Green Bridge: It’s all about scale

05/25/2017

Caltrans’ recently released draft environmental impact report is the latest step in the process to replace the Green Bridge with a more structurally sound version. Our community has been very involved in the project, from convincing Caltrans to hold more community meetings than it normally provides and to send newsletters to keep us updated, to submitting a large number of comments.  

The scale of our response has far outsized that for any other small project Caltrans has undertaken in years. That is a very good thing, because this bridge is the lifeline between our communities. With delivery trucks, school buses, emergency vehicles and residents visiting local shops, daily traffic on the bridge is significant, even on days not inundated with tourists.  

Scale is something I first learned about in high school, when I took a freehand drawing class. Many years later, in another art class, I learned more about the relationship of each object in my picture to the objects around it. The same principles were apparent when I created my gardens and furnished my house. In each of these instances, I learned that the oversized scale of any one item could throw off the whole project, giving the eye a sense of unease.

Scale is also important when it comes to bridges and their construction. The scale of even our small bridge could create an imbalance in our lives and surroundings. We all knew this when Caltrans initially proposed to have construction underway for three years. The disruption to our lives for this overly long time period was untenable. When an accelerated bridge construction method was suggested, many of us felt more at ease, even though we knew the crossing would be closed for up to three weeks.

Environmentalists are concerned about the scale of the damage caused to flora and fauna in the area. But by keeping the construction period shorter and the footprint smaller, the scale of that damage is much reduced.

The one remaining important scale factor concerns which bridge design alternative is chosen. The draft report gave us three options, with two others merely included for comparative purposes. The real choice is between a three-span, short steel-truss bridge; a three-span concrete bridge; and a full-span, steel-truss bridge. All would be built on accelerated schedules.

Since the widths of the lanes, shoulders and sidewalk are the same for each of these alternatives, one needs only to focus on the overall width and height of each design, as well as how well the scale of each visually fits into the immediate area and the overall aesthetic of our communities.   

The current bridge is 34 feet wide, with seven-foot-high steel trusses (the sides). The smallest alternative is the three-span concrete bridge, coming in at 43 feet wide and two feet high. If we wished to add an ornamental steel truss on the sides of the bridge to resemble our existing bridge, that would add an additional two feet to the width and another five to seven feet to the height. The end result is a bridge of the same height or shorter than the Green Bridge, but wider by nine to 11 feet.

The three-span, short steel-truss alternative is the next largest in scale. The height of this bridge would rise to 12 feet, and the width would be 47 to 50 feet, an increase of five feet in height and 13 to 16 feet in width. It resembles the Green Bridge, but is almost 50 percent larger in scale than the existing bridge.

The final option, the full-span, steel-truss bridge, would be similar in width to the short steel-truss alternative, at 47 to 50 feet wide. Yet its would far outweigh any proper sense of scale for our area. The basic design for this alternative would be 21 feet high and would have cross bars over the top of the bridge, from the steel truss on one side to the steel truss on the other. If the option with the arched truss were chosen, the height of the bridge and overhead bars would increase to 30 feet. The scale of both full-span options far surpasses what the surroundings can absorb and still provide that ease to the eye that I learned about years ago in art class.  

An appropriate scale is critically important for us to consider as we comment to Caltrans about our concerns and preferences for the final design. Personally, I want to come around the corner on Highway 1 or Levee Road and look up to see a bridge that reflects the rural, natural surroundings of the area I have grown to love, whose scale is appropriate to the buildings next to the bridge, and whose size does not overwhelm the beauty of Lagunitas Creek and our community.

 

Cathleen Dorinson, a member of Mainstreet Moms, lives in Point Reyes Station.