Sound Transit East Link Project & Program Managers have been assuring folks potentially impacted by Sound Transit’s East Link project for years that tunneling is completely safe...

Take a look at this article by the Seattle Post-Intelligencer (click here).Perhaps the potential impacts from tunneling aren’t always so benign…

“Sound Transit is monitoring a Beacon Hill neighborhood after a large sinkhole formed on a resident’s property about 135 feet above the northbound light rail tunnel, the agency said Friday.

Obayashi Corp., the agency’s contractor, sent crews to plug the hole with cement-like filler material. The property owner notified Sound Transit March 29 about the hole with concerns that tunnel construction caused it. Tunnel boring was completed more than a year ago.

“The strange thing is we don’t know exactly how it was formed. We would have had to have done extensive geological investigation into the hole, which would have incurred costs and taken time,” Sound Transit spokesman Geoff Patrick said. “We’re not aware of any reason to be concerned. That said, we’re going to be closely monitoring the area around there.”

Comments from the article:

“Here is my take on this from a well driller’s perspective. The tunnel boring machine disrupted the continuity of either a perched aquifer or alluvial layer. Heavy rains now flow downward, unrestricted, towards the tunnel which serves as a new artificial aquifer (around its circumference). Higher water flow (velocity) underground leads to sinkholes. Reporters take note: Ask to review the hydrological reports for tunnel drain systems (this week especially). Review the soil sample reports from material collected in tunnel outfall scuppers. What you will find is that the same soil from that sink hole is showing up in the tunnel drainage systems. Metro will show higher than normal silt in storm drains”

And again:

“They can’t just plug it up without knowing the cause. Whatever caused it can cause more sink holes. Something there is probably unstable. It might be caused by some construction error that will be repeated in future Sound Transit tunnels. This can cause damage to homes near the tunnel. (The people living there need to file complaints and try to establish some kind of liability just in case.) It can *kill* people when trains start going through. Please, please, please…go hire an expert — a geotechnical engineer — and get an assessment. If they know what they’re doing it should be just a few thousand dollars. YOU HAVE TO DO IT!!! Morons. I don’t think they *want* to find out anymore about the problem — it might cost them a huge amount of money and time to fix it.

Perhaps Sound Transit should go ahead & incur the geological costs necessary to ensure lives and unnecessary damage to private property….