bare land of an industrial zone where there is an existing stone crushing plant amongst others Possible Environmental Impacts during Construction Effect on ecology impacts on flora and fauna Risk of soil erosion through the removal of existing trees or shrubs Noise and vibration as a result of site concrete batching, cutting and welding of equipment Traffic implications due to the transportation of materials and equipment on site Dust emission through the transportation of raw materials Effect on existing water bodies Public Nuisance in terms of noise, dirt, dust, odours and traffic implications Waste Generation excess materials and unusable parts or defective pieces Alteration to visual aesthetic 37 P a g e

3 7.2.2 Mitigating Measures during Construction As mentioned earlier in section 4.6, the proposed site is a vast quarry of boulders where there is no vegetation and water courses or rivulets which might be affected during the construction phase. The picture below shows the site at present date where is can be observed that no such environment sensitive areas exist. Figure 7.2: Proposed Site Risk of Soil Erosion The site is a very rocky area where the risk of soil erosion is minimal and no vegetation on site will be removed which can cause such a risk. 38 P a g e

4 Noise and Vibration The predicted overall noise emission during the construction phase will be about 60 to 70 db(a). However, construction works will be carried out during working hours that is 8:00 a.m to 4:30 p.m. Moreover, taking into consideration the location of the site, which is 1.3 km buffer zone from the nearest residential area with the sound attenuation this will not reach the residential area Traffic Implications The raw materials for the construction of the reinforced concrete bases will be available within the same crushing plant as such this will not affect the road users. Also for the modular parts of the plant will be transported during weekend and off peak hours to minimise the risk of traffic jam Dust Emission Dust emission during the transportation of raw materials will be minimised through using existing water sprinklers in the crusher plant Public Nuisance The design and construction works will be carried out respecting all the concerned standards and the effect on noise, traffic and dust has been already addressed above. It should also be pointed out that the construction will take place within an area where public does not have access and is far from the residential zone Waste Generation The waste generation during the construction phase will be stored in a designated area and cart away on a weekly basis. After the construction and erection of the plant the site will be tidy up and all excess material will be carted away. 39 P a g e

5 Visual Aesthetic The plant has been carefully design so that it does not looks bulky and architectural design of the offices has been done to match the surroundings. Moreover, the trees and decorative plants will be planted around the plant to reduce visual impact. 40 P a g e

6 Table 7.1: Summary of Environmental Impacts & Mitigating measures during Construction Possible Impact Sources or Causes Mitigating Measures Ecology Noise Pollution Traffic Congestion Dust Emission Public Nuisance Solid Waste Pollution Visual Aspect Pollution of surface and groundwater Destruction of vegetation Risk of Soil Erosion Transportation of materials by heavy good vehicles Works due to construction works Transportation of raw material Transportation of modular parts of asphalt plant Transportation of raw materials Nuisance due to dust Disturbance due to noise Due to excess materials or faulty parts Large structure Site is not environment sensitive and is located within an existing stone crushing plant. Site is an existing vast quarry of boulders; hence it is a rocky area. Working hours from 8.00 a.m to 4.30 p.m Buffer zone of 1.3 km from nearest residential area reduce below 60 dba before reaching sensitive receptors Raw material available from within same crushing plant Transportation during weekend & off peak hours as far as possible Water sprinklers will be used Covering of materials will be done during transportation Area is inaccessible to public Buffer zone of 1.3km from nearest residential area Waste stored in a designated area Carting away scheduled on a weekly basis Architectural design carried out to merge with the surroundings Use of non-reflective paint to reduce glare Buffer zone of 1.3 km Cluster of comparable activities around the site Trees & Decorative Plants also included 41 P a g e

7 7.3 Operation Phase The operational phase is the most important phase in the assessment on environmental impacts and is the time during which the proposed Asphalt Plant will be functioning. The installation and operation of the plant will certainly have certain impacts on the environmental receptors. However, mitigating measures will be incorporated in the design, installation and operation to minimise those impacts. The potential environmental impacts associated to the operational phase of an Asphalt Plant are as follows: Dust Emission Gaseous Emissions and Odours Noise nuisances Traffic Implications Impact on Flora/Fauna Already discussed in the construction phase Solid waste generation Wastewater generation Impact on land use Visual Impacts Impacts on Human 42 P a g e

8 7.3.1 Dust Emission Sources and Impact of Dust Emission The main source of stack dust is from raw materials (typically stone aggregates) that are used for the production of the asphalt and are of the inert type. Any airborne pollutants from the process or transport of raw or finished product can potentially settle on the ground. Hydrocarbons in dust may also result from the combustion depending on the type of fuel. The stack dust can be generated from the followings: Loading and unloading of aggregates to the stockpiles During transportation of aggregates Loading of aggregates in the feeder bins The most common air pollutants from hot mix asphalt plants are particulate matter with a diameter of no more than 10 microns (PM 10 ) which is generated by the aggregates. The size of particles is directly linked to their potential for causing health problems. Small particles less than 10 micrometers in diameter pose the greatest problems, because they can get deep into your lungs, and some may even get into your bloodstream. Exposure to such particles can affect both your lungs and your heart. Referring to the enforcing agency in Mauritius under the Environment Protection Act, the emission standards are as follows: Table 7.2: Air Quality Standards (Particulate) Pollutant Maximum limits (µg/m 3 ) Average Timing Total Suspended Particles (TSP) hr Annual Average PM hr 43 P a g e

9 Mitigating Measures The emission of dust occurs in the first stages of the production of asphalt (until mixing). The most significant source of process particulate emission is the drying process. Other sources of emission include storage of raw materials, cold feed unit, filler silos, hot side screens and elevators. The main initiative on dust problems will be to try to prevent its creation in the first place and the mitigation measures are as follows: The proposed Asphalt Plant is equipped with the latest technology in terms of pollution control devices. For dust control the plant has two dust collectors one is the primary dust collection unit and the other one is the secondary dust collection unit. The primary dust collection unit entraps the larger dust particles from the dryer drum. The secondary dust collection unit is the wet dust collector and operates on an extreme turbulence venturi principle. The dust embedded in the water droplets form a kind of sludge which is then collected in a separator. By using this system the TSP emission is around 50 to 100 µg/m 3. Moreover fast growing trees will be planted to act as a dust barrier Raw materials will be covered to prevent dust emission Sprinklers will be installed along the access road to prevent dust emission from the soil. Raw materials will be covered during transportation 44 P a g e

10 7.3.2 Gaseous and Odour Emissions Sources of Gaseous and Odour Emissions Apart from particulate matter, the most common air pollutants are: Sulphur Dioxide (SO2) Nitrogen Oxides (NOx) Volatile Organic compounds (VOCs) Carbon Monoxide (CO) SO 2 The burning process in the dryer is the main SO 2 source, influenced by the sulphur content of the fuel. SO 2 is absorbed by certain mineral aggregate, e.g. limestone, and the alkaline dust-layer in the dust filter. Other mineral materials, e.g. furnace slag, can increase the SO 2 -emission. NOx Emission of NOx mainly originates from the burner in the drying drum. The emission depends on the nitrogen content of the fuel, the amount of excess air, flame temperature and burner type. VOCs Volatile Organic Compounds emission consists of a large group of substances generally described as hydrocarbons. Their molecular structure is characterised by the combination of carbon and hydrogen atoms. Additionally these substances can also contain oxygen, nitrogen, sulphur and phosphorus. These are referred to as TOCs (Total Organic Compounds). When measured as emissions from asphalt plants the individual carbon elements are added together to give a figure for Total Carbon. The emission of hydrocarbons finds its origin in the use of organic constituents and organic fuels in the production process. Especially by the heating or combustion emissions, these substances take the form of vapour or of reaction products. The most important source of emission of hydrocarbons is the incomplete combustion of fuel. Type of fuel, operating conditions and vapours from bitumen in the mixing process (which may be present in some cases) result in different compositions of the 45 P a g e

11 waste gases in respect of their organic constituents. The hydrocarbons that find their origin in the combustion are mainly emitted by the stack; these emissions can be reduced by regular maintenance of the burner and optimization of the combustion volume. CO Emission is mainly associated with the combustion process in the dryer. The spaces for generation and utilization of the heat have a smooth transition in the dryer and the drums, so the combustion of the fuel is influenced by the direct contact of the burner flame with mineral material. An unfavourable drum geometry where a combustion space is too small also leads to incomplete combustion of the fuel Impacts of Gaseous and Odour Emissions The impact of NOx, CO and particulate emissions on the human health, depending upon the degree of exposure, have been correlated with nausea, localized pains, weakness in extensor muscles, tremors, palpitations, indigestion, dizziness, irritation of the eyes, nervousness and anxiety. The impact of atmospheric pollution on the environment is characterized by acidification of the atmosphere and of an eventual build-up of its concentration in the atmosphere. This may result in extreme cases in the production of acid rain which can have very devastating consequences on the environment including flora, fauna, water bodies and particular buildings made from limestone. The most common and immediate consequences of uncontrolled emissions of pollutants in the atmosphere is the production of smog. 46 P a g e

12 Table 7.3: Air Quality Standards (Gaseous) Pollutant Maximum limits (µg/m 3 ) Average Timing SO hr 24hr Annual average NOx hr CO 25,000 10,000 1 hr 8 hr Mitigating Measures It is of importance to note that since the promoter is purchasing a brand new plant and that the unit will be fitted with the latest pollution control equipment, the latter does not envisage any severe impact on the air quality on the proposed site and within its vicinity. SO 2 The SO2 emissions are primarily influenced by two factors: the sulphur content of the fuel and the rate of absorption in the alkaline dust layer formed on the filter. By using fuel with lower sulphur content or achieving a higher degree of absorption, a reduction of SO 2 emissions can be accomplished. The use of basic minerals as e.g. limestone in the particulate collectors can help to absorb SO 2. However, it should be noted that the emissions of SO 2 will be minimal and therefore do not pose any environmental threat. 47 P a g e

13 NOx The formation of NO x is predominantly determined by burner and flame characteristics (flame temperature, burner type, and amount of excess burning air). Also the nitrogen content of the fuel influences NO x emission. The emission of gas-fired plants is lower than for oil-fired plants. Improved burner technology of the plant will substantially reduce NO x emissions from the plant. CO An incomplete combustion results among other things in the formation of CO. Abatement of CO emissions therefore require improvement of the combustion process. The correct air-fuel mixture and appropriate retention time will be adopted in order to ensure complete combustion thereby limiting CO production. VOCs The emission of VOCs finds its most important origin in the incomplete combustion of fuel. The kind of fuel and the burner characteristics as well as the geometry of the drying drum influence the eventual amount and composition of the organic emission. Another source is the heating of bitumen materials. The emission can be reduced by several different measures which are as follows: Proper operating conditions Sufficient flame volume Clean combustion No contaminants in the process 48 P a g e

14 7.3.3 Noise Emission Sources of Noises Noise occurs at different places in the process for examples in the conveyor belts, dryer and mixer drum, internal and external traffic. The noise is estimated to be in the range of 90 to 100 dba (Leq) at a few metres from the equipment Impact of Noises The increase in level of noise generated as a result of the proposed development will not affect the neighbourhood since no residential development occurs within a distance of more than 1.3km from the proposed site and no noise will be heard due to the attenuation of the noise. However, all staffs working on the asphalt plant will be affected with the noise Mitigating Measures For the personnel they will be supplied with Personal Protective Equipment (PPE) in order not to impair on their health as a result of over exposure to noise. It is expected that the resultant noise generated will be within the required norms. According to the EPA and regulations the standards are as follows: Industrial Noise : hrs... 60*dB(A) L eq Neighbourhood Noise : hrs... 55*dB(A) L eq hrs db(a) L eq hrs db(a) L eq hrs db(a) L eq Moreover, the exhaust Asphalt plant is fitted a very good acoustic design to arrest noise pollution. The placement of a sound absorber or screen at the intake will also be envisaged 49 P a g e

15 7.3.4 Traffic Implications Sources of Traffic Raw materials The materials that will be used for the production of asphaltic concrete are bitumen and aggregates. These need to be transported to the plant for production. Distribution of Asphaltic Concrete Asphaltic concrete will be distributed to the promoter s sites through the Company s lorries or if need be will hire at peak times. The capacity of the lorries will be 15 to 30 tons depending on the amount needed on site. The peak production for the plant will be around 500 tons per day, required around 17 lorries Traffic Reduction The bitumen need to be transported to the St. Julien for the production of asphaltic concrete, however only 5 to 6 lorries will be needed per months. The aggregates will be supplied by United Basalt Products (UBP) which is situated within 50 to 100 metres of the proposed site. This will considerably reduce traffic if this needs to be transported from another source. As the crushing plant is located within the same internal compound this will not impact on the road users. For the distribution of asphaltic concrete, it will be limited to off-peak hours so that it does not affect the flow of traffic. Moreover, the number of trips is negligible compared to the existing traffic flow. 50 P a g e

16 7.3.5 Solid Waste Generation Sources of Solid Waste The solid waste will constitute only of domestic waste and sludge. The production of asphalt produces waste sludge. All sludge waste and fuel is to be bonded onsite (the entire operation will be self contained and bonded). It is estimated that on average 0.8 kg of domestic waste is generated on a daily basis by each employee of the Company Mitigating Measures Sludge Disposal Once the waste sludge dries, it is required to be disposed of to the landfill by a licensed waste carrier. Alternatively, the waste sludge can be recycled to the process in order to minimise the amount of waste generated and reduce handling problems. It is expected that all sludge will be recycled to the process, thus limiting any sludge disposal problem. Domestic Waste Disposal Domestic waste will be stored in designated bins and carted away to the transfer station and ultimately to the landfill by local authorities. Moreover, good housekeeping will be implemented on the premises which will ensue that the site is kept tidy all the time. The services of a fully experienced cleaning company may be arranged during the operational phase of the plant. 51 P a g e

17 7.3.6 Wastewater Generation Sources of Wastewater Process Wastewater As mentioned in the impact assessment sub-section of the operational phase, process wastewater is generated from the wet dust collector and the cleaning of the equipment and floor area. Domestic Wastewater Domestic wastewater will be generated by the staff and workers working at the Asphalt Plant. It is estimated that 10 persons will be working on the Asphalt Plant once put into operation Mitigating Measures Process Wastewater All wastewater from dust collector will be channelled to dedicated settling tanks and the effluent will be recycled back to the process upon sedimentation. Since detergents might be used at times for spraying, it is imperative that the effluent is led to an individual separator, because the detergents will otherwise cause oil contaminated effluent to emulsify and thereby permitting the oil to pass unhindered through the conventional separator. Domestic Wastewater All domestic wastewater will be disposed via a septic tank and absorption pit. The design of the wastewater disposal facility is based on an average of 10 staffs working on fulltime on the proposed plant. With reference to the geotechnical characteristics of the site, it is expected that the proposed wastewater disposal technique will be to the satisfaction of the Wastewater Management Authority (WMA). 52 P a g e

18 7.3.7 Impact on Land Use As already discussed in Section 4.5 and 4.6, the proposed site is a rock quarry and is enclosed within an industrial area comprising of stone crushing and block manufacturing. Hence, it is highly suitable for the foresaid activity since it is a zone where similar activities are carried out. Furthermore, the setting up of the asphalt mixing plant in this region is ecologically favoured due to the fact that comparable activities are concentrated within the region forming a cluster, thereby limiting the environmental impacts of several dispersed individual activities. Moreover, the setting up of the asphalt plant itself will not have any permanent impact on the proposed site since it can be shifted at any time to another location without having any residual impact on the land form according to the Environmental Impact Statement (EIS) supplied by the supplier a copy of the EIS has been enclosed in Annex 8 for reference purposes Visual Impacts The plant has been carefully design so that it does not looks bulky and architectural design of the offices has been done to match the surroundings. Also, trees and decorative plants will be planted around the plant to reduce visual impact. The proposed site is not visible from the main roads and it is situated within a cluster of similar activities. Thus, the location of the site itself will act as a buffer to visual impact for the proposed development. 53 P a g e

19 7.3.9 Impacts on Human Health Problems There are several health related issues concerning the operation of an Asphalt Plant. Fumes coming out of the plant may cause wheezing, coughing headaches, nausea and in some cases irritation to skin. As discussed earlier in dust emission particles can cause lungs disease known as silicosis. Asphalt plant represents a source of noise pollution and may affect sensitive receptors. It is a health hazard for the workers and as mentioned above the estimated to be in the range of 90 to 100 dba (Leq) at a few metres from the equipment Mitigating Measures for Health and Safety Concerning the health problems associated with the fumes and dust the emission level of this plant is within the standards limit. As such there is no risk of health hazards in regards to the air quality for the personnel working on the Asphalt Plant. Moreover, the supplier has given a certificate which has been attached in Annex 8 which shows that the air emission is within the International and National standards. Asphalt Plants can be very dangerous, accidents may occur at any time. Hence it is important to have a proper policy for the Health and Safety Issues. The following measures will be adopted in order to ensure the effectiveness of safety within the premises. To prevent bitumen burns it will be compulsory for the workers handling hot bitumen to wear full-body protection. All transportation, handling and storage of bitumen will be handled safely by experienced personnel. The dust from the manufacturing process may pose respiratory hazards, hence protective air mask will be provided to the operators for the loading and unloading of aggregates Ear-muffs will be provided those working on the plant First Aid kit will be available on site for the workers in case of emergency The Material and Data Sheet (MSDS) for each chemical product will be made accessible on site and displayed. 54 P a g e

20 Safety signs will be posted throughout the site and entry and exit will be clearly mentioned Regular health check up will be conducted for the employees working on the plant 55 P a g e

21 Table 7.4 : Summary of Environmental Impacts & Mitigating measures during Operation Impact Sources or Causes Mitigating Measures Damage to Nature Pollution of surface or ground water due to oil spillage Damage to flora and fauna due to combination of gaseous emission with rainwater forming acid rain Transportation of raw materials Bundwall will be erected around storage tanks Asphalt plant is equipped with latest pollution control unit Working hours from 8.00 a.m to 4.30 p.m Allowable Emission (according to EPA 2002) Predicted Emission by Asphalt Plant Noise Pollution Transportation of asphaltic concrete Operation of the asphalt plant Buffer zone of 1.3km from nearest residential area Ear-muffs will be provided those working on the plant db(a). < 60 db (A) Use of natural dampers to attenuate noise Traffic Congestion Transportation of raw materials Transportation of asphaltic concrete Raw material available from within same crushing plant Transportation carried out during off peak hours Transportation of raw materials & asphaltic concrete Use of water sprinklers Dust Emission Operation of the asphalt plant During loading and unloading of aggregates Plantation of fast-growing trees that act like dust barriers Asphalt plant is equipped with latest pollution control unit with two dust collectors TSP = 150 µg/m3 TSP 150 µg/m3 Vehicles will be covered 56 P a g e

22 Impact Sources or Causes Mitigating Measures Impact on Humans Solid Waste Pollution Gaseous Pollution Due to noise Due to dust Hot bitumen may cause thermal burns Waste sludge from the production of asphaltic concrete Domestic wastes from workers on site Use of ear muffs and protective air masks Buffer zone of 1.3km from nearest residential area Good ventilation is allowed around work areas Workers must wear full body protection when handling hot bitumen A first aid kit will be available on site Regular health check provided for employees Safety signs posted at entry of site Waste sludge will be recycled Waste sludge disposed at landfill by appropriate waste carrier Domestic waste will be stored in designated bins and carted away to the transfer station and ultimately to the landfill by local authorities. Allowable Emission (according to EPA 2002) Sulphur Dioxide (SO2) Limestone to absorb SO2 will be use SO₂ = 350 µg/m3 Nitrogen Oxides (NOx) Appropriate burner and flame characteristics NOᵪ = 350 µg/m3 Carbon Monoxide (CO) Volatile Organic compounds (VOCs) Correct air-fuel mixture and appropriate retention time Proper operating conditions, sufficient flame volume, clean combustion CO = 10, 000 µg/m3 Predicted Emission by Asphalt Plant SOᵪ 300 µg/m3 NOᵪ 140 µg/m3 CO 800 µg/m3 VOC 450 µg/m3 57 P a g e

23 Impact Sources or Causes Mitigating Measures Allowable Emission (according to EPA 2002) Predicted Emission by Asphalt Plant Wastewater Generation Alternate Power sources Process wastewater will be generated Domestic wastewater In case of power cut which may delay all other following operations Process wastewater will be recycle through setting tanks and by individual separator Domestic waste water will be disposed in septic tanks and absorption pits A fully operational generator will be stand by Plant may looks bulky Buffer zone of 1.3 km is provided Visual Impacts Land Use May affect flora and fauna Fast growing trees will be planted Architectural design of the office will be done to match the existing surroundings Already a rock quarry Located in an operating crushing plant No residual impact on land use and environment 58 P a g e