Sunbury Neighbourhood Association

Sunbury Viaduct

In Gateway's discussion guide, there is not much detail about how their four-lane highway would get over the BNSF railway at Centre Street and River Road, but earlier pre-design consultations (2001) have detailed a viaduct that would begin just west of the cannery and continue over the creek.

We have commissioned an artist's conception of what a viaduct as described might look like as it crosses the Sunbury Neighourhood at River Road and Centre Street. 

Gateway staff have objected to our descriptions of the viaduct, but have not provided any alternative drawings or descriptions beyond what was offered in 2001.  That description is detailed below:

 

4.2.6 Structures BNSF Overhead The BNSF Overhead consists of twin parallel superstructures 382 m long. The east approach consists of an embankment retained by Mechanically Stabilized Earth (MSE) walls on the south side and west abutment face. The west approach comprises a low approach embankment and 72 m long pile-supported cellular abutment. The overhead is located on a constant 1900 m radius curve in plan, and mostly on a crest curve with a K value of 36. The cross section is generally superelevated at 2%, and consists of 4 lanes of 3.7 m, with 2.0 m shoulders and a 2.8 m median. At the east end, there is an auxiliary 3.7 m lane and 1.5 m shoulder that is accommodated by flaring the deck. Each superstructure consists of between 3 and 5 modified Type VI precast concrete I-girders arranged in spans of between 26 m and 50 m in length. Each superstructure is supported on a single column with pier cap and pile cap. Columns are staggered as necessary to accommodate the highly skewed BNSF rail tracks and realigned Centre Street. For structural efficiency, precast girders are made semi-continuous for most girder spans. The gap between superstructures is shown as 20 mm and will be detailed with impact attenuators to preclude seismic pounding damage. An alternative approach is to provide sufficient air gap to accommodate seismic deformations, estimated at 610 mm. Each superstructure will be continuous between abutments where movement joints will be located. It is anticipated that the east approach embankment can be constructed by using preloading, ground improvement or subexcavation as required to control long term settlements. On the west approach, it is expected that fill heights will be restricted to the 1.5 to 3.0 m range, and will require a combination of preloading and lightweight fill to control long term deformations. Where the approaches are more than 3 m above grade, it is expected that a lightweight pilesupported cellular abutment design will be used. This is less costly than the alternative girder spans and is provided with perimeter walls to prevent the storage of combustible materials beneath the deck. The western most bridge span is shown with a restricted-height roadway beneath the spans for property access. A separate tunnel with increased headroom is shown through the abutment structure for use by off-highway equipment. The BNSF Overhead also spans Cougar Canyon Creek, avoiding direct impact to the creek.

 

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