SEDIMENT SAMPLING AND ANALYSIS SAMPLING PLAN (SAP) FOR BRISBANE RIVER AND MORETON BAY, NOVEMBER 2004

This report presents the findings of the Port of Brisbane Corporation’s (PBC’s) November 2004 Sampling and Analysis Plan (SAP) for the Brisbane River and Moreton Bay (entrance channel).  The SAP is undertaken prior to routine maintenance dredging, which is required to maintain minimum depths of clearance within defined navigational areas of the Brisbane River and Moreton Bay.  This dredging within the Brisbane River and Moreton Bay Marine Park is planned for early 2005 and will be carried out by the T.S.H.D. Brisbane, PBC’s Trailing Suction Hopper Dredge.
 
 The overall purpose of this project is to:
 
 1. Test and analyse sediments for a range of chemical and physical properties, including:
 heavy metals;
 nutrients;
 hydrocarbons;
 organotins including tributyltin (TBT);
 organochlorine (OC) and organophosphorus (OP) pesticides;
 other selected contaminants; and
 particle size distributions.
 
 2. Compare contaminant levels with accepted sediment quality criteria (e.g. the National Ocean Disposal Guidelines for Dredged Material (NODGDM, Commonwealth of Australia 2002) where available) and/or previous SAP results as required.
 
 The results of the SAP are used by PBC to assist in the assessment of disposal options for  dredged material from shipping channels and berths.  Disposal options include reclaimed areas (onshore) or placement to designated material placement areas within Moreton Bay.  Consistent with previous years, the Corporation will beneficially reuse this material as fill with the reclaim
 works associated with the port expansion project.  The Corporation continues to undertake SAP studies to identify any potential contaminant issues in advance of dredging to ensure that placement of the material is appropriately controlled.
 
This study involved the acquisition and analysis (for the parameters described broadly above) of sediment cores from 48 sampling locations in accordance with the NODGDM.  Of the 48 sample locations, 45 were from areas of the Brisbane River and Moreton Bay requiring dredging and three were from background condition sites.
 
A summary account of the parameters that exceeded NODGDM screening levels in the 2004 SAP and comparisons with previous SAP studies of the Brisbane River and Outer Bar are as follows:
 
· Silver concentrations were below the screening level at all but one sampling location (11-8), which is the only sampling location that has previously exceeded the screening level.  The screening level for silver has been consistently exceeded at sampling location 11-8 in previous SAP studies.  Silver concentrations were generally lower than those observed in previous SAP studies.

· Copper concentrations were below the screening level at all but one sampling location (6-2) exceeded the screening level for the 2004 SAP.  Copper concentrations at each sampling location were within the range of concentrations observed in previous SAP studies.

· Mercury concentrations were below the screening level at all but two sampling locations (4-13 and 10-1).  Mercury concentrations at each sampling location were generally within or below the range of concentrations observed in previous SAP studies and generally lower than the average concentrations calculated for the 1998 to 2003 SAPs.

· Nickel concentrations were above the screening level at many of the sampling locations (approximately 67%).  Nickel concentrations were mostly within or below the range of concentrations observed in previous SAP studies and generally below the average concentrations calculated for the 1998 to 2003 SAPs.

· Lead concentrations were below the screening level at all but one sampling location (13-4).  Lead concentrations at each sampling location were generally within the range of concentrations observed in previous SAP studies, or within the overall range of values observed previously across the total dredging area.

· Zinc concentrations were below the screening level at all but two sampling locations (4-0 and 6-2).  Zinc concentrations were mostly within the range of concentrations observed in previous SAP studies.

· TBT concentrations (normalised to 1% TOC) were above the screening level at many (approximately 58%) of the sampling locations.  TBT concentrations were generally within the range of concentrations observed in previous SAP studies.  A general decline in TBT values in dredging areas from upstream (sites 4 to 7) to the mouth is apparent, consistent with the previous SAP studies.

· Total PAHs (normalised to 1% TOC) were below the screening level at all but one sampling location (2-0). Total PAHs were variable across the study area, but were generally within the range of previous SAP studies, with the notable exception of the sampling location 2-0 (a background condition location in the vicinity of South Bank), which was just below the maximum level.

· DDD concentrations exceeded the screening level at four of the 15 sampling locations tested for OC pesticides.  DDD concentrations were generally within the range of concentrations observed in previous SAP studies, with the notable exception of sampling location 3-0 (a background condition location) which was significantly above the maximum level.

· DDE concentrations exceeded the screening level at three of the 15 sampling locations tested for OC pesticides.  DDE concentrations were generally within the range of concentrations observed in previous SAP studies, and were typically below the average of the 1998 to 2003 SAPs, with the exception of sampling location 3-0 [the same background condition location with the elevated DDD] which was significantly above the screening level, but still within the overall range of values observed in previous SAP studies.

· Total DDT concentrations exceeded the screening level at seven of the 15 sampling locations tested for OC pesticides.  Total DDT concentrations were generally within the range of concentrations observed in previous SAP studies and/or within the overall range of values observed in previous SAP studies.
 
Only the Moreton Bay (entrance channel) dredging area would likely be assessed as suitable for sea disposal on the basis of the comparison of 95% UCL values with screening levels. Nickel was the only parameter which exceeded screening at the 95% UCL for this dredging area.  Nickel has been routinely measured above screening throughout the dredging and background sites, and is believed to relate to the local geology rather than introduced contamination.

All sample locations, except sampling location 2-0, were found to meet HIL-A soil investigation criteria  for the parameters tested.  Sampling location 2-0 had a calculated total PAHs value of 43,690 µg/kg, which exceeded the HIL-A value of 20,000 µg/kg.  The 95% UCL based on the data of the three background condition sampling locations was however found to be below the HIL-A value for total PAHs.  The 95% UCLs, for generalised dredging areas, also complied with HIL-A criteria.  Therefore the maintenance material is considered suitable for land disposal to reclamation areas on the basis of chemical contaminant levels.  It should be noted that the screening and maximum levels specified in the NODGDM are far stricter than the soil investigation levels appropriate for assessing the suitability of placement of dredged material on land.  The NODGDM are for the consideration of material for placement at sea where a variety of organisms live on or in the sediment.  For land disposal, health investigation levels are applied, and conservatively compared with residential development standards being the strictest health investigation levels.
 
For all samples collected, with the exception of sampling location 1-0 (at a background condition site which is not dredged), the net acidity was below the level of reporting given by ALS which is less than the action criteria specified in QASSIT (1998) and Dear et al. (2002).  Therefore, whilst the sediment sampled in the dredging areas has the potential to generate sulfidic acidity, it also has the potential capacity to neutralise the acid generated.  As the planned maintenance dredging will only remove sediment that has in-filled the navigation channels since the previous dredging in 2004, it is unlikely that material with any significant acid sulfate soil material will be dredged.  However, a consideration of monitoring and management actions to control the risk of acid sulfate soils should be taken when dredging this material, relevant to the site of disposal or reuse.
 
A general correlation of contaminant levels with clay content was evident, and normalising the 2004 SAP data to 1% clay definitely has the effect of reducing the variability of the data.
 
Many of the parameters of the detailed suite were again recorded below detection limits, which further supports the recommendation of Hydrobiology (2003 & 2004) that PBC consider reducing the testing program for these parameters.  The parameters of the detailed suite that could be excluded from future SAP studies, on the basis of not having been detected to date include:
 
· Halogenated aromatic hydrocarbons;
· Phenols; and
· Synthetic pyrethroids.
 
BTEX parameters were not detected in the sediment samples of the last two SAPs and could also be considered for exclusion from further testing, although to a lesser extent than the above parameters, given the potential sources of BTEX in the urban catchment.
 
Consideration should be given to the inclusion of OC pesticides in the basic suite of parameters, given the persistent levels of DDT and its breakdown products (DDD and DDE), and the detection of chlordane and dieldrin in past SAP studies.  Increasing the number of sampling locations that are tested for these parameters (i.e. from 15 to 48) would assist in developing a better understanding of their spatial extent and temporal trends.