Science Response 2011/013
Review of the Sydney Tar Ponds Remediation Project Marine Environmental Effects Monitoring Program Year 1 Results
On February 4, 2011, Fisheries and Oceans Canada’s (DFO) Environmental Assessment and Major Projects Division (EAMP), Maritimes Region, requested that DFO Science, Maritimes Region, provide advice regarding the Year 1 results of the Sydney Tar Ponds Remediation Project Marine Environmental Effects Monitoring Program (MEEMP), as well as the potential affects on MEEMP of dredging and infilling of Sydney Harbour that may be undertaken in support of the proposed Sydport container terminal. The request for science advice supports DFO EAMP’s involvement as an expert authority in the Sydney Tar Ponds Remediation Project pursuant to the Canadian Environmental Assessment Act. Specifically, DFO EAMP asked:
- Are the conclusions of each Sydney Tar Ponds Remediation Project marine monitoring method valid based on the Year 1 monitoring results and baseline observations?
- Should the marine monitoring methods be changed, based on the Year 1 monitoring conclusions, to better improve the monitoring program?
- Is the proposed dredging and infilling of Sydney Harbour, which may be undertaken in support of the proposed Sydport container terminal, likely to affect the marine monitoring methods and future results of the Sydney Tar Ponds Remediation Project MEEMP? For each MEEMP method where potential effects from Sydney Harbour dredging and infilling are likely to occur, should the MEEMP method continue as proposed, be re-designed, or be discontinued? If re-designed, provide suggestions and/or recommendations for a revised MEEMP method.
A Science Special Response Process was used to provide DFO Science advice on these questions due to a requested deadline to provide the advice by February 18, 2011. This Science Response is based on the results of DFO Science research that has been undertaken in Sydney Harbour, as well as the knowledge gained from the Sydney Tar Ponds MEEMP in Year 1.
The major conclusions of this Science Response are:
- Polycyclic aromatic hydrocarbon (PAH) levels in surface sediments have increased by factors of 2 to 10 at all sampling locations and for all individual PAHs in Year 1 of the MEEMP monitoring program compared to the pre-construction phase of the Tar Sands remediation project.
- The increases observed in sediment PAH, but not in metal and polychlorinated biphenyl, levels indicate they are associated with transport from the Tar Ponds remediation site into the harbour by water or atmospheric pathways. The detection of these PAH increases in harbour sediments attests to the general value and utility of the MEEMP.
- The recent increase in PAH concentrations observed in Sydney Harbour sediments is statistically significant and in excess of environmental quality guidelines. However, the elevated PAH levels observed in Year 1 of the remediation phase remain significantly lower than those typical of inputs to the sediments during the peak of industrial activities from the 1960s-1980s. Once Sydney Tar Ponds (STP) remediation activities are finished, natural capping or attenuation of contaminant concentrations in the sediments will probably resume. Under these conditions, the increased PAH inputs measured during the remediation phase would primarily be evident as a local concentration maximum in the sediment record and have minimal biological impacts.
- It is strongly recommended that sediment cores be collected and analyzed for contaminants as an integral component of the MEEMP. Coring will permit downcore analyses of PAH concentrations and reveal the recent history of PAH contamination of the harbour. The latter will provide critical information on the source and magnitude of recent PAH inputs to the harbour and permit more accurate and realistic modeling of PAH transport.
- The higher PAH values measured by the Slo-Corer in comparison to the Grab sampler at several stations suggests that the Slo-Corer is more effective at collecting recently deposited, surface “fluff” material. The Slo-Corer (or a similar, alternative device) should continue to be employed in the monitoring program, as it is able to provide both quality control and sediment core collection.
- PAH water concentrations may have increased at some locations. The characterization of this effect is constrained, however, by experimental detection limit issues, potential biasing of water concentrations through the presence of highly contaminated suspended sediments, and possible quality control problems.
- It is recommended that filtered and unfiltered water samples be compared to determine the extent to which PAH levels may have been affected by the presence of highly contaminated, suspended sediments.
- The sampling protocol for the intertidal benthic community monitoring is considered to be inadequate to capture the natural variability at each site. It is recommended that this component be discontinued in its present form. To be most effective, it is recommended that the protocol be changed to include replication at each site adequate enough to fully characterize patterns in natural variability.
- It is recommended that the sample preparation protocol for the crab tissue component be modified in order to lower the analytical detection limit for PAHs by, for example, pooling together the legs and claws of 5 to 10 crab samples.
- The Sydney Harbour dredging and terminal construction projects will substantially affect benthic communities owing mainly to the generation of turbidity plumes resulting in particle transport into the South Arm. Continued monitoring of benthic communities is recommended to establish a new, post-dredging, environmental baseline against which future effects of Tar Ponds remediation can be evaluated.
- Since the sediments due to be excavated are mainly silts and sands and distinguished by low contaminant levels, it is anticipated there will be minimal transport of contaminants into the inner harbour as a result of dredging. The principle effect will be to bury the more highly-contaminated surface sediments with coarser-grained, less contaminated material thereby further remediating sediments of the inner harbour.
- It is recommended that caged bivalve studies and crab tissue sampling be discontinued during dredging, but recommence thereafter.
- To accommodate dredging activities, it is suggested that benthic sampling stations 2-1, 2-2, and 2-3 should be relocated to the east side of the harbour.
- It is considered unlikely that dredging operations or container terminal construction will produce environmental signals that will significantly interfere with the interpretation of the longer term monitoring results for the Tar Ponds remediation project.
- It is recommended that the MEEMP monitoring program be continued despite any environmental perturbations associated with the dredging/terminal construction projects. In particular, the trend of increased sediment PAH levels associated with the Tar Ponds remediation should continue to be monitored and associated biological effects fully characterized.
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