11.0 NOISE EMISSIONS RISKS AND MANAGEMENT

Transcription

1 11.0 NOISE EMISSIONS RISKS AND MANAGEMENT This PER and associated appendices make reference to both the Approved Gorgon Gas Development and the Revised Gorgon Gas Development, which is the subject of this PER. For clarification purposes, the following definitions are provided: the Approved Gorgon Gas Development or the Approved Development refers to the development proposed in the EIS/ERMP (Chevron Australia 2005a) and subsequently approved under Statement No. 748 and EPBC Reference: 2003/1294 the Gorgon Gas Development Revised and Expanded Proposal or the Revised Gorgon Gas Development or the Revised Proposal refers to the development proposed in this PER, which is yet to gain approval the Gorgon Gas Development refers to the entire proposal. This descriptor may be used when the reference is being made to elements of the Revised Proposal described in the PER when they replace the elements of the Approved Development which have changed to create the final product as proposed in this PER Assessment Framework or Policy EPA Objective To protect the amenity of nearby residents from noise impacts resulting from activities associated with the proposal by ensuring the noise levels meet statutory requirements and acceptable standards (EPA 2004b) State (WA) Legislation Sections 51, 62(4), 65 and 74(3)/50, and 75 of the Environmental Protection Act 1986 (WA) (EP Act) provide the legislative framework for managing noise impacts. The noise limits cited by the EP Act are assigned in the Environmental Protection (Noise) Regulations 1997 (Noise Regulations) and further guidance exists in EPA Guidance Statement No. 8 (EPA 2007a) (Section ). Regulation 7 of the Noise Regulations requires that noise emitted from any premises must comply with assigned noise levels when received at any other premises. The assigned levels are specified under regulation 8 of the Noise Regulations, according to the type of premises receiving the noise. Proposals need to demonstrate compliance with the relevant noise levels prescribed in the Noise Regulations State (WA) Guidelines The noise assessment for the Revised Proposal Gas Treatment Plant was conducted in accordance with the requirements of EPA Draft Guidance Statement No. 8 - The Assessment of Environmental Factors, Environmental Noise (EPA 2007a) Detailed Assessment of Potential Impacts Overview The change in levels of terrestrial noise emissions from the Revised Proposal are linked to the operation of the additional LNG train and the increase in number of non-routine flaring events associated with the operation of the additional train. Noise emissions from marine activities are also expected to increase due to the increase in LNG and condensate tanker offtakes and associated infield marine vessel activities. At Barrow Island, noise emissions from the Revised Proposal have the potential to affect sensitive terrestrial and marine fauna. NOISE EMISSIONS RISKS AND MANGEMENT 235

2 The focus of the noise emissions assessment for the Revised Proposal is on operational phase noise emissions, changes to noise levels during the construction phase are considered to be insignificant. The detailed noise emission assessment results are presented in terms of noise levels at sensitive receptors around the Gas Treatment Plant. Specific discussion of the potential effects of noise emissions from the Revised Proposal to terrestrial and marine fauna are provided in Sections 6.1 and 7.1 respectively Background Noise Levels A baseline noise survey on Barrow Island was conducted by SVT Acoustic Engineering Consultants during the period 20 January to 10 February 2004 and reported in the draft EIS/ERMP (Chevron Australia 2005a). A summary of the results of the study is presented in Table Noise levels at the existing Chevron Camp were found to be dominated by the local air conditioning units, whilst the background noise levels at the proposed Gas Treatment Plant Site were found to be dominated by noise from winds and the nearby sea. Table 11.1: Background Noise Levels Location Existing Chevron Camp Proposed Gas Treatment Plant Site hrs Monday to Saturday Background Noise Levels L90 db(a) hrs Monday to Saturday hrs on Sunday hrs Monday to Saturday hrs on Sunday Noise Acceptance Criteria Noise levels within the Proposed Gas Treatment Plant were assessed against the maximum noise exposure levels for workers as specified in the National Standard for Occupational Noise (NOHSC:1007[2000]), which are: an eight-hour equivalent continuous A-weighted sound pressure level (Laeq,8h), of 85dB(A) a C-weighted peak noise level of 140 db(c). Occupied buildings in the vicinity of the Gas Treatment Plant and the Gorgon Construction village/ Turnaround Camp will be built to comply with the recommended noise levels in AS2107:2000 (Acoustics Recommended design sound levels and reverberation times for building interiors). Ambient noise levels from the development will be assessed against the noise acceptance criteria listed in Table These criteria are referenced from the Western Australian Noise Regulations. NOISE EMISSIONS RISKS AND MANGEMENT 236

3 Table 11.2: Assigned Noise Limits for Industrial and Noise-Sensitive Premises Type of Premises Receiving Noise Time of Day Assigned Level (db) LA 10 LA 1 LA max Industrial and All hours utility premises 1 Noise-sensitive 2 All hours 60 + Influencing factor 75 + Influencing factor 80 + Influencing factor NOTES: LAmax: A noise level that is not to be exceeded at any time. L A1 : A noise level that is not to be exceeded for more than 1% of the time. LA 10 : A noise level that is not to be exceeded for more than 10% of the time. 1. Industrial and utility premises: classification under Schedule 1, Part A (5) of the Noise Regulations any premises used for sand, gravel, clay, limestone, or rock excavation (i.e. a quarry). 2. Noise-sensitive: applies at locations further than 15 m from a building associated with a noise-sensitive use. It is proposed to apply the assigned noise limits for industrial and utility premises to the proposed Gorgon Administration Area, and the noise sensitive development noise limits to the Gorgon Construction Village and existing Chevon Camp. Where the noise is received 15 m from a dwelling (or the like) on noise sensitive premises, the Noise Regulations require that the assigned levels be determined by inclusion of the influencing factor. The factor accounts for the presence of industrial/utility or commercial land or major roads within 450 m of the receiving premises. In the case of the Gorgon Construction Village and the existing Chevron Camp, there is no such development or a major road within 450 m of these, therefore the influencing factor should be taken as nil decibels Predicted Noise Emissions from Approved Development Predicted noise levels for the Approved Development at the Gorgon Construction Village/Turnaround Camp were modelled as part of the assessment of the Approved Development. These noise levels were subsequently re-estimated by Kellogg Joint Venture Gorgon (KJVG) as part of the engineering design for the Approved Development Gas Treatment Plant. The results for the sensitive noise receptors (e.g. Gorgon Administration Area, Gorgon Construction Village/Turnaround Camp and the existing Chevron Camp) are summarised in Table These noise levels are considerably below the assigned noise limits for the Gorgon Administration Area and the Gorgon Construction Village and existing Chevron Camp as per Table Table 11.3: Predicted Sound Pressure Levels db(a) at Sensitive Receptors Location Gorgon Administration Area Approximately 54 Gorgon Construction Village 38 Existing Chevron Camp 36 Approved Development Predicted Sound Pressure Levels db(a) NOISE EMISSIONS RISKS AND MANGEMENT 237

4 Noise Modelling Methodology for the Revised Proposal Noise Model Chevron Australia utilised in-house noise modelling capabilities provided by its Gas Treatment Plant engineering contractor, KJVG. KJVG has used proprietary Plant Noise Modelling System (PNMS) software, in combination with commercial software (SoundPlan) for the development of the Revised Proposal Gas Treatment Plant noise models and the prediction of in-plant and surrounding environmental sound pressure levels near the Gas Treatment Plant site and at specified sensitive receptor locations. The full modelling study report (KJVG 2008b) is presented in Appendix D Receptors of Interest The noise modelling study was conducted as a desktop study with the purpose of establishing cumulative noise levels from the Revised Proposal Gas Treatment Plant operations for the following sensitive receptor locations: existing Chevron Camp proposed Gorgon Construction Village/Turnaround Camp proposed Gorgon Administration Area Noise Model Assumptions and Inputs The PNMS software follows the prediction methodology defined in the Engineering Equipment Material Users Association (EEMUA), Publication No. 141 "Guide to the Use of Noise Procedure Specification" (EEMUA 1985) and International Standard ISO : Acoustics-Attenuation of Sound during Propagation Outdoors, Part 2: General Prediction Method, The PNMS software is used to assemble a matrix of Sound Power Level input data. The SoundPlan software then uses this PNMS data to calculate and graphically present both in-plant and noise levels experienced at the specified sensitive receptor locations. Both in-plant noise and community noise predictions are performed using the ISO prediction method (EEMUA 1985). Equipment noise limits were based on the general project requirement of 82 db(a) at 1 m from equipment casings or surfaces, with the exception of air coolers, where the prescribed limit is 85 db(a) at 1 m underneath the air cooler fan. Noise contour maps were calculated at an elevation of 1.5 m above grade. These maps represent a composite model of the noise emissions from the Gas Treatment Plant Results of Noise Modelling This section summarises the noise emission modelling results for the Revised Proposal with regard to the sensitive receptor locations and compares these to the predicted noise levels for the Approved Development. In summary, although the predicted noise levels from the Revised Proposal at sensitive receptors are predicted to increase in comparison to the Approved Development, this increase is relatively small and noise levels still comply with the assigned levels under the Western Australian Noise Regulations. Noise predictions for the Revised Proposal at the specified sensitive receptor locations are provided in Table 11.4, Figure 11.1 and Figure These predictions do not consider the ambient noise conditions, which in some cases could overpower noise contributions from the Gas Treatment Plant. NOISE EMISSIONS RISKS AND MANGEMENT 238

5 Table 11.4 presents a comparison of the Revised Proposal results to the Approved Development noise study results conducted by KJVG for the Approved Development Gas Treatment Plant. Table 11.4: Predicted Environmental Sound Pressure Levels in db(a) Location Approved Development Predicted Sound Pressure Levels db(a) Revised Proposal Predicted Sound Pressure Levels db(a) Gorgon Administration Area 54 (approx.) 60.6 Gorgon Construction Village Existing Chevron Camp The increase of in predicted sound pressure levels (i.e. between 6 and 8 db(a) on average) is due to several factors: the increase in sound power level of the Gas Treatment Plant due to contributions of the additional LNG train, Acid Gas Removal Units (AGRUs), and CO 2 re-injection compressor the change of assumptions for the ground type over which sound is propagating. It is now assumed that an acoustically hard ground is present for all areas over which sound is propagating, which is in accordance with noise level prediction methodology outlined in EPA Guidance Statement No.8 (EPA 2007a) the small change in temperature and humidity assumptions to align with requirements outlined in EPA Guidance Statement No. 8 (EPA 2007a). NOISE EMISSIONS RISKS AND MANGEMENT 239

6 Figure 11.1: Noise Contours within the Gas Treatment Plant and at Plant Boundary NOISE EMISSIONS RISKS AND MANGEMENT 240

7 Figure 11.2: Noise Levels at Sensitive Receptor Locations [db(a)] NOISE EMISSIONS RISKS AND MANGEMENT 241

8 Additional Sources of Noise During Operations An additional noise emission source during operations will be the wet and dry gas ground flares during a process upset or emergency flaring scenario. A noise modelling study for the ground flare was conducted (separate to the noise modelling undertaken for the Revised Proposal) as part of the engineering design for these systems specifically comparing a ground versus an elevated flare configuration. The study modelled noise emissions for the highest flowrate emergency flaring event (i.e. a propane compressor relief to the dry flare at a flowrate of 582 kg/s). The overall sound power level for the selected ground flare options was 156 db(a) as supplied by the flare vendor. Table 11.5 presents the results of a noise study for noise levels from the ground flare at 1.75 m above ground. Table 11.5: Flare Noise Study Results Sound Pressure Levels in db(a) Distance from Source (metres) > With the present location of the ground flare (on the western side of the Gas Treatment Plant plot plan) the noise levels likely to be experienced at the Gorgon Construction Village/Turnaround Camp and the existing Chevron Camp during plant upset or emergency events are well below 65 db(a). These noise levels may never be experienced as a flaring rate of the magnitude used in the study is considered to be a very unlikely event Discussion of Modelling Results Due to the large separation distance between the Gas Treatment Plant and the sensitive receptor locations at the Gorgon Construction Village/Turnaround Camp, and the existing Chevron Camp, contribution from the Revised Proposal Gas Treatment Plant operations to noise levels at these locations is expected to be minimal and the resultant noise levels will still comply with the noise levels prescribed in the Western Australian Noise Regulations. The levels at the existing Chevron Camp will continue to be dominated by local sources of noise (i.e. air conditioning units). The same is expected to occur at the proposed Gorgon Construction Village/Turnaround Camp which will also have local sources of noise (e.g. air conditioning units, a diesel generator etc.). The Administration Area, although in proximity to the Gas Treatment Plant, will be built and acoustically insulated to ensure the relevant Australian occupational health and safety standards are met Marine Vessel Noise Emissions Movements of marine vessels (e.g. LNG carriers, condensate export tankers, supply vessels and infield vessels, tugs and pilot boats) will increase due to the increase in throughput at the Gas Treatment Plant under the Revised Proposal. This increase in vessel movements will not increase cumulative noise levels, however it will increase the frequency of which the noise source (e.g. marine vessel) is present/operating in the Port of Barrow Island. The noise emissions from the marine vessels will be concentrated NOISE EMISSIONS RISKS AND MANGEMENT 242

9 around the LNG Jetty and the MOF which are approximately 4 and 2 km respectively from the beaches at Town Point. Speed restrictions imposed on LNG carriers and condensate tankers within the Port limits will ensure that noise associated with engines will be kept as low as reasonably practicable. LNG carriers and condensate tankers, escorted by infield vessels (pilot boat and tugs) will also follow a pre-determined safe access corridor to the LNG Jetty, which will therefore result in noise affecting the same marine areas in and out of the Port of Barrow Island. Supply vessel visits will not increase at the same proportion as the increase in LNG carriers and condensate tanker visits and therefore the frequency at which this noise source is present in the Port of Barrow Island should not significantly increase. Support vessels (i.e. pilot boat and tugs) will be purpose built to GJV s specifications and requirements. These specifications include a number of environmental considerations including light spill, noise and air emissions, as well as marine discharges Proposed Management Actions The noise control philosophy for the Revised Proposal [refer to full Noise Study Report (KJVG 2008b) (Appendix D) is aligned with the design basis planned for the Approved Development. This philosophy is reiterated below: All compressor suction/discharge/recycle piping and connected piping are to be insulated with an appropriate acoustic insulation system. Acoustic enclosures limiting noise to 90 db(a) at 1 metre from the equipment surface for gas turbine drives for Mixed Refrigerant Compressors and Propane Compressors are recommended. No enclosures on compressors and expanders for safety and operability reasons. No enclosures on generators themselves for safety and operability reasons. Compressor gas turbine drive and generator gas turbine drive intake/exhaust ducting are to be acoustically insulated. Exhaust silencers are required for gas turbine drives of generators. Use of vibration isolation pads, such as Fabreeka or equivalent, for compressor suction/ discharge pipe supports to reduce the noise radiation from pipe supports. Low noise type air coolers not to exceed sound pressure level of 85 db(a) per fan 1 metre below fan centre. Inlet silencers required for the gas turbines of Mixed Refrigerant and Propane Compressors. Exhaust silencers required for gas turbine drives of Mixed Refrigerant and Propane compressors. Inlet silencers for generator gas turbine drives are required. Noisy control valves, if any, and compressor recycle valves and their downstream piping are to be acoustically insulated. Personnel hearing protection will be mandatory in the designated Restricted Areas in the Gas Treatment Plant, where sound pressure levels exceed 85 db(a). These measures define the best practice approach to noise mitigation for this type of Gas Treatment Plant. NOISE EMISSIONS RISKS AND MANGEMENT 243

10 11.4 Predicted Residual Environmental Risk Noise emissions from the Revised Proposal are not considered to pose any significant new or additional risks to noise sensitive receptors in comparison to the Approved Development. Furthermore, there are no unacceptable cumulative impacts related to noise emissions as a result of the Gorgon gas Development. Based on the modelling completed, increases in noise levels at the Gorgon Construction Village and the existing Chevron Camp are expected to be minimal and well below the noise levels prescribed in the Noise Regulations. The noise design philosophy (developed to be consistent with EIS/ERMP commitments made in relation to the Approved Development) is expected to manage the increase in noise emissions from the Revised Proposal to a level consistent with that considered acceptable and therefore approved for the Approved Development, and to meet the EPA objective on noise emissions (section ). NOISE EMISSIONS RISKS AND MANGEMENT 244