Fortnightly Water Quality Report

Transcription

1 0 Fortnightly Water Quality Report Ichthys Nearshore Environmental Monitoring Program Weeks 79/80: 24 February 2014 to March 2014 Weeks 79/80: 24 February 2014 to 9 March 2014 Prepared for INPEX October 2014

2 Document Information Prepared for INPEX Project Name File Reference L384-AW-REP-10179_0_49_Water Quality Fortnightly Report Weeks 79_80.docm Job Reference Weeks 79/80: 24 February 2014 to 9 March 2014 Date October 2014 Contact Information Cardno (NSW/ACT) Pty Ltd Cardno (WA) Pty Ltd Cardno (NT) Pty Ltd Level 9, The Forum 11 Harvest Terrace Level 6, 93 Mitchell Street 203 Pacific Highway West Perth WA 6005 Darwin NT 0800 St Leonards NSW 2065 Telephone: Telephone: Telephone: Facsimile: Facsimile: Facsimile: International: International: International: Document Control Version Date Author Author Initials Reviewer Reviewer Initials A 19/03/2014 Chris Beadle CB Isabel Jimenez IJ 0 20/03/2014 Chris Beadle CB Isabel Jimenez Christopher Holloway IJ CGH 1 15/10/2014 Chris Beadle CB Christopher Holloway CGH 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 Cardno Page ii

3 Table of Contents 1 Summary Reporting Period Trigger Exceedance Summary Summary of Dredge Operations 2 2 Wind, Rainfall and Tidal Conditions 3 3 Turbidity 5 Tables Table 1-1 Water Quality summary period 1 Table 1-2 Level 1 wet season trigger exceedance summary (24 February 2014 to 9 March 2014) 2 Table 1-3 Summary of East Arm Dredge Operations (data provided by INPEX) 2 Table 3-1 Summary notes on turbidity plots for the period 24 February 2014 to 9 March Figures 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 9 March Darwin predicted tide for the fortnight to 9 March 2014, based on harmonic constituents for Darwin defined by the Australian Hydrographic Service ( 4 BoM AUSWAVE Model significant wave height the for output location 11 km north-north-east of Charles Point for the fortnight to 9 March Water Quality monitoring sites 7 Channel Island (reactive coral site) 8 Weed Reef 1 (reactive coral site) 9 Weed Reef 2 (reactive coral site) 10 Fannie Bay (reactive seagrass site) 11 Fannie Bay 2 (contingency reactive seagrass site) 12 Lee Point (reactive seagrass site) 13 Lee Point 2 (contingency reactive seagrass site) 14 Woods Inlet (reactive seagrass site) 15 East Point (surrogate seagrass reactive site from 4 March 2014 to 9 March 2014) 16 Casuarina Beach (seagrass site) 17 Charles Point 2 (seagrass and coral site) 18 Mandorah (coral site) 19 Northeast Wickham Point (coral site) 20 South Shell Island (coral site) 21 Spoil Ground (spoil ground disposal site) 22 Upper East Arm 1 (harbour dredging site) 23 Prepared for INPEX Cardno Page iii

4 1 Summary This fortnightly report presents telemetered water quality data collected as part of the Ichthys Water Quality and Subtidal Sedimentation Monitoring Program during weeks 79 and 80 (24 February 2014 to 9 March 2014) since the commencement of dredging operations. The fortnightly report provides an assessment of the water quality trigger levels for the fortnight and has been based on this period to highlight the springneap tidal cycle. This report collates information from 14 different telemetered Water Quality monitoring sites selected to assess the turbidity associated with dredging and spoil disposal activities. Duplicate monitoring systems have been deployed at four of the reactive monitoring locations to provide backup data collection at these critical sites. 1.1 Reporting Period This summarises dredging activities, metocean (wind, wave, rainfall and tidal) conditions and water quality (turbidity) results for the period defined in Table 1-1. Table 1-1 Period Start Water Quality summary period Period End Monday, 24 February 2014 Sunday, 9 March Trigger Exceedance Summary During this reporting period, five Level 1 wet season Frequency triggers were exceeded at Channel Island on 3 March 2014 to 6 March 2014 (Table 1-2 and Figure 3-2). The reported trigger exceedances occurred during a large spring tidal phase, of which the daily average tide range on 3 March 2014 (6.8 m) is predicted to be the second largest daily average tide range of 2014 (see Section 2) and the largest daily average tidal range since 29 September 2011 (6.9 m). Furthermore, the magnitude, timing and duration of similar active forcing conditions (tide, waves, wind and rainfall) prior to the exceedance had not been observed since the 2010 baseline dataset, which also recorded elevated turbidity during similar spring tidal conditions. As such, the INPEX Exceedance Attributability and Implementation Report primarily attributed these trigger exceedances to natural causes. From 4 March 2014 to 9 March 2014, data were not available from the Fannie Bay primary logger (due to cable connection issues) or contingency logger (due to loss of transmission). Consequently, during this period East Point was adopted as a surrogate reactive seagrass water quality monitoring site in the absence of functioning telemetry of data from water quality loggers at Fannie Bay. Surrogate threshold conditions at East Point to indicate a potential Level 1 wet season intensity trigger exceedance at Fannie Bay were developed based on correlation analyses of daily-averaged turbidity between the sites during periods of moderate to high wave energy. These surrogate threshold conditions were: predicted offshore significant wave heights exceeding 0.5 m, and daily-averaged turbidity measured at East Point exceeding 52 NTU. No surrogate exceedances were recorded at East Point during the reporting period (Table 1-2). Data retrieved from the Fannie Bay contingency logger over the period of transmission loss also indicated no exceedance of the Level 1 wet season triggers. No exceedances of the wet season trigger levels were recorded at Lee Point, Fannie Bay, Weed Reef 1, Weed Reef 2 or Woods Inlet during this reporting period. Figures showing Darwin metocean information and all turbidity logging sites for the reporting period are included in Sections 2 and 3, respectively. Table 1-2 provides a summary of the trigger exceedances observed during the reporting period. Prepared for INPEX Cardno Page 1

5 Table 1-3 Level 1 wet season trigger exceedance summary (24 February 2014 to 9 March 2014) Intensity Frequency Duration Wet Season Coral Triggers for Channel Island >44 NTU >26 NTU > 3 days per 7-day rolling period >26 NTU over 7 consecutive days Channel Island 1 3 to 5 March 5 to 6 March 2014 None (n=3) (n=2) Channel Island 2* 3 to 5 March 5 to 6 March 2014 None (contingency logger) (n=3) (n=2) Wet Season Coral Triggers for Weed Reef >65 NTU >46 NTU > 3 days per 7-day rolling period >46 NTU over 6 consecutive days Weed Reef 1 None None None Weed Reef 2 None None None Wet Season Seagrass Triggers >63 NTU >52 NTU > 5 days per 7-day rolling period >52 NTU over 5 consecutive days Fannie Bay None None None Lee Point None None None Woods Inlet None None None Wet Season Seagrass Triggers >52 NTU East Point None (Fannie Bay surrogate) *Trigger exceedance summaries for contingency loggers are provided for information only. 1.3 Summary of Dredge Operations East Arm dredging progress as of 9 March 2014 is approximately 73% complete. Table 1-3 provides a summary of East Arm dredge operations undertaken during the reporting period. Backhoe dredging for the Gas Export Pipeline (GEP) commenced on the 6 March 2014 along the trunkline off Mandorah between Kilometre Post (KP) 861 and 863. Table 1-4 Summary of East Arm Dredge Operations (data provided by INPEX) East Arm Activities Undertaken Volume Material Dredged (Reporting Period) The Cutter Suction Dredger (CSD) Athena continued dredging in SP3 (Turning Basin) throughout the reporting period, loading Trailer Suction Hopper Dredgers (TSHDs) Vox Maxima and Queen of the Netherlands. The TSHD Rotterdam and at times the Vox Maxima conducted direct trailer works in SP4 (Approach Channel) during the reporting period. ~612,400 m 3 Prepared for INPEX Cardno Page 2

6 2 Wind, Rainfall and Tidal Conditions Atmospheric conditions at Darwin Airport, sourced from the Bureau of Meteorology (BoM), are presented in Figure 2-1 and the predicted tides at the Port of Darwin are shown in Figure 2-2. The reporting period was characterised by moderate (in the range of 15 km/hr to 30 km/hr) westerly winds from 24 February 2014 to 1 March 2014, with gusts up to 40 km/hr. From 2 March 2014 to 9 March 2014, wind speeds were in the range of 5 to 25 km/hr, which were initially from the south-east but then shifted to north-westerlies around 7 March Some notable rainfall events occurred during the reporting period, with 13.4 mm, 16.2 mm, and 15.4 mm of rainfall recorded on 28 February 2014, 7 March 2014 and 8 March 2014, respectively. Cumulative rainfall from 1 March 2014 to 9 March 2014 was 31.6 mm, compared to the March monthly average of mm. The total number of rain days exceeding 1 mm rainfall from 1 March 2014 to 9 March 2014 was 2 days, compared to the March average of 17.0 days 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 9 March BoM Climate Statistics for Australian Locations ( Prepared for INPEX Cardno Page 3

7 The largest predicted maximum tidal range for the reporting period was 7.0 m on 3 March 2014, which also had the second largest predicted daily average tide range of 2014 of 6.8 m. The minimum tidal range for the reporting period was 1.2 m on 24 February 2014 (Figure 2-2). Figure 2-3 shows significant wave height output from the BoM AUSWAVE model located approximately 11 km north-north-east of Charles Point (Latitude 12.3 º S, Longitude º E). This figure shows that significant wave height was moderately elevated from 24 February 2014 to 1 March 2014 as a result of moderate westerly winds, and peaked at 1.1 m on 26 February A small peak (0.6 m) in significant wave height was also observed on 9 March Darwin predicted tide for the fortnight to 9 March 2014, based on harmonic constituents for Darwin defined by the Australian Hydrographic Service ( BoM AUSWAVE Model significant wave height the for output location 11 km north-northeast of Charles Point for the fortnight to 9 March 2014 Prepared for INPEX Cardno Page 4

8 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 are telemetered half hourly and daily averages calculated from the available readings (48 records per day) between 00:00 and 23:59 on each day. The data have 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 Figure 3-2 to Figure 3-17, the raw (half hourly) turbidity data are presented as a grey line and the daily average by the solid black line. The daily-averaged 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. Daily averages based on less than 48 points are generally due to the removal of points due to QA/QC procedures. 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 Figure 3-2 to Figure 3-17 in accordance with the International Oceanographic Data and Information Exchange (IODE) procedure. Level 1 wet season trigger values for the reactive sites Channel Island, Weed Reef 1, Weed Reef 2, Fannie Bay, Lee Point, and Woods Inlet, as well as the surrogate reactive site East Point are shown in Figure 3-2 to Figure Table 3-1 provides summary notes on the information presented in the figures below. Table 3-1 Summary notes on turbidity plots for the period 24 February 2014 to 9 March 2014 Notes Daily average turbidity across the region (Figure 3-2 to Figure 3-17) shows moderate differences between the Darwin Harbour Inner sites (Mandorah, Woods Inlet, Weed Reef, South Shell Island, Northeast Wickham Point, Channel Island and Upper East Arm) and Darwin Outer sites (Charles Point, Lee Point, Fannie Bay, East Point, Casuarina Beach and Spoil Ground). From 24 February 2014 to 1 March 2014, the offshore zone (Darwin Outer) was affected by moderate but persistent westerly winds, which resulted in moderately elevated wave conditions in the Beagle Gulf (see Section 2). The elevated sea state and littoral mixing in Darwin Outer coastal waters appears to have contributed to the increase in turbidity within the coastal zone sites of Darwin Outer, most notably at the seagrass sites Lee Point, Casuarina Beach and East Point. From 2 to 10 March 2014 turbidity at the Darwin Outer sites showed a steady decrease as the sea state calmed. Turbidity at the Darwin Harbour Inner sites were less impacted by oceanic conditions, and showed strong correlation to the spring-neap tidal phase. Turbidity was generally greater during spring tides across the majority of the Darwin Harbour Inner sites, with the highest turbidity recorded at Northeast Wickham Point, which peaked at a daily average turbidity of 58.3 NTU on 4 March 2014 (Figure 3-14). Turbidity at Weed Reef and Channel Island was also elevated during the reporting period, with daily average turbidity at Channel Island above the Level 1 wet season coral Frequency/Duration threshold of 26 NTU from 2 March 2014 to 6 March 2014 (Figure 3-2). As a result, Intensity trigger exceedances were recorded at Channel Island from 3 March 2014 to 5 March 2014 with Frequency trigger exceedances on 5 March 2014 and 6 March 2014 (see Section 1.2). The largest predicted maximum tidal range for the reporting period occurred on 3 March 2014 (7.0 m). The daily average tide range on 3 March 2014 is predicted to be the second largest of 2014 (6.8 m). Fannie Bay primary logger experienced turbidity data loss from 26 February 2014 to 9 March 2014 due to turbidity logger cable issues. Transmission was lost from the Fannie Bay contingency logger from 3 March 2014 to 9 March 2014 due to issues relating to satellite data delivery from the Irridium Simple Mail Transfer Protocol (SMTP) Service. The complete dataset was retrieved from the logger on 11 March Lee Point experienced turbidity data loss from 26 February 2014 to 10 March 2014 due to cable connection issues in the bottom logger. The Lee Point contingency logger was recording and transmitting data during this period. Data quality at Mandorah deteriorated from 28 February 2014 to 10 March 2014 due to turbidity sensor wiper jam. Data quality at South Shell Island deteriorated from 26 February 2014 to 10 March 2014 due to a turbidity sensor wiper jam. Prepared for INPEX Cardno Page 5

9 Notes Upper East Arm ceased transmitting from 24 February to 9 March 2014 due to cable connection issues in the bottom logger. Prepared for INPEX Cardno Page 6

10 Water Quality monitoring sites Prepared for INPEX Cardno Page 7

11 Channel Island (reactive coral site) Prepared for INPEX Cardno Page 8

12 Weed Reef 1 (reactive coral site) Prepared for INPEX Cardno Page 9

13 Weed Reef 2 (reactive coral site) Prepared for INPEX Cardno Page 10

14 Fannie Bay (reactive seagrass site) Prepared for INPEX Cardno Page 11

15 Fannie Bay 2 (contingency reactive seagrass site) Prepared for INPEX Cardno Page 12

16 Lee Point (reactive seagrass site) Prepared for INPEX Cardno Page 13

17 Lee Point 2 (contingency reactive seagrass site) Prepared for INPEX Cardno Page 14

18 Woods Inlet (reactive seagrass site) Prepared for INPEX Cardno Page 15

19 East Point (surrogate seagrass reactive site from 4 March 2014 to 9 March 2014) Prepared for INPEX Cardno Page 16

20 Casuarina Beach (seagrass site) Prepared for INPEX Cardno Page 17

21 Charles Point 2 (seagrass and coral site) Prepared for INPEX Cardno Page 18

22 Mandorah (coral site) Prepared for INPEX Cardno Page 19

23 Northeast Wickham Point (coral site) Prepared for INPEX Cardno Page 20

24 South Shell Island (coral site) Prepared for INPEX Cardno Page 21

25 Spoil Ground (spoil ground disposal site) Prepared for INPEX Cardno Page 22

26 Upper East Arm 1 (harbour dredging site) Prepared for INPEX Cardno Page 23