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Thursday, May 23, 2013
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NPS wants to quiet roar from Interstate 80
by Gregory R. Norfleet · News · August 17, 2012
Stand next to Interstate 80 for eight hours and the decibel level from tires on pavement and roaring engines could cause hearing damage.
People who live in West Branch may be accustomed to the constant din of noise, but staff at the Herbert Hoover National Historic Site think it takes away from the otherwise serene atmosphere of the gravesite and the historic nature of the birthplace cottage.
Teacher-Ranger-Teacher Lynette Cummings has spent many summer days standing outside the cottage, measuring the decibel levels. When she met with this reporter in late July, the meter bounced from the 40s to the 60s. After watching it for a minute or so, she settled on 52 dba.
Just over 40 is equivalent to a “quiet urban night time” or “small theater/large conference room,” according to NoiseQuest.com. Just over 60 is like standing three feet from a non-stop talker. And that 52 Cummings settled on — rather than when it spiked as chatting visitors walked by or trucks honked on I-80 — is like a “quiet urban daytime,” or large business office, or a dishwasher in the next room.
Cummings teaches physics, chemistry and physical science at West Branch High School. She is taking readings for the Hoover Complex in part to teach her students about sound — and its affects on general health — and to help the historic site make a case for federal funding for buffering highway noise.
“It’s supposed to be like the 1870s,” she said of the park ambiance.
Cummings takes measurements also at the Quaker Meetinghouse and the blacksmith shop because the focus is on the historic section of the park. But she also checks the gravesite and the prairie near the westbound on-ramp of I-80.
The historic “core” ranges between 40s and 50s, she said; the gravesite is in the 50s and 60s; and the prairie averages from 60s to 70s — the higher end is like a vacuum cleaner 10 feet away.
The prairie can, with moderate to heavy traffic, reach into the low 90s, she said, like a food blender from three feet away.
“Eight hours of that can cause hearing damage,” she said.
Bob Palmer, outgoing chief ranger, said ideas to reduce the noise are as simple as planting trees with heavy foliage to building a wall similar to what Scattergood Friends School placed next to the interstate. One other possibility: quieter pavement on I-80.
Though the project is still in the data-collection phase, Palmer would like to see the decibel level of the park decrease by 10, at least, through a combination of factors.
“It would improve the quality of our resources,” he said.
But such improvements are at the mercy of the park’s budget as well as the park’s management plan, though there is a process for changing the latter.
Cathy Cutler is a transportation planner with the Iowa Department of Transportation out of Cedar Rapids. West Branch is in the DOT’s District 6.
She said the DOT has a practice of considering “protected resources” like the Hoover Complex — in part because the DOT accepts federal funding. Also, the DOT’s own project of widening I-80 to six lanes includes replacing the old road with “quiet concrete” — a DOT practice of the last 10 years.
Cutler said highways are built with textured tops to prevent ponding or pooling in rain, or some icing in winter. While the concrete is still soft, workers in the past dragged tines from left to right — “transverse” tining — to produce the texture. For quiet concrete, they drag the road in the same direction as travel — “longitudinal” tining — reducing the noise, she said.
Charles Bernhard, who works for the DOT’s office of location and environment, said Arizona was able to reduce sound by up to 4 decibels with a rubberized pavement.
That’s enough for the human ear to notice a difference, but not a lot, he said.
West Branch’s Parkside bridge was replaced two years ago and lengthened to span a six-lane highway. However, Cutler said the section passing by West Branch is not in the five-year plan. |
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