After months of trying to determine whether dewatering Bertha's rescue pit caused ground settlement in Pioneer Square last year, the Washington State Department of Transportation finally has an answer: Yes. And not really. And well, maybe. Kinda.
WSDOT published two reports this morning, one conducted by geotechnical firm Shannon & Wilson, and the other commissioned by Seattle Tunnel Partners (Bertha's contractor) and conducted by Brierley Associates. The first blamed the ground settlement on dewatering related to Bertha's rescue pit. The second said the ground dipped due to "natural settlement and other dewatering activities" and "tunnel-related dewatering only contributed in areas immediately surrounding the pit."
In sum, STP's study—even though it looked at the exact same data that Shannon & Wilson's did—found that STP's own activities weren't primarily to blame. Surprise! What the hell could account for the difference between the two accounts?
Maybe additional satellite data:
Shannon and Wilson's report, utilizing in part information from satellites, also identifies settlement in areas surrounding the project—in some cases, outside the ongoing monitoring area. Though satellite imagery is helpful to indicate trends, ground monitoring is the most reliable gauge of ground activity, which is why WSDOT's monitoring program relies mostly on ground sensors throughout the project area.
What this means going forward is if someone gets sued for something settlement-related, WSDOT and STP will almost surely have a beef. For example: Who is going to pay for that 20-inch cast-iron water main that's sunk more than an inch below Pioneer Square? In April, Seattle Public Utilities said that the pipe needed to be fixed immediately, and could cost some $4 million.
But the state said—as it has repeated several times—that settlement has now stabilized. Council Member Mike O'Brien doesn't buy it. "When I look at the numbers… to me it looked like settling is continuing," O'Brien said. "They kind of said, well, maybe, at that point it was really small, last month was more. None of that really gave me confidence that settlement has stopped."
A WSDOT panel announced earlier this year that, even with all of the project's mishaps, Bertha would remain within her budget. But with a running tally of conflicts between the state and its contractor, how that prognostication will hold up remains unclear.
In other news, WSDOT also announced this morning that damage found during Bertha's disassembly "was more extensive in some areas than anticipated." On top of that, some additional damage was created while the machine was being taken apart. "For example, the outer seals and the steel retainers that hold them in place were destroyed," WSDOT's update read. "There was also damage to the cutter drive motor pinions and the main bearing bull gear."
Really, you guys? Well, at least Bertha has one good thing going on. She's got a new Twitter boyfriend. His name is Polar Pioneer.
Other than that, though, it's all grim. As Mike Lindblom notes, all the new damage to Bertha is going to cause her to miss her August restart date.