| OTIA III State Bridge Delivery Program |
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| Web brief (Jan 08) |
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Keeping the McKenzie River swimmingly clean, clear and quiet
Do fish have ears? What is a fish’s keenest sense? These questions are what keep biologists up at night, and, at ODOT, heavy highway contractors as well.
So, what are the answers? No, fish don’t have ears in the conventional sense—they actually detect movement and vibrations in the water. Yet ironically, the keenest sense for most fish is…hearing! Sound moves through water the same way it does through air, so fish hear water movement and vibrations through finely tuned nerve endings.
Which is why ODOT and bridge program contractor Hamilton Construction Co. used a tool that muffles the potentially deafening noise generated by heavy machinery operating on Bundle 215, Interstate 5: McKenzie River to Goshen Grade over the McKenzie River. To help mitigate the sound waves caused by drilling, which would disturb fish and other creatures in the river, Hamilton uses a bubble curtain: a ring on the bottom of the river that discharges air, causing bubbles to rise continually and isolate vibrations and noise.
Whether repairing highways or building bridges, ODOT adopts a tread-lightly approach to the natural environment. On a bridge project where rivers and streams are concerned, in the ideal world, the only things allowed to touch the water are the pilings driven into the stream bed. That means everything from building materials to dredged river bottom and even heavy-equipment noise must be kept out.
“Hamilton and its contractors have really strived to meet, and in some cases exceed, the environmental standards and goals of the bridge program through their design-build project delivery,” said Hal Gard, ODOT geo-environmental manager. “This has been a very positive project for the users of the McKenzie River and the state of Oregon.”
The first priority is to determine when the contractor can work without disturbing the habitat and nesting patterns of fish, bats, eagles and other birds. These in-water work dates are negotiated on each project between the construction companies and the regulatory agencies, such as the Oregon Department of Fish and Wildlife.
A temporary work bridge is necessary both to support heavy equipment—the cranes and drills needed to build the new bridge—and to protect the water below. Hamilton’s work bridge over the McKenzie River is unique in that its storm-draining system not only collects all the water that falls on the bridge but ferries it to shore for treatment. A double layer of Visqueen—a thin sheet of plastic—lies under the plywood surface as a vapor barrier to collect any spills before they reach the water.
“Everything from construction needs to be isolated from the environment,” said Jim Sly, project manager and vice president of Hamilton. “Down to the level that if something dribbles out of a drill, it’s contained, and a crew member can shovel it into a Dumpster to be hauled away.”
The river must even be protected from its own riverbed, because dredged dirt creates turbid water that stresses fish and other aquatic creatures. Yet to set pilings that support the permanent bridge, Hamilton must drill shafts 30 to 40 feet into the river bottom. The muck the drill brings up is therefore put in steel containers and transported to a garbage site. For the drilled shafts themselves, the company uses a permanent steel casing that contains the concrete and keeps the water clean.
Even on projects as enormous as highway bridges, ODOT and its contractors try to live up to the standard for environmental stewardship that is attributed to the 19th century American Indian leader Chief Seattle: “Take only memories, and leave only footprints.” A policy that we are sure the fish and other creatures residing in Oregon’s waterways greatly appreciate.
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