DAMPIER PORT WHARF CONSTRUCTION

Transcription

1 DAMPIER PORT WHARF CONSTRUCTION WATER QUALITY DESCRIPTORS Report: MSA142R1 Report to: Dampier Port Authority Address Perth WA 6000 Australia MScience Pty Ltd, 239 Beaufort St, Perth, WA 6003, AUSTRALIA

2 REPORT NO. TITLE Document Information MSA142R1 DAMPIER PORT WHARF CONSTRUCTION : WATER QUALITY DESCRIPTORS DATE 27 October 2009 JOB CLIENT MSA142 Dampier Port Authority USAGE PRECIS KEYWORDS This report provides contextual data for a broader impact assessment of a wharf development being undertaken by the Dampier Port Authority. Turbidity and temperature statistics are reported for six sites at varying distances from the proposed Dampier Port Authority dredging works. Data sets cover the period November 2007 to September 2009 during the Pluto LNG Development dredging operations for 5 sites and seven months of predredging data from one other site. Dampier Port Turbidity Temperature Water Version-Date Released by Purpose V1. 27 Oct 2009 JAS Client Use DISCLAIMER Information in this report is provided solely for the user's information and, while thought to be accurate at the time of publishing, is provided strictly as the best understanding of MScience and without warranty of any kind. MScience, its agents, employees or contractors will not be liable for any damages, direct or indirect, or lost profits arising out of the use of information provided in this report beyond its immediate implications. 2

3 TABLE OF CONTENTS SUMMARY... ii 1.0 Introduction Methods Results Turbidity Data Temperature data References TABLES FIGURES Table 1. Sites and locations... 2 Table 2. Temporal coverage of data for sites Table 3. Summary statistics for the five routine monitoring sites and site CHC4 from the pre-dredging baseline Table 4. Water temperature statistics ( C) at the five routinely monitored sites Figure 1. Map showing site locations Figure 2. ELI1 turbidity data (NTU) Y-axis truncated at the 99%ile and does not show maxima... 1 Figure 3. KGBY turbidity data (NTU) Y-axis truncated at the 99%ile and does not show maxima... 2 Figure 4. MIDI turbidity data (NTU) Y-axis truncated at the 99%ile and does not show maxima... 3 Figure 5. SUP2 turbidity data (NTU) Y-axis truncated at the 99%ile and does not show maxima... 4 Figure 6.SWIT turbidity data (NTU) Y-axis truncated at the 99%ile and does not show maxima... 5 Figure 7. Water temperatures at site ELI1 around coral communities... 6 Figure 8. Water temperatures at site KGBY around coral communities... 7 Figure 9. Water temperatures at site MIDI around coral communities... 8 Figure 10. Water temperatures at site SUP2 around coral communities... 9 Figure 11. Water temperatures at site SWIT around coral communities i

4 SUMMARY The Dampier Port Authority (DPA) is evaluating the environmental impacts and management requirements for their proposed wharf expansion project. The construction activities required for the project will impact on the turbidity of waters of Mermaid Sound around the project through the suspension of sediments. To assist in evaluating the magnitude of these effects and their relevance to levels experienced historically by nearby benthic communities, DPA have requested that This report provides summary statistics of turbidity from intensive monitoring programs conducted over the last few years at sites within a few kilometres of the proposed construction area. Data provided include: 23 months of turbidity data recorded at 10 minute or 30 minute intervals during Woodside Burrup Pty Ltd s Pluto dredging campaign: data here includes 4 sites around the proposed project that are likely to have been impacted by plumes from dredging and a site outside of the modelled zone of influence; and 7 months of turbidity data recorded at 10 minute intervals from a site close to the proposed project, prior to the commencement of the Pluto dredging project. Water temperature data are also provided for the 5 Pluto monitoring sites for the November 2007 September 2009 period. Water temperature is not fundamentally impacted by dredging, but can provide a major impact on coral bleaching and is presented as possible contextual data for interpreting future monitoring. ii

5 1.0 INTRODUCTION Dampier Port Authority (DPA) is conducting an environmental assessment of the potential impacts of constructing additional port facilities adjacent to their current wharves and berths. Part of that assessment involves investigation of their possible impacts on water quality and how those may alter background water quality. The waters of Mermaid Sound, within the limits of the Dampier Port sustain a number of anthropogenic influences which impact on water quality on a daily basis. Many of these, including shipping movements, tug operations and dredging have significant impacts on the suspended sediment concentrations of these waters especially waters in the more southerly sections of Mermaid Sound around the DPA operations. Thus measure of background water quality is not simply a representation of what water quality would be without anthropogenic activity. DPA has requested that MScience Pty Ltd (MScience) provide descriptions of the turbidity and temperature environment of waters adjacent to the proposed construction activities. This report provides that data, based on water quality data collected for Woodside Burrup Pty Ltd as part of the Pluto LNG Project. That project has collected water quality on a continuous basis since late 2007 at a number of sites within Mermaid Sound. On behalf of DPA, Worley Parsons has provided a list of water quality statistics and sites for which information is required. That list of water quality monitoring sites includes: KGBY, SUP2, SWIT and ELI1; plus one additional reference site not previously subject to dredge plumes. Data for the above sites cover the period since dredging commenced on the Pluto LNG Project in November 2007 up to September 2009 when the data set for the DPA assessment was closed. This data set includes periods when there were several months without dredging, periods of intense dredging, strong weather conditions including the passage of cyclones and periods of extended calm weather. Additional water quality statistics for nearby sites are also available as part of the baseline data set collected prior to the start of Pluto dredging (EPA 2007). Statistics for the closest of those sites are presented. -1

6 2.0 METHODS Sites Site locations are specified in Table 1 and shown in Figure 1. Table 1. Sites and locations Code Site Name Easting Northing ELI1 East Lewis Island KGBY King Bay MIDI Middle Intercourse Island SUP2* Supply Base SWIT* South Withnell CHC4 WEL Site C * denotes a site with a telemetered logger using an OBS3 D&A Instruments sensor Data Collection Turbidity data was collected using nephelometers. Sites with telemetered instruments used the D&A Instruments OBS3+ sensor to record NTU, while other sites used in situ logging Wetlabs (ECO-NTU-SB OBS) turbidity recorders. The program collecting data at CHC4 used SAS turbidity loggers from Dr Peter Ridd of James Cook University, Townsville, Queensland. Data recorded prior to November 2008 were collected at 10 minute intervals and then at 30 minute intervals after that time. All data points have been presented within the figures plotting NTU by time, but to avoid biasing descriptive statistics to periods prior to November 2008, the ten minute data has been subsampled to yield only 1 point per 30 minute period. Temperature data is collected as hourly readings by Onset Tidbit or Hobo loggers attached to the frame holding the nephelometer (i.e. at the same depth as the corals). Data Processing Turbidity data collected using optical backscatter sensors is prone to a number of factors which interfere with the instrument s ability to provide a reading indicative of the actual turbidity in the water surrounding the instrument. Data collected here was processed by a combination of automated and supervised checks to remove false data according to Table 2. -2

7 Table 2.Types of spurious readings corrected during data processing. Fault Detected as Outcome Spike(a)* Reading >2.5*(average of reading before and after) Set to average of reading either side Spike(b)* Readings > 200NTU flagged by program, visual assessment based on readings either side. Set to missing or kept depending on pattern of adjacent readings Creep Negative NTU Lower limit of readings rises over time and does not drop below the rising trend line of minimum values. Value >0.0 Set to 0.1 Correct by resetting lower bound by removing the trend to align the lower values with those either side of the creep. Zero reading Value = 0.0 Set to missing Data have been assigned a Summer or Winter category (the former occur within months November to April, with the latter in May to October). NTU data is converted to suspended sediment concentration (SSC) estimates within the Pluto monitoring program using the equation SSC(mg/L) = 3.055NTU. This calibration was derived from laboratory tests of relevant sediments stirred to maintain total suspension at James Cook University. That relationship is an amalgamation of results from a large number of sites, often with conservable heterogeneity between sediments. Further work has shown that in situ relationships are most usually between 1 and 2 (i.e. SSC(mg/L) = [1 to 2] NTU). Table 3. Temporal coverage of data for sites. Code Starts Ends ELI KGBY MIDI SUP SWIT CHC

8 Figure 1. Map showing site locations. -4

9 3.0 RESULTS 3.1 TURBIDITY DATA Table 4. Summary statistics for the five routine monitoring sites and site CHC4 from the pre-dredging baseline. ELI1 (NTU) Season N Means Median 20%ile 80%ile 99%ile Maximum Summer Winter All KGBY (NTU) Season N Means Median 20%ile 80%ile 99%ile Maximum Summer Winter All MIDI (NTU) Season N Means Median 20%ile 80%ile 99%ile Maximum Summer Winter All SUP2 (NTU) Season N Means Median 20%ile 80%ile 99%ile Maximum Summer Winter All SWIT (NTU) Season N Means Median 20%ile 80%ile 99%ile Maximum Summer Winter All CHC4 (NTU) Season N Means Median 20%ile 80%ile 99%ile Maximum Summer Winter All

10 Figure 2. ELI1 turbidity data (NTU) Y-axis truncated at the 99%ile and does not show maxima Scatterplot of ELI against Date 99% NTU Nov Feb-08 1-Jun-08 9-Sep Dec Mar-09 6-Jul-09 80% 50% 14-Oct-09 Date -1

11 Figure 3. KGBY turbidity data (NTU) Y-axis truncated at the 99%ile and does not show maxima 45 Scatterplot of KGBY against Date 40 99% NTU Nov Feb-08 1-Jun-08 9-Sep Dec Mar-09 6-Jul Oct-09 80% 50% Date -2

12 Figure 4. MIDI turbidity data (NTU) Y-axis truncated at the 99%ile and does not show maxima 20 Scatterplot of MIDI against Date % 12 NTU % 50% 0 14-Nov Feb-08 1-Jun-08 9-Sep Dec Mar-09 6-Jul Oct-09 Date -3

13 Figure 5. SUP2 turbidity data (NTU) Y-axis truncated at the 99%ile and does not show maxima 40 Scatterplot of SUP2 against Date 35 99% NTU % 50% 0 14-Nov Feb-08 1-Jun-08 9-Sep Dec Mar-09 6-Jul Oct-09 Date -4

14 Figure 6.SWIT turbidity data (NTU) Y-axis truncated at the 99%ile and does not show maxima Scatterplot of SWIT against Date 99% SWIT Nov Feb-08 1-Jun-08 9-Sep Dec Mar-09 6-Jul-09 80% 50% 14-Oct-09 Date -5

15 3.2 TEMPERATURE DATA Summary statistics for water temperature for the five routinely monitored coral sites are provided in Table 4 with plots of all data in Figures Over the January March 2008 period, these sites experienced water temperatures above 32 C for over 3 weeks which caused extensive bleaching of 10% to 40% of corals at these sites. Table 5. Water temperature statistics ( C) at the five routinely monitored sites. ELI KGBY MIDI SUP2 SWIT Season Summer Winter Summer Winter Summer Winter Summer Winter Summer Winter Mean Minimum Maximum Median %ile %ile Figure 7. Water temperatures at site ELI1 around coral communities 34 Scatterplot of ELI1 against Date Temperature(C) Aug Feb Nov-07 1-Jun-08 9-Sep Mar Dec-08 6-Jul-09 Date 14-Oct Jan-10-6

16 Figure 8. Water temperatures at site KGBY around coral communities 36 Scatterplot of KGBY against Date Temperature (C) Nov Feb-08 1-Jun-08 9-Sep Dec Mar-09 6-Jul Oct Jan-10 Date -7

17 Figure 9. Water temperatures at site MIDI around coral communities 34 Scatterplot of MIDI against Date Temperature(C) Aug Feb Nov-07 1-Jun-08 9-Sep Mar Dec-08 6-Jul-09 Date 14-Oct Jan-10-8

18 Figure 10. Water temperatures at site SUP2 around coral communities 34 Scatterplot of SUP2 against Date Temperature(C) Nov Feb-08 1-Jun-08 9-Sep Dec Mar-09 6-Jul Oct Jan-10 Date -9

19 Figure 11. Water temperatures at site SWIT around coral communities 34 Scatterplot of SWIT against Date Temperature (C) Aug Feb Nov-07 1-Jun-08 9-Sep Mar Dec-08 6-Jul-09 Date 14-Oct Jan-10-10

20 4.0 REFERENCES EPA (2007). Pluto LNG Development, Burrup Peninsula: Woodside Energy Ltd. Perth WA, Report and Recommendations of the Environmental Protection Authority, Bulletin 1259, Perth WA. -11