FW: Boat Harbour IR Response Conformity and Technical Review

Hi Lauchie,

ECCC has completed its review of the proponent’s responses to IRs IAAC-14, 66 and 50.  We have undertaken a Conformity Review of IAAC 14 and our determination applies only to our portion of that IR (ECCC-06).  We understand conformity issues may be identified by other departments and we do not feel our comments should influence the overall determination however we are prepared to discuss if necessary.

IAAC-66 has been satisfactorily addressed in the response and Technical Review comments for IAAC-50 are provided below

• IAAC-14 (ECCC-06) – The response conforms to ECCC-06 with the provision of the October 22, 2021 Memorandum from GHD to NS Lands (Response to IR IAAC-14 and IAAC-40).  As IAAC-14 also included information requests from other federal and provincial departments, ECCC understands the overall determination on conformity requires input from those other departments.  We are prepared to discuss any concerns identified by others with the Response. 

• IAAC-66 (ECCC-02) - ECCC provided general comments regarding the use of the HELP model and monitoring the actual performance of the disposal cell.  These have been satisfactorily addressed with the proponent’s response.

• IAAC-50 (ECCC-14) - ECCC accepts the use of the 95 percent UCLM in calculating the Exposure Point Concentrations as part of the ecological risk assessment process in order to describe site conditions. While a reference to HC guidance is provided to support this statistical approach, ECCC also includes this option in the Federal Contaminated Sites Action Plan (FCSAP) Ecological Risk Assessment Guidance (2012). 

      The proponent has provided the additional detail that ECCC was seeking in terms of how the SSTL is being utilized to further refine the

      area proposed for active remediation in each wetland and the estuary (e.g. Figure 7.3-25, page 510/808, Volume IV of V, EIS).  We

      understand that the SSTL has been used in a forward calculation, predicting what area of highest concentrations require removal in order

      that the overall wetland will meet the target of 29 pg/g D/F TEQ.  While this approach will reduce the amount of material to be

      dredged/managed and reduce the overall loss of wetland, ECCC is requesting clarification on the following:

1. How does this approach fit in with the proposed Surface Weighed Average Concentration (SWAC) approach that was proposed earlier to ECCC (June 2019) as a means of determining if the dredging has met the remedial goal?  For such an approach, the SSTL would be the target, often with a caveat that no single individual sample will be above “X”, even if the SWAC passes.  Has this “X”, (maximum criteria) been proposed yet?  
2. Will this also mean the area to be dredged in the Boat Harbour Stabilization Lagoon will be refined or is this proposed approach for the wetlands and estuary alone?
3. In the post-remediation phase, is there the potential for recontamination (e.g. is there potential for suspended material with higher concentration contamination settling back onto the surface sediments and/or the areas of higher contamination left behind migrating into the dredged areas, possibly exceeding the SSTL or “X”, the maximum established concentration (see Question 1 above)?

       Based on our review of the response, it is ECCC’s view that options need to be identified for the post-remediation phase should

       exceedances be identified during future monitoring and sediments require additional management.  Requiring the development of an

       adaptive management plan could address this need.

Stephen Zwicker