Blacktip Project Draft EIS Supplement 10. Draft EIS Section 7 Existing Marine Environment 10.1 Section 7.2 Physical Environment 10.1.1 Section 7.2.3 Bathymetry and Seabed Features OEH 5: The detailed path of the pipeline is still unknown but undulations are known to occur along the seabed. Given this, evaluation of pipe construction requirements and the effect these may have on the seabed should be presented. Include discussion of the area of seabed likely to be impacted by works and the measures that will be employed to minimise this disturbance. OEH 5: Evaluation of pipeline construction requirements and the effect these may have on the seabed should be presented. The detailed design of the pipeline which will commence upon or just after project sanction will look to further optimise the pipeline route to further reduce adverse pipeline interaction with significant seabed undulations. Adverse pipeline interactions with significant seabed undulations typically result in the pipeline free spanning in these areas. Route optimisation involves localised adjustments to the route to reduce the amount of free spanning. In some areas it will not be possible to reduce free span lengths to below acceptable and allowable operating values and in these areas, it will be necessary to correct or support these free spans. The fact that the pipeline will be trenched along the majority of the route is a natural method of correcting for these free spans. The area of the seabed likely to be affected by the works is very minor. Only the seabed directly under the pipeline where the pipeline is not trenched will be affected (0.5 m width). In areas where the pipeline is trenched then only the seabed immediately adjacent to pipeline will be affected. The total width is dependent on the final trenching methodology selected but will typically be in the order of 10–50 m. 10.1.2 Section 7.2.4 Oceanography and Water Quality NTG 51: Information on water quality nearshore is available from the work undertaken by LeProvost Dames and Moore for Teikoku Oil (Bonaparte Gulf) Co Ltd in 1994. This information includes turbidity, water temperature and salinity. Records of current speed and direction have relevance to modelling of discharges in the nearshore environment. NTG 51: Information on water quality nearshore is available from the work undertaken by LeProvost Dames and Moore for Teikoku Oil (Bonaparte Gulf) Co Ltd in 1994. The Proponent conducted an extensive current measurement programme in 2004 with the deployment of seven current meters along the pipeline route and at the platform location. These were deployed for approximately six weeks and the data was analysed and a detailed metocean report (Metocean Engineers 2004) was prepared. The site-specific results of that report are being used as the basis for environmental loading for the platform and pipeline design. This data is far DRIMS Ref: 1911698 March 04 Supplement PAGE 139 Supplement Blacktip Project Draft EIS more relevant to the Blacktip Project than the data presented in LDM (1994). However, in most cases the LDM (1994) data is consistent with that recorded by the Proponent in 2004. LDM (1994) provide some water temperature, secchi depth and salinity records, collected in November 1993 mostly around the lower Joseph Bonaparte Gulf. Water temperature ranged from 29.5–30.9°C, marginally higher than that recorded in May 2004 (28–29°C) during the marine environmental survey. Salinity in November 1993 ranged from 36 to 36.9 ppt, compared to 33 to nearly 35 ppt in May 2004. This minor difference is probably attributable to some limited freshwater input still occurring in May 2004 following an extended wet season. The secchi depth records recorded by LDM (1994) are not directly comparable to the turbidity measures collected in May 2004 during the marine environmental survey. However, both confirm that waters of the Joseph Bonaparte Gulf are very turbid. Environmental Parameters Governing Design Criteria - Internal waves NTG 118: The Western Australian branch of the Global Ocean Observing System published a draft paper entitled ‘Timor Sea Focus Area and PIT’ in 28 August 2002. The focus of the paper was a ‘so called high frequency current phenomena’ (pp 1 WAGOOS 2002). The interest for the offshore hydrocarbon industry was the impact that these currents may have on engineering design. Has the proponent considered the presence of high frequency currents as a criterion for detailed design engineering studies to be undertaken for the offshore component of the Blacktip Project? In consideration of the strong tidal influence on the current regime within Joseph Bonaparte Gulf, what further environmental investigations will the proponent conduct in relation to the presence of high frequency currents at the proposed location? It is indicated in that Figure 2 of the WAGOOS 2002 draft paper that the Blacktip Project area is within or adjacent the southern boundary of the focus area for the Timor Sea. NTG 118a: Have the presence of high frequency currents been considered as a criterion for detailed design engineering studies? NTG 118b: What further investigations will be conducted in relation to high frequency currents at the proposed location? The paper referred to was co-authored by a Woodside employee, Mr S Stroud, who was also involved in the development of the metocean criteria that has been and will continue to be adopted for the Blacktip Project. Mr Stroud has confirmed that the draft paper has no relevance to the Blacktip Project, and internal waves are not a problem for this project. With the current measurements the Proponent performed, we specifically looked for internal waves out at the platform end of the pipeline and did not identify any. The Proponent conducted an extensive current measurement campaign in 2004 with the deployment of seven current meters along the pipeline route and at the platform location. These gathered data for around six weeks and the data was analysed and a detailed metocean report (Metocean Engineers 2004) was developed. The site-specific results of that report are being used as the basis for environmental loading for the wellhead platform and pipeline design. March 05 DRIMS Ref: 1911698 PAGE 140 Supplement Blacktip Project Draft EIS Supplement No further environmental investigations are currently planned as the campaign conducted in 2004 gathered sufficient data to allow the Proponent to progress with a pipeline and platform design that will comply with the applicable codes and standards. Currently the Proponent is conducting further work in refining the storm wave model to better define storm wave conditions in the nearshore area. These refinements will then be used in detailed design of the pipeline. 10.2 Section 7.3 Ecological Environment Biota – Condensate Mooring OEH 73a: Further, the Supplement should detail the type of biota present at the condensate mooring (Section 11.3 [S7.3?]). OEH 73a: The Supplement should detail the type of biota present at the condensate mooring The biota at the mooring location is typical of the nearshore soft sedimentary habitats described in Section 7.3.2, with species distributions as described in Section 7.3.4–7.3.7, Volume 1 of the Draft EIS. As part of the Blacktip offshore environmental survey (Appendix B, Volume 2 of the Draft EIS), water quality parameters were measured and benthic grab samples were collected at the condensate export mooring location (three samples) and in and around the nearby PW discharge location (12 samples). Water turbidity was extremely high even in the dry season, peaking near 40 NTU and generally above 20 NTU, indicating that benthic light levels will be very low and very unlikely to support photosynthetic flora. It is difficult to make specific statements on light requirements, turbidity levels and the distribution of seagrass and corals as this seems to be species and location specific. However, turbidity levels in the Joseph Bonaparte Gulf are extremely high in comparison to other Australian locations. For example, turbidity data collected from Weipa, Queensland in the Gulf of Carpentaria observed dry season turbidity levels typically between 5–12 NTU and wet season levels typically between 30–40 NTU (WBM 2003). Seagrass in Weipa is limited to shallow water (< 6 m) and stony corals do not occur. The Blacktip condensate export mooring, by comparison, is located in 17 m of water and subjected to considerably higher turbidity levels. Given the depth of water at the Blacktip condensate export mooring (17 m) and high turbidity levels, the condensate export mooring area is unlikely to support photosynthetic flora such as seagrass and macroalgae. The grab samples collected at the Blacktip condensate export mooring site revealed that the sediments comprised very coarse sands that supported a higher abundance and species richness of infauna than sites sampled further offshore and further inshore: The composition of the infaunal community is unusual as continental shelf infauna is generally dominated by polychaete worms. However, nearly three times as many crustaceans were collected as polychaetes; bryozoans and hydroids were the next most abundant group after the crustaceans; and, nearly as many molluscs and echinoderms were collected as polychaetes (Volume 2, Appendix B of the Draft EIS). DRIMS Ref: 1911698 March 05 Supplement PAGE 141 Supplement Blacktip Project Draft EIS No corals, macroalgae or seagrasses were collected in the grab samples. A list of the infauna found in and around the condensate export mooring is provided in Appendix B, Volume 2 and summarised in Table 9. Table 9 Biota Found in and around the Condensate Export Mooring Taxa Abundance (as a % of total) Crustaceans 36 Decapods 24 Amphipods 6 Bryozoans 19 Echinoderms 14 Ophiroids 12 Hydrozoans 12 Annelids 10 Molluscs 3 Average abundance per 90 x 100 mm core 24 individuals Average number of species per 90 x 100 mm core 10 species 10.2.1 Section 7.3.1 Regional Setting NTG 52: The statement ‘high turbidity and river flows appear to limit epibenthic development’ does not hold true in Darwin Harbour, which in parts has a very diverse epibenthic assemblages and it is also likely to be untrue for the Joseph Bonaparte Gulf.