Section 3.10: Site Plans and Technical Data - Rick Neufeld Comments

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Northern Gateway Pipelines Inc. Section 3.10: Site Plans and Technical Data Table of Contents The maximum anticipated dredging and blasting area for the marine terminal is conservatively based on the proposed jacket structure concepts as described in Section 2.3. The actual dredging and blasting volumes will be determined during the detailed design based on the final selected marine structure type, construction methodology, and optimization of the berth location. Since there are no existing submarine pipelines, cables or other underwater installations within the vicinity of the proposed project site, there should be no complicating factors associated with existing facilities. 2.2.3.1 Dredging of Overburden Material In some areas of the site the underwater bedrock is exposed, while in other areas there is a relatively thin layer of overlying marine sediments (i.e., overburden). Based on an assumed average overburden depth of 1.5 metres, it is estimated that up to approximately 30,000 m 3 of underwater dredged material may need to be removed for construction of the marine terminal. Chemical analysis of the overburden sediments was carried out to determine if there is any contamination of the in-situ materials. Several samples of sediment were collected in the immediate vicinity of the marine terminal site as well as control samples from locations on the east side of Kitimat Arm. The sediment samples were analyzed for total metals, BTEX, PAHs, total PCBs, dioxins and furans, porewater ammonia, and sulphide. Additional tests were also conducted for toxicity to benthic invertebrates. The test results indicated there was no toxicity in the sediments (Reference 1). The lack of toxicity implies there is no need to dredge and remove the in-situ material for purposes of hazard mitigation. The option to dredge will be at the discretion of the contractor, depending on the construction methodology used, and will also be subject to best construction practices as approved by the Department of Fisheries and Oceans (DFO) and Environment Canada. The option of leaving the overburden sediments in place during rock blasting or pile drilling can be advantageous for various reasons including: The overburden material will be helpful in properly seating drill bits and initiating the drill holes for the explosive charges during the drilling phase of the rock blasting work; The presence of overburden material will help reduce the blast overpressures when the charges are detonated; The overburden material will be helpful in sealing the casing, and properly seating and initiating the drill during the drilling of the individual pile sockets into the rock; and, If rock benches are blasted into the rock slope, overburden material left in place can be dredged and disposed off with the rock spoils simultaneously in a single work phase. Page 2-6 FINAL - Rev. 0 January 20, 2010
Northern Gateway Pipelines Inc. Section 3.10: Site Plans and Technical Data Table of Contents Regardless of the sequencing of dredging work, clam-shell dredging is the most suitable method for removing overburden sediments and rock spoils, given the deep water conditions and location of the marine terminal. Dredging equipment will likely consist of a derrick barge which is fitted with a clam shell bucket. A silt curtain will be deployed in the top 5 metres of the water column to protect fish from turbidity during dredging. Considering the lack of toxicity, the dredged overburden sediment can be disposed of by either sidecasting the spoils into deeper water, ocean disposal at an approved site, or removing the spoils and stockpiling them on a flat deck barge for subsequent disposal at an uplands facility. Further discussions will be held with DFO and Environment Canada regarding disposal options and permitting matters. 2.2.3.2 Underwater Rock Blasting An upper limit to the amount of underwater rock material required to be removed is conservatively estimated at 36,000 m 3 . This volume of rock is based on the jacket structure concept and assumes benches will be blasted into the rock face to accommodate the jacket foundations. Detailed blast volume schedules showing the amounts of estimated rock material to be removed at each berth will be prepared later during the detailed design phase. Rock removal procedures may vary depending on the volume of rock to be removed for a particular foundation. For structures with small foundation footprints, such as those with individual piles that are drilled and socketed into the rock face, rock removal techniques employing divers and pneumatic equipment may be used for minor rock surface preparation and removal of small amounts of rock to facilitate pile drilling operations. For structures with larger foundation footprints, such as jacket or caisson structures, the rock benches can be formed by drilling a series of small blast holes into the rock face in such a pattern that when explosive charges are detonated in the holes, they will shape the rock face to the desired geometry. Typically the blast holes are drilled into the rock face from a drill derrick which essentially is a barge with multiple drill rigs arranged to allow for the efficient and simultaneous drilling of holes in a regular grid pattern. In order to mitigate the effects of the underwater blasting on local fish and marine mammals, several measures will be utilized during the blasting work including: • Blasting only during specific time windows; • Detonating blast charges in sequence and not simultaneously, in order to keep blast overpressures low; • Utilizing bubble curtains which can reduce blast overpressures by 8 to 10 times; and, • Monitoring blast overpressures and submitting hydrophone records to the Department of Fisheries and Oceans (DFO). The majority of rock blasting will take place in water ranging from 10 metres to 32 metres deep. The rock spoils typically range in size from 75 mm cobbles up to 1 metres sized boulders. The spoils can be removed with the same derrick barge and clam shell equipment that is used for dredging. The spoils are typically side-cast into deeper water for disposal. January 20, 2010 FINAL - Rev. 0 Page 2-7
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Section 3.10: Site Plans and Technical Data - Rick Neufeld Comments

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