Since our blog went up, Considering the Q2Q More Than Just a Bridge, we have had over 1200 views and a great deal of conversation on Twitter and Facebook about it. The response has been overwhelming and predominately positive. We love the idea of having this conversation and at least spurring on a community conversation of our future.
We did the initial concept as a discussion piece to promote the idea that Architecture, Engineering and public transportation infrastructure has a place in the realm of placemaking, community and public art. Communities benefit when they are proud of their bridges, sidewalks and roadways. More than ways to travel, they can also be destinations.
All over the world in large and small cities there are towers and bridges that serve very basic needs (think of the CN Tower for example) but are also major achievements in Architecture, Engineering and public statement.
All this being said, there are a myriad very real technical and financial concerns on top of public acceptance and planning. Many projects have started out with grand ideas only to fail because they weren’t taken seriously from the conceptual stage.
The Q2Q bridge is no exception to this. There are very complicated issues relating to marine traffic, preserving the natural environment, proximity to residences, operation, and of course cost. There is only so much money and the design and construction of the bridge are only the beginning.
One of our community leaders posed a series of well thought out questions. Here they are:
The clearance window for a non-opening bridge is well defined in the Navigable Waters Protection Act. At the narrowest part of the channel (where the train bridge is) it is 22m above Mean High Tide (about 20m above the boardwalk) at a width of about 90m. If you move towards the bifurcation of the channel towards Poplar Island, this window widens to allow two ~50m channels to each arm (it isn’t right in the middle, as the deeper part of the channel is considered. CHS Navigation Chart 3491 gives a good idea of the channel limitations). It is hard to tell from your rendering how far downstream the apex of your parabola extends, but it can be inferred that the window at that point is likely 100-110m wide. Does your design stay out of a 22m x 100m window over the navigable part of the channel?
We have, at this point, made the assumption that the main channel runs to the south of Poplar Island and as such have angled the arch in that direction. We have fine tuned the arch to have a slight kink in it at the point when it reaches the required clearance of 22m and for a distance 330 ft (100.5m). This puts the closest point of the arch roughly 415′ from the tip of Poplar Island. With our design, however, there is an opportunity to angle it slightly in different directions. There is room within the design to widen the aperture with the right engineering in order to suit the proper channel location.
The current guidelines for accessible transportation routes allow for an 8% grade only if there is a flat platform every once in a while to arrest speed, allow rest. Your design appears to be ~500m long with no grade shifts, which would therefore require slopes of 5%. To achieve 20m grade separation above the boardwalk at the peak requires 400m at each side, making the span at least 800m long, plus the 100m-wide window, resulting in a 900m long span. Can you fix this math for me, because I am struggling to remember the equation for a parabola?
Our tweaked design follows the intent of the BC Building Code as well as those pertaining to Accessibility. We have provided an 8% (1:12) slope with resting / stopping areas every 27 ft. These areas are roughly 15 ft x 6ft and have benches. The design allows for a continuous ramp for cycling with these rest points to the side.
The south foot appears to land in the area of trees just west of the train bridge which is protected riparian area, where tree removal would not be permitted under the Riparian Areas Regulation and Fish Protection Act. Any way you can avoid chopping those trees down?
We have adjusted the design to bring the feet of the arch in and over the beach area slightly so as to avoid the riparian areas. Remember, this is an initial concept. Once hired, our job is to ensure the design meets or exceeds all criteria.
Residents along the Quayside have been concerned about visual intrusion of the structure. As much of this structure is near parallel to the shore, this would appear to place a sloped walkway across the field of view of a much larger number of the residents of the Quayside.
While it is true that this design “slices” across many more residents along both sides of the river, the comments we have read regarding the design that has been presented to them have objected to a large elevator tower wrapped in stairs. We feel that our design provides a very thin slice that almost disappears from view and the arched superstructure that supports the pedestrian walkway is almost sculptural and dramatic providing a visual attraction to the Quay. Much like the Gateway Arch in St. Louis, Missouri.
In addition, we have been able to respect the 90 ft clearance from any face of residential buildings.
Any idea at all what this would cost to build?
Answer (Sort of…)
This is by far the hardest question to answer but we are sure is one of the biggest for the City of New Westminster.
While we are certainly not Quantity Surveyors nor steel manufacturers, we have spent some time researching pedestrian bridge costing. What we have found is that there is a huge range in the costs of these bridges. We have compiled some relative examples below:
- Queensborough Interchange, New Westminster, BC –
- Single steel span pedestrian bridge
- ~160m (with concrete deck) –
- $24,828,860 (2012 dollars, Incl. soft costs)
- Swan River Pedestrian Bridge, Perth, Western Australia –
- 560m x 9m (2015) –
- $54M (Incl. soft costs)
- Frances Appleton Bridge, Boston, Massachusetts –
- 68m x 4.3m (2016) –
- $12.5M (Incl. soft costs)
- Fort York Bridge, Toronto, Ontario –
- 232m span (2016)
- $19.7M (Not incl. soft costs)
- Knoxville South Waterfront Bicycle/Pedestrian Bridge, Knoxville, Tennessee –
- 521m span (2015) –
- $20M (Not incl. soft costs)
- Trail Pedestrian / Pipe Bridge, Trail, BC –
- 280m x 4m (2016)
- $12.2 m (Not incl. soft costs)
As can be seen from the numbers above for relatively comparable bridges (apart from the Queensborough Interchange Pedestrian Bridge which uses concrete and is not a suspension bridge), the costs per linear meter vary greatly.
That being said, we had the opportunity to review the detailed cost breakdown of the Trail Pedestrian / Pipe Bridge whose tender was awarded in September of 2015. We also reviewed the Class D estimate done by Opus Dayton Knight in 2011. The Trail bridge is the most similar to our design in terms of it being a suspension bridge over a delicate river and being constructed all from steel. The only significant difference apart from the aesthetics, is that the Trail bridge also has a complicated component of a sewer pipe attached to it as well as a pumping station. These two components affected the overall pricing significantly.
From reviewing the initial Class D estimate, which, it should be noted, was 1/8 of the actual awarded price for the bridge, we can break down the cost of the sewer component from the bridge component. It appears that this part constitutes roughly 32% of the overall budget. Therefore, we can infer that of the $12.87M cost of the overall bridge, the project would have cost in the order of $9.9M ($35,663.21/m) without the sewer pipe.
So, now down to our design.
Our Q2Q Bridge is roughly 584m, which, at the recent approved price of the Trail Bridge at $35,663.21/m, would cost in the order of $20.8M. However, we must take a few things into consideration:
- The Trail Bridge has two large end piers as well as two significant piers and towers that are constructed within the river. This is a very costly component which our design does not employ.
- The Trail Bridge uses a significant amount of concrete in the piers which our design should not by comparison.
- The Trail Bridge uses a steel deck which is more expensive than the wood deck we are proposing.
- Trail is a remote community and as such see a great inflation in the cost of construction and we can expect a lower cost here in New Westminster.
We do understand that the City of New Westminster presently has a budget of around $14M however given the information above it appears that this budget may not be realistic. Certainly given that the bridges noted do not have the added complexity and costs of two draw bridges, five piers (three of which are in the river) and elevators. Remember that the City report calculated the budget for the Pier Park Elevator with the overpass and stairs at $1.85M. Only through a true direct analysis of apples to apples with the City of New Westminster numbers can a real comparison cost be done.
- As a final note, here are the advantages we see in our design:
- No need for elevators with long term maintenance costs.
- No need for draw bridges with long term maintenance cost.
- Little regular maintenance compared to the design presented to date.
- No need for pedestrian / cyclist traffic control due to drawbridges and marine traffic. (which necessitates that the draw bridges in open position as normal until needed by pedestrians / cyclists. At present it is unclear how these draw bridges will be activated. Will an operator be required?)
- Little to no environmental impact on the Fraser River
- Fewer security concerns.
- The creation of a “Destination Bridge”
Thank you again for letting us be a part of the conversation.