SAN FRANCISCO (CBS SF) — It’s still merely a proposal, but a suggested fix for San Francisco’s sinking Millennium Tower will not be cheap.

Since the luxury tower — with housing units coming with seven-figure pricetags — was opened in 2009 it has sunk 17 inches and tilted 14 inches to the west and 6 inches to the north. And the movement hasn’t stopped.

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The proposal could cost $500 million — $150 million more than it actually cost to build the tower.

“We’re just hoping for the best, that’s all we can do at this point,” said Tower homeowner Rupa Parik. “Obviously, it’s frustrating.”

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The proposal calls for roughly 300 steel and concrete piles to be bored down to the bedrock. The goal is to stabilize one side of the building and let the other side sink until it levels off. Then additional piles will be placed to stabilize the building.

“We’re trying to have faith in the proposal they have come forward with,” Parik said. “It’s really the best we can hope for.”

Soil tests are underway for this proposed project and engineers and contractors are working with the city to get the proper permits. Some are skeptical of this proposed retrofit but homeowners realize there is no easy fix.

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“Knowing the way the building is constructed, it (the fix) will be a challenge,” Parik said. “It’s going to be a challenge for anyone to come up the right measure at this point.”