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 Method of Installation Individual support piles will typically be drilled using a conventional drill derrick and either doweled or socketed into the rock. Each pile may require minor rock surface preparation to initiate drilling operations. If there is sufficient overburden to stabilize the pile tip and form a seal for the drilling operation, rock surface prep may not be required. Once the piles are fixed in the rock, concrete top plugs with extended reinforcement cages will be cast in the heads of each pile. Formwork will be set up to form and pour the concrete pile caps around the pile heads. The pile caps are typically cast in two separate pours. The first pour, includes casting the lower half of the pile cap around the individual pile heads. This not only forms the bottom half of the pile cap, but also provides a bearing surface for seating the precast concrete box-girders. The precast concrete boxgirders can then be efficiently erected with barge cranes onto the bottom half of the pile caps. The pile caps are completed with a second pour which is cast on top of the first pour between the ends of the precast box-girders. The second pour allows the deck and pile cap to act monolithically and achieve the frame action necessary to resist lateral loads. A cast-in-place concrete deck slab and curb can then be poured on the precast box-girders. The deck slab will act compositely with the precast box-girders completing the erection of the main structural components. Topside equipment, guardrails, pipes etc. can be installed afterward as required. The final selection of the preferred structural option will be made at the detailed design phase of the project. However, it is anticipated that the pile and deck option will be selected as it requires significantly less rock blasting and associated disturbance of the marine habitat compared to the jacket structure option. It also minimizes the potential design and construction issues associated with the quality of the rock. 2.3.3 Berthing Structures The two proposed concepts for the berthing structures include a full jacket structure option and a buttressed (stiff-leg) option. 2.3.3.1 Full Jacket-Structure Option Proposed Type of Construction Similar to the loading platforms, the berthing structures were conceived as modular jacket structures using the same member sizes and dimensions as the loading platforms. Although the berthing structures have an additional outboard frame for supporting a fender unit as shown in Drawing No. 008, they can generally use the same modular template as the loading platforms. By standardizing the dimensions, the number of unique fabrication details and welding procedures for each jacket is minimized, which reduces construction cost, improves quality and reduces construction time. Method of Installation The method of installation for the berthing jacket structures is the same as the loading platform jacket structures. Page 2-12 FINAL - Rev. 0 January 20, 2010
Northern Gateway Pipelines Inc. Section 3.10: Site Plans and Technical Data Table of Contents 2.3.3.2 Buttressed (Stiff-Leg) Option Proposed Type of Construction An alternative to the full jacket structure is a buttressed or “stiff-leg” concept as shown in Drawing No. 009. Instead of individual berthing structures as proposed in the full jacket concept, each set of side-by-side berthing structures is combined into one structure. Each combined structure is comprised of individual vertical piles which are tied together at the top by partial jackets and/or bracing, and which are laterally supported by two stiff-leg space frames that are mounted to onshore concrete abutments. The concrete abutments in turn, are anchored with rock anchors to transfer the load directly into the bedrock. This concept takes advantage of the relatively close rocky shoreline by providing a more direct means of transferring horizontal loads to the bedrock. Since the horizontal loads bypass the vertical piles, the piles and their rock sockets can be optimized for vertical loads only and can be reduced in size compared to the full jacket concept. The stiff legs also provide a convenient means of supporting the catwalks and access trestles to the berthing structures. The partial jackets that tie the individual piles together are prefabricated fully-braced frames that are similar to the full jacket structures but are only approximately 8 metres high. The partial jackets can either sit on the individual piles, or can have hollow legs that slide onto the piles. Their purpose is to transfer horizontal loads from the fender units directly into the stiff-leg buttresses. In lieu of prefabricated partial jackets, individual struts and bracing members can be field welded directly onto the piles to achieve the same objective. However, partial jackets are preferable, since shop fabrication provides higher quality control and it is more efficient to erect a single jacket structure compared to multiple individual members, especially considering the restricted work windows due to tidal fluctuations. The partial jackets are also advantageous since the fender support frames can be made integral with the jacket frame. The stiff-leg buttresses are prefabricated fully-braced trusses, similar to full jacket structures, except they span horizontally instead of vertically. The combined frame and stiff-leg structures act together as a large space truss capable of efficiently transferring horizontal loads that act either perpendicular or parallel to the berth. The two stiff-legs are splayed out in a “V” pattern from each end of the combined dolphin frame in order to better resolve the horizontal forces. The stiff-leg concept is less amenable to a modular fabrication scheme, since each stiff-leg is likely to be unique due to the varying distances between the berthing dolphins and abutment locations. Although the locations of the abutments could be adjusted to allow for stiff-legs of equal lengths, the trade-off would be additional rock blasting and cut and fill work on the waterfront slopes. Method of Installation Similar to the individual pile concept for the loading platforms, the individual support piles for the berthing structures will be drilled using a conventional drill derrick and either doweled or socketed into the rock. Prior to the erection of the stiff-leg frames, the stiff-leg abutments will need to be constructed. The abutments will be cast-in-place mass concrete formed and poured directly on bedrock. Some minor rock surface prep may be required including cleaning away any loose or deleterious material. The transfer of load from the abutment to the bedrock will be achieved with rock anchors that are drilled and installed through preformed holes in the abutment. The stiff leg anchor bolts can be cast monolithically with the abutment. January 20, 2010 FINAL - Rev. 0 Page 2-13
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Section 3.10: Site Plans and Technical Data - Rick Neufeld Comments

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