13 QUALITY AND NOISE - NTEPA

Project Sea Dragon

Core Breeding Centre and Broodstock Maturation Centre, Bynoe Harbour

Draft Environmental Impact Statement

PART B ‐ ENVIRONMENTAL ASSESSMENT 13‐256

13 AIR QUALITY AND NOISE

13.1 TERMS OF REFERENCE ADDRESSED IN CHAPTER

This chapter provides a description of potential air and noise impact from incineration and power facilities

associated with the Project as required under Section 4.1 and 4.3.3 of the ToR.

Two options for disposal of prawn mortalities are being considered by Seafarms i.e. disposal by incineration or

transport and disposal offsite to landfill. In the event incineration is selected as the preferred option, the

assessment air quality emissions from the incinerator applies to the proposed action.

Potential air and noise emissions from the power facility on site has been assessed to address Section 4.1 of the

ToR.

Table 13‐1 summarises the requirements of the ToR and references where they have been addressed in this

EIS.

TABLE 13‐1 TERMS OF REFERENCE

Terms of Reference Sections

4 Risk Assessment

4.1 The EIS should be undertaken with specific emphasis on the

identification, analysis and mitigation of potential impacts through a

whole‐of‐project risk assessment.

Chapter 6 and 13

4.3.3 Mitigation and monitoring

If incineration is proposed, the EIS should refer to the NT EPA

Guideline Disposal of Waste by Incineration at

https://ntepa.nt.gov.au/waste‐pollution/guidelines/guidelines, for

information that should be considered.

Chapter 13

Appendix 19

13.2 OVERVIEW

Based on the risk assessment undertaken in Chapter 6, incineration and power station facilities have been

identified as potentially impacting sensitive receptors within close proximity to the facilities. This chapter

provides a summary of the assessment criteria, assessment method and predicted impacts at the nearest

sensitive receiver when the Project is at full scale operation, and outlines management measures.

The nearest sensitive receptor to the incineration and power generation facilities is the accommodation facility

located approximately 60 m to the southwest. The power station and accommodation locations are shown in

Figure 1‐4 and Figure 13‐1. The incinerator will be located in close proximity to the power facility fuel storage,

currently within the common facilities area, and be housed in a shed.

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FIGURE 13‐1 LOCATION OF PROPOSED POWER FACILITY AND ACCOMMODATION FACILITY

The National Environment Protection Council (NEPC) set uniform standards for Australian ambient air in

February 2016. These are known as the National Environment Protection (Ambient Air Quality) Measure (Air

NEPM), which sets non‐binding standards and ten‐year goals. In the absence of specific Northern Territory

regulated standards, appropriate criteria have been adopted from other jurisdictions and the most stringent

NEPM goals and standards have been used as a benchmark. It should be noted that the NEPM is for ambient

monitoring and not for the regulation of specific point sources.

There is no specific guidance in the Northern Territory for the assessment and management of air quality

impacts however guidelines exist for disposal of waste by incineration (Guideline for disposal of waste by

incineration, NT EPA 2013).

A conservative screening level assessment has been undertaken to determine the potential air quality impacts

to sensitive receptors within the area as a result of incineration and power generation facilities proposed

during operation of the project. Occupational air quality impacts on workers at these facilities has not been

assessed.

13.2.1 Air emissions from power facility

The proposed power facility at the site will generate 6 MW of power A worst case scenario was assessed

including nine CAT32 diesel generators, packaged in containers. One of the generators would remain in

standby, and the assessment assumes that eight would be operating at any one time. The exact generator

model and layout is subject to detailed design and commercial arrangements.

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Emissions from the diesel generators have been obtained from the product specification and are summarised

in Table 13‐2. The most significant air pollutant generated by this facility, based on the ratio of its emission rate

to impact assessment criterion, will be nitrogen dioxide (NO2) released as oxides of nitrogen (NOx) from onsite

diesel generation units. NOx from combustion consists largely of nitric oxide (NO) and partly NO2, and after

emission from the stack NO is transformed to NO2 through oxidation with atmospheric ozone. This process is

accelerated in warmer temperatures and sunlight.

In accordance with the US EPA Guideline of Air Quality Models (2005), the US EPA emission database specifies

a 5.7 % exhaust exit ratio of NO2 to NOx for Caterpillar reciprocating diesel generators. For a screening

assessment, a conservative ratio of 10% has been assumed – this allows for some oxidation to occur in the

near‐field immediately after release from an exhaust.

Even though the immediate exhaust exit NO2 to NOx ratio is likely to be below 10%, the high heat and

ultraviolet light levels can lead to rapid oxidation in a tropical climate and a ratio of 30% is a conservative

assumption. A scenario has also been assessed assuming a ratio of 30%.

TABLE 13‐2 DIESEL GENERATION NOX EMISSIONS

Pollutant Emissions

(g/hp‐hr)*

Emissions g/s

(1 generator)

Emissions from 8 generators

(g/s)

NOx 5.8 1.73 13.84

NO2 – 10% conversion 0.173 1.384

NO2 – 30% conversion 0.519 4.152

*grams per horsepower‐hour

As the air quality criteria is the 100th percentile, worst case conditions would generally occur in every direction

from the power facility for at least one hour per year. A review of wind rose data from Dum In Mirrie (BoM site

014277) shows that winds are predominantly from the west (wet season), and east (dry season) with very little

wind from the south during the year.

A screening level air quality assessment was undertaken using AUSPLUME assuming worst‐case meteorological

conditions. Each generator is assumed to have a 7 m high, 0.2 m diameter stack, with an exit velocity of

21.9 m/s. The exit velocity is based on exhaust flow rates given in the CATC32 specification. Eight out of the

nine generators are assumed to be operating concurrently.

13.2.2 Air emissions from incineration

The proposed incinerator is a small dual chamber system. Waste is burnt in the primary chamber and hot gases

and emissions are burnt in the secondary chamber. The incinerator will be located in close proximity to the

power facility fuel storage and be housed in a shed.

An incinerator with a burn rate of 50 kg/hr is proposed in order to dispose of prawn carcasses/mortalities. At

full scale operation of the BMC and CBC the potential incineration task is approximately 200 kg of prawn

carcasses each week. Given the capacity of the proposed unit, this equates to the incineration of 50 kg of

prawn mortalities for one hour four times per week. However initially, the task is much less. The incinerator is

proposed to be located adjacent the power facility, approximately 90 m away from the accommodation facility.

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The NT Guideline for Disposal of Waste by Incineration (2013) sets out emission limits for incinerators as well

as other requirements listed below:

Two chambers

A minimum temperature of 850 ºC in the primary chamber

Air supply to achieve efficient combustion of all wastes

A minimum retention time of two seconds

No impingement of exhaust gases onto building or sensitive sites.

The guideline also recommends a radial buffer distance of 500 m between the incinerator and any sensitive

land uses such as the accommodation facilities. The incinerator may achieve the air quality goals under normal

operation, however should equipment fail, accidents occur or following other causes, then a buffer is a means

to let these residual emissions dissipate without adversely impacting on sensitive land uses or amenity. The

guideline does not consider the volume of waste being incinerated, nor the frequency of operation.

Waste is burnt in the primary chamber and hot gases and emissions are burnt in the secondary chamber. The

incinerator will be located in close proximity to the power facility fuel storage and be housed in a shed.

The proposed incinerator with a two second retention, secondary chamber meets requirements of the NT EPA

guideline listed above, however the proposed buffer distance of 500 m has not been achieved (refer to Figure

13‐2).

13.2.3 Noise from power facility

Noise levels for each generator (CAT32, 800 eKW) were modelled assuming a sound pressure level of 85 dB(A)

at one metre, as required in the design specification. The generators are enclosed within containers and the

noise level is assumed to be outside of the container.

NT EPA offers guidance for noise levels from construction sites (Noise guidelines for development sites in the

Northern Territory (NT EPA 2014) however has no guidelines for operational noise impacts. Intrusive noise

impacts are often assessed as acceptable where the industrial noise source does not exceed the background

noise level by more than 5 dB(A). An example of this is the NSW Industrial Noise Policy 2000 which classifies

intrusive noise as being ‘noise that intrudes above the background level by more than 5 decibels’.

13.3 POTENTIAL IMPACTS


The worst case predicted hourly NO2 levels at a distance of 60 m from the power facility is an hourly average

peak of 123 µg/m³, which is 50% of the impact assessment criterion. The distance of 60 m represents the

approximate distance of the accommodation facility in the proposed concept layout (Figure 1‐4).

Assuming the conservative 30% conversion of NOX to NO2, an additional model scenario was run. The predicted

peak hourly NO2 at the accommodation facility is 370 µg/m³, which exceeds the criterion. A buffer of 300 m

from the power facility is needed in order to reduce the maximum predicted impact to the criteria level of 246

µg/m³.

The screening air quality assessment shows that operation of the power facility has the potential to exceed the

maximum hourly average NO2 level at the accommodation facility.

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13.3.2 Air emissions from incineration

The UK government considers that “The use of an onsite incinerator with afterburner can be considered to

represent BAT for animal remains disposal” (BAT = Best Available Technology) (DEFRA, 2002, p.viii). Further,

the UK consider "shells from shellfish with soft tissue" as Category 2 ABP (Animal by Product) and allow for

small onsite incineration (with similar operational controls to that of the NT EPA Guideline) and this is classed

as low risk.

Relevant allowable emission limits from incinerators in the Northern Territory are presented below in Table

13‐3. Arsenic and mercury are included as they are possible in an industry related to marine organisms. Also

note that the United Kingdom Department for Environment, Food & Rural Affairs (DEFRA) (2002) found that

dioxin and furans can be generated by small carcass incinerators with afterburners – poultry farms, general

farms and hunt kennels generating levels above recognised best practice standards (a pig farm incinerator

operating on diesel was right on the 0.1 ng/m³ limit).

TABLE 13‐3 SUMMARY OF RELEVANT ALLOWABLE INCINERATOR EXHAUST EMISSIONS

Substance Emission limit Source

Particles (as TSP) 50 mg/m³ NTEPA Waste Incinerator Guidelines adopting the

Biohazard Waste Industry (BWI) of Australia and

New Zealand Industry Code of Practice for the

Management of Clinical and Related Wastes

NOx (as NO2) 350 mg/ m³

SO2 150 mg/m³

HCl 100 mg/m³

Arsenic 0.5 mg/m³

Mercury 0.05 mg/m³

Dioxins / furans 0.1 ng/m³

The proposed incinerator is a small facility and will operate for a limited number of hours during the day, a few

days a week. With such a low mass throughput, a risk assessment approach has identified very low residual

impact upon the environment. Residual risk associated with potential impact can be managed through the

adoption of standard operating procedures that require the facility to be operated when favourable winds limit

exposure to accommodation facilities. Choosing to operate the facilities when accommodation is vacant may

also be possible.

13.3.3 Noise emissions from power facility

Existing background noise levels at the site would be very low, as there are no existing industrial noise sources.

As the power facility will operate during both the day and night time, it is expected that background noise

levels would be below 30 dB(A). In areas where the background noise level may drop below 30 dB(A), a level of

30 dB(A) is adopted. The criteria for this site would therefore be the background plus 5 dB(A), which is 35

dB(A). The day time noise level and criteria would potentially be higher than the night time however as the

power facility operates with a relatively constant noise level the night time would be the most stringent criteria

that needs to be assessed against.

A preliminary noise model has been prepared to gain an understanding of predicted noise levels at the

accommodation village and also how far the power facility should be from the accommodation to minimise

potential noise impacts. The following assumptions in Table 13‐4 were made in the preliminary noise model.

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TABLE 13‐4 NOISE MODEL ASSUMPTIONS

Input/assumption Data used in the model

Prediction algorithm ISO 9613‐2 ‘Acoustics – Attenuation of sound during propagation

outdoors’

Modelling software Cadna A 4.6

Ground absorption coefficient 1 for soft ground

Generator height 4 m

Number of generators operating 8 (worst case scenario)

Sound pressure level at 1 m 85 dB(A)

Meteorological conditions Atmospheric propagation conditions were modelled with noise

enhancing wind conditions for noise propagation (downwind

conditions) or equivalently a well‐developed moderate ground

based temperature inversions

Preliminary model results show that the predicted noise level at the accommodation facility would be 56 dBA,

which exceeds the adopted noise criteria by more than 20 dBA.

Refer to Figure 13‐2 for an indication of predicted noise contours generated from eight operating generators.

13.4 MITIGATION AND MONITORING

Preliminary air and noise assessments of the proposed power facility and incinerator have been undertaken to

determine potential impacts on the nearest sensitive receiver. The nearest sensitive receivers to the power

facility are personnel at the accommodation facility approximately 60 m away.

The outcomes of the assessment recommended that the accommodation facility be moved to a location that is

approximately 520 m from the power facility in order to achieve both noise and air quality outcomes.

Therefore, as part of detailed design, the location of the power facility will be moved approximately 520 m

south along the access road. In the event incinerator is the preferred method for disposing of prawn

mortalities, the incinerator will also be moved 520 m south along the proposed access road. In the event the

incinerator is not the preferred method for disposing of prawn mortalities, and noise attenuation to achieve

noise criteria was applied to the power facility, the separation distance of 520 m would still be required to

achieve air quality outcomes related to the power facility.

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FIGURE 13‐2 AIR AND NOISE MODELLING RESULTS

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The screening air quality assessment shows that operation of the power facility has the potential to exceed the

maximum hourly average NO2 level at the accommodation facility. The noise assessment for the diesel

generator in dictates a 520 m separation distance would reduce ambient noise at the accommodation facilities

to meet the proposed threshold. A further screening modelling run was performed with this distance. In this

instance, the 1‐hour assessment criterion of 246 µg/m³ can be achieved with an NO2 to NOx ratio of 43%. This

ratio is well within the expected worst‐case scenario due to the tropical conditions.

Even with an oxidation rate producing a 43% NO2 to NOx ratio, the 1‐hr NO2 criterion will not be exceeded at

the accommodation facility 520 m away.

By increasing the separation distance between the power facility and accommodation facility to 520 m, the

potential impact on air quality from power facility air emissions would be a residual risk of Very Low.

13.4.2 Air emissions from incinerator

The following mitigation and design requirements are recommended:

Exhaust should be three metres higher than the top of any building within 100 m of the incinerator

Exhaust efflux velocity should be 10 m/s or more during all operational hours of waste incineration

Once operational, a stack test be undertaken to confirm emission limits comply with requirements of the

NT EPA Guideline for Disposal of Waste by Incineration

Conduct a risk assessment accounting for the small number of hours operating and calculate a mass

balance to assess the potential amount of arsenic and mercury that may be found in prawn carcasses in

prawn carcasses that may be present in exhaust emissions.

By increasing the separation distance between the incinerator and accommodation facility to 520 m, the

potential impact on amenity from incineration air emissions would be a residual risk of Low.

13.4.3 Noise emissions from power facility

Results show that a distance of approximately 520 m would be needed for the sound level emitted from all

eight generators operating at one time to be 35 dB(A) at the accommodation facility. For comparative purposes

the approximate distance to achieve a noise level of 40 dBA would be 320 m and 45 dBA would be 200 m from

the power facility.

Therefore, by increasing the separation distance between the power facility and accommodation facility to

520 m, the potential impact on amenity from power facility noise emissions would be a residual risk of Low.

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13 QUALITY AND NOISE - NTEPA