ION - Waterloo Region's Light Rail Transit

[ZEBuilder]

There is Speed River and Grand River. Also elevated across the Fairview Mall parking lot, Fairway Road and the CP Rail line. Elevated crossing over the Hwy 8 exit ramp. Elevated on Shantz Hill Road. Elevated again over the CP Rail crossing first and then CN Rail.

So, while not tunnelled, the amount of bridges and elevated sections is quite significant, compared to essentially zero in phase 1. I'm not qualified to assess how much of the cost impact is due to these bridges and elevated segments, though, how much to construction cost inflation, and how much to something else.

The bridges and elevated sections add significant cost compared to road running the LRT but that is to be expected.

The bridges themselves aren't inherently difficult to construct or design, but the type of bridge and then the soil conditions will both change how difficult it is to construct and thus impact the cost. Most of the time on short to medium span bridges the preferred design is an integral or semi integral abutment bridge. These don't have an expansion joint, thus minimizing maintenance costs, but instead you generally need deep foundations, again this is soil dependent, semi integral can be found on strip footings but is again soil dependent. Other bridge types can utilize shallow foundations but depending on the geotechnical conditions may require deep foundations. So long story short bridge type can change cost significantly just by picking one bridge type over another. This isn't something decided until detailed design which is still a ways away. Regardless soil conditions will govern the foundation type and can quickly inflate costs.

***In Ontario for large projects (bridges, infrastructure, highways) the foundation work is generally two fold. A geotechnical engineering team will be brought in to determine  the surficial conditions, they will produce the factual information report regarding the soil/rock, everything one needs to design a foundation, the report may or may not include foundation recommendations. The project then goes to tender with the factual report, expected loadings (from the structural engineer) with a stipulation that the contractor retains an engineer to design the foundation based on what was provided. This moves risk to the contractor and is extremely typical of large infrastructure projects. However if a design says the contractor must use a 2.5m caisson the risk is on the engineer writing that stipulation.***

Now for our bridges it's good to understanding the surficial conditions around the bridge sites to determine what may make the foundations complicated and potentially drive up the cost.

From Fairway to the Grand River bedrock is rather deep, there is minimal likelihood of having a bridge footing founded on bedrock, hence you will likely have caissons or H piles, this alone means more work and more cost. From the Grand River to Sportsworld the bedrock is shallower but still deep enough that you aren't excavating to bedrock for a footing so again likely will require caissons or H piles. Now around the Speed River and north of Eagle St where the remaining 3 bridges are bedrock is rather shallow, it is entirely possible that those bridges can be built with strip footings provided the bedrock is shallow enough that excavation isn't horrible. Obviously one would need to know the actual soil conditions before one designs something but it is certainly possible with how shallow bedrock is in that area that it could be relatively simple foundations, but again depending on the bridge type you may need to have a more complex foundation and hence more cost.

For the bridge crossing Fairway and the CP tracks (10+180 to 10+690) you're looking at a 510m long bridge that would likely need to be found on deep foundations. For the bridge next to the River Rd extension (11+640 to 11+770) you're looking at a 130m long bridge through the same soils that would likely need to be found on deep foundations. For the bridge crossing the Grand River and running along 8 (12+010 to 13+480) you're looking at a 1.47km long bridge through soils that would likely require deep foundations. For the bridge crossing the Speed River (16+460 to 17+000) you're looking at 540m where bedrock is relatively shallow, so strip footings could be possible however one has to be careful about scour so you may see a mix of both even though bedrock is shallow. For the bridge crossing the CP tracks (17+650 to 18+090) you're looking at 440m on shallow bedrock so strip footings may be possible. Then the last one is the CN tracks (19+760 to 19+850) so 90m again on some shallow bedrock so strip footings could be used.

Geotech Report references:
Low Cut and High Fill FIDR Highway 8 widening north and south of the Grand River: FIDR Highway Low Cut/High Fill
High Mast Lighting FIDR Highway 8 widening Grand River to Maple Grove: FIDR High Mast Lighting
CNR Overhead @ 401 10 lane widening: FIDR CNR overhead widening
Speed River Bridges @ 401 10 lane widening: FIDR Speed River Bridges Widening (Not very useful but reflects CNR overhead bedrock and OGS data)
102 Fountain Geotech (Preston Springs): CVD Preliminary Geotech Report
Ontario Geological Survey Bedrock data: OGSEarth

All in all it's 3.18km of bridges most are 10m (33ft) or so from the ground surface to top of track but some range up to 17m (56ft). Of which 2.11 km will likely require deep foundations to adequately support, the remaining 1.07km will likely see a mix of shallow and deep footings. So foundations alone are going to be an incredible cost. There's a reason the Preston to Galt cost estimate is 960 million less, you're avoiding 2.65 km of bridge (83% of the total Fairway to Galt bridge length).

For comparisons sake the Frederick St Bridge replacement is about 30 million dollars for less than 100m, so our 3.18km of bridge would be about 950 million dollars, obviously Frederick is wider but it is way simpler in terms of not needing so many foundation elements. Or even the Roseville Rd replacement, its narrower and is about 17 million dollars for about 70 meters, so our 3.18km would be about 800 million, so again not a crazy cost estimate at all when you're looking at 17km of LRT track and catenary, 3.18 km of bridges, 2km of retaining wall, and roughly 5.4km of road reconstruction (3.4km of Hespeler, 1.3km of King St/Shantz Hill, 700m of road around Preston (side streets, King and Eagle). 

The Surrey-Langley SkyTrain extension is roughly 375 million per km and is entirely elevated so given ours is only 177 million per km and 20% is elevated its not an insane cost.