Bridge for Kids | |
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Coordinates | 47°06′35″N 122°12′49″W / 47.10972°N 122.21361°W |
Crosses | Carbon River |
Locale | Rocky Road NE, Orting, Washington |
Official name | Orting Emergency Evacuation Bridge |
Characteristics | |
Design | Suspension bridge with uneven footings |
Total length | 540 feet (160 m) |
Width | 20–30 feet (6.1–9.1 m) |
Clearance below | 18.5 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[update], the $40 million bridge was still in the planning phase.[2]
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[update], 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]
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]