09-02 offshore huc 9 3 eng final oct 04

Azeri, Chirag & Gunashli Full Field Development Phase 3 Environmental & Socio-economic Impact Assessment Final Report

9.3 Offshore Facilities Offshore Installation, Hook-Up and Commissioning

Once constructed, the following offshore facilities will be installed at the Phase 3 offshore locations:

12 slot drilling template; •

•

•

•

•

DUQ and PCWU jackets;

DUQ and PCWU topsides;

The platforms bridge-link; and

Two subsea manifolds and associated facilities. Installation of each offshore facility will be carried out separately and at different times in the Phase 3 development schedule as detailed in Chapter 5, Figure 5.3. Whilst the level and type of activity varies depending upon the facility being installed, there are many similarities between the different operations and the subsequent potential for environmental impacts. Therefore one impact assessment has been conducted for all installation activities. There will be considerable vessel activity in the Phase 3 offshore location during the installation of each facility and for the hook-up and commissioning (HUC) phase of the programmes. In addition to the vessel movements required to transfer the individual facilities to site, some support vessels will be located on site to support the installation and HUC activities throughout the programme whilst others will supply equipment and materials and travel between the shore and the offshore location. The results of the impact assessments for these activities are described below. 9.3.1 Environmental Impacts The results of the environmental impact assessment are summarised in Table 9.4. All of the installation and subsequent HUC activities will take place in a relatively small area of the Caspian Sea at the Phase 3 offshore location and over a relatively short period of time (refer to Section 5 Project Description). As such the residual environmental impacts associated with these activities, following their mitigation, are ranked low and are not predicted to be significant. As discussed in Section 9.2, contractors will be required to implement specific management measures intended to minimise/mitigate environmental impact as part of their contract conditions. Details of the key mitigation measures considered in the impact assessment are summarised in the following subsections together with procedures/standards/comments specific to some of the proposed activities.

31648-046 ACG Phase 3 ESIA. Chapter 9 9/17 October 2004


Table 9.4 Summary of Environmental Impact Assessment for Offshore Facility Installation, Hook-Up and Commissioning (HUC)

ID Activity Environmental Aspects Environmental Mitigation

Cum

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Con

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Ent

al Im

pact

nv

ironm

eSi

gnifi

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Justification / Comments Residual Environmental Issues to be Addressed

B Offshore Installation, Facility Hook-up and Commissioning of Offshore Facilities1

B1 Vessel operationsincluding facility tow out, transportation and positioning2

Atmospheric emissions, noise, wastes, effluent discharges, physical seabed disturbance.

Bilge water, certified sewage treatment system to sewage water standards;

All solid and hazardous wastes shipped to shore;

Waste management planning and implementation.

Anchor procedure

▲ L

Localised minor impacts that are rapidly dispersed.

Issue of waste management raised during consultation.

Concern over disturbance of the benthic habitat raised during consultation.

Waste treatment & disposal

Refer to Section 10.2.

Benthic sensitivity

Refer to Section 9.3.1.4.

B2

Installation of templateand jackets (including piling)

As B1 and facility physical presence. As B1;

Short duration.

L

Disturbance over a localised area and over a short time period.

Fish, seals and birds will adopt temporary avoidance behaviour due to noise but will return to the area.


As B1

B3 Grouting of jackets to seafloor

Physical seabed disturbance, toxicity. Minimise grout losses by accurate estimation of grout;

ROV post installation survey. LDisturbance over a localised area, low toxicity


Benthic sensitivity


B4 Floatover and installation of topsides and bridge link

As B1 and facility physical presence. As B1 and B2 L

As B1 and B2 As B1 and B2

B5 Hydrotesting of bridge link

Liquid waste and effluent. As B1.

Hydrotest water potable water supplied from onshore and no chemical additives used before discharge to sea.

L Discharge of freshwater will rapidly disperse and salinity levels will not be significantly affected.


1 Offshore facilities includes: Jackets; topsides; drilling templates, subsea manifolds and facilities; bridge link 2 There will be eight tow out/transportation activities – template x 1, jacket x 2, topsides x 2, bridge link x 1, subsea manifolds and associated facilities (e.g. umbilicals and flowlines) x 2, – each of these activities will occur at a different time



ID Activity Environmental Aspects Environmental Mitigation

Cum

ulat

ive

Con

trib

utio

n

Envi

ronm

enta

l Im

pact

Si

gnifi

canc

e

Justification / Comments Residual Environmental Issues to be Addressed

B7 Installation and testing of subsea facilities

Liquid waste and effluent.

Physical presence.

As B1;

No trenching for installation of subsea facilities.

Caspian specific toxicity test will be used to confirm the OCNS ranking of E (lowest toxicity) for the hydraulic fluid.

L

Disturbance over a localised area and over a short time period.


As B1

B8 Power Generation (black start)

Atmospheric emissions. Short duration for diesel fired power generation. ▲ L Low contribution to overall air emissions from the project.

None.

B9 Leak/integrity testing Atmospheric emissions.

Liquid wastes.

Maximise onshore commissioning

Inert gas decanted into other system and re-used where practical

Hydrotesting using potable water with no chemical additives

Controlled venting in open atmosphere.

▲ L

Only during commissioning phase, small volumes. None.

B10 Fire system tests Liquid wastes. Chemical management to select low toxicity and biodegradable foam. L No residual impacts as just seawater. None.

B11 Helicopter operations Atmospheric emissions, noise.

Regular maintenance;

Defined flight path, scheduling. L Low contribution to overall air emissions from the

project. None.


Azeri, Chirag & Gunashli Full Field Development Phase 3 Environmental & Socio-economic Impact Assessment Final Report 9.3.1.1 Vessel Atmospheric Emissions Vessel activity at the Phase 3 offshore location and between the site and the shore will result in increased atmospheric emissions from vessel engine and power generation exhausts and liquid waste discharges to sea such as sewage waters and machinery space (bilge) waters. These emissions and discharges will occur over a relatively short time period and will rapidly disperse after release, resulting in a short-lived low impact to the offshore atmosphere and sea respectively, within a very localised area. Vessel air emissions will be small and emitted species concentrations will be low and will be minimised through regular servicing and maintenance of vessel engines and generators. The total volumes that will be released from all vessel activity for the entire Phase 3 offshore installation and HUC programme have been estimated based on predicted diesel consumption rates and the duration of the activities. Table 9.5 Estimated Emissions to the Atmosphere during Offshore Facility

Installation and HUC (tonnes)

CO2 CO NOX SOX1 CH4 NMVOC

DUQ Installation & HUC 8,131 20 150 20 1 6

PCWU Installation& HUC 5,914 15 109 15 0.5 4 Export Pipeline Installation, Tie-in and

Commissioning 14,880 37 274 30 1.4 11

Subsea System Inst. & HUC (including water injection lines) 19,142 48 353 48 2 14

Sub-Totals (Installation & HUC): 48,067 120 886 113 4.9 35 PM – Particulate Matter NMVOC – Non-Methane Volatile Organic Compounds 1Based on Sulphur content in diesel of 0.8% (marine diesel) 9.3.1.2 Sewage and Drainage for Vessels, Barges, etc. In order to minimise environmental impacts from vessel activity related to the project, a number of controls in relation to liquid discharges from vessels will be put in place. Sewage water disposal will be conducted in adherence with the sewage water standards for the project and will be treated in a US Coast Guard certified or equivalent Marine Sanitation Device (MSD) if discharged to sea. The effluent stream will be monitored for the presence of floating solids on the sea surface. Sewage waters generated on board vessels that do not have a US Coast Guard certified MSD fitted will be off-loaded and transferred to shore for disposal at a municipal sewage treatment works. All sewage sludges will be pumped out of the vessels and off-loaded for transfer to shore for disposal. Table 9.6 presents the estimated total volume of sewage that will be discharged based on the assumption that all vessels operating offshore will have MSD fitted and hence will discharge to sea. It is assumed that each person will produce 0.22 m3 grey water and 0.1 m3 black water per day. In total, an estimated 5,392 m3 of grey water and 3,429 m3 of black water will be discharged to sea during installation of the platform facilities and subsea system.

31648-046 ACG Phase 3 ESIA Chapter 9 9/20 October 2004

Azeri, Chirag & Gunashli Full Field Development Phase 3 Environmental & Socio-economic Impact Assessment Final Report Table 9.6 Estimated Volume of Sewage During Offshore Facility Installation and HUC

(tonnes)

Activity Vessels Number

Of Vessels

POB Duration (Days)

Grey Water (m3)

Black Water (m3)

Tugs 3 14 77 712 323 DUQ Jacket/Topsides Installation Barge 1 14 77 237 108

Tugs 3 14 56 517 235 PCWU Jacket/Topsides Installation Barge 1 14 56 173 78

Lay-barge 1 210 50 2,310 1,050 Anchor handling vessel 4 15 50 660 300 Pipe-haul barges & tugs 2 14 25 154 70 Diving Support vessel 1 26 35 200 91 Survey vessel 1 26 30 172 78

Subsea System Installation

Dada Gorgud 1 26 45 257 117 TOTAL 5,392 3,429 Sump oils pumped out of the vessel bilge will be contained and treated on board to reduce the oil content to the PSA standard of no visible sheen on disposal at sea. Effluents will be monitored for their oil-in-water content. Oily bilge waters from vessels that do not have oily water treatment facilities on board will be off-loaded and transferred to shore for disposal. 9.3.1.3 Solids and Liquid Wastes Other solid and liquid wastes will be transported to shore for disposal in accordance with the AzBU waste management plan, excluding food waste, which will be macerated and discharged overboard. Food waste discharges will slightly increase the organic matter content in close vicinity to the discharge but this will be rapidly diluted and dispersed and impacts will not be significant. 9.3.1.4 Seabed Disturbance Installation activities will result in a direct disturbance to the seabed at the offshore location. Seabed disturbance will be greatest during installation and securing in place (i.e. piling) of each jacket. The installation of the drilling template, the water injection lines, umbilicals, and the two subsea water injection manifolds will also cause seabed disturbance. The installation vessels for the water injection lines will be held in place by anchors. During the installation of the umbilicals, the DSV vessel will use dynamic positioning and so seabed disturbance will be reduced. The interaction with the seabed will result in the localised destruction of benthos in the area occupied by the facilities, and the smothering of benthic communities in the immediate vicinity of the facilities, due to mobilisation and resettlement of seabed sediments. The seabed at the Phase 3 platform location consists of very fine particles and sand of medium particle size. Benthic studies have indicated species diversity typical to this region of the Caspian Sea and no areas of seabed sensitivity have been identified. As such the residual impact associated with installation of the offshore activities has been predicted to be low. 9.3.1.5 Grouting Once the piles have been installed the jacket legs will be further secured into position by grouting. The grouting process will leave some excess grout on the seabed surface. In order to minimise any toxic effects related to this activity the cement grouting of offshore pilings will use Portland Cement prepared to BS12 Type 52.5 with seawater. No chemical additives will be used thereby minimising the toxicity to the marine environment. The grout requirements will furthermore be carefully calculated to minimise unnecessary over-use. There are three primary possibilities for environmental interaction following discharge and these are:

Seabed smothering; •



Alkalinity effects on the seawater in contact with the cement; and •

• Chromium leaching from grouting cement into surrounding seawater. The amount of cement is carefully calculated using the lessons learnt during ACG Phase 1 and Phase 2 and consequently, this will be reduced to as small an areas as possible, which will be restricted to within the footprint of the platform. This will result in smothering of the underlying benthic communities. This is not therefore considered to be a significant impact. During the cement curing process, there may be an effect on the alkalinity of the seawater in immediate contact with the cement. Raised alkalinity may affect a small quantity of plankton in the immediate vicinity, but plankton will not be abundant at the depth at which discharge will take place. Testing has shown that alkalinity effects will be limited to part of the period between initial setting time and final setting. This may range from between 1 and 10 hours, although effects are not predicted after initial setting (1 hour). A small volume of water may be temporarily affected during this time, but the effect will be limited as alkaline components leach out of the cement and disperse in the surrounding water. As discussed in the environmental description (Section 6) fish occur at all depths in the Caspian and may be expected to be at this depth in the Contract Areas. However, any fish will detect the raised alkalinity and will avoid the immediate vicinity. No significant environmental impact is predicted from these localised effects of alkalinity. Chromium (Cr III and VI) is an acknowledged handling hazard of grouting cement, although there is no evidence that establishes the aquatic ecological hazard of chromium in cement. In addition, it is unlikely that a significant amount of Cr would leach into the surrounding seawater. If leaching occurred, this would be limited to the surface of the cement. A worst-case assumption would be for leaching to occur from the surface 2cm of the cement during the initial setting period, and this would represent a maximum of 5% of the total amount of Cr that may be present (approximately 24g of Cr VI and 360g of Cr III). Based on dilution rates, if these quantities were released, it would require volumes of 1,600m3 and 24,000m3 of seawater to dilute them to Environmental Quality Standard (EQS) concentrations. Thus, water quality would not be significantly affected at a distance of more than 15 m. In reality, since the concrete will form a localised layer on the seabed, the distance within which water quality would be affected will be considerably less. Leaching rates would also decline rapidly during the setting process. However, these worst-case assumptions indicate that the potential zone of impact is very small, and that Cr concentrations would be well below the safe threshold very close to the location of use. 9.3.1.6 Noise The increased vessel activity during these activities and the installation activities themselves will result in an increase in underwater noise. Seals and fish in the Caspian are accustomed to the noise generated from passing vessels and may exhibit avoidance behaviour initially but would be expected to return to their preferred location as they become accustomed to the disturbance. The most significant noise source during offshore facility installation would be the piling of the jackets into place. A total of 12 piles will be used to secure each jacket and the pile driver normally operates at up to 40 “blows” per minute and at its source, can produce noise emissions up to 206 dB (BP, 2001). Overall impacts resulting from these noise emissions would last for between seven and 10 days for each jacket installation programme and are hence considered to be short-lived. It is expected that fish and marine animals would initially move away from the area during this time, returning once the piling activities were complete. The overall noise impacts are therefore considered to be low with no residual effects expected. 9.3.1.7 Hydrotesting A small amount of equipment will require hydrotesting offshore, such as pipework on the bridge link between the two platforms. This will be carried out using potable water shipped


Azeri, Chirag & Gunashli Full Field Development Phase 3 Environmental & Socio-economic Impact Assessment Final Report from shore. Chemical additives will not be used and the water will be discharged to the sea following the hydrotest. As only small quantities of fresh water will be discharged at a controlled rate, it is not considered a significant environmental impact.



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09-02 offshore huc 9 3 eng final oct 04

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