Bridge for Kids
Coordinates47°06′35″N 122°12′49″W / 47.10972°N 122.21361°W / 47.10972; -122.21361
CrossesCarbon River
LocaleRocky Road NE, Orting, Washington
Official nameOrting Emergency Evacuation Bridge
Characteristics
DesignSuspension bridge with uneven footings
Total length540 feet (160 m)
Width20–30 feet (6.1–9.1 m)
Clearance below18.5 feet (5.6 m)
Location

The Bridge for Kids is a proposed bridge across the Carbon River in Orting, Washington, about a mile upstream of where it joins the Puyallup River. It would provide an emergency evacuation route for school children to escape a future lahar flow from Mount Rainier, consisting of an up to 10-meter (33 ft) high flood of mud, rock and boulders.[1][2] As of 2016, the $40 million bridge was still in the planning phase.[2]

Background

Historic mudflows from Mount Rainier
Steel highway bridge embedded in lahar from 1980 eruption of Mount St. Helens

Lahars from the Cascade Volcanoes are historically common.[3][4] Orting is situated in the floodplain of the Puyallup River and on top of the debris field of past lahars from Mount Rainier,[5] including the Osceola Mudflow. The Osceola Mudflow followed an eruption 5,600 years ago that left a horseshoe-shaped crater in Mount Rainier comparable to that of the 1980 eruption of Mount Saint Helens and deposited debris across a 212-square-mile (550 km2) area as far as Commencement Bay on Puget Sound.[3] Another event, the Electron Mudflow, produced a lahar that was 30 meters (98 ft) deep when it reached the Puget Sound lowland.[3]

The current lahar risk is considered extremely high in Orting,[6] with an estimated one in seven chance of a catastrophic event in a resident's lifetime.[1] Land use planning and emergency management in Orting differs from that in surrounding Pierce County, allowing development and location of schools in this area.[5]

The Mount Rainier Volcano Lahar Warning System has existed since 2000 to give residents in high-risk areas some advance warning of an approaching lahar, but evacuation drills in Orting have shown that motorized transportation (school buses) is not a viable option for removing students from the lahar zone due to road congestion and time factors.[7]

Evacuation planning at Orting schools started in 1995, and it was then that the insufficiency of infrastructure began to be an issue.[1] As of 2016, drills were showing student evacuation times via an existing 2 miles (3.2 km) foot route to still be in excess of the notification window.[2]

Bridge design

A yearlong design process was started by Pierce County in consultation with Washington State Department of Transportation and other agencies and a citizens' group in January, 2009, after considering other evacuation means such as pathways and a tunnel under the river.[8] The bridge would be 20–30 feet (6.1–9.1 m) wide and accommodate 12,000 people in 30 minutes. Orting is estimated to have a 40 minute evacuation window after the Mount Rainier Volcano Lahar Warning System is activated.[7]

Preliminary design renderings from 2014 show a pedestrian suspension bridge with stairsteps approaching a lower pier, and another pier 150 feet (46 m) higher on a ridge above Orting, near the community of Tehaleh.[2][9][10] Part of the bridge deck would contain stairs and lie at a 40% slope.[10]

See also

References

  1. 1 2 3 Lisa M. Pinsker (April 2004), "Paths of Destruction: The Hidden Threat at Mount Rainier", Geotimes, American Geological Institute
  2. 1 2 3 4 John Hopperstad (June 1, 2016), Parents near Mount Rainier fight for bridge to escape deadly lahar (Television news), Tacoma, Washington: Q-13 Fox
  3. 1 2 3 Significant Lahars at Mount Rainier: Osceola Mudflow, United States Geological Survey, November 10, 2014, Lahars are common at Mount Rainier...
  4. ↑ Steve Maynard (June 6, 2012), "Report: Mount Rainier lahar could cause $13 billion in property damages", The News Tribune, Tacoma, archived from the original on September 15, 2016, retrieved September 4, 2016, Mount Rainier has produced major lahars every 500 to 1,000 years and smaller flows more frequently. The most recent major lahar to reach the Puget Lowland was the Electron Mudflow about 600 years ago. It was more than 100 feet thick at the community of Electron and as much as 20 feet thick at Orting.
  5. 1 2 Julia S. Becker; Wendy S.A. Saunders; Clare M. Robertson; Graham S. Leonard; David M. Johnston (January 2010), "A synthesis of challenges and opportunities for reducing volcanic risk through land use planning in New Zealand § Potential for reducing volcanic risk through land use planning: Case studies from USA, Japan and New Zealand", The Australasian Journal of Disaster and Trauma Studies, 2010–1, ISSN 1174-4707
  6. ↑ Eli Saslow (April 18, 2015), "Town waiting for an eruption found it after firing its first black police officer", The Washington Post, Life for Orting's 8,000 residents depended on predicting what would one day come roaring down the slopes of Mount Rainier, 30 miles away. They had sirens for lava, sensors for earthquakes and alarms for the volcanic mudflow that geologists believed would one day bury the town.
  7. 1 2 Kari Plog (October 25, 2014), "Politicians, scientists, local leaders revisit Orting's Bridge for Kids at summit", Tacoma News Tribune
  8. ↑ Bridge for Kids Fact Sheet (PDF), Washington State Department of Transportation, 2009, archived from the original (PDF) on 2017-02-03, retrieved 2016-08-01
  9. ↑ "Orting unveils plans for Bridge for Kids at Emergency Summit" (Cable television program), Pierce County News, Pierce County, Washington, October 30, 2014 6:00–7:00
  10. 1 2 Pierce County, Washington & BergerABAM (2014), Orting Emergency Evacuation Bridge Design (blueprint) – via bridge4kids.org
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