Weekly Water Quality Report

Transcription

1 Weekly Water Quality Report Ichthys Nearshore Environmental Monitoring Program Week 6: to October 2012 Week 6: 1 to 7 October 2012 Prepared for INPEX October 2012

2 Weekly Water Quality Report Ichthys Nearshore Environmental Monitoring Program Document Information Prepared for INPEX Project Name Ichthys Nearshore Environmental Monitoring Program File Reference - Reporting Period Week 6: 1 to 7 October 2012 Date October 2012 Document Control Version Date Author Author Initials Reviewer A 17/10/2012 Chris Beadle CB David van Senden DvS 0 17/10/2012 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: Telephone: Telephone: Facsimile: Facsimile: Facsimile: 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 INPEXOctober 2012 Page ii

3 1 Summary This is the sixth weekly reporting period for the Ichthys project water quality monitoring program in Darwin Harbour. The weekly report provides an assessment of the water quality trigger levels for the preceding week and incorporates figures covering the preceding fortnight 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. No turbidity trigger exceedances have been recorded on the QA/QC d turbidity data for the reporting period (1 October 7 October 2012). 1.1 Reporting Period This Weekly 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 Period Start Water Quality Summary Period Period End Monday 1 October 2012 Sunday 7 October Trigger Exceedance Summary No exceedances were recorded during this reporting period. Figures showing Darwin metocean information and all turbidity logging sites for the reporting period are included in the following sections. Table 1.2 provides a summary of the trigger exceedances observed during the exceedance period (i.e. 2 nd week of the reporting period). Table 1-2 Trigger Exceedance Summary (01/10/2012 to 07/10/2012) Intensity Frequency Duration Coral Triggers >23 NTU >20 NTU > 4 days per 7-day rolling period >20 NTU over 4 consecutive days Channel Island None None None Seagrass Triggers >17 NTU >13 NTU > 3 days per 7-day rolling period >13 NTU over 4 consecutive days Woods Inlet None None None Fannie Bay None None None Lee Point None None None 1.3 Summary of Dredge Operation 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) Summary of Dredge Operations (Data provided by INPEX). On 3 October 2012, a third BHD Simson commenced operation in unison with the BHD Baldur within the MOF area. With the commencement of Simson, BHD Hippopotes was put on standby and will conduct intermittent dredging operations when either the Simson or Baldur cease operations for maintenance (maximum of two BHDs will operate at any one time). 83,708 m 3 Volume Material Dredged (Cumulative to Date) 180,064 m 3 Prepared for INPEX Page 1

4 2 Wind and Tidal Conditions Atmospheric conditions at Darwin Airport, sourced from the Bureau of Meteorology, and the predicted tides at Port Darwin are shown in Figure 2.1. The period is characterised by warm spring air temperatures and diurnal wind pattern with strong breezes in the afternoon decreasing overnight. Tidal amplitude for the reporting period ranged from 6.29 m (2 October 2012) to 2.41 m (7 October 2012) indicating shift in tidal phase from spring to neap. Figure 2-1 Darwin Airport (data source Bureau of Meteorology) air temperature and atmospheric pressure, wind speed and direction and rainfall and Darwin predicted tide for the fortnight to 7 October Prepared for INPEX Page 2

5 3 Turbidity Turbidity time series for the reporting period are shown in the figures below for all sites (Figure 3-1). The data have been subjected to a 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 the figures below 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 daily average are indicated at the top of the plot. 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. Dry season trigger values for the four trigger sites; Channel Island, Woods Inlet, Fannie Bay and Lee Point are shown in Figures 3.2 to 3.5. The data indicate the strong variability between sites and correlation with the tidal signal. Table 3.1 provides summary notes on the information presented in the figures below. Table 3-1 Summary notes on turbidity plots Notes The maximum spring tidal range occurred on 2 October 2012 (6.29 m). Turbidity was generally greater during spring tides across the majority of sites. None of the trigger sites experienced turbidity trigger exceedances during this reporting period. Upper East Arm water quality data is currently considered unreliable and should be interpreted with caution given the large amount of suspect data. Prepared for INPEX Page 3

6 Figure 3-1 Water Quality Monitoring Sites Prepared for INPEX Page 4

7 Figure 3-2 Channel Island (coral impact site) Prepared for INPEX Page 5

8 Figure 3-3 Woods Inlet (seagrass impact site) Prepared for INPEX Page 6

9 Figure 3-4 Fannie Bay (seagrass impact site) Prepared for INPEX Page 7

10 Figure 3-5 Lee Point (seagrass impact site) Prepared for INPEX Page 8

11 Figure 3-6 North East Wickham Point (coral impact site, no triggers) Prepared for INPEX Page 9

12 Figure 3-7 Weed Reef 1 (coral control site) Prepared for INPEX Page 10

13 Figure 3-8 Weed Reef 2 (coral control site) Prepared for INPEX Page 11

14 Figure 3-9 East Point (seagrass contingency site) Prepared for INPEX Page 12

15 Figure 3-10 Casuarina Beach (seagrass contingency site) Prepared for INPEX Page 13

16 Figure 3-11 Gunn Point (spoil disposal ground impact site) Prepared for INPEX Page 14

17 Figure 3-12 Charles Point 1 (seagrass control site) Prepared for INPEX Page 15

18 Figure 3-13 Charles Point 2 (seagrass control site and coral contingency control site) Prepared for INPEX Page 16

19 Figure 3-14 Mandorah (coral contingency control site) Prepared for INPEX Page 17

20 Figure 3-15 South Shell Island (coral impact site, no triggers) Prepared for INPEX Page 18

21 Figure 3-16 Upper East Arm (harbour dredging control site) Prepared for INPEX Page 19