Guest Post and Images by Bill Badrick
Building a bridge in the 21st century must be done better and differently than it was done in the past. As we develop plans to build a modern bridge over the Columbia River, we must reflect our understanding of global warming and our dedication to salmon preservation. The Columbia River Crossing (CRC) Bridge should illustrate our best design response to difficult conditions. It should be green and multi-modal. It should have light rail, bicycle, and pedestrian service to balance the car and truck capacity. The CRC Bridge will have a massive carbon footprint, and we need to mitigate it with green design.
SCGH opens up to hear about one simple and powerful way to do this: build a “park roof” on top of the CRC Bridge. The park roof will be a tool to capture the rainfall that would otherwise land on the road surface and mix with the oil and gas that falls off of vehicles. Traditionally, stormwater pollution is expensive to treat—pollution treatment facilities cost in the area of 12 to 15 million. In addition to the facility, a conventional bridge roadway must be made to slope to drains, which fill hundreds of pipes that are routed to the treatment plant. All of these metal drains and pipes cost money and add to the carbon footprint of the bridge. By contrast, the park roof would need only a small gauge recycled plastic pipe sprinkler system that can be powered by solar panels. By capturing the rain fall with the park roof, we can save money—and save the salmon.
The federal government’s recent studies on green roofs, which had previously been predicted to absorb 75% of rainfall, found that they actually captured nearly 95% of the rainfall. Based on these findings, the park roof will save us a great deal of money and improve the carbon footprint dramatically. The CRC park roof will be about 370,000 square feet, and Portland receives roughly 37.5 inches of rain a year. This amounts to almost 14 million cubic feet of water captured and almost $170,000 saved.
From a design perspective, the park roof also promises benefits. The roof will be a curved cap to the bridge, making the bridge a good deal more aerodynamic. This efficient design shape will reduce structural stresses, thus reducing cost. It is likely the savings due to better wind performance will account for the cost of the additional park support frame. Plus, as bridges are engineered to be three times stronger than needed, the additional 23 lbs/sq ft load will be absorbed on the base structure with no additional load cost. It is important to note that the park ‘dirt’ is made of very lightweight engineered growing medium, anchored to a matrix net to make it wind and erosion proof—this is not your grandma’s garden.
The park roof will be a one-of-a-kind, world-class green public facility. It can be the sign and symbol of Green Portland, Green Oregon, and Green Northwest! We love our solar plants and windmill fleets, but they are out of sight, and thus out of mind. The CRC park roof will greet every visitor driving from the north and every airline passenger flying into the airport. The vast arcing park high above the mighty Columbia River will draw green tourists from around the world.
An eco-tourist business is what we should naturally grow—with our stunning natural landscapes, many outdoor activities, and open, progressive thinking. The final icing on the cake to draw this new enormous green travel business is a powerful symbol that clearly represents our green beliefs. The park roofed, multi-modal CRC Bridge can be our ‘Green Golden Gate’—our ‘Green Gateway’ to the Northwest.
About the author: Bill Badrick creates park roof proposals in large pastel artworks to educate and inspire politicians and change-agents to think outside the box when it comes to our large and visually prominent bridges and buildings.
© 2013 SCGH, LLC.