The Wild Side of Bridge Construction
The following post was authored by Eric Anderson, Deputy Project Leader at Ridgefield National Wildlife Refuge and employee of the Refuge for 24 years.
The River ‘S’ Bridge replacement project has been a sight to behold, with massive 300-ton capacity cranes, rebar cages the size of redwood trees, and enough concrete trucks to constitute a parade. But this isn’t any old bridge, it’s a bridge at a National Wildlife Refuge. Thus, it’s fair to ask how a project of this magnitude impacts the wildlife for which we restore and improve habitat. And it’s a question I’ve received more than a few times since construction began in March. So let’s dig into the project and our efforts to limit disturbance to wildlife and their habitat.
A Front Row Seat for Geese
One common concern I’ve heard is what impact there has been to wintering waterfowl on the Refuge. The ideal construction strategy would of course be to avoid the ‘wintering’ waterfowl season. Unfortunately, ideal isn’t always realistic. In the case of a project that is estimated to take a year, it is impossible to avoid any single season for the needs of wildlife. And working only in the summer would add years and significant cost to the project.
The field next to the construction area is called North River Pasture. In my 24 years at the Refuge, it has been my experience that geese generally use North River Pasture from February through April. With construction, I predicted geese would avoid this field entirely due to the bustle of construction near the bridge. In late March, I was on the bridge observing the day’s construction and much to my surprise, about 200 geese were south of the bridge in dirt exposed from the project. I have to assume that new grass was growing in the fresh dirt and the geese were seeking out the young sprouts. I expressed my surprise to the project foreman, to which he replied the geese were actually frequent visitors to that spot and how they made a great backdrop for project photos.
I recently had the opportunity to view time-lapse photography of the progress of the bridge. As expected, the construction site was swarming with the jerky movements of machines and workers. But keeping to the tradition of North River Pasture, the field was also regularly grazed by flocks of geese throughout the Spring, maintaining a comfortable distance from the foreman and his machines.
Here’s that time-lapse video. At about 51 seconds in, you’ll see a gaggle of geese take a front-row seat for the construction action:
How We’re Reducing Disturbance
Now, it would be false to claim that construction is having zero impact to wildlife. We have, however, factored concern for wildlife and wildlife habitat into the bridge’s schedule and construction methods. Examples include:
The permits to conduct ‘in-water’ work are set to avoid migration and critical life stages of native and anadromous (migrating) fish.
Related to fish habitat, the barges next to the bridge are fitted with special floating aprons that are designed to minimize the turbidity (particles floating in the water that reduce clarity) induced by the undulation of equipment working from the barge. Workers monitor turbidity surrounding the project area during in-water construction to ensure that their activities are not significantly degrading water quality.
Workers are required to test in-stream pH (acidity level) during concrete pours to monitor for increased alkalinity and reduced water quality.
During the installation of temporary work pilings, special ‘bubble’ curtains are installed around each piling to baffle/diffuse the hydroacoustic waves (underwater sound waves) within the water column created by the pile driving activity. Pile driving activities are monitored to ensure that noise and energy levels in the water column are at safe levels for aquatic wildlife.
As the season transitions into summer, my welcome distraction while inspecting the bridge has switched from the yip of cackling geese to a dozen purple martins tending to their gourds. They too seem to be tolerating the project. And in good time, our patience with months of construction will be rewarded with safe and reliable access to the River ‘S’ Unit for years to come.