A condo tower in downtown San Francisco has earned the title The Leaning Tower of San Francisco over the last few months, when the San Francisco Chronicle revealed it had sunk 16 inches and tilted two inches to the northwest since it was built eight years ago.

The city blames Millennium Partners, the developers, for driving piles only 80 feet deep into mud and sand instead of 200 feet deep, where the bedrock would reinforce them. The developers blame the Transbay Joint Powers Authority, which is digging a tunnel next door for a new subway line near the building.

The potential fixes are costly, and the legal battles will likely be costlier. Now condo owners in the tower are getting anxious about their own home values. Owners, from tech executives to sports figures and real estate investors, have filed property assessment appeals, and as part of the appeal process, these owners must estimate what they believe is the current worth of their unit.

According to the San Francisco Examiner, condos in The Millennium Tower were valued between $563,000 and $12.6 million, with 141 of the 350 units valued over $1 million. Now, during the appeals process, condo owners have estimated the current worth of their homes at $0, $1, or $2 - more reasonable estimates cut the original value in half.

An accountant with Raimondo Pettit Group who is filing the appeal for a condo owned by Joe Montana told SF Examiner that "zero dollars might be a good number if the property can't be sold at any price."

Mayor Ed Lee has assured the public that the tower is still safe.

At the heart of this debacle is a simple question--who's at fault? The pending legal battles should provide an answer to that question. The only thing that isn't in doubt is that there's more than enough blame to go around.

Before the Transbay Joint Powers Authority begin digging the tunnel next door, it studied the building's current condition and analyzed how its construction plans could affect the tower. The report from 2010 showed the Millennium had already sunk 10 inches just two years after completion, which was four inches more than the builders had originally predicted it would settle. The Transbay Joint Powers Authority also spent $58 million to buttress the Millennium underground before it started to excavate.

The developers still argue the city is at fault, considering other buildings in the San Francisco area were built in a similar manner as the Millennium, which means those structures also hadn't driven piles into the bedrock. Studies have not been conducted on other towers built under the same to see if those, too, may be sinking.

One thing's for sure, whoever is found at fault (i.e. the developers or the city), will be shelling out millions to stabilize the MIllennium Tower before it gets worse. And they could potentially be fending off lawsuits from upset condo owners. It's also possible this spurs more advocacay for zoning laws that require structures to dig into the bedrock so this situation doesn't happen in the future.