Science Response 2016/007

Technical review of final 3D modelling - potential effects of marine structures on site hydrodynamics and sedimentation from the construction of the Pacific Northwest liquefied natural gas terminal

Context

Pacific NorthWest Liquid Natural Gas Ltd.> (PNW LNG) is proposing to construct a large scale liquefied natural gas (LNG) export terminal near Prince Rupert, BC, within the Skeena River estuary (herein after referred to as the ‘Project’).  The Project would involve the development of combined suspension bridge and pile trestle from Lelu Island to a terminal berth, a materials offloading facility (MOF), pioneer dock and access bridge to Lelu Island.

The proposed suspension bridge would connect Lelu Island and Agnew Bank, approximately 1,500 m to the northwest of Flora Bank, and would be supported by two isolated in-water supporting structures, referred to as the Southwest (SW) Tower and the Anchor Block. From the seaward end of the bridge, a trestle supported by steel pilings would continue for approximately 1,300 m to a berth and traffic deck.

On April 8, 2013 the Canadian Environmental Assessment Agency (CEAA) issued a Notice of Commencement that they had begun an environmental assessment pursuant to the Canadian Environmental Assessment Act (CEAA 2012) for the PNW LNG project located on Lelu Island.

The Environmental Impact Statement (EIS) and Addendum submitted by PNW LNG to the Canadian Environmental Assessment Agency on 28 February 2014 and 12 December 2014, respectively, provided information with regard to potential effects of marine operations and marine structures upon the sea bed and habitat at Agnew and Flora Banks. The Addendum also provided detailed responses to Information Requests posed by the Government of Canada in regard to sediment deposition, and included a report that provided a sediment transport and deposition analysis. This report was based on work that utilized 2D models and was conducted by PNW LNG’s marine engineering consultant, Hatch Ltd.

On February 23, 2015, PNW LNG received a new Information Request from CEAA requesting additional 3D hydrodynamic and sedimentation modelling. A Terms of Reference was developed to guide the additional assessment. The Proponent responded to the February 23rd CEAA request by submitting a report dated May 5, 2015 entitled “3D Modelling of Potential Effect of Marine Structures on Site Hydrodynamics and Sedimentation” (Hatch, 2015a).

Fisheries and Oceans Canada (DFO) Science Branch had provided informal advice to DFO Fisheries Protection Program (FPP) on previous drafts of baseline and post-construction modelling undertaken by PNW LNG to assess the potential effects of marine operations and marine structures on the sea bed and habitat at Agnew and Flora Banks. Following the Proponent’s submission of the May 5, 2015 report (Hatch, 2015a), FPP placed a request to Science Branch to provide a formal technical review of PNW LNG's draft 3D baseline and post-construction hydrodynamic modelling. A Canadian Science Advisory Secretariat (CSAS) Science Response (DFO, 2015) was developed in response to this request from FPP. The CSAS Science Response (DFO, 2015) outlined primary areas of concern with respect to the Hatch (2015a) 3D modelling report. These concerns were conveyed in a DFO response (June 2, 2015) to CEAA.

On June 2, 2015, PNW LNG received notice from CEAA that they had not satisfied the requirements of the Information Request #2, noting that the technical reviews provided by Natural Resources Canada (NRCan), and DFO, “indicates that their expert advice and direction to PNW in conducting its modelling work was not sufficiently taken into consideration, which has resulted in a lack of information”. CEAA indicated to PNW LNG that their conclusions needed to be substantiated by further rigorous and thorough modelling results. CEAA informed PNW LNG that additional information was required before they could complete their environmental assessment report. Five key concerns regarding 3D modelling were identified in the June 2, 2015 CEAA correspondence. These were itemized as follows:

• Concerns regarding the wind and wave input forcing fields used to drive the 3D model.
• Concerns with the modelling of extreme storm events.
• Concerns with the modelling of flows in proximity to large structures (the Anchor Block and SW Tower).
• Concerns regarding the long term simulations and use of time-averaged forcing inputs to drive the model.
• Concerns regarding model outputs related to sediment transport.

PNW responded to CEAA’s June 2, 2015 Information Request with submission of a report dated November 10, 2015 and entitled “Pacific Northwest LNG 3D Modelling Update - Supplemental Modelling Report” (Hatch, 2015b). DFO FPP is now requesting that DFO Science review PNW LNG’s final submission of modelling of potential effects of proposed structures to Flora Bank and Agnew Bank areas in response to CEAA’s Information Request and provide advice regarding the following:

1. Assess whether the five key concerns as outlined above have been addressed with sufficient accuracy and adequacy to facilitate an evaluation of PNW LNG’s conclusions.
2. If the information and model results from PNW LNG are found to be sufficient; evaluate the validity of PNW LNG’s conclusions, based on information and results as presented in the Supplemental Modelling Report.

This Science Response Report results from the Science Response Process of December 2015 on the Technical review of final 3D modelling - potential effects of marine structures on site hydrodynamics and sedimentation from the construction of the Pacific Northwest liquefied natural gas terminal.

Complete document (PDF, 185 KB)

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