Port of Brisbane Corporation Sediment Sampling and Analysis Program: Brisbane River and Moreton Bay

April 2000

Prepared by: Coffey Geosciences

Coffey Geosciences Pty Ltd was commissioned by PBC to undertake a Sediment Sampling and Analysis Program (SAP) in the Brisbane River and Moreton Bay. The purpose of the SAP is to define sediment quality for each dredging operation by: assessing sediment characteristics and contaminants, and comparing contaminant levels with accepted sediment quality criteria (ie ANZECC Interim Ocean Disposal Guidelines)

Methods involved taking core samples at 29 location in the Brisbane River and 6 sites in the Outer Bar area of Moreton Bay. Locations for core samples, the sampling & analysis techniques involved were based on previously commissioned SAP events undertaken in 1998 (refer record Nos 63 & 65). All work was undertaken in accordance with ANZECC Guidelines and PBCs Dredge Management Plan (record No 30). Samples were submitted to NATA approved laboratories with laboratory QA/AC measures. Analyses included particle size analysis (sieve and hydrometer analysis), settling rate, moisture content, total organic carbon, total nitrogen, total phosphorus and 75 other analytes (including trace metals, organochlorine pesticides, phenolic compounds, organo tins, PAHs, etc).

Relevant thresholds for each parameter were provided, either using the ANZECC Screening Level (SL-low effects range) or Maximum Level (ML-high effects range) or a calculated indicative Background Level (BL -2x mean of 98 data).

Results of the SAP indicated, that where the ANZECC Guidelines provide criteria, all analytes were below the Screening Level (SL) except: Lead (at 1 site), Mercury (at 2 sites), Nickel (30 sites) TBT (at 3 sites). There were only 2 sites with analytes which exceeded the Maximum Level (ML), namely Mercury (at site BH13.4), and Nickel (at site BH9.1). All analytes which did not have specified ANZECC criteria (SLs or MLs) were below the indicative Background Level except: Total TPH (at 1 site); Manganese (at 4 sites), Total Phosphorus (at 17 sites) and Total Nitrogen (at 1 site).

Nickel and Phosphorus showed the greatest number of exceedences. Elevated nickel concentrations were considered to occur because source materials for the Brisbane River sediments are naturally elevated in nickel and the elevated phosphorus levels were considered to be a result of anthropogenic activity (eg sewage effluent).

Means of all contaminants in the sediments were calculated in accordance with ANZECC Guidelines. The means of all contaminants were found to be below twice the BL. Hence, the report found that, according to the ANZECC Guidelines, the material to be dredged could be classified as "uncontaminated" for the purpose of sea disposal. Comparisons with other ports indicated Port of Brisbane sediment contaminant data is similar to, or lower in concentrations than Melbourne port. However, differing hydrodynamic situations at various ports may contribute to the differing contaminant status.

The report provides recommendations on future sampling protocols and analysis.