Table 1. Data type collected and instruments used across three major dredging projects in the Pilbara (Western Australia) since 2007 including start and finish dates and volumes dredged.
| Burrup Peninsula (MS757) | |
| Project works | Capital dredging project to create a navigation channel (16 km, 12.5 m seawater depth), turning basin (600 m radius, 12.5 m seawater depth), and berth pocket (400 m × 60 m, 13.5 m seawater depth) |
| Volume dredged | ~12.5 Mm3 |
| Dredging Period (d) | 22 Nov 2007 to 21 May 2010 (911 days). Baseline days: Turbidity 5–123 (15) NTU, Light: 0–117(109) μmol photons m-2 s-1. Dredging days: Turbidity 47–984 (905) NTU, Light 0–82 (82) μmol photons m-2 s-1 |
| Instrumentation | (1) Optical backscatter (OBS) (JCU Geo-physical Lab), (2) Wetlabs (ECO-NTU-SB OBS turbidity recorder), (3) Alec Instruments (COMPACT CLW—Miniature Turbidity/Chlorophyll Data Logger) (HOLD and DPAN only). Readings every 30 minutes. 32 sites in total (S1 File). |
| Sediment type: | Surficial sediments are mixed siliciclastic and carbonate unconsolidated sediments ranging from gravel to fine silts. For the nearshore sites, close to the dredging activities, surficial sediments were finer (sand, silt and clay = ~30%) and coarser (sand = 70%, silt 10%, clay 10%) at the more offshore sites. For the nearshore sites (DPAN, HOLD, CHC4) the SSC = Turbidity × 1.174. |
| Barrow Island (MS800) | |
| Project works | Capital dredging project to create a materials offloading facility (MOF) approach channel (1.6 km, 6.5 m seawater depth), Berthing Pocket dredged to approximately 8 m seawater depth. LNG Jetty access channel and turning basin (900 m circle, 13.5 m seawater depth). LNG berthing Pocket dredged to approximately 15 m seawater depth. |
| Volume dredged | ~7.6 Mm3 |
| Dredging Period (d) | 19 May 2010 to 31 Oct 2011 (530 days). Baseline days: Turbidity 2–786 (184) NTU, Light: 10–735 (241) μmol photons m-2 s-1.Dredging days: Turbidity 361–566 (482) NTU, Light 388–548 (474) μmol photons m-2 s-1 |
| Instrumentation: | Sideways mounted optical backscatter device (nephelometer) and Photosynthetically Active Radiation (PAR) was recorded using a 2π quantum sensor (JCU Geo-physical Lab, see Thomas & Ridd 2005). Readings every 10 minutes. 36 sites in total (S1 File) |
| Sediment type: | Predominantly unconsolidated, undisturbed carbonate sediments forming a thin veneer (0.5–3 m thick) overlying limestone pavements ranging from rubble to typically gravelly sand mixed with fine silts and clays. Low TOC content <0.8%. Sediments at deeper sites were typically finer. SSC = Turbidity × range of 1.1 to1.6 |
| Cape Lambert (MS840) | |
| Project works | Capital dredging project to create an approach area and channel (15.6 m seawater depth), turning basin (10.0 m seawater depth) and berth pocket (20 m seawater depth), and tug harbour extension (6.8 m seawater depth) |
| Volume dredged | ~14 Mm3 |
| Dredging Period (d) | 22 Dec 2010 to 15 Sept 2012 (633 days). Baseline days: Turbidity 13–536 (399) NTU, Light: 0–279 (91) μmol photons m-2 s-1.Dredging days: Turbidity 629–699 (685) NTU, Light 0–686 (649) μmol photons m-2s-1 |
| Instrumentation: | (1) Wetlabs (ECO-NTU-SB OBS turbidity recorder) every 30 mins. ALEC ALW-CMP loggers. (2) WET Labs ECO-PAR-SB (30 min) ALEC ALW-CMP. Readings every 30 minutes. 15 sites in total (S1 File)) |
| Sediment type: | Unconsolidated predominantly carbonate sediments, composed of medium to coarse sand (70–90%) at a range of 1–5 km from dredging but typically finer sediments (fine sands, silt and clay) closer to the nearshore areas. SSC = A[Turbidity] eB[Turbidity]D +C, where A = 0.670 B = 0.256, C = 0.275 and D = 0.0391 |
The range in number of seawater quality sample days during baseline (Baseline days) and dredging (Dredging days) are included at each location for turbidity and light data. Values in parentheses represent the median number of sampling days across sites where that seawater quality parameter was measured. MS refers to the Federal Ministerial approval Statement, searchable on the WA EPA website: http://www.epa.wa.gov.au).