Driving on Styrofoam, Building on Pillows

Geofoam at SR 519

Geofoam at SR 519

You may have seen this recent blog headline: In New York, Buildings ‘Sleep’ on These Giant Red Pillows. Since that headline was called out in an engineering-related notice, you might have assumed it had something to do with seismic stability or that it was related to geotechnical engineering. After all, a recent Washington State Department of Transportation project (SR 519) used giant blocks of styrofoam in the foundation for access ramps and pedestrian areas.

To be more specific, SR 519 had the first application of geofoam approved by the Seattle Department of Transportation. Geofoam, or lightweight expanded polystyrene, is essentially a type of Styrofoam, and is used as lightweight fill in areas where heavier materials would be problematic. For the SR 519 project, using Geofoam helped protect hundred-year-old utilities. Meanwhile, highrises now can have huge rubber or fluid-filled shock absorbers, or Teflon-coated pegs.

But if you clicked on that blog headline about pillows expecting to see an earthquake engineering technology, you would have been delightfully wrong. The blog entry is about a stunning art installation, not about engineering. Although you might wonder whether there is an underlying truth to the art.

Take a look.

Potential New Airborne Pile Driving Criteria for Marbled Murrelets

The marbled murrelet is a small seabird listed as threatened under the Endangered Species Act in the Pacific Northwest. Most Pacific Northwest subpopulations are declining. In Puget Sound declines are about seven percent a year. If the decline goes unchecked, the species may disappear locally. As a result, the US Fish and Wildlife Service has developed conservative policies to protect the species from disturbances from waterfront development activities.

In 2011, the USFWS adopted new underwater criteria for evaluating the effects of impact pile driving (for steel piles) to diving marbled murrelets. Since these criteria were adopted, pile driving operations in areas where marbled murrelets may be present require using USFWS-certified marbled murrelet observers to patrol the impact zone during all impact pile driving operations.

These criteria don’t address temporary hearing loss or behavioral effects. For behavioral effects, the USFWS is considering extending the criteria to airborne noise and driving piles with impact or vibratory drivers. The agency believes that airborne noise in the range of 14 decibels above the background level can interfere with murrelet calls to each other on the water, potentially affecting foraging behavior. The concern is that foraging effectiveness may be decreased or compromised, particularly during the breeding season when the birds are actively feeding young. In the Pacific Northwest, marbled murrelets nest in old growth forest habitats, often great distances from the marine environments they feed in. The belief is that any delay or compromise in feeding efficiencies may affect reproductive success.

New airborne criteria, if adopted, may greatly affect the current zone of impact or distance from pile driving operations in which Endangered Species Act “take,” (harrassment or harm) may occur. The 14-decibel airborne sound level under evaluation is substantially lower than the current 92-decibel level, which is a general guideline with no enforcement authority. This could affect the nature, level of effort, and cost of future monitoring programs required during pile driving operations in Puget Sound. We will continue to post further developments of potential new criteria as they come available. Stay tuned!