Mystery orb on Smith Tower keeping tabs on Seattle tunnel project
Mar 12, 2015, 5:30 AM | Updated: 10:32 am
The white orb on the Smith Tower is a sensor device monitoring ground settlement. (Photo courtesy of Brian Pellin)
(Photo courtesy of Brian Pellin)
Seattle Public Utilities has installed a temporary sensor device on Smith Tower after concerns over ground settlement caused by the Seattle tunnel project.
“We have critical infrastructure in the area that we’re concerned about and we’re keeping a very close eye on it,” said Andy Ryan, the Seattle Public Utilities spokesman. “This was part of our response to keeping an eye on our infrastructure.”
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A Gamma Remote Sensing device was installed on a corner of the tower around Feb. 20. The device monitors ground and structural settlement over a wide area, including Pioneer Square, according to Ryan.
Ground settling has occurred in the area directly above where the Washington State Department of Transportation and Seattle Tunnel Partners have pumped groundwater to facilitate repairs of Bertha. The boring machine is currently being disassembled at the repair access pit.
The tunnel project is believed to be responsible for settling of the ground in the area.
The state and city departments of transportation are monitoring the area near the tunnel project. About an inch of settlement near the repair access shaft was detected in December. Though drilling wasn’t blamed, settlement did coincide with the time frame when crews began removing water from the pit, transportation spokesman Todd Trepanier said in December.
A map released by the Department of Transportation shows areas within Pioneer Square have some of the highest amounts of ground settlement.
There are no sensors in Seattle like the device on Smith Tower, Ryan said. However, three GPS receptors were placed in the Pioneer Square area before it was installed. The Department of Transportation also has “hundreds” of sensors around the tunnel project.
“There is lots of monitoring going on in that area,” Ryan said.
The device, which monitors everything within its line-of-sight, was installed for a short test period. If the results are “good,” it will stay for approximately six weeks, Ryan said.
The device is expected to be removed by May 1.
