7 predicted environmental impacts & mitigation...

Asphalt Mixing Plant EIA Report

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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


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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.

7.2.1 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


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7.2.2 Mitigating Measures during Construction

7.2.2.1

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

7.2.2.2 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.


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7.2.2.3 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.

7.2.2.4 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.

7.2.2.5 Dust Emission

Dust emission during the transportation of raw materials will be minimised through using existing

water sprinklers in the crusher plant.

7.2.2.6 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.

7.2.2.7 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.


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7.2.2.8 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.


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Table 7.1: Summary of Environmental Impacts & Mitigating measures during Construction

Possible Impact Sources or Causes Mitigating Measures

Ecology

Pollution of surface and groundwater Site is not environment sensitive and is located within an existing stone

crushing plant. Destruction of vegetation

Risk of Soil Erosion Site is an existing vast quarry of boulders; hence it is a rocky area.

Noise Pollution

Transportation of materials by heavy good vehicles Working hours from 8.00 a.m to 4.30 p.m

Works due to construction works Buffer zone of 1.3 km from nearest residential area reduce below 60

dBA before reaching sensitive receptors

Traffic

Congestion

Transportation of raw material Raw material available from within same crushing plant

Transportation of modular parts of asphalt plant Transportation during weekend & off peak hours as far as possible

Dust Emission Transportation of raw materials Water sprinklers will be used

Covering of materials will be done during transportation

Public Nuisance Nuisance due to dust Area is inaccessible to public

Disturbance due to noise Buffer zone of 1.3km from nearest residential area

Solid Waste

Pollution

Due to excess materials or faulty parts Waste stored in a designated area

Carting away scheduled on a weekly basis

Visual Aspect

Large structure 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


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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


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7.3.1 Dust Emission

7.3.1.1 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 (PM10) 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/m3) Average Timing

Total Suspended Particles

(TSP)

150

50

24-hr

Annual Average

PM10

100 24 hr


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7.3.1.2 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/m3.

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


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7.3.2 Gaseous and Odour Emissions

7.3.2.1 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)

SO2

The burning process in the dryer is the main SO2 source, influenced by the sulphur content of the

fuel. SO2 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 SO2-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


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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.

7.3.2.2 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.


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Table 7.3: Air Quality Standards (Gaseous)

Pollutant Maximum limits (µg/m3) Average Timing

SO2

350

200

50

1 hr

24hr

Annual average

NOx

200 24 hr

CO

25,000

10,000

1 hr

8 hr


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.

SO2

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 SO2 emissions can be

accomplished. The use of basic minerals as e.g. limestone in the particulate collectors can help to

absorb SO2. However, it should be noted that the emissions of SO2 will be minimal and therefore do

not pose any environmental threat.


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NOx

The formation of NOx 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 NOx emission. The emission of gas-fired plants is lower than for oil-fired plants.

Improved burner technology of the plant will substantially reduce NOx 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


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7.3.3 Noise Emission

7.3.3.1 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.

7.3.3.2 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.


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 :

07.00 --- 21.00 hrs ... 60*dB(A) Leq

21.00 --- 07.00 hrs ... 55*dB(A) Leq

Neighbourhood Noise :

07.00 --- 18.00 hrs ... 60 dB(A) Leq

18.00 --- 21.00 hrs ... 55 dB(A) Leq

21.00 --- 07.00 hrs ... 50 dB(A) Leq

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


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7.3.4 Traffic Implications

7.3.4.1 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.

7.3.4.2 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.


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7.3.5 Solid Waste Generation

7.3.5.1 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.


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.


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7.3.6 Wastewater Generation

7.3.6.1 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.


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).


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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.

7.3.8 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.


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7.3.9 Impacts on Human

7.3.9.1 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.

7.3.9.2 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.


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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


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Table 7.4 : Summary of Environmental Impacts & Mitigating measures during Operation

Impact Sources or Causes Mitigating Measures

Allowable

Emission

(according to EPA

2002)

Predicted

Emission by

Asphalt Plant

Damage to

Nature

Pollution of surface or ground water due

to oil spillage Bundwall will be erected around storage tanks

Damage to flora and fauna due to

combination of gaseous emission with

rainwater forming acid rain

Asphalt plant is equipped with latest pollution

control unit

Noise Pollution

Transportation of raw materials Working hours from 8.00 a.m to 4.30 p.m

60 - 70 dB(A). < 60 dB (A)

Transportation of asphaltic concrete Buffer zone of 1.3km from nearest residential area

Operation of the asphalt plant Ear-muffs will be provided those working on the

plant

Use of natural dampers to attenuate noise

Traffic

Congestion

Transportation of raw materials Raw material available from within same crushing

plant

Transportation of asphaltic concrete Transportation carried out during off peak hours

Dust Emission

Transportation of raw materials &

asphaltic concrete Use of water sprinklers

Operation of the asphalt plant Plantation of fast-growing trees that act like dust

barriers TSP = 150 µg/m3 TSP ≤ 150 µg/m3

During loading and unloading of

aggregates Asphalt plant is equipped with latest pollution

control unit with two dust collectors

Vehicles will be covered


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Impact Sources or Causes Mitigating Measures Allowable Emission

(according to

EPA 2002)

Predicted

Emission by

Asphalt Plant

Impact on

Humans

Due to noise Use of ear muffs and protective air masks

Due to dust Buffer zone of 1.3km from nearest residential

area

Good ventilation is allowed around work areas

Hot bitumen may cause thermal burns 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

Solid Waste

Pollution

Waste sludge from the production of

asphaltic concrete Waste sludge will be recycled

Waste sludge disposed at landfill by appropriate

waste carrier

Domestic wastes from workers on site Domestic waste will be stored in designated bins

and carted away to the transfer station and

ultimately to the landfill by local authorities.

Gaseous Pollution

Sulphur Dioxide (SO2) Limestone to absorb SO2 will be use SO₂ = 350 µg/m3 SOᵪ ≤ 300

µg/m3

Nitrogen Oxides (NOx) Appropriate burner and flame characteristics NOᵪ = 350 µg/m3 NOᵪ ≤ 140

µg/m3

Carbon Monoxide (CO) Correct air-fuel mixture and appropriate

retention time CO = 10, 000 µg/m3 CO ≤ 800 µg/m3

Volatile Organic compounds (VOCs) Proper operating conditions, sufficient flame

volume, clean combustion

VOC ≤ 450

µg/m3


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Impact Sources or Causes Mitigating Measures Allowable Emission

(according to

EPA 2002)

Predicted

Emission by

Asphalt Plant

Wastewater

Generation

Process wastewater will be generated Process wastewater will be recycle through

setting tanks and by individual separator

Domestic wastewater Domestic waste water will be disposed in septic

tanks and absorption pits

Alternate Power

sources In case of power cut which may delay

all other following operations A fully operational generator will be stand by

Visual Impacts

Plant may looks bulky Buffer zone of 1.3 km is provided

Fast growing trees will be planted

Architectural design of the office will be done to

match the existing surroundings

Land Use

May affect flora and fauna Already a rock quarry

Located in an operating crushing plant

No residual impact on land use and environment

7 predicted environmental impacts & mitigation...

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