The rebuild process continued into week ten with the building of the upstream sections of what are called "wing walls", these are the flared sections at each end of the bridge that help increase the stability of the river banks leading into the bridge and to help deflect the water into a channel to flow under the bridge in high water situations. Without these, water would relentlessly wear away at the river banks that tie into the bridge.
As seen in the photograph to the right, a great deal of progress has also been made in recreating the main infill sections on both ends of the bridge. This week saw the team filling in nearly half the excavated depth from the bridge footings to the eventual road height.
In the foreground of the photograph, you can see the spandrel wall taking more shape.
Check out the Week 10 Time-Lapse and Walkthrough YouTube videos below to see the work in progress!
Rebuilding the infill will be a crucial element in the overall stability of the bridge as a whole. Primarily, the infill will be recreated but stacking large granite blocks, as referenced in the previous weeks article, and then using smaller stone to fill in the voids, thus creating a denser and more stable base for the finished roadway.
Rebuilding the infill area by use of this process essentially creates a fourteen foot thick wall to support the roadway and arch span.
During this phase of the rebuild it is crucial to work both ends of the jobsite simultaneously. If too much weight were to be applied at one end or the other of the arch span it could compromise the entire structure, causing a collapse of the arch.
In the photographs below you can see the setting of the large granite through stones, which are integral to creating the infill area. Note the number on the granite block in the photograph to the left below...that is one of the carefully catalogued original stones that are being reused and replaced in its original position.
There will also be a drainage system installed under the roadway, which will tie into an outlet (the culvert shown in the photograph above right). The outlet is placed on the downstream side of the bridge to avoid it adding any water runoff above the bridge during stormwater and flooding situations.
The progress made on the spandrel walls are evidenced in the photographs below.