Fortnightly Water Quality Report Ichthys Nearshore Environmental Monitoring Program Weeks 20/21: to 20 January 2013 Weeks 20/21: 7 to 20 January 2013 Prepared for INPEX June 2013
Fortnightly Water Quality Report Ichthys Nearshore Environmental Monitoring Program Document Information Prepared for INPEX Project Name Ichthys Nearshore Environmental Monitoring Program File Reference Reporting Period Weeks 20/21: 7 to 20 January 2013 Date June 2013 Document Control Version Date Author Author Initials Reviewer A 31/01/2013 Chris Beadle CB David van Senden DvS 0 01/02/2013 David van Senden DvS Christopher Holloway CGH B 10/04/2013 Chris Beadle CB David van Senden DvS 1 03/06/2013 Chris Beadle CB David van Senden DvS Reviewer Initials Cardno (NSW/ACT) Pty Ltd Cardno WA Pty Ltd Cardno NT Pty Ltd Level 9, The Forum 11 Harvest Terrace Level 6 93 Mitchell St 203 Pacific Highway West Perth WA 6005 Darwin NT 0800 St Leonards NSW 2065 Telephone: 08 9273 3888 Telephone: 08 8942 8200 Telephone: 02 9496 7700 Facsimile: 08 9486 8664 Facsimile: 08 8942 8211 Facsimile:02 9499 3902 www.cardno.com.au This document is produced by Cardno solely for the benefit and use by the client in accordance with the terms of the engagement for the performance of the Services. Cardno does not and shall not assume any responsibility or liability whatsoever to any third party arising out of any use or reliance by any third party on the content of this document. Prepared for INPEX June 2013 Page ii
1 Summary This fortnightly report covers weeks 20 and 21 of dredging operations for the Ichthys Project and the telemetered water quality data collected as part of the Water Quality and Subtidal Sedimentation Monitoring Program (7 20 January 2013). The fortnightly report provides an assessment of the water quality trigger levels for the fortnight and been based on this period to highlight the spring-neap tidal cycle. This report collates information from 15 different telemetered Water Quality monitoring sites deployed at key locations to assess the turbidity associated with dredging and spoil disposal activities. Duplicate monitoring systems have been deployed at the four reactive sites to provide backup data collection at these critical sites. 1.1 Reporting Period This Fortnightly Water Quality Report summarises dredging activities, wind and tidal conditions and water quality (turbidity) results for the period defined in Table 1-1. Table 1-1 Water Quality Summary Period Period Start Period End Monday 7 January 2013 Sunday 20 January 2013 1.2 Trigger Exceedance Summary Eight wet season seagrass triggers were recorded during this reporting period at Lee Point (Table 1-2). Figures showing Darwin metocean information and all turbidity logging sites for the reporting period are included in Sections 2 and Figure 2-3, respectively. The reported trigger exceedances were attributable to one of the largest spring tidal phases coinciding with strong offshore wind a wave conditions. It is unclear whether these trigger were attributable to dredging and spoil disposal activities. Table 1-2 provides a summary of the trigger exceedances observed during the exceedance period. Table 1-2 Wet Season Trigger Exceedance Summary (7/1/2013 to 20/01/2013) Intensity Frequency Duration Wet Season Coral Triggers >44 NTU >26 NTU > 6 days per 7-day rolling period >26 NTU over 7 consecutive days Channel Island None None None Wet Season Seagrass Triggers >63 NTU >52 NTU > 5 days per 7-day rolling period >52 NTU over 5 consecutive days Woods Inlet None None None Fannie Bay None None None Lee Point Trigger Exceeded on 14 January, then from 18-20 January Trigger Exceeded from13-20 January Trigger Exceeded from 13-20 January Prepared for INPEX Page 1
1.3 Summary of Dredge Operations Table 1-3 provides a summary of the dredge operations undertaken during the reporting period. Table 1-3 Activities Undertaken Volume Material Dredged (Reporting Period) Volume Material Dredged (Cumulative to Date) Summary of Dredge Operations (Data provided by INPEX). The CSD dredge Athena commenced dredging in SP2 (jetty pocket) during the reporting period, pumping dredge spoil into TSHD Queen of the Netherlands and Vox Maxima. Final dredge activities within SP1 were completed during the reporting period with the completion of slope dredging and berth pockets with minor high spot sweeping by the tug boat Oceanus underway to complete SP1 to design. 422,097 m 3 2,999,853 m 3 Prepared for INPEX Page 2
2 Wind and Tidal Conditions Atmospheric conditions at Darwin Airport, sourced from the Bureau of Meteorology (BoM), and the predicted tides at the Port of Darwin are shown in Figure 2-1. The period is characterised by hot summer days and diurnal wind pattern with strong breezes in the afternoon decreasing overnight. From 16 January to 20 January, strong and persistent westerly winds affected Darwin. During the reporting period daily rainfall totalled 20.0 mm on 12 January 2013, 24.4 mm on 13 January 2013, 42.2 mm on 19 January 2013 and 20.0 mm on 20 January 2013. Cumulative rainfall for January 2013 (up to 20 January) was 168.8 mm, compared to the January monthly average of 426.6 mm 1. This indicates that this summer period has been a particularly dry one. The total number of rain days exceeding 1 mm was 12 days compared to the January average of 19.1 days 1. The minimum tidal range for the reporting period was 1.3 m on 19 January 2013, with a maximum of 7.5 m occurring on 13 January 2013 (Figure 2-2). Figure 2-1 Darwin Airport (data source Bureau of Meteorology) air temperature and atmospheric pressure, wind speed and direction and half hourly rainfall (daily totals presented numerically on top of plot) for the fortnight to 20 January 2013. 1 BoM Climate Statistics for Australian Locations (www.bom.gov.au/climate/averages/tables/cw_014015.shtml) Prepared for INPEX Page 3
Figure 2-2 Darwin predicted tide for the fortnight to 20 January 2013, based on harmonic constituents for Darwin defined by the Australian Hydrographic Service (http://www.hydro.gov.au/). Figure 2-3 Darwin Significant wave height measured at the IMOS buoy located offshore Darwin for 15-22 January 2013. Prepared for INPEX Page 4
3 Turbidity Fortnightly turbidity time series for the reporting period are shown in the figures below for all monitoring sites (Figure 3-1). Turbidity data is recorded half hourly and daily averages calculated from the available readings (48 records per day) between 0000 and 2359 on each day. The data has been subjected to an automated three step QA/QC procedure including; removal of negative values, removal of flat line sections and removal of outliers by a de-spiking algorithm (Wong et al. 2012). In Figures 3.2 to 3.16, the raw (half hourly) turbidity data are presented as a grey line and the daily average by the solid black line. The daily average turbidity is shown and the number of data points used in the calculation of the daily average is indicated at the top of the plot. Values less than 48 are due to QA/QC. The times of instrument servicing (should they fall within the fortnight) are highlighted by a green square ( Service ) symbol and missing data by red squares ( Suspect ) in Figures 3.2 to 3.16 in accordance with the International Oceanographic data and Information Exchange (IODE) procedure. Wet season trigger values for the trigger sites; Channel Island, Woods Inlet, Fannie Bay and Lee Point are shown in Figures 3.2 to 3.5. Table 3-1 provides summary notes on the information presented in the figures below. Notes Table 3-1 Summary notes on turbidity plots for the period 7 to 20 January 2013. The maximum tidal range for the reporting period occurred on 19 January 2013 (7.5 m). Turbidity was generally greater during spring tides across the majority of sites. From 10 January 2013 to 20 January 2013 the outer harbour sites (including Gunn Point, Lee Point, Casuarina Beach, East Point, Fannie Bay, Mandorah, Charles Point 1 and Charles Point 2 all experienced elevated turbidity. During this time Lee Point incurred Intensity, Frequency and Duration exceedances (see Table 1.2). Daily average turbidity across the study area (Figure 3.2-3.16) shows marked differences between the Outer Harbour and Inner Harbour sites during the reporting period. During this period the offshore zone was affected by significant oceanic influences (waves and winds). Figure 2.3 indicates that there was a considerable increase in significant wave height from 4 to 20 January. (from the AIMS IMOS buoy at the outer end of the shipping channel). Significant rainfall on the 19th and 20th of January, 2013 (48 mm and 20mm respectively at Darwin airport, Figure 2.1) and associated run-off from the catchments, particularly the large Shoal Bay catchment, most likely contributed additional suspended load to the coastal zone. Increasing seastate in the outer harbour coastal waters and rainfall appear to have contributed to the increase in turbidity within the coastal zone sites of the outer harbour. The turbidity at the Inner Harbour sites is generally low as expected during the neap tides with the exception of the Upper East Arm site where rain-induced runoff contributes to the turbidity at this upper estuarine site. Upper East Arm data quality deteriorated on 14 January 2013 and resumed transmittal on 17 January 2013. The data telemetry transmission interval at Gunn Point was inadvertently set to two hourly (12 records per day) during maintenance of the logger, however the bottom logger is recording at 15 minute intervals. This data will be included in the Bimonthly Water Quality Report. Gunn Point ceased transmitting on 20 January 2013. Mandorah data quality deteriorated on 13 January 2013 and resumed transmittal on 20 January 2013. North East Wickham data quality deteriorated on 13 January 2013 and resumed transmittal on 20 January 2013. As part of INPEX contingency planning, duplicate loggers have been deployed at the four reactive sites. The duplicate loggers minimise the risk of down time in relation to reporting on turbidity levels. Having instrumentation malfunction is not unexpected, especially in the Darwin Harbour environment and the extensive logger network provides redundancy to the water quality monitoring program. Prepared for INPEX Page 5
Figure 3-1 Water Quality Monitoring Sites Prepared for INPEX Page 6
Figure 3-2 Channel Island (coral impact site) Prepared for INPEX Page 7
Figure 3-3 Woods Inlet (seagrass impact site) Prepared for INPEX Page 8
Figure 3-4 Fannie Bay (seagrass impact site) Prepared for INPEX Page 9
Figure 3-5 Lee Point (seagrass impact site) Prepared for INPEX Page 10
Figure 3-6 North East Wickham Point (coral impact site, no triggers) Prepared for INPEX Page 11
Figure 3-7 Weed Reef 1 (coral control site) Prepared for INPEX Page 12
Figure 3-8 Weed Reef 2 (coral control site) Prepared for INPEX Page 13
Figure 3-9 East Point (seagrass contingency site) Prepared for INPEX Page 14
Figure 3-10 Casuarina Beach (seagrass contingency site) Prepared for INPEX Page 15
Figure 3-11 Gunn Point (spoil disposal ground impact site) Prepared for INPEX Page 16
Figure 3-12 Charles Point 1 (seagrass control site) Prepared for INPEX Page 17
Figure 3-13 Charles Point 2 (seagrass control site and coral contingency control site) Prepared for INPEX Page 18
Figure 3-14 Mandorah (coral contingency control site) Prepared for INPEX Page 19
Figure 3-15 South Shell Island (coral impact site, no triggers) Prepared for INPEX Page 20
Figure 3-16 Upper East Arm (harbour dredging control site) Prepared for INPEX Page 21