The blame game continues in the saga of Millennium Tower, which we learned last month had sunk 16 inches into the ground since it was completed seven years ago, and is also tilting a couple inches more than it should be, apparently as a result of unstable soil. The latest salvo from Millennium Partners, the developer of the tower, came at a Tuesday news conference in which they cited "reckless behavior" on the part of the Transbay Joint Powers Authority (TJPA), who have been developing the Transbay Transit Center next door to the tower since 2010, as covered by ABC 7 and the Chronicle. And they point to the dewatering process for the transit center — in which water is removed from the soil during excavation to create more stable conditions for building — as having caused a drop in the water table that is to blame for the excessive settlement of their tower.

Millennium Partners founder Christopher Jeffries spoke at the conference, coming out swinging and telling reporters that his firm was the first to raise the dewatering issue with the TJPA and the Department of Building Inspection in 2009, after their own dewatering process prior to 2008 had been shown to cause greater settlement of their new tower than expected. Per the Chron, knowing that the Transit Center construction would require further dewatering next door, "Those concerns were incorporated into an easement agreement between the authority and the developer that requires the public agency to monitor the water table and track the Millennium’s settlement."

He also rejected the idea, brought by the TJPA and some others, that Millennium Partners' decision not to drive foundation piles down to bedrock, but only to drive 80-foot piles, was to blame for the excessive settlement — though it has been noted by experts that this is one of the tallest and heaviest towers ever to be constructed over what was once past the shoreline of Yerba Buena Cove, i.e. all landfill on top of bay mud. "The state of the art of foundation design in San Francisco has not been to go to bedrock," Jeffries said, noting that every other tower up to the time that Millennium was built only drilled piles down 80 feet. “The only buildings built to bedrock are these four," he said, pointing to four new towers all built or under construction on TJPA property: 181 Fremont, Salesforce Tower at 101 First Street, 350 Howard Street, and the Transit Center itself. "This represents a dramatic change in how buildings are designed in San Francisco, and it’s a standard that has all of a sudden been imposed in the press as what everyone should be doing in San Francisco."

Yesterday, City Attorney Dennis Herrera subpoenaed Millennium Partners, as KRON 4 reports, to determine if the developer made all the necessary disclosures under state law that it should have to condo buyers, knowing that the tower was settling/sinking at an above-average rate.

At the conference, Millennium Partners founding director Philip Aarons responded saying, "We are a little surprised by the subpoena... There has never been anything that we were hiding."

The TJPA, a public agency which if successfully blamed in court could mean the spending of public dollars to settle lawsuits from condo owners, continues to say that its work has had no impact on the tower's settlement, and that Millennium Partners knew long before the Transit Center construction began that it had a problem.

Experts say the tower could continue to sink up to 30 inches, or nearly three feet, in the next few years, in addition to tilting, and though likely not to impact the seismic or structural stability of the tower itself, could cause issues such as cracks in walls and malfunctioning elevators. Also, the terrible press and negative perception of a building sinking into mud is likely to have an impact on condo resale prices, which has prompted a class-action lawsuits by owners.

Supervisor Aaron Peskin has also weighed in to suggest that there may have been "political interference" at the time of the tower's approval that glossed over this important issue.

And in related news, as the Business Times explains, Millennium Partners' reputation could be so tarnished after this whole story unfolds that it could jeopardize the success of their other major project, now under construction at 706 Mission Street. The 190-unit tower, delayed about a decade by fights from neighbors in the Four Seasons tower, is set to have the Mexican Museum in its base, and could fetch record-setting prices for its units, unless buyers get scared off.

All previous coverage of the Millennium Tower saga on SFist.